australian guidelines for the estimation and classification of

australian guidelines for the estimation and classification of
AUSTRALIAN GUIDELINES
FOR THE
ESTIMATION AND CLASSIFICATION OF
COAL RESOURCES
2014 EDITION
Prepared by the Guidelines Review Committee
on behalf of
the Coalfields Geology Council of New South Wales
and
the Queensland Resources Council
Contents
1
PREFACE........................................................................................................................... 1
2
SCOPE ................................................................................................................................ 1
3
GLOSSARY ....................................................................................................................... 2
4
DATA FORMS................................................................................................................... 4
5
6
4.1
Points of Observation .................................................................................................. 4
4.2
Supportive Data ........................................................................................................... 4
ESTIMATING RESOURCES AND ASSESSING CONFIDENCE ................................. 5
5.1
Overview ..................................................................................................................... 5
5.2
Critical assessment of relevant local, geographical and geological settings ............... 5
5.3
Identifying critical data ............................................................................................... 6
5.4
Data analysis, error and verification ........................................................................... 6
5.5
Domaining ................................................................................................................... 9
5.6
Statistical analysis ....................................................................................................... 9
5.7
Geostatistical analysis ............................................................................................... 10
5.8
Geological modelling ................................................................................................ 11
REASONABLE PROSPECTS ......................................................................................... 12
6.1
Inventory Coal ........................................................................................................... 12
6.2
Coal Resources .......................................................................................................... 14
7
REPORTING AND DOCUMENTATION OF RESOURCES ........................................ 15
8
AUDITS............................................................................................................................ 16
9
FUTURE REVIEWS ........................................................................................................ 16
Figures
Figure 1: Relationship between precision and accuracy ........................................................... 8
Figure 2: Relationships between Inventory Coal, Resource and Reserve Classifications ....... 13
Figure 3: Example of a “spotted dog” – what not to do........................................................... 25
Figure 4: Coal sampling and its implication for working section definition ........................... 27
Figure 5: Representation of a variogram ................................................................................. 28
Tables
Table 1: Glossary of terms ........................................................................................................................................................ 2
Appendices
Appendix A - List of relevant Australian Standards (as at 2014)
Appendix B - Coal composition, moisture states and reporting bases
Appendix C – Questions and Answers
Appendix D – Precision of test methods and schedule for reporting results
Appendix E – Recommended reading
Appendix F - JORC Code, 2012 Edition Table 1 report template
1
PREFACE
1.1
Prior to September 1999 the estimation and reporting of Coal Resources and Coal Reserves in Australia were
prescribed by the "Australian Code for Reporting Identified Coal Resources and Reserves (February 1986)". This code
was ratified by the Government Geologists’ Conference in April 1986 and appended to the "Australasian Code for
Reporting of Identified Mineral Resources and Ore Reserves" (The JORC Code), prepared by the Joint Ore Reserve
Committee (JORC) in February 1989. The JORC Code was subsequently revised in 1992 and 1996. In 1999, a
significant revision occurred which resulted in the inclusion of the reporting of Coal Resources and Coal Reserves into the
“Australasian Code for Reporting of Mineral Resources and Ore Reserves”. This 1999 edition of the JORC Code
referenced the 1999 edition of the “Guidelines for the Estimation and Reporting of Australian Black Coal Resources and
Reserves”. The guidelines were updated in 2003 as the “Australian Guidelines for Estimating and Reporting of Inventory
Coal, Coal Resources and Coal Reserves” (the 2003 Guidelines), and were referenced in the 2004 and 2012 editions of
the JORC Code.
1.2
“The JORC Code 2012 Edition”, herein referred to as “the Code”, provides minimum standards for public reporting
of Exploration Results, Mineral Resources and Ore Reserves. The Code states in guidance notes for Clause 42 that for
guidance on the estimation of Coal Resources and Reserves and on statutory reporting not primarily intended for
providing information to the investing public, readers are referred to the “Australian Guidelines for Estimating and
Reporting of Inventory Coal, Coal Resources and Coal Reserves” or its successor document as published from time to
time by the Coalfield Geology Council of New South Wales and the Queensland Resources Council.
1.3
This successor document, the “Australian Guidelines for the Estimation and Classification of Coal Resources”,
herein referred to as “the Coal Guidelines”, represents a substantial update of that work. It will continue to be reviewed
periodically and re-issued as required.
1.4
This document is not part of the Code, however adherence to the processes and procedures outlined in the Coal
Guidelines is recommended by the Code. This document must be read in conjunction with the Code, and if any conflict is
perceived between this document and the Code, the Code takes precedence. Guidance notes to Clause 42 of the Code
states these guidelines do not override the provisions and intentions of the JORC Code. Competent Persons should as
always exercise their judgement in the application of these guidelines to ensure they are relevant to the circumstances
being reported. They may not be applicable for use in all situations in Australia or overseas.
1.5
Some of the wording in the Coal Guidelines has been copied from the Code and the reader should note that
requirements of the Code are mandatory if reporting of an estimate is said to meet the standard of the Code.
1.6
References to Coal Reserves in the previous version of this document were a partial replication of Ore Reserves
documented in the Code. Since Coal Reserves are adequately covered by the Code they are now not replicated in the
Coal Guidelines.
2
SCOPE
2.1
The scope of this document is to:
• Provide guidance reflecting good practice, which is recommended to be followed when classifying and estimating
Coal Resources;
• Provide guidance for the determination of reasonable prospects for eventual economic extraction (“reasonable
prospects”) as this pertains to coal deposits;
• Include a variety of assessment tools that can be used for the estimation and classification of Coal Resources, to
replace the application of suggested maximum distances between Points of Observation that were included for
guidance in previous versions of this document; and
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• Provide a definition of Inventory Coal (as included in this document) for the purposes of Government and nonpublic reporting.
2.2
The Coal Guidelines are broad in nature to accommodate the wide variation of coal deposits in terms of rank,
quality and geological environment. This document is intended for use in Australian coalfields but may also provide
guidance internationally.
2.3
3
In this document important terms have a definition provided in the Glossary.
GLOSSARY
3.1
The following terms and their intent are used in this document.
Table 1: Glossary of terms
Term
Definition and usage
Australian
Standards
Australian Standards are published by Standards Australia and govern, amongst many other
things, the manner in which coal and coke are sampled, analysed, tested and the results
reported. There are Australian Standards to cover virtually all tests relevant to coal resource
evaluation (refer Appendix A) and it is anticipated that coal analysis work carried out in
Australia will be conducted according to these standards.
AS1038 is the prefix used to identify the principal Australian Standards that detail the
methods for analysis, testing and reporting of quality in higher-rank coal and coke. AS2434
is the prefix used for a similar series of Australian Standards for analysing and testing lower
rank coals. There are other relevant standards, including AS4264 (sampling) and AS2519
(Guide to technical evaluation of higher rank coal deposits).
Basis
(Reporting)
Basis refers to the state of the sample on which the quality assessment is based, and
considers the moisture and ash values within the sample. The basis of any quality
parameter should be stated in all forms of data storage and in all reports.
Raw data may include data at a range of bases and it is important that the basis is known.
The most common are: as received, air dry, dry and dry ash free and these are described in
Appendix B. Other bases used include ash-free moist, dry mineral matter free and dry
minerals and inorganics free. These are not described here.
In terms of coal quality parameters that are relevant to reporting of Coal Resources, most
that are moisture dependent are reported at air dry basis (the value of which should be
stated).
In terms of reporting of coal quantities, in situ moisture is the correct reporting basis and this
should also be stated. In situ moisture is the moisture content of the coal, undisturbed in the
ground.
Coal
Reserve
Coal Reserve has the same meaning as “Ore Reserve” as defined in the Code.
Coal
Resource
Coal Resource has the same meaning as “Mineral Resource” as defined in the Code.
Composition
Composition of coal refers to the chemical characteristics of a coal sample. These in turn
depend on the combination of rank, type and grade of the coal, and also the extent to which
the coal may have been modified by beneficiation.
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Term
Definition and usage
Confidence
Confidence in Resource classification refers to the assessment of the critical data for a coal
deposit and likely variation in the resource estimate following additional exploration.
Critical
Variables
Critical variables are those physical and chemical properties of coal that may potentially limit
reasonable prospects for eventual economic extraction. Understanding the distribution of
critical variables within the deposit is of importance in defining the confidence of classification
for the Coal Resource.
Density
The density of a coal sample is dependent on the rank, type, mineral matter and moisture
contents of the coal. The moisture content of a sample will be affected by the manner in
which it has been handled, broken, dried, or analysed. The determination (best estimate) of
the density of coal in situ requires the conversion of those densities and moistures
determined in a laboratory. The industry standard method follows the Preston and Sanders
formula (Preston and Sanders, 1993) which utilises the best estimate of the in situ moisture
(from a Moisture Holding Capacity test or an Equilibrium Moisture test on a higher rank coal)
in conjunction with the laboratory-determined air dry density and air dry moisture content of
the sample. For further information refer to Q4 (Appendix C) and Preston (2005).
Exploration
Target
Exploration Target has the same meaning as “Exploration Target” as defined in the Code.
In situ
In situ refers to the condition of the coal as being undisturbed in the ground. An estimate of
Coal Resources should state the condition of the coal in the ground and the values for
moisture and density.
Inventory
Coal
Inventory Coal refers to an estimate of in situ coal that does not consider or does not pass
the reasonable prospects test. It may include coal that currently has low prospectivity due to
natural or cultural features that preclude mining. For further information refer to section 6.1
and Appendix C (Q1 to 3).
Quality
(Coal)
Quality is a term that encompasses all aspects of rank, type and grade that contribute to
giving a coal its properties, as indicated by a standard suite of tests. Quality is normally
considered in the context of coal’s potential utilisation and how it might favourably or
unfavourably affect the utilisation process.
Rank (Coal)
Rank is a concept that describes the degree of coalification (physical and chemical
transformation from vegetable material to coal) that has been achieved by plant materials, as
a consequence of elevated temperature maintained over time and to a much lesser degree,
pressure. The causal factor is principally deep burial of plant materials within the earth’s
crust. Rank is indicated by a range of properties, including moisture and calorific value for
low rank coals and mean maximum reflectance of vitrinite for higher rank coals.
Type (Coal)
Coal type refers to the composition of a coal in terms of its organic components, recognised
as its macerals. The macerals are recognised according to a standard classification system,
which refers to the original plant material from which they were formed and the degree of
subsequent decomposition and degradation.
Grade (Coal)
Coal Grade refers to the inorganic constituents of a coal (the mineral matter) in terms of their
total proportion (% mineral matter or its residue on combustion, ash) and in terms of their
individual constituents (e.g. % Na, S, P etc.).
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4
DATA FORMS
4.1
Points of Observation
4.1.1 Points of Observation are sections of coal-bearing strata, at known locations, which provide information about the
coal by observation, measurement and/or testing. They allow the presence of coal to be unambiguously determined.
4.1.2 Points of Observation have varying degrees of reliability and can include surface or underground exposures, bore
cores, calibrated downhole geophysical logs and representative drill cuttings in non-cored boreholes. Points of
Observation may be classed by Quantity or Coal Quality. Each class should be clearly tabulated and presented in plans
on a seam by seam basis.
4.1.3 Resource confidence outlines should be determined by the merging of Quantity confidence limits (tonnes) with
Coal Quality confidence limits. The final confidence limits should be the more constrained of the two. Deposits without
Coal Quality data cannot qualify as a Resource as there is no data to establish the relative value required for the
reasonable prospects test.
4.1.4 In most coal deposits the density of Quantity Points of Observation is greater than the density of Coal Quality
Points of Observation. As a result, Coal Quality Points of Observation are generally viewed as the principal delimiter of
Resource categories. There are however deposits in which the quantity variability is greater than the quality variability.
This would include highly faulted or structurally complex deposits. In these cases Resource confidence and outlines may
be delimited by the Quantity Points of Observation.
Coal Quality Points of Observation
4.1.5 A Point of Observation for coal quality evaluation is normally obtained by testing samples obtained from surface or
underground exposures, or from bore core samples having an acceptable level of core and sample recovery to be
considered representative.
4.1.6 Relevant coal analysis data should be acquired to determine the nature of the coal and the potential products for
Coal Quality Points of Observation. If beneficiation is required to achieve a desired product mix and/or additional quality
parameters are required to confirm the suitability of the coal, then yield and relevant product quality data should be
included in the criteria for Coal Quality Points of Observation. If this is not the case, then the absence of such data should
be justified.
Quantity Points of Observation
4.1.7 A Point of Observation for quantity evaluation is normally obtained by measurements of surface or underground
exposures and bore intersections. The seam thickness and location must be unambiguous. Seams covered by downhole
geophysical logs in non-cored boreholes can provide Quantity Points of Observation.
4.1.8 Points of Observation for quantity estimation may not necessarily be used for coal quality evaluation and the
relevant spacing and location of each should be reported separately.
4.2
Supportive Data
4.2.1 Supportive Data are observations supporting the existence of coal, gathered by interpretive or indirect methods.
Supportive Data may include results from geological mapping, 2D and 3D seismic, magnetic, gravity and other
geophysical and geological surveys.
4.2.2 Supportive Data can be used with Points of Observation to improve confidence in seam continuity. An example is
depth adjusted 3D seismic data which may be used to define seam structure location between boreholes.
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4.2.3 Detailed calibration of downhole geophysical logs with seam core sample analyses may allow the estimation of the
in situ density and raw coal ash in non-cored boreholes. In this case, the interpreted raw ash estimates could be used to
improve the confidence level in continuity between Coal Quality Points of Observation.
4.2.4 Supportive Data should not be used quantitatively in any seam thickness estimate unless there is clear technical
justification to do so. When reporting Supportive Data, the technical basis of the interpretation should be stated.
5
ESTIMATING RESOURCES AND ASSESSING CONFIDENCE
5.1
Overview
5.1.1 Resources are classified based on the confidence in the geological data and the estimate. The Resource
categories as defined by the Code are Inferred, Indicated and Measured, which, in order, reflect increasing levels of
confidence in the Resource estimate.
5.1.2 In order to classify Coal Resources, an assessment of the confidence in the estimate of all significant variables
should be undertaken. Classification categories (Inferred, Indicated and Measured) are also likely to cover a range of
confidence levels. The criteria used to determine this confidence should be clearly documented.
5.1.3 For example, reporting a Coal Resource of coking quality requires that coking coal test work has been undertaken.
It should be established that there is sufficient confidence that the stated product can be produced, as it would be
misleading to report such a product type without suitable evidence. In the same way it is necessary to establish sufficient
confidence in the physical parameters (e.g. thickness, dip, faulting) of the coal seam which may be subject to greater
sensitivity than the quality.
5.1.4 The accuracy and precision of an estimate can also impact on confidence when the variable of interest is of a
critical nature. Where variables of interest have a range that is likely to produce a negative impact in the reasonable
prospects test, it is important to define the confidence in the measurement and estimation of those variables.
5.1.5 Confidence in classification categories of an estimate can be determined by a variety of methods and criteria. The
combination of the most applicable methods and criteria to demonstrate confidence in the estimate should be used to
support the classification assigned. Such methods and criteria include but are not limited to:
•
Critical assessment of relevant local, geographical and geological settings
•
Identifying critical data
•
Data analysis, error and verification
•
Domaining
•
Statistical analysis
•
Geostatistical analysis
•
Geological modelling
5.1.6 Any Resource estimate should be accompanied by an assessment of the most influential risks to that estimation.
Risks associated with Resource estimation include (but are not limited to) regulatory compliance and governance issues,
drill and sampling management, and geological modelling risk, as well as computational uncertainty due to structure,
stratigraphy, and coal quality variability.
5.2
Critical assessment of relevant local, geographical and geological settings
5.2.1 A comprehensive understanding of the relevant geology and geography of the deposit will inform the data
resolution required to define Resource confidence. Understanding the geology of the deposit should be the most
important factor and the starting point in Resource classification and estimation.
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5.2.2
Assessment of the geology of the coal deposit should include, but not be limited to, consideration of the following:
•
Regional geological setting;
•
Comparison to neighbouring projects, including an understanding of geological similarities and differences; and
potential hazards previously encountered in the region;
•
The nature of the coal seam, including whether the seam is thick and continuous, or is made up of multiple thin
seams and whether there is abundant splitting etc.;
•
Structure of the deposit, including seam dip, faulting, folding etc.;
•
Post-depositional influences, including depth of weathering, unconformities and wash-outs;
•
Intrusions, including the impact on seam persistence or structure and on coal quality;
•
Geotechnical properties of the coal and the non-coal strata and their influence on the proposed mining method;
•
Coal composition and rank and the impact upon coal quality parameters and potential coal product(s);
•
Geographical features and the relationship between structural and depositional features, particularly with respect
to topographical variability, river systems, weathering and oxidation.
5.3
Identifying critical data
5.3.1 Coal deposits have key attributes critical to economic viability.
determination of tonnage, quality, confidence and reasonable prospects.
These attributes are paramount to the
5.3.2 Seam thickness, areal extent (including structural influences), moisture and density are the attributes determining
tonnage estimates. The estimate of tonnages should be on an in situ moisture and in situ density basis. An outline of the
methodology employed to determine both in situ moisture and in situ density should be provided.
5.3.3 The Resource estimation process must consider quality parameters that may be critical to the mineability and
marketability of the product(s). This is crucial if the value of the marketable products has an impact on both cut-off limits
and reasonable prospects. It may be useful to compare the quality of the resource with that of normally utilised and traded
coals. Such an assessment may result in the identification of a critical parameter that needs to be further tested during
ongoing exploration and/or incorporated into resource cut-off limits and categorisations.
5.3.4 It is necessary to analyse variability and confidence for individual seams in relation to critical parameters and
assign confidence and cut-off limits on a seam basis. In a multi-seam deposit it may be practical to consider groups of
seams, although this should be clearly justified.
5.3.5 If washed coal is to be marketed, then washed product yield is a critical parameter in the estimate. If limited
product yield data are available then downgrading the confidence category of the Resource should be considered.
Satisfactory relationships between yield and other product parameters (including ash percentage) can be used to support
retention of the confidence categories determined for the in situ coal.
5.3.6 If metallurgical coal products are proposed to be marketed from the deposit, additional parameters need to be
analysed, including coal rank (such as vitrinite reflectance and ultimate analysis), coal petrography, coking properties,
phosphorous and critical trace elements. If hard coking coal is considered to be part of the product mix, the results of
coke strength tests must support such a conclusion.
5.4
Data analysis, error and verification
5.4.1 Coal exploration data are dominantly obtained from exploration boreholes, in the form of cuttings and/or cores
supplemented with downhole geophysical logs. Data may also be obtained from aerial topographic surveys, surface,
underground and highwall mapping, trenching, and aerial and ground geophysical surveys.
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5.4.2 The importance of understanding the history of the data, including the processes of collection, transfer, validation,
conversion and storage, and the time taken to thoroughly understand the data, identify errors and cleanse the data, cannot
be underestimated.
5.4.3 All data should be analysed statistically to understand the properties and relationships within the data-set and to
identify any anomalous results. Attention is drawn to the requirement to consider the criteria in the Code (Table 1, Section
1 - Sampling Techniques and Data) on an “if not, why not” basis.
5.4.4
Some considerations pertinent to analysis of coal exploration data are highlighted in the following sections:
Validation of topographic and survey data
5.4.5 Borehole collar, topographic survey and other geographic data need to be validated to confirm that the correct
survey datum and grid system has been used. The accuracy of survey methods used needs to be considered in addition
to checking collar information against topographic data to identify anomalous locations.
5.4.6 Boreholes are not always vertical as assumed in many coal exploration programmes. Borehole deviations need to
be checked and the lack of adequate downhole survey information should be taken into account during estimation and
reporting.
Sample representivity
5.4.7 It is important to consider that potential loss of material from within a sample may be critical, irrespective of the
relative percentage lost. The analysed sample should be representative of the in situ material within the interval of
interest. Downhole geophysical data should be used to confirm the location and nature of any core loss in coal seams.
5.4.8 Good sample recovery is required for representative samples and it is important to identify and document what is
considered acceptable for sample recovery. Unacceptable losses must be identified and where appropriate the sample
rejected as a Point of Observation. Calculated mass recovery (from raw sample mass, relative density, core diameter)
can be used to identify field measurement errors. Sample integrity and its impact on particle size distribution should be
considered.
5.4.9 In the design of coal sampling and testing programmes consideration needs to be given to the sample top size
and available mass to conduct the required tests.
5.4.10 Ideally, sampling should be carried out using data collected at the ply level for the full coal seam. This will provide
a better understanding of the geological controls on coal quality characteristics. Sampling should not be controlled by
mining criteria, as the parameters may change in the future, depending on factors such as economics or client product
specifications.
Sample history and impact on coal quality and geomechanical properties
5.4.11 Sampling methods, sample preparation and analysis protocols need to be carefully reviewed to identify potential
sources of error that may result in problems with data precision and accuracy.
5.4.12 Careful consideration should be given to evaluate the history of the sample storage as well as the handling from
the field to the final analysis. Oxidation is of great importance in the early loss of coking properties; drying has impacts on
geomechanical properties, coal moisture and density; and freezing and sample handling has impacts on particle size
distribution.
5.4.13 Checks should be carried out on the various types of data, tracing the results back to the original source(s) and
validating the relevant quality assurance / quality control (“QAQC”) systems.
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Validation of coal quality data
5.4.14 An initial check of coal quality data should be carried out to confirm agreement between sampling intervals and
lithological intervals.
5.4.15 Data can then be filtered, sorted, statistically analysed, cross-plotted (e.g. relative density vs. ash, calorific value
vs. ash), and visualised (e.g. histograms of value ranges) to understand the data and to check for errors.
5.4.16 It should be confirmed that all samples taken have been analysed to relevant testing standards.
5.4.17 The basis of analysis of all parameters needs to be confirmed, and used consistently when data are combined.
5.4.18 Coal quality data may require normalisation where exploration has been in progress for a number of years and
different approaches to sampling and test-work have been undertaken over time.
5.4.19 Quality data gathered from individual plies will usually require compositing into working sections; however
attention is drawn to the fact that data from many analyses, by their nature, cannot be validly composited (e.g. caking
properties).
Spatial analysis
5.4.20 Coal seam correlations and geological structure should be confirmed using down-dip and along-strike sections.
5.4.21 Careful evaluation of data posting and contour plots for the various parameters (e.g. thickness, coal quality), on a
seam by seam and/or ply by ply basis, is required to validate the data (e.g. by checking for bulls-eyes in contour plots), to
understand the lateral and vertical variations in the coal deposit, and to identify any separate geological domains (which
can be confirmed using variography).
Accuracy, precision and error
5.4.22 Data measurements must be considered in terms of both precision and accuracy. The differences between
precision and accuracy are demonstrated graphically in Figure 1.
Figure 1: Relationship between precision and accuracy
(a) low accuracy & precision, (b) low accuracy, high precision, (c) high accuracy, low precision, (d) high accuracy & precision
5.4.23 All measurements taken contain some statistical error (observational error). Error does not refer to a mistake, but
rather is the deviation between the measured value and its true value. Error occurs throughout the process of data
collection. It is important that these various forms of error and how they may occur and be dealt with in reporting is
understood (refer Appendix D).
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5.4.24 Error may occur in:
•
Sampling;
•
Data measurement;
•
Data management;
•
Interpretation;
•
Estimation; and
•
Reporting.
5.4.25 Consideration of the error(s) that may occur in each form of measurement and the accumulation of those errors
must be made to provide an indication as to the precision and accuracy of the estimate being made. Data should be
stored, used and reported in a method that reflects this precision.
5.4.26 A variety of techniques can be applied to assess error in all forms of data capture. This requires implementation of
rigorous and documented QAQC systems to assess the measurement, undertake evaluation and determine the
significance of any error. The following techniques should be considered in developing QAQC protocols:
•
Documented work practices
•
Training and accreditation of personnel taking measurements
•
Repetitive testing of known standards throughout normal data capture cycles
•
Evaluation of standard and blank measurements over time
•
Duplication testing by independent parties
•
Independent audits
5.5
Domaining
5.5.1 Coal deposits are typically heterogeneous and include variations in seam characteristics. There may be both
lateral and vertical variation in the structural complexity, quality characteristics, or other attributes. A key aspect of any
estimate is to define the areas of a deposit that have similar features. These areas are known as geological domains.
5.5.2 Key features for domain definition may include: seam splitting and coalescing, intensity of structural deformation
(such as folding or faulting), seam dip, igneous intrusions (and their impact on coal characteristics), washouts, seam
subcrop (and weathering effects) and coal quality trends. Different domains may need to be identified for each of these
features for each seam.
5.5.3 Domains may encompass features that impact on the mineability, marketability, or reasonable prospects of that
part of the deposit. Analysis and modelling of data should be undertaken on a domain basis.
5.5.4 A deposit may have several geological domains, each of which may require a different data density to provide
similar levels of confidence in the estimation of tonnage and/or quality.
5.6
Statistical analysis
5.6.1 A reasonable estimate of the population distribution for the key parameters should be obtained provided the
method of sampling of the coal deposit has allowed the variability in geological and coal quality characteristics to be
demonstrated.
5.6.2 It is important that the sampling techniques undertaken should represent both the spatial distribution and the
variability of those parameters considered critical to the deposit.
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5.6.3 An analysis can be undertaken to develop an understanding of population sample statistics for key parameters,
such as:
•
Number of samples
•
Minimum and maximum variable values
•
Mean and median
•
Standard deviation
•
Variance
•
Coefficient of variation
•
Standard error of mean
•
Confidence limits of the mean
5.6.4 The use of such tools as histograms (normal and/or log), scatter plots, box and whisker plots, the coefficient of
variation and cumulative distribution frequencies should be used to illustrate the distribution of data in the sampled
population. These should support the understanding and confidence in the geological domains defined throughout the
geological terrain.
5.6.5 Examination of the extreme ends of a sampled population distribution may indicate the presence of outliers
(anomalous results or errors). Good practice is to check such results and determine a likely cause for the anomaly, and
hence the data adequacy, before inferring anything about the sample value. Data analysis should be undertaken prior to
excluding (with supporting justification) such samples from the population.
5.6.6 Not all variables sampled will follow a normal (Gaussian) distribution and consideration should be given to the
impacts of this when reporting certain statistical results.
5.7
Geostatistical analysis
5.7.1 Geostatistical analysis provides a mechanism to understand and quantify a variable’s continuity and the degree to
which it is spatially correlated. The process can also provide an evaluation of the sample data geometry, and considers
the volume (‘support’) of the data and the volume or area being estimated. Geostatistics provides a useful measure of the
uncertainty of an estimate. Careful consideration of data selection, data validation, domain definition and identification of
critical data are required for reliable geostatistical analysis.
5.7.2 Because coal represents a heterogeneous mixture of constituents, there is a range of coal quality parameters that
should be considered for geostatistical analysis. With multiple variables, consideration of the primary defining drivers in
the choice of critical variables is necessary. Continuity for different variables should be considered when determining the
maximum influence of any data applied in any estimate. When numerous variables are assessed, the critical variable with
the highest variability should take precedence in determining this maximum influence. This could be a deleterious
component with a material negative economic impact. In all circumstances, the geostatistical result should be rationalised
with respect to the geological interpretation.
5.7.3 If a specialist geostatistician undertakes this work, it should be done in consultation with a coal geologist who has
familiarity and understanding of the geological interpretation and the features of the deposit and the dataset. The results
of geostatistical analysis should never be applied in isolation from other factors in the resource estimation, such as the
mining method, the geological interpretation, and the data reliability.
5.7.4 The project area may need to be divided into domains of geological and statistical consistency for variography and
geostatistical analysis. Estimates can often be more easily executed if the same domains are selected for all variables,
but the geological and geostatistical validity of this should be considered. If the spatial controls on one variable are clearly
different to those of the others, then recognition of different domains may be warranted. There must to be sufficient data
points available within each domain for the analysis to be representative.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
10
5.7.5 Variography for coal variables is challenging when there are no closely spaced boreholes, because the short
range variance (nugget) becomes difficult to define and there is a risk that the continuity of the variable may be
overestimated. Variograms modelled using few data points also risk underestimating or overestimating the continuity of a
variable, especially if those data points are broadly spaced.
5.7.6 Clear documentation of the data selected for use in variogram modelling, any manipulations of the data, and the
domains used are required in reports. If a variogram is applied to more than one seam, cross-validation should also be
conducted on those seams.
5.7.7 The variogram may assist in defining distances of continuity between Points of Observation. In isolation, this is
not considered appropriate as it fails to consider all the other necessary factors contributing to the confidence in the
estimate, such as sample geometry, mining methodology, local geological features and reliability of sample data. Sole
use of the variogram is risky, in particular for variables with high nugget variance and/or short ranges.
5.7.8 Variability when estimated through geostatistical techniques is a function of the dimensions in which variance is
reported. Larger volumes will be less variable than smaller ones. When quoting variances, the scale of the estimated
blocks should be stated. For example Resource classification may be considered in terms of the expected mine
production over a given time period.
5.7.9
Further description of variograms and geostatistical methods is provided in Q16 and 17 (Appendix C).
5.8
Geological modelling
5.8.1. A geological model is a mathematical depiction that reflects the geological interpretation of the deposit. A good
understanding of the geology should be established before constructing the model, as this will guide selection of the most
appropriate modelling technique for the deposit.
5.8.2 It is important to understand the principles underlying the software package being used. This includes
understanding the steps required in the modelling process, and the order in which they must be completed to ensure the
finished geological model represents the geological interpretation.
5.8.3 For the purposes of ensuring consistency in the modelling process a workflow (i.e. the defined sequence or steps
to generate the model) should be established. This workflow should be documented for the purposes of materiality,
transparency, and auditing. An explanation of what should be included is included in Q18 (Appendix C).
5.8.4 The geological model may be divided into several domains based upon the geology and data distribution. Care
should be taken in extrapolating trends across domain boundaries. Refer to section 5.5 for description of domains.
5.8.5 Inputs into the geological model should be verified as reliable and representative of the geology prior to its
construction. Any data excluded from the geological model should be documented, along with justification for its
exclusion. Care should be taken to ensure the selection of data does not introduce bias to the geological model.
5.8.6 The impact of combining data from different sources and/or of different resolution into one geological model
should be understood, such as the combination of ply and working section data. The impact of different generational
sources of data may also be manifest as modelling discontinuities, such as boundaries between different mines or regional
data sets.
5.8.7 If it is necessary to include artificial data to create a geological model that is consistent with the geological
interpretation, these should be clearly identified both in the model and recorded in the supporting documentation. Such
data should be reviewed and reassessed as new data are obtained.
5.8.8 Appropriate modelling parameters should be selected based on the density and distribution of the data, the data
trends and the local geological interpretation. The suitability of these parameters should be confirmed using quantitative
methods.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
11
5.8.9
Consideration of modelling parameters may include:
•
Selection of modelling algorithm
•
Selection of model type
•
Resolution of the grid mesh/block size
•
Search neighbourhood
•
Interpolation between data
•
Reasonable extrapolation of trends in thickness and coal quality,
5.8.10 The selection of modelling parameters may differ by variable (e.g. thickness, ash, fluidity). The geological model
should be constructed to provide maximum flexibility for subsequent mine planning options; however, this may be limited
by the available data. The version of the geological model used for the estimation of Resources should be archived.
5.8.11 Validation should occur at all stages of the modelling process, and should identify and quantify the strengths and
limitations of the geological model. The intended use of the geological model should be clear in the documentation, and
the geological model should be confirmed as fit for purpose through peer review. A review of the geological model should
be carried out in the event of a material change.
5.8.12 A geological model should represent the geological interpretation. Typical validation checks may include:
•
Visual checks of the data such as by contour plots and sections
•
Data honouring
•
Statistical checks between the borehole and model data
•
Reconciliation with previous models
•
Validation of the model in relation to local geological understanding and trends
•
An assessment of the sensitivity of the model to changes in geological interpretation, modelling assumptions or
additional data
5.8.13 Common issues in geological models that can effect or compromise Resource estimations include:
6
•
Not checking computer calculations
•
Over-smoothing or overcomplicating the model
•
Phantom coal being generated through automated modelling processes, a poor geological interpretation, or not
understanding mined-out areas
•
How the model caters for missing seams in boreholes
•
Coal losses being generated through incorrect pinching out of seams
•
Unreasonable extrapolation of trend surfaces
•
The manner of dealing with unconformities and other limiting surfaces such as weathering and topography
•
Dealing with different data densities in the same model
•
Not confirming digital data against original data
•
How the model deals with composited data, and whether correct weighting is applied to composite calculations
•
Assumptions about the reliability and accuracy of the data
•
Edge effects (including flattening of seam dips away from real data)
REASONABLE PROSPECTS
6.1
Inventory Coal
6.1.1 Inventory Coal is any occurrence of coal in the ground that can be estimated and reported without being
constrained by economic potential or other modifying factors. That is to say estimates of Inventory Coal tonnages are not
subject to or constrained by the reasonable prospects test. By definition Inventory Coal includes all known Coal
Resources.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
12
6.1.2 The location, quantity, quality, geological characteristics and continuity of Inventory Coal are known, estimated or
interpreted from specific geological evidence and knowledge. In a similar fashion to Coal Resources, Inventory Coal is
sub-divided in order of increasing geological confidence into Inferred, Indicated and Measured categories (refer Figure 2).
Figure 2: Relationships between Inventory Coal, Resource and Reserve Classifications
6.1.3 Inventory Coal is a term that enables a more complete estimate of unconstrained coal tonnages in situ to be
reported to Government for the State’s purposes or for purposes of strategic planning internally within companies that hold
or manage mineral tenements.
6.1.4
Estimates of Inventory Coal must not be publicly reported.
6.1.5 Where estimates of Inventory Coal and Coal Resources are presented together in a non-public report, a statement
must be included in the report which clearly indicates whether the Inventory Coal, as reported, is inclusive of, or additional
to the Coal Resource.
6.1.6 An estimate of Inventory Coal is fundamentally different from an Exploration Target as defined in the Code, in that
the latter is generally restricted to either one of two situations being:
•
an aspirational or hypothetical (coal exploration) target based on little or no direct data but perhaps at best,
supported by regional trends or a conceptual geological model or
•
an estimate of potential coal in situ, which is at best an ‘order of magnitude’ estimate and which is based on
extremely limited data (insufficient coverage, density or integrity) to properly allow the classification of Inventory
Coal or Coal Resources estimates in accordance with the provisions of the Code or the Coal Guidelines.
6.1.7 Where some exploration has been conducted on an area, but is insufficient to enable the estimation and reporting
of either Inventory Coal or Coal Resources with at least an Inferred level of confidence, it may be appropriate to report an
Exploration Target based on those exploration results.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
13
6.1.8 The reader is referred to clauses 17-19 of the Code for the strict public reporting conditions, including cautionary
statement and the required information to be disclosed to enable investors to assess the significance of the Exploration
Target. The statement cautions that it is uncertain if further exploration will result in the estimation of a Coal Resource.
6.2
Coal Resources
6.2.1 A Coal Resource as defined in the Code is not simply a summation of all coal drilled or sampled, regardless of
coal quality, mining dimensions, location or continuity. It is a realistic estimate of the coal that, under assumed and
justifiable technical, economic and development conditions, is more likely than not to become economically extractable.
6.2.2 These Coal Guidelines do not prescribe a specific approach to arriving at the key assumptions, or the level of
detail required. Neither do they set out the economic indicators that need to be satisfied or the level of satisfaction that
needs to be achieved for the coal to be said to have reasonable prospects and hence be classified as a Resource. The
Coal Guidelines simply provide prompts as to the factors that need to be considered and documented, including but not
limited to mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social,
governmental and regulatory factors.
6.2.3 Guidance to Clause 38 of the Code states that in discussing ‘reasonable prospects for eventual economic
extraction’ there is a requirement for an assessment (albeit preliminary) in respect of all matters likely to influence the
prospect of economic extraction including the approximate mining parameters. While a Scoping Study may provide the
basis for that assessment, the Code does not require a Scoping Study to have been completed to report a Coal Resource.
6.2.4 Clause 20 of the Code states that the basis for the reasonable prospects assumption is always a material matter,
and must be explicitly disclosed within the Public Report using the criteria listed in Table 1 for guidance.
6.2.5 Guidance to Clause 20 of the Code discusses what may be considered as reasonable time frames for extraction
of bulk commodities such as coal, and notes that in all cases, the considered time frame should be disclosed and
discussed by the Competent Person.
6.2.6 An assessment must be made that considers those factors which will affect costs and revenues, as well as those
factors which might affect the “licence to operate”. The physical attributes of the deposit, together with the beneficiation
characteristics, are those which heavily influence costs. Critical product coal quality attributes that determine the potential
utilisation of the coal and the mix of product types will be the major influences on revenue. Licence to operate includes the
regulatory, social, cultural, political and environmental factors that may inhibit or limit mine development, or add to the cost
of development. It may be necessary to seek expert comment on these factors.
6.2.7 Clearly the reasonable prospects test is sensitive to the geological, geotechnical and coal quality parameters that
will have been investigated as a precursor to the estimation process. In some cases the prospectivity of a coal deposit
can be assessed by comparing the known parameters with analogues in nearby areas. However, rarely is it easy to
properly assess the economic worth of a coal deposit without at least a basic appreciation of costs of extraction and likely
revenues to be received. These matters are normally considered during the Resource study and in concert with engineers
and other specialists.
6.2.8 Realistic cut-off parameters should be determined and applied to the deposit that take into account the likely
mining scenario and the potential utilisation of the coal with reference to experience regarding similar operations. In
deposits where both open cut and underground Coal Resources are considered to exist, the limits for each mining
method, as well as thickness and coal quality constraints relevant to each mining method should be disclosed.
6.2.9 In a potential open cut mining scenario, emphasis on strip ratio, minimum mineable seam thickness, maximum
non-separable parting thickness, pit wall stability and depth of weathering are important considerations. If beneficiation of
the raw coal is envisaged, the clean coal yields should be factored into cut-off considerations, including strip ratios. It may
be desirable to consider optimisation techniques to examine various options to support an assessment of cut-offs.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
14
6.2.10 In an underground mining scenario, aspects such as depth, faulting, igneous intrusions, working section thickness,
seam dip, physical properties of roof and floor lithologies, hydrogeology, stress regime, gas content, composition and
permeability should be considered. In multi-seam underground deposits, the nature and thickness of the interburden
material may be a critical consideration, as this might preclude extraction of some of the target coal seams.
6.2.11 The results of any relevant technical and economic studies should be considered. Reference to existing
operations in a similar region and geological setting should also be referred to where possible and relevant. Caution
should be exercised if limits on coal quality, including ash percentage and deleterious elements (e.g. sulphur and
phosphorus) are strictly applied. Such quality aspects should be noted, but may not be of sufficient significance to declare
that such a coal is not considered a Resource. Incorporation of mining limits, including depth, strip ratio, minimum (and
maximum, if appropriate) mineable thickness, seam dips or intra-seam parting thickness are similarly to be treated with
caution.
6.2.12 Consideration should be given to whether the tonnage and coal quality are sufficient to ensure satisfactory returns
over a reasonable life of mine. If the estimated coal tonnage is not sufficient to support a mining operation this may
preclude the coal’s potential for future development unless sufficient upside can be identified (e.g., potential to increase
the tonnage, or potential synergies with adjacent Coal Resources).
6.2.13 A coal deposit may be alienated from current markets if it is located in an extremely remote area devoid of relevant
infrastructure, and where potential development in a reasonable timeframe may be difficult to justify.
6.2.14 Consideration should be given to whether all the coal is accessible for exploration and/or development. Coal
Resources may only be estimated within the boundaries of valid exploration, development or mining tenures held by the
reporting company, its subsidiary companies or its Joint Venture partners.
6.2.15 Areas with surface land access restrictions, such as a gazetted or proposed national park, would normally be
excluded and the coal within these areas excised from a Coal Resource estimate. There may also be instances where
coal adjacent to or underlying major rivers, bodies of stored water, urban developments or major infrastructure, such as
railway lines, major bridges and highways, requires careful consideration and documentation in terms of potential future
development of all or parts of the deposit. In these instances (and always assuming that the coal is sufficiently attractive
and technically possible to mine) there may be additional costs and social or legal impediments to mining. Consideration
needs to be made regarding a determination as to whether there are reasonable prospects for mining to take place within
the time frame stated. Any such coal excluded from a Coal Resource may be included in Inventory Coal in a non-public
report.
7
REPORTING AND DOCUMENTATION OF RESOURCES
7.1
Complete relevant sections of Table 1 of the Code, ensuring that all relevant sections are filled out on an “if-not
why-not” basis. For Exploration Results this requires sections 1 and 2, for Coal Resources sections 1, 2 and 3.
Suggestions of aspects to be considered are also provided in Appendix F.
7.2
It is the responsibility of the Competent Person to determine and justify the confidence categories for any given
deposit. Documentation should be prepared that fully describes the estimation process and assumptions used. The
documentation should address all items in Table 1 of the Code (refer Appendix E) and may include:
•
The criteria used to differentiate between Inventory Coal and Coal Resources, i.e. define what is used to
determine the reasonable prospects test.
•
Tables of the estimates displaying: tenures, confidence categories, areal extents, thickness ranges, in situ
densities, depth ranges and coal quality ranges relevant to the estimate for each seam or seam grouping.
•
Reference to the probable mining method.
•
The moisture basis of the estimate(s) and the moisture adjustment factor (if applied).
•
A description of all factors used to limit the estimate(s).
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
15
8
•
A declaration as to whether or not the Resource report complies with the requirements of the Code.
•
The name, qualifications and experience of the Competent Person and the relationship with the tenure holder(s)
and/or operators.
•
The date of the report publication.
AUDITS
8.1
It is good practice to undertake an audit or peer review of the Resource estimate particularly where it is a maiden
estimate or where a material change has occurred from previous Resource estimates.
9
FUTURE REVIEWS
9.1
These Coal Guidelines will be reviewed by a committee of industry and government representatives authorised by
the Coalfield Geology Council of NSW, the Queensland Resources Council and representatives from other coal producing
states.
9.2
The aim of subsequent revisions will be to provide clarification if required and to extend the level of commentary
within the Coal Guidelines.
9.3
Submissions in writing for suggested amendments or changes should be directed to:
The Secretary
Coalfield Geology Council of NSW
C/o New South Wales Department of Trade and Investment
P.O. Box 344,
Hunter Regional Mail Centre NSW 2310
Or
The Director of Operations
Queensland Resources Council
133 Mary Street,
Brisbane, Qld, 4000.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
16
Appendix A - List of relevant Australian Standards (as at 2014)
Standard
Description
AS-1038.10.0-2002 (R2013)
Determination of trace elements - Guide to the determination of trace elements
AS 1038.10.1-2003 (R2013)
Determination of trace elements - Coal, coke and fly-ash - Determination of eleven trace elements Flame atomic absorption spectrometric method
AS 1038.10.2-1998 (R2013)
Determination of trace elements - Coal and coke - Determination of arsenic, antimony and selenium Hydride generation method
AS 1038.10.3-1998 (R2013)
Determination of trace elements - Coal and coke - Determination of boron content - ICP-AES method
AS 1038.10.4-2001 (R2013)
Determination of trace elements - Coal, coke and fly-ash - Determination of fluorine content Pyrohydrolysis method
AS 1038.10.5.1-2003 (R2013)
Coal, coke and fly-ash - Trace elements - Determination of mercury content - Tube combustion method
AS 1038.10.5.2-2007
Coal and fly-ash - Trace elements - Determination of mercury content - Acid extraction method
AS 1038.11-2002 (R2013)
Coal - Forms of sulfur
AS 1038.12.1-2002
Higher rank coal - Caking and coking properties - Crucible swelling number
AS 1038.12.2-1999 (R2013)
Higher rank coal - Caking and coking properties - Determination of Gray-King coke type
AS 1038.12.3-2002
Higher rank coal - Caking and coking properties - Dilatation
AS 1038.13-1990 (R2013)
Tests specific to coke
AS 1038.14.1-2003 (R2013)
Higher rank coal ash and coke ash - Major and minor elements - Borate fusion/flame atomic absorption
spectrometric method
AS 1038.14.2-2003 (R2013)
Higher rank coal ash and coke ash - Major and minor elements - Acid digestion/flame atomic absorption
spectrometric method
AS 1038.14.3-1999 (R2013)
Higher rank coal ash and coke ash - Major and minor elements - Wavelength dispersive X-ray
fluorescence spectrometric method
AS 1038.16-2005
Assessment and reporting of results
AS 1038.17-2000 (R2013)
Higher rank coal - Moisture-holding capacity (equilibrium moisture)
AS 1038.18-2006
Coke - Size analysis
AS 1038.19-2000 (R2013)
Higher rank coal - Abrasion Index
AS 1038.2-2006
Coke - Total moisture
AS 1038.20-2002 (R2013)
Higher rank coal - Hardgrove grindability index
AS 1038.21.1.1-2008
Higher rank coal and coke - Relative density - Analysis sample/density bottle method
AS 1038.21.1.2-2002 (R2013)
Higher rank coal and coke - Relative density - Analysis sample/volumetric method
AS 1038.22-2000 (R2013)
Higher rank coal - Mineral matter and water of constitution
AS 1038.23-2002 (R2013)
Higher rank coal and coke - Carbonate carbon
AS 1038.24-1998 (R2013)
Guide to the evaluation of measurements made by on-line coal analysers
AS 1038.25-2002 (R2013)
Coal - Durham cone handleability
AS 1038.26-2005
Higher rank coal and coke - Guide for the determination of apparent relative density
AS 1038.4-2006
Coke - Proximate analysis
AS 1038.5-1998
Gross calorific value
AS 1038.6.1-1997 (R2013)
Higher rank coal and coke - Ultimate analysis - Carbon and hydrogen
AS 1038.6.2-2007
Higher rank coal and coke - Ultimate analysis - Nitrogen
AS 1038.6.3.1-1997 (R2013)
Higher rank coal and coke - Ultimate analysis - Total sulfur - Eschka method
AS 1038.6.3.2-2003 (R2013)
Higher rank coal and coke - Ultimate analysis - Total sulfur - High-temperature combustion method
AS 1038.6.3.3-1997 (R2013)
Higher rank coal - Ultimate analysis - Total sulfur - Infrared method
AS 1038.6.4-2005
Higher rank coal and coke - Ultimate analysis - Carbon, hydrogen and nitrogen - Instrumental method
AS 1038.8.1-1999 (R2013)
Coal and coke - Chlorine - Eschka method
AS 1038.8.2-2003 (R2013)
Coal and coke - Chlorine - High-temperature combustion method
AS 1038.9.1-2000 (R2013)
Higher rank coal and coke - Phosphorus - Ash digestion/ molybdenum blue method
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Standard
AS 1038.9.2-2000 (R2013)
Description
Higher rank coal - Phosphorus - Coal extraction/ phosphomolybdovanadate method
AS 1038.9.3-2000 (R2013)
Coal and coke - Phosphorus - Ash digestion/ phosphomolybdovanadate method
AS 1038.9.4-2006
Higher rank coal - Phosphorus - Borate fusion/molybdenum blue method
Other Australian Standards that may require consideration for analysis and testing in lower rank coals include:
Standard
Description
AS 2434.1-1999 (R2013)
Determination of the total moisture content of lower rank coal
AS 2434.2-2002 (R2013)
Lower rank coal - Determination of volatile matter
AS 2434.3-2002 (R2013)
Lower rank coal - Determination of the moisture holding capacity
AS 2434.4-2002 (R2013)
Dried lower rank coal and its chars - Determination of apparent density - Mercury displacement method
AS 2434.5-2002 (R2013)
Lower rank coal and its chars - Determination of moisture in bulk samples of lower rank coal and in
analysis samples of char
AS 2434.6-2002 (R2013)
Lower rank coal - Ultimate analysis - Classical methods
AS 2434.7-2002 (R2013)
Lower rank coal - Determination of moisture in the analysis sample
AS 2434.8-2002 (R2013)
Lower rank coal - Determination of ash
AS 2434.9-2000 (R2013)
Method for the analysis and testing of lower rank coal and its chars - Determination of four acidextractable ions in lower rank coal
Additional standards that may also require consideration include:
Standard
Description
AS 2096-1987
Classification and coding systems for Australian coals
AS 2418-1995
Coal and coke - Glossary of terms
AS 2916-2007
Symbols for graphic representation of coal seams and associated strata
AS 2519-1993
Guide to the technical evaluation of higher rank coal deposits
AS 2617-1996
Sampling from coal seams
AS 2856.1-2000 (R2013)
Coal petrography - Preparation of coal samples for incident light microscopy
AS 2856.2-1998 (R2013)
Coal petrography - Maceral analysis
AS 2856.3-2000 (R2013)
Coal petrography - Method for microscopical determination of the reflectance of coal macerals
AS 3899-2002 (R2013)
Higher rank coal and coke - Bulk density
AS 3980-1999 (R2013)
Guide to the determination of gas content of coal - Direct desorption method
AS 4156.1-1994 (R2013)
Coal preparation - Higher rank coal - Float and sink testing
AS 4156.2.1-2004
Coal preparation - Higher rank coal - Froth flotation - Basic test
AS 4156.2.2-1998 (R2013)
Coal preparation - Higher rank coal - Froth flotation - Sequential procedure
AS 4156.3-2008
Coal preparation - Magnetite for coal preparation plant use - Test methods
AS 4156.3-2008/Amdt 1-2009
Coal preparation - Magnetite for coal preparation plant use - Test methods
AS 4156.4-1999 (R2013)
Coal preparation - Flowsheets and symbols
AS 4156.6-2000 (R2013)
Coal preparation - Determination of dust/moisture relationship for coal
AS 4156.7-1999 (R2013)
Coal preparation - Coal size classifying equipment - Performance evaluation
AS 4156.8-2007
Coal preparation - Sample pre-treatment - Drop-shatter
AS 4264.1-2009
Coal and coke - Sampling - Coal - Sampling procedures
AS 4264.1-2009/Amdt 1-2011
Coal and coke - Sampling - Coal - Sampling procedures
AS 4264.2-1996
Coal and coke - Sampling - Coke - Sampling procedures
AS 4264.4-1996
Coal and coke - Sampling - Determination of precision and bias
AS 4264.5-1999
Coal and coke - Sampling - Guide to the inspection of mechanical sampling systems
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Appendix B - Coal composition, moisture states and reporting bases
Organics
Minerals
Volatile matter
Fixed carbon
Ash Yield
Organic
Inorganic
Moisture
As liquid
or gas
----------------------------- Dry mineral matter free basis (dmmf) -----------------------------
------------------------------------------------ Dry, ash free basis (daf) -----------------------------------------------
---------------------------------------------------------------- Dry basis (db) ----------------------------------------------------------------
Moisture
-------------------------------------- In situ or bed moisture -----------------------------------
-------------- Moisture holding capacity -----------------
Air dry (ad) moisture
Note:
1)
water of hydration of minerals, and organically bound water form part of the volatile matter
2)
as received (ar) moisture may be greater or less than in situ moisture depending upon the condition of the sample
and the presence of surface moisture
Desired Basis
Given Basis
As Received value
multiplied by
As Received
Air Dry
Dry
Dry Ash Free
Air Dry value
multiplied by
Dry value
multiplied by
Dry Ash Free value
multiplied by
100 100 100
100 100
100 100
100 100
100 100
100 100 100 100 100
100 100
100 100
100 100
100 100
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Appendix C – Questions and Answers
Q.1
The JORC Code makes no mention of the term “Inventory Coal”. Why do the Coal
Guidelines allow the term to be used, and what does it include?
Inventory Coal is the term that applies to all coal in the ground that can be estimated and classified according to geological
confidence, and does not require a Competent Person to account for either potential commercial considerations or land
use constraints. All coal that can be estimated on the basis of relative confidence levels and has passed the “reasonable
prospects for eventual economic extraction” test can become a Coal Resource as defined by the JORC Code
Coal companies very often have a category, similar in concept to Inventory Coal that is used for internal company
purposes – terms such as “global coal estimate”, “in situ coal” have been widely used for many years.
Coal Resource estimates may tend to increase or decrease over time, depending on the views and perceptions of what
passes or fails the reasonable prospects test between different Competent Persons and also the economic considerations
and limitations adopted by different coal mining and exploration companies. However, within a coal deposit, defined by
the extent (lateral and vertical) of geological data (Points of Observation), the Inventory Coal estimate will tend to remain
relatively constant until the geological data limits change, e.g. new holes are drilled or old holes deepened.
The concept of Inventory Coal, within the Coal Guidelines, but outside the scope of the JORC Code, fulfils this need and
provides a platform for estimates of Coal Resources to be updated and reviewed over time as and when conditions which
impact the reasonable prospects test change. When first introduced into the 2003 edition of the Coal Guidelines the term
was defined as “…any occurrence of coal in the ground that can be estimated and reported without necessarily being
constrained by economic potential, geological or other modifying factors.”
Estimates of Inventory Coal (like those of Coal Resources) are based primarily on Points of Observation and may be
supplemented by Supportive Data. As data density and distribution allows, estimates of Inventory Coal are to be reported
as Measured, Indicated and Inferred confidence categories and rounded to a relevant level of accuracy (in a similar
manner to Coal Resources, refer to Clause 25 of the JORC Code). Estimates of Inventory Coal are to be expressed as
raw coal on an in situ basis.
If not otherwise reported as Coal Resources, the Competent Person may estimate as Inventory Coal, coal that is not
currently accessible for mining because of statutory restrictions on access to land (gazetted or proposed national parks or
environmental conservation areas). These may include features such as rivers or watercourses, reservoirs or lakes
(particularly those of major regional significance), major public infrastructure (e.g. rail, bridges) or areas of urbanisation.
The Competent Person may, in many cases, choose to exclude coal underlying such features from a Coal Resource
estimate, but may report such coal in the Inventory Coal category in non-public reports wherever sufficient data is
available.
The JORC Code does not contemplate use of the term Inventory Coal, nor does it provide for the estimation of coal which
might fall into this category or allow for it be publicly reported (as defined in the Code). The main application of the
Inventory Coal report is likely to be for submission to relevant government agencies and internally by coal exploration
companies for priority setting.
Q.2
Why estimate Inventory Coal?
Estimates of Coal Resources and/or Coal Reserves alone, do not present a complete picture of the coal that is in the
ground. In considering only these types of estimates, decision makers, either regulatory (e.g. the Crown/State) or within
exploration or mining companies may be completely unaware of what other coal is present in an area. Inventory Coal
estimates can be used by various agencies representing the States’ interest, to make fully informed, ‘arms-length’
decisions regarding a mining or development proposal. One of the considerations required is whether or not a proposed
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
coal mining project will maximise recovery and minimise the potential for the project to impact on, or potentially sterilise,
other identified mineral (broad ‘common usage’ context to include coal) occurrences.
Another use of Inventory Coal estimates is in the estimation of fugitive gas.
Examples where Inventory Coal can be significantly greater than the resource include the following:
•
coal which doesn’t meet the reasonable prospects test
•
selective mining of a single coal seam or coal seams within multiple seam sequences;
•
partial recovery (mining) of a thick coal seam using underground mining methods;
•
coal rendered uneconomic by overlaying spoil or diverting watercourses.
•
ground restricted or constrained for other uses
Q.3
I am preparing a report containing an estimate of Coal Resources. Can I include
any estimates of Inventory Coal in the report?
That depends upon the type of report being prepared and its intended purpose.
Reports intended for the investment market (‘Public Reports’)
The Code defines what it means by a ‘Public Report’ as those ”…prepared for the purpose of informing investors or
potential investors and their advisors on Exploration Results, Mineral Resources or Ore Reserves …”. The Code provides
examples that include but are not limited to “…annual and quarterly company reports, press releases, information
memoranda, technical papers, website postings and public presentations.”
If a report is being prepared for the purpose of informing investors, potential investors or their advisors, as set out in the
Code, the report must not include estimates of Inventory Coal.
For example, if the report was being prepared for inclusion in a company prospectus for a proposed listing on the
Australian Securities Exchange, it is not acceptable to include or make reference to estimates of Inventory Coal in the
report.
Other (‘Non-public’) Reports
The Code however recognises that at times, a report which contains certain ‘documentation’ that does not comply with the
Code may be required.
Reporting on, and documentation of, coal either internally within a company or to government agencies may be required
from time to time. Reports of this nature could generally be referred to as ‘non-public reports’ in that their primary purpose
is not to inform the investing public or their advisors.
It could for example be to allow for a more complete record of all coal occurrences to be presented, to assist with an
internal company decision or in making a recommendation to management. At this stage in the internal decision-making
process within a company, it may be important to know, but not necessarily make a determination on, the technological,
economic, land use or other constraints that might apply to a particular area under consideration.
In these cases, some of the coal occurrences documented in these types of reports may fall within the definition of
‘Inventory Coal’ as defined in the Coal Guidelines.
If a report is being prepared for internal company purposes only, then the Coal Guidelines could be used to assist in the
preparation and reporting of Inventory Coal estimates.
If a report is primarily prepared as a technical geological report documenting the results of exploration activity undertaken
by a company on an exploration tenement and is being submitted to a government department or other regulatory agency
for compliance purposes, then estimates of Inventory Coal may, and indeed should be included in the report. When Coal
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Resources are included in such ‘non-public’ reports, the Coal Guidelines may help preparing the estimates. Inventory
Coal is classified in terms of confidence in the estimate, as Measured, Indicated or Inferred.
The report must include a clear and unambiguous statement as to whether or not the estimates of Inventory Coal are
inclusive or exclusive of the Coal Resources.
When reporting estimates of Inventory Coal, any factors or physical features used to ‘limit’ the estimates should be clearly
stated. Where these limits relate to the areal extent of the estimates, it should be clearly represented graphically on maps,
plans or sections that accompany the report.
In doing so, in accordance with the recommendation of the Code, all reports of this type should include a statement to the
effect that …”In so far as the report includes estimates of Inventory Coal (a term not recognised by the JORC Code) the
report does not comply with the Code.” (refer Guidelines to Section 6 of the JORC Code, page 5, 4th paragraph).
Q.4
How is coal density applied to the Coal Resource estimate?
The expression to determine in situ coal tonnes is simply:
= ℎ ! ⁄" Seam area and thickness are simple, well known concepts, but coal density is less well understood. Nevertheless it
needs to be considered just as carefully as the other two factors.
For Coal Resource estimates to be both numerically accurate with respect to the density factor and correct from a process
logic perspective, all coal quantities should be estimated at in situ moisture and in situ density. The approach to
estimating in situ moisture must be supportable and the resultant values realistic.
Whilst it is not strictly correct to equate density with relative density, for most practical purposes in resource estimation,
density and relative density are numerically the same. In Australia density determinations are reported according to
Australian Standards as relative density, in accordance with two testing methods, namely:
i.
On air dry coal according to AS1038.21.1.1-2008 (the density bottle method). This is the most common and
recommended method;
ii.
On coal of unknown moisture according to AS1038.26-2005 (apparent relative density). Use of this method is
not recommended.
Using as reported air dry relative density (RD) values to estimate coal tonnes (i.e. as determined by the density bottle
method) will lead to an over estimate if not carefully dealt with during reserve estimation. However after correcting the airdry relative density to the in situ moisture basis, it is this value that should be used for tonnage estimation purposes.
If apparent relative density (ARD) is determined according to method (ii) above, the moisture will not be known, thereby
making it very difficult to properly correct this to in situ moisture and in situ relative density. Use of this standard, and of
uncorrected apparent relative density values, is not recommended.
Methods for adjusting air dry relative densities to in situ relative densities and also for bringing apparent relative densities
to an acceptable level of accuracy are outlined in Preston and Sanders, (1993) and Preston (2005).
Note that in most cases “in situ relative density” < “apparent relative density” < “air dry relative density”. Bituminous coal in
situ relative density generally has a range between 0.02 to 0.05 t/m3 below the laboratory determined relative density
(AS1038.21.1.1-2008).
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Q.5
How is in situ moisture estimated?
It is currently not possible to measure in situ moisture empirically as the methods of sampling changes the moisture
content. It can best be estimated by reference to other moisture indicators (e.g. air dry moisture, moisture holding
capacity etc.) and to coal rank, type and grade. Generally as rank increases, in situ moisture decreases. Certain inertinite
macerals have greater moisture carrying capacity than others and can give rise to high moisture relative to rank. Coals
high in liptinite tend to display lower moisture relative to coals rich in other macerals of the same rank. High ash coals
tend to carry less moisture, since there is a lower proportion of the more porous coal in the sample.
ACARP Report C10041 (Fletcher, IS and Sanders RH, 2003, Estimation of in situ moisture and product total moisture)
details studies of in situ moisture and provides some mechanisms for its estimation, primarily by relating it to parameters
such as Air Dry Moisture, Moisture Holding Capacity, Equilibrium Moisture and others. These methods are based upon
statistical analysis and whilst they do provide indicative results for a range of coals, they may not necessarily provide
correct results for specific coal deposits. Judgement must be applied to any results obtained from the application of
equations published in the ACARP report.
Q.6
The revised Coal Guidelines no longer include suggestions regarding maximum
distances between Points of Observation for the various confidence categories.
Why were these removed?
The 2003 Guidelines made it clear that the distances between Points of Observation for the various confidence categories
(Measured, Indicated and Inferred) are those which would not normally be exceeded unless there was sufficient technical
justification to do so. These were suggested recommended maximum distances thought to be applicable in the main
coalfields of eastern Australia. They were not prescribed distances or distances endorsed by the 2003 Coal Guidelines
regardless of the geological characteristics of the coal being classified.
It was apparent that there was confusion on this topic within the coal industry as there were numerous examples of
misinterpretation of the intent of this aspect of the 2003 Coal Guidelines, and using these recommended maximum
distances in a manner that suggested a prescriptive intent. Classifications based solely on maximum distances were
being made without due and deliberate consideration of the geology of the deposit.
By removing suggested maximum distances between Points of Observation for each confidence category in the Coal
Guidelines, the responsibility is placed back with the Competent Person to determine the criteria for classification.
Q.7
When estimating Coal Resources, is it reasonable to extrapolate beyond the last
Points of Observation?
Continuity is defined as being ‘…the state of being continuous or unbroken’. Continuity of a coal seam and its
characteristics, both physical and quality, is demonstrated with greater confidence between Points of Observation than
outside the last Point of Observation. Nevertheless it is considered that some level of extrapolation may be justifiable if a
solid case can be made to support the continuity of the coal seam. This case would take into account the known
characteristics of the coal seam both at a regional and local level and specifically where there is good data to support an
understanding of its nature. In all cases it will be the confidence in the critical variables that will determine the extent of
extrapolation.
Where the coal seam is known to show a high level of variability in either physical character or key quality variables, it is
difficult to see how a case could be made for extrapolation of any significant distance, and there may also be a case for no
extrapolation. Where a coal seam is known to be persistent and predictable in character, the case (again supported by
evidence) may be made to extrapolate by some percentage of the allocated Point of Observation spacing. These
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Guidelines do not support the view that there is an automatic licence to extrapolate a distance “half the nominal drill
spacing”.
In all cases, transparency and materiality require that the basis on which the resource is extrapolated to these limits is
explained clearly. Note also that for Inferred Coal Resources involving extrapolation beyond Points of Observation, the
provisions described in Clause 21 of the Code apply.
Q.8
When reporting, how should the Coal Resource estimate be rounded to reflect the
level of confidence in the estimate?
The JORC Code suggests the Competent Person consider the use of 2 significant figures (Clause 25) in most situations
and one significant figure may be necessary on occasions to convey properly the uncertainties in resource estimation.
Clause 25 should be considered the initial default for rounding for every resource estimate. The accuracy of coal quality
parameters are defined by their relevant standards. Reporting of values for these parameters should not exceed the
relevant significant figures or level of accuracy.
Q.9
How are downhole geophysical logs used in the classification of a Coal
Resource?
Downhole geophysical logs can help to provide increased confidence in an understanding of the physical attributes (i.e.
location, depth and thickness etc.) of coal seams in an area. They may also contribute, to a more limited extent, to an
increased level of confidence regarding the variability in and continuity of certain basic chemical properties of those
seams.
In coal exploration drilling, downhole geophysical logging (sometimes referred to as ‘wireline logging’) is undertaken on a
routine basis to assist with identifying the lithologies intersected within a hole, particularly coal seams. Where borehole
conditions allow, these logs (in particular the natural gamma, density and calliper combination) can be used to make
reasonably accurate estimates of the top and bottom (roof and floor) boundaries of the coal seams intersected. This
makes them of particular use in holes where no coring has been undertaken and also when the thickness cannot be
reliably determined from core lengths
When sampling coal for analytical testing in holes where coal seams have been cored, geophysical logs (in particular
density/calliper log combinations) can also be used to more reliably determine zones of significant core loss than would
otherwise be the case.
Downhole geophysical logs are also an invaluable tool to assist with stratigraphic and coal seam correlations in coalfield
studies, both on a regional scale and at a more localised ‘deposit’ or mine level.
The suite of logs run routinely in each hole should include at least long and short spaced density, (natural) gamma and
calliper logs. Within an area of investigation/deposit, the responses of geophysical logs can be interpreted through
comparison of the trace responses with the detailed core description from the core holes. This can then enable more
reliable use to be made of the geophysical log responses (data) obtained from logs of other non-cored holes in the vicinity.
Logs should be compared, or standardised, using the typical response from one, or more, reference holes within each
deposit.
An intersection of the full coal seam in a non-cored hole that has been geophysically logged (with at least density and
calliper logs) may be used as a Quantity Point of Observation that would allow for that point to be used for the purposes of
volumetric estimation/calculation.
Visual ‘calibration’ of the geophysical responses against the lithologies logged within cored boreholes is recommended
before geophysical logs from other non-cored boreholes elsewhere within the area of evaluation be considered for use in
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
this way, to ensure that the interpretation of the geophysical responses is compatible with the lithologies observed in the
cored boreholes.
When visually ‘calibrated’ in this way, geophysical logs of non-cored holes may be used for making approximate
qualitative comparisons of certain basic coal quality and rock strength parameters with adjacent (or nearby) cored
boreholes. In cases where the geophysical responses have been calibrated against laboratory derived coal quality
analyses, and where the reproducibility of a particular geophysically derived parameter (for example ash value or density
derived from the density/caliper log) is within acceptable tolerances, then that geophysically derived coal quality parameter
could be used to support the raw coal quality continuity. However, geophysically derived coal quality attributes will not
include any coking parameters as these can only be determined by the physical testing of coal samples.
Some borehole geophysical log responses, particularly density, gamma, neutron-neutron and sonic logs, may be
correlated to the physical laboratory test results obtained from borehole core samples. From this, relationships may be
established between, for example, laboratory-determined rock strength and sonic velocity. These geophysical tools
respond to rock density, fracture spacing, rock strength and porosity. More specialized geophysical logs, such as dipmeter logs and optical or acoustic scanner logs may be used to measure the structural orientation of the bedding and the
identification of structural features.
Q.10
What is a “spotted dog”?
The ‘spotted dog’ is a Resource estimate classification which displays the poor practice of estimating Measured, Indicated
and Inferred Resources over disconnected circles of influence around individual Points of Observation or along a line of
Points of Observation. An example is provided in Figure 3.
Figure 3: Example of a “spotted dog” – what not to do
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Confidence regarding the extent of a zone of Measured, Indicated or Inferred Resources is always inadequate where there
is a lack of support in both x and y dimensions from adjacent Points of Observation. An isolated point, two connected
points, or a line of points do not demonstrate continuity in both directions (unless there is Supportive Data within the area
of extrapolation).
The spacing of Points of Observation in the diagram above is considered sufficient by the Competent Person to
demonstrate continuity to an Inferred status over the whole deposit and extrapolation in all directions. There is not always
sufficient confidence in both x and y dimensions to support Measured and Indicated status between every Point of
Observation. Consequently it is invalid to draw circles of Measured and Indicated status around every Point of
Observation. This example has only considered spacing of Points of Observation and not any other matters discussed in
the Coal Guidelines that should be considered by the Competent Person when classifying the estimate (refer Section 5).
For further discussion refer to the paper by Stephenson et al, 2006.
Q.11
What is a “JORC compliant” Resource estimate?
Resource estimates are not “JORC compliant”. The JORC Code is a code for public reporting, not a Code that regulates
the manner in which a Coal Resource is estimated. The term “JORC compliant” therefore refers to the manner of
reporting not to the estimates. Use of the words “JORC compliant” to describe Resources or estimates is potentially
misleading. The words “JORC compliant” should be replaced by: “Reported in accordance with the JORC Code”.
Additionally it could be stated that “Resources are estimated (or based on documentation prepared) by a Competent
Person as defined by the JORC Code”. Refer to Clause 6 of the JORC Code, 2012.
Q.12
Is tonnage of coal the only parameter required to be reported in public reports?
No, the quality of the reported coal tonnage should also be reported.
Q.13
Can material comprising more than 50% raw ash be estimated as coal?
The international standard for coal classification (ISO11760-2005) defines coal as being “carbonaceous sedimentary rock
largely derived from plant remains with an associated mineral content corresponding to an ash yield less than or equal to
50% by mass (dry basis)”. Material with a raw ash value (dry basis) of more than 50% is described as either “non-coal” or
“shale”.
It is recognised that coal seams are heterogeneous, consisting of plies less than or greater than 50% (db) raw ash.
Multiple thin non-coal bands with an ash value > 50% (db) in a coal seam may be included in the defined working section,
whilst thick separable non coal bands should not be included in the Coal Resource. The nominal industry minimum
thickness for separable non coal bands varies between 0.1 to 0.5m depending on the mining method.
In cases where the bulk of the Resource has a raw ash >50% the rationale for reasonable prospects should be detailed,
including yield.
Q.14
Can a single sample that covers several seams or plies be used as a Coal Quality
Point of Observation?
Best sampling practice requires samples be taken in a way that represents the variability of the geological population. It is
only by sampling in such a manner that the distribution is then understood. Often sample analysis does not adhere to this
principle, but comprises samples or composited samples that have the internal variability over a short range masked by
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
the sample being taken over wider intervals, or having intervals (sometimes discontinuous in nature) combined together
(Figure 4).
The decision to allow such data to be used as a Coal Quality Point of Observation depends on whether or not the sample
is representative of the way in which the analysis will be utilised. For example taking a composited sample value for a
number of plies (in isolation of any other supportive data) and then stating each ply had a consistent value would be
misleading. It may however be valid to state that the analysis values are representative of a combined unit.
When there is a lack of confidence that the analysis reported for a sampled interval represents the working section being
reported then this must be taken into account during the assessment of confidence.
Legend
Non coal
Coal
(superior)
Coal
(inferior)
Sampling variability provides the
greatest opportunity to understand
multiple working section scenarios.
Valid working sections could be A,
AB, ABC, ABCD, ABCDE, ABCDEF,
BC, BCD, BCDE, BCDEF, C, CD,
CDE, CDEF, D, DE, DEF and F.
Non sampled intervals will result in
composite bias if working section
ABCD was created. Valid working
sections would be A, B, BC, or D.
)
Larger sampling only allows for small set of
working sections to be considered. Missing
intervals may bias results. Valid working
sections would be B and C.
Figure 4: Coal sampling and its implication for working section definition
Q.15
How is coal quality data composited?
The methodology of compositing coal quality data needs to be clearly understood. Be aware that some parameters are
not additive (such as caking properties or ash fusion temperatures). Quality parameters should be composited as
required. Some examples are given below:
•
Relative Density (RD) is composited on a thickness basis
•
Raw Quality parameters should be composited by mass multiplied by RD (thickness substitutes for mass to deal
with core loss)
•
Clean coal composites should be calculated on a mass multiplied by yield basis
•
Clean coal composites yield should be calculated on a mass basis
•
Clean coal composite ash analyses (dry basis) should be calculated on a mass multiplied by yield ash (db)
basis.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Q.16
What is a variogram?
A variogram (Figure 5) provides an assessment of the spatial continuity of a given variable. The variogram consists of
parameters quantifying very short range variability (the nugget), the total variability (the sill) and the distance at which
there is no correlation (the range). The nugget incorporates a component of sampling and analytic error, as well as the
difference expected from two nearly coincident Points of Observation.
The range can be isotropic (same in all directions) or anisotropic (different ranges in different directions). Coal deposits
are by their very nature typically anisotropic.
Several types of mathematical functions (‘variogram models’) may be fitted to the experimental variogram calculated from
the data (e.g. spherical, exponential). The type of model should be stated in reports. The shape of the variogram model
close to the origin (especially the slope) is important and can have a significant impact on further applications.
An increasing or decreasing trend in the data as a function of the direction considered (or ’drift’”) is a common feature of
coal variables. When considering variables with drift, the domains, variography or geostatistical estimates can be adjusted
in an effort to minimise the impact upon the variogram and the estimate.
Sensitivity analysis, which involves changing the parameters of the variogram or search, and back-estimation (or “crossvalidation”) are both useful validation tools.
Figure 5: Representation of a variogram
The variogram may assist in defining distances of continuity between Points of Observation. In isolation this is not
considered appropriate as it fails to consider all the other necessary factors contributing to the confidence in the estimate,
such as sample geometry, mining methodology, local geological features and reliability of sample data. Sole use of the
variogram is risky, in particular for variables with high nugget variance and/or short ranges.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Q.17
What geostatistical methods can be used to aid Resource Classification?
There are several methods for using geostatistical analysis as an aid to Coal Resource classification. Some of the more
common methods are briefly described below, with the reader referred to the recommended reading list (Appendix E) for
more detailed information.
Global estimation variance
A geostatistical approach to assessing global estimation variance (i.e. a measure of the variance of errors for a given
volume or area, informed by a specific number and pattern of Points of Observation) can be used to calculate the
theoretical optimum borehole spacing for a deposit at a given confidence interval and volume. This is sometimes termed
Drill Hole Spacing Analysis. The optimum spacing may be used to recommend a distance of continuity between points of
observation for use in resource assessment. The method is simple to implement, and correctly uses the variogram as a
measure of the continuity of the variable.
Issues using this method can arise if variograms are based on sparse, broadly spaced data, where the continuity of the
variable is consequently overestimated. As a consequence the results of this method should be applied with due
consideration of the geological interpretation.
Kriging variance
Kriging is an estimation method that takes into account the variogram model, the sample geometry and the volume (or
area) of the region being estimated. It is often described as a best linear unbiased estimate, meaning of all weighted
averages, kriging will attain the lowest error variance for a given data geometry, variogram and search. An estimate of the
error variance known as the “kriging variance” can be calculated for each block. The kriging variance is a measure of the
confidence in an estimate. Several different methods of using kriging variance to aid Coal Resource classification are
possible, including the use of relative kriging variances or kriging efficiencies (which are derived from the kriging variance).
The method is advantageous as it uses the geometry of the sample data, and allows a local assessment of the uncertainty
of the estimate; however, kriging can have a smoothing effect on the estimate.
One of the key questions regarding Coal Resource classification is whether the addition of new data would materially
change the estimate. Kriging variances can be useful in answering this question.
Conditional simulation
Conditional simulation is a process for assessing the uncertainty of a parameter within a geological context. A simulation
model consists of a large number of ‘realisations’ or spatial images of the variable that are compatible with the variogram,
histogram and data observations, each one having an equal probability of representing the unknown reality. Conditional
simulation realisations agree with each other at points of observation, but differ away from these locations in a manner
consistent with the variogram model.
The variation in a set of conditional simulation realisations can be used to assess the uncertainty associated with the
Resource estimate and also to generate confidence intervals at global (domain) or local (block) scale.
A larger number of realisations in a set of conditional simulations will allow more reliable analysis. It is also important to
check that the set of realisations is unbiased. To ensure this, the simulation characteristics (histogram, variogram etc.)
should closely reproduce the original data. The average of a set of realisations for conditional simulation may also be
compared to the kriged estimate, and should closely agree at global and local level. Conditional simulation requires more
familiarity with geostatistics than kriging; it can be computationally intensive, and is more sensitive to the effects of drift
than kriging.
An increasing or decreasing trend in the data as a function of the direction considered (or “drift”) is a common feature of
coal variables. When considering variables with drift, the domains, variography or geostatistical estimates can be adjusted
in an effort to minimise the impact upon the variogram and the estimate.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Q.18
What should good geological modelling documentation include?
It is recommended that each model has documentation that details the following details:
•
The model should be date stamped or have some date identification;
•
Seam and variable codes need to be defined including moisture basis for quality variable;
•
Those involved in the construction of the model should be identified;
•
The intended purpose of the model ("Fitness for Purpose") and any limitations or risks associated with using the
model should be noted;
•
Reference the data used to construct the model, reasons for excluding any data, and the date of the last data
used in the model;
•
The survey datum;
•
The source and accuracy of Digital Terrain Model (DTM) data and any manipulation of the data;
•
Methods used to construct the model should be clearly described;
•
Any manipulation of data (such as changes in moisture basis) should be documented;
•
Notes on differences with previous models;
•
Model validations and audits of the process should be referenced (and stored with the archived model).
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Appendix D – Precision of test methods and schedule for reporting of results
Uncertainty of measurement
Users of the Australian Standards (AS 1038 and AS 2434) series of coal and coke test methods and those who use the
results obtained by these methods should be aware of the variability of the results which may be obtained, which is
commonly referred to as the uncertainty of measurement.
The best estimate of the variability of these test methods is the repeatability (within laboratory) and reproducibility
(between laboratories) values quoted within each test method in the Standard and the meaning of these terms is
summarised below. Reference should be made to Clauses 5 and 6 in AS 1038 for explanation of their use. In addition,
reference should be made to the latest edition of the relevant Standard to verify the repeatability and reproducibility data.
Repeatability
The Repeatability of the determination of the volume percentage of a component is that difference between two single
determinations each based on the same number of point counts carried out by the same operator on the same sample
using the same apparatus, within which 95% of such differences would be expected to lie.
Reproducibility
The Reproducibility of the determination of the volume percentage of a component is that difference between two single
determinations each based on the same number of point counts carried out by two different operators on two different sub
samples taken from the same sample, using different equipment, within which 95% of such differences would be expected
to lie.
Extracts are from AS 2856.3-2000 Table 2; AS 2856.2-1998 Table 1 and AS 1038.16-2005 Table C1. Reproduced with
permission from SAI Global Ltd under Licence 1310 –c119. To be extracted, reproduced and distributed with the
“Australian Guidelines for the estimation and classification of Coal Resources”.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Australian
Standard
AS 1038.1
AS 1038.3
ISO Standard
589
331562
Material
Determination
r
(Repeatability)
Coal
Coal
Mas total moisture %
Mad analysis moisture % <5
Mad analysis moisture % ≥5
Aad ash % <10
Aad sh % ≥10 ≤30
Aad ash % >30
VMad volatile matter % <25
VMad volatile matter % ≥25
AS 1038.5
1928
Coal, coke
qgr,v,ad (SE) gross calorific value MJ/kg (gross specific energy)
AS 1038.6.1
609
Coal
Cad carbon (total) %
Had hydrogen %
AS 1038.6.2
Coal
Nad nitrogen %
AS 1038.6.3.1
334
Coal, coke
Sad sulfur (total) % (Eschka) ≤2
Sad sulfur (total) % (Eschka ) >2
AS 1038.6.3.2
351
Coal, coke
Sad sulfur (total) % (high temperature combustion) ≤1.5
Sad sulfur (total) % (high temperature combustion) >1.5
AS 1038.6.3.3
Coal
Sad sulfur (total) % (Infrared) ≤1.5
Sad sulfur (total) % (Infrared) >1.5 < 6
AS 1038.8.1
587
Coal, coke
Clad chlorine (Eschka) %
AS 1038.8.2
352
Coal, coke
Clad chlorine (high temperature combustion) %
AS 1038.9.1, 9.2,
622
Coal, coke
Pad phosphorus % <0.02
9.3
Pad phosphorus % ≥0.02
AS 1038.11
157
Coal
Ss,ad sulfate sulfur %
Sp,ad pyritic sulfur % <0.5
Sp,ad pyritic sulfur % ≥0.5
AS 1038.12.1
501
Coal
CSN crucible swelling number 3 determinations
CSN crucible swelling number 5 determinations
AS 1038.12.2
502
Coal
Gray-King coke type
AS 1038.12.3
8264
Coal
T1, T2, T3 dilatometer characteristics: temperature °C
c dilatometer characteristics max. contraction %
d dilatometer characteristics max. Dilatation negative %
dilatometer characteristics: Dilatation positive %
AS 1038.12.4.1
Coal
Gieseler plastometer properties (continuous torque) — max. fluidity dd/min < 20
Gieseler plastometer properties (continuous torque) — max. fluidity dd/min ≥ 20 to <10 000
Gieseler plastometer properties (continuous torque) — max. fluidity dd/min ≥ 10 000
AS 1038.12.4.1
Coal
Gieseler plastometer properties (continuous torque)— characteristic temp °C
AS 1038.12.4.2
Coal
Gieseler plastometer properties (discontinuous torque) — max. fluidity dd/min < 20
Gieseler plastometer properties (discontinuous torque) — max. fluidity dd/min ≥ 20 to <5 000
Gieseler plastometer properties (discontinuous torque) — characteristic temp °C
Reproduced with permission from SAI Global Ltd under Licence 1310 –c119
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
R
(Reproducibility)
0.5
1.5
0.1
—
0.15
—
0.1
0.15
0.15
0.25
0.2
0.6
0.2
0.5
0.2
1
0.13
0.30
0.3
0.6
0.1
0.2
0.03
0.08
0.05
0.1
0.1
0.2
0.03
0.08
2%
10%
0.03
0.05
2%
8%
0.01
0.02
0.01
0.02
0.002
0.003
10%
15%
0.02
0.03
0.05
0.1
0.07
0.15
½
1
½
1
one letter, or one unit in the subscript
7
15
5
8
5
8
5[1+(d/100)]
5[2+(d/100)]
0.3 log10
0.6 log10
0.1 log10
0.2 log10
0.2 log10
0.4 log10
7
15
0.3 log10
0.6 log10
0.1 log10
0.2 log10
7
15
See
Note 1
Report to
nearest
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.01
0.1
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.001
0.001
0.01
0.01
0.01
½
½
N/A
5
See Standard
See Standard
See Standard
See Standard
See Standard
See Standard
See Standard
See Standard
See Standard
See Standard
Australian
Standard
AS 1038.13
ISO Standard
Material
Determination
Tests specific to coke
Shatter index % 40 mm
Shatter index % 10 mm
556
M40 Micum index %
M10 Micum index %
556
I40 IRSID index
I20 IRSID index
I10 IRSID index
ASTM tumbler test stability + 25 mm %
ASTM tumbler test hardness + 6.3 mm %
JIS drum test 30 revs < 90% + 15 mm
JIS drum test 30 revs ≥ 90% + 15 mm
JIS drum test 150 revs < 80% + 15 mm
JIS drum test 150 revs ≥ 80% + 15 mm
CRI coke reactivity index % ≤30
CRI coke reactivity index % >30
CSR coke strength after reaction % >60
coke
CSR coke strength after reaction % ≤60
AS 1038.14.3
Ash
Ash analysis (XRF) for other Ash Analyses Methods refer to the Standards.
SiO2% 45 to 70
Al2O3% 20 to 35
Fe2O3% 1.5 to 13
CaO% 0.5 to 3.5
MgO% 1.0 to 2.0
Na2O% 0.1 to 1.0
K2O% 0.5 to 2.0
TiO2% 1.0 to 2.5
Mn3O4% 0.02 to 0.25
P2O5% 0.05 to 1.0
SO3% 0.5 to 1.5
BaO% 0.04 to 0.2
SrO% 0.01 to 0.1
ZnO% 0.01 to 0.03
AS 1038.15
540
Ash
Ash fusion temperature °C deformation < 1300°C
Ash fusion temperature °C deformation ≥ 1300°C
Ash fusion temperature °C sphere
Ash fusion temperature °C hemisphere
Ash fusion temperature °C flow
Reproduced with permission from SAI Global Ltd under Licence 1310 –c119
R
(Repeatability)
R
(Reproducibility)
See
Note 1
Report to
nearest
6
6
3
1
5
2.5
2
2
2
4.0
1.5
2.5
1.5
2.5
5.0
2.5
5.0
—
—
—
—
1
0.42
0.25
0.007X + 0.035
0.035
0.073
0.063
0.012X + 0.009
0.037
0.010
0.022X + 0.01
0.049X + 0.001
0.021
0.004
0.006
30
50
30
30
40
1.44
1.01
0.027X + 0.063
0.089
0.13
0.11
0.062X + 0.016
0.10
0.017
0.078X + 0.014
0.16
0.043
0.195
0.011
80
150
60
60
80
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
A
A
A
A*
A
A
A
A*
A
A
A*
A*
A
A
A
A
A
A
A
A
Coke
616
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
—
—
—
—
—
—
—
—
—
—
—
0.1
0.1
0.1
0.1
0.1
See Standard
10
10
10
10
10
Australian
Standard
AS 1038.17
AS 1038.19
ISO
Standard
1018
12900
AS 1038.20
AS 1038.21.1.1
5074
AS 1038.21.1.2
AS 1038.23
AS 1038.25
AS 2856.3—2000
AS 2856.2-1998
Material
Determination
Coal
Coal
MHC Moisture-holding capacity %
AI Abrasion index ≤ 20
AI Abrasion index > 20
HGI Hardgrove grindability
RD Relative density—Analysis sample/density bottle < 1.6
RD Relative density—Analysis sample/density bottle ≥ 1.6
RD Relative density—Analysis sample/volumetric < 1.6
RD Relative density—Analysis sample/volumetric ≥ 1.6
Cm,ad carbonate carbon %
Fs Handleability s /kg <1
Fs Handleability s /kg ≥1
Microscopical determination of the reflectance of coal macerals
Maximum Reflectance Sample Size 30
Maximum Reflectance Sample Size 50
Maximum Reflectance Sample Size 100
Random Reflectance Sample Size 30
Random Reflectance Sample Size 50
Random Reflectance Sample Size 100
Coal Petrography Maceral Analysis
Theoretical Standard Deviation and repeatability of the percentage of a component based on 500 count
points
Volume % of component 5
Standard deviation of the volume percentage 1
Volume % of component 20
Standard deviation of the volume percentage 1.8
Volume % of component 50
Standard deviation of the volume percentage 2.2
Volume % of component 80
Standard deviation of the volume percentage 1.8
Volume % of component 95
Standard deviation of the volume percentage 1
Coal
Coal, coke
Coal, coke
925
Coal
Coal
7404-5
Coal
Coal
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
R
(Repeatability)
0.6
2
10%
2
0.03
0.04
0.03
0.04
0.01
5%
10%
%
0.026
0.019
0.014
0.027
0.02
0.015
R
(Reproducibility)
1.2
—
—
5
0.08
0.08
0.1
0.12
0.02
10%
20%
%
0.076
0.073
0.071
0.092
0.088
0.087
2.8
5.1
6.3
5.1
2.8
not specified
not specified
not specified
not specified
not specified
See
Note 1
A
C
C
C
A
A
A
A
A
Report to
nearest
0.1
1
1
1
0.01
0.01
0.01
0.01
0.01
0.1
1
0.01
0.01
0.01
0.01
0.01
0.01
0.1
0.1
0.1
0.1
0.1
Appendix E – Recommended reading
ASX, 1 December 2013, ASX Listing Rules Chapter 5; Additional reporting on Mining, Oil and Gas Production
and Exploration Activities http://www.asx.com.au/documents/rules/Chapter05.pdf
ASX, 1 December 2013, ASX Listing Rules Guidance Note 31 Reporting on Mining Activities
http://www.asx.com.au/documents/rules/gn31_reporting_on_mining_activities.pdf
AusIMM, 2011, Field Geologists’ Manual (Fifth Edition), Monograph 9, The Australasian Institute of Mining and
Metallurgy; Carlton, Victoria 3053, Australia.
AusIMM, 2014, Monograph 30 Mineral Resource and Ore Reserve Estimation – The AusIMM Guide to Good
Practice (second edition), (The Australasian Institute of Mining and Metallurgy; Carlton, Victoria 3053, Australia).
Casely, Z., Bertoli, O., Mawdesley, C., and Dunn, D., 2010, Drill hole spacing analysis for coal resources, in
Proceedings of 6th Bowen Basin Symposium 2010, Mackay, QLD, Australia
Coombes, J., 2008, The Art and Science of Resource Estimation: A practical guide for geologists and engineers,
Coombes Capability, Perth
Cornah, A., Vann, J., and Driver, I., 2013, Comparison of three geostatistical approaches to quantify the impact
of drill spacing on resource confidence for a coal seam (with a case example from Moranbah North, Queensland,
Australia), International Journal of coal Geology, Volume 112, 1 June 2013, Pages 114–124
Dohm, C., 2005, Quantifiable Mineral Resource Classification: A logical approach, Quantitative Geology and
Geostatistics Volume 14, 2005, pp 333-342
Edwards, A.C. (ed), 2001, Mineral Resource and Ore Reserve Estimation – The AusIMM Guide to Good
Practice, Monograph 23, 720p (The Australasian Institute of Mining and Metallurgy; Carlton, Victoria 3053,
Australia).
Fletcher I.S. & Sanders, R.H., 2003, Estimation of In Situ Moisture and Product Total Moisture, ACARP Project
C10041.
Journel, A.G., and Huijbregts, C.J., 1978, Mining Geostatistics, Academic Press, London
King, H.F., McMahon, D.W. and Bujtor, G.J., 1982, A Guide to the Understanding of Ore Reserve Estimation,
AusIMM Supplement to the Proc. No 281.
Preston, K., 2005, Estimating the In situ Relative Density of Coal – Old Favourites and New Developments, in
JW Beeston (ed.), Bowen Basin Symposium 2005, The Future for Coal – Fuel for Thought, Geological Society of
Australia Inc., Coal Geology Group and the Bowen Basin Geologists Group, Yeppoon, October 2005
Preston, KB, and Sanders, RH., 1993, Estimating the In situ Relative Density of Coal, in Australian Coal
Geology, Volume 9, Journal of the Coal Geology Group of the Geological Society of Australia Inc.
Sinclair, A.J. and Blackwell, G.H., 2002, Applied Mineral Inventory Estimation. Cambridge University Press.
Standards Australia Subcommittee on Coal Mining and Geology, 1993, AS2519-1993(R2013), Guide to the
technical evaluation of higher rank coal deposits, Standards Australia.
Stephenson, PR, Allman, A, Carville, DP, Stoker, PT, Mokos, P, Tyrrell J and Burrows, T., 2006, Mineral
Resource Classification – It’s Time to Shoot the ‘Spotted Dog’!, in Proceedings Sixth International Mining
Geology Conference, pp 91-95 (The Australasian Institute of Mining and Metallurgy; Carlton, Victoria 3053,
Australia).
Ward, C.R. (ed.), 1984, Coal Geology and Coal Technology. Blackwell Scientific Publications; Carlton, Victoria
3053, Australia
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Yeates, G., and Hodson, D., 2006, Resource Classification – Keeping the end in sight, in Proceedings Sixth
International Mining Geology Conference, pp 97-104 (The Australasian Institute of Mining and Metallurgy:
Carlton, Victoria 3053, Australia)
Zhou B. and Esterle J., 2007, Improving the Reliability of Density and Grade Estimation from Borehole
Geophysical Log Suites. ACARP Report C15036 (CSIRO Exploration Report P2007/62).
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Appendix F – JORC Code, 2012 Edition Table 1 report template
Section 1 Sampling Techniques and Data - (Criteria in this section apply to all succeeding sections.)
Criteria
Sampling
techniques
JORC Code explanation
Nature and quality of sampling (eg cut channels, random chips, or specific specialised
industry standard measurement tools appropriate to the minerals under investigation, such
as down hole gamma sondes, or handheld XRF instruments, etc). These examples should
not be taken as limiting the broad meaning of sampling.
Include reference to measures taken to ensure sample representivity and the appropriate
calibration of any measurement tools or systems used.
Aspects of the determination of mineralisation that are Material to the Public Report.
Drilling
techniques
Drill sample
recovery
In cases where ‘industry standard’ work has been done this would be relatively simple (eg
‘reverse circulation drilling was used to obtain 1 m samples from which 3 kg was pulverised
to produce a 30 g charge for fire assay’). In other cases more explanation may be required,
such as where there is coarse gold that has inherent sampling problems. Unusual
commodities or mineralisation types (eg submarine nodules) may warrant disclosure of
detailed information.
Drill type (eg core, reverse circulation, open-hole hammer, rotary air blast, auger, Bangka,
sonic, etc) and details (eg core diameter, triple or standard tube, depth of diamond tails,
face-sampling bit or other type, whether core is oriented and if so, by what method, etc).
Method of recording and assessing core and chip sample recoveries and results assessed.
Guidance - Coal
Discussion should be provided on the types of sampling techniques used and the reliability of
the samples produced. The methods could include provision of physical samples from
boreholes, surface outcrops, trenches, and mining faces (open cut and underground) or
measurement from downhole geophysical logging. Description should be provided of the type
of sample generated (e.g. chip or core samples, channel or strip samples, gas, water,
geophysical log interpretation). Detail should be given of the scale of sample size (i.e. ply,
parting, waste, seam, working section, etc.).
Describe measures taken to maximise chip or core recovery, and to ensure each ply is
adequately represented by length and mass. Core loss, core expansion, lost circulation,
borehole caving, the drilling fluid or any other influence on sample representivity should be
recorded.
Discussion of geophysical logging should include tool descriptions, calibration procedures,
filtering, borehole conditions, and if logging was undertaken in air, mud or water or through
drill rods. Suitable metadata should be recorded for each geophysical log.
Describe how geophysical logs have been used to determine ply or sample intervals where
these boundaries are not evident in the core.
Describe how coal intervals have been determined; from analysed core samples, visual
determination from core, interpretation of geophysical log(s )etc. Describe how seam depths,
thickness and quality (e.g. density) have been defined?
Describe fully the drilling method (e.g. diamond core, reverse circulation, blade, PCD,
hammer, auger, blast hole, etc.), borehole size, core size (e.g. HQ, NQ, HMLC, 4C, etc.), core
barrel size, and the sampling techniques (e.g. single, double or triple tube, cyclone, collar,
etc.) utilised. If orientated cores were taken, provide details on how the orientation was
established.
Report how core loss was determined. Identify if sample loss was associated with any
structural or stratigraphic influence (e.g. faulting, intrusion, heating, thin banding of coal and
non-coal material, hard bands, etc.). If geophysical logs were used to determine seam
thickness then describe how this was done and what adjustments were made to the logs and
sample details.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Criteria
JORC Code explanation
Measures taken to maximise sample recovery and ensure representative nature of the
samples.
Whether a relationship exists between sample recovery and grade and whether sample bias
may have occurred due to preferential loss/gain of fine/coarse material.
Logging
Whether core and chip samples have been geologically and geotechnically logged to a level
of detail to support appropriate Mineral Resource estimation, mining studies and
metallurgical studies.
Whether logging is qualitative or quantitative in nature. Core (or costean, channel, etc.)
photography.
The total length and percentage of the relevant intersections logged.
Sub-sampling
techniques and
sample
preparation
If core, whether cut or sawn and whether quarter, half or all core taken.
If non-core, whether riffled, tube sampled, rotary split, etc and whether sampled wet or dry.
For all sample types, the nature, quality and appropriateness of the sample preparation
technique.
Quality control procedures adopted for all sub-sampling stages to maximise representivity of
samples.
Measures taken to ensure that the sampling is representative of the in situ material
collected, including for instance results for field duplicate/second-half sampling.
Whether sample sizes are appropriate to the grain size of the material being sampled.
Quality of assay
data and
laboratory tests
The nature, quality and appropriateness of the assaying and laboratory procedures used
and whether the technique is considered partial or total.
Guidance - Coal
Describe how sample recovery was assessed and what measures were utilised during drilling
to maximise recovery.
Record where circulation was lost, where drilling methods affected sample integrity, and
where contamination of samples occurred. Document if sample loss could bias associated
analytical results (e.g. the bright vitrinite component was lost resulting in a higher ash sample).
Clearly describe the manner in which core and non-core boreholes or other Points of
Observation were logged (geologically, geotechnically and geophysically) and whether or not
this was adequate to support the Coal Resource estimate.
Document when the borehole was drilled, when the sample was taken, the condition of the
core, the procedures used to ‘clean’ the core, how the sample was taken, how it was stored,
any methods used to minimise oxidation or deterioration of caking properties, and the time
period between sampling and analysis. Report on the styles of logging, how any samples
have been recorded, and whether or not suitable photographs were taken.
Confirm that the logging has provided adequate coverage of the full length of each sample
and the coal seam.
Coal core samples are largely fully sampled, yet the process of how samples are taken in the
field and stored prior to analysis can have a marked impact on results. Confirm that core of
coal seams has been fully sampled. Describe techniques used to ensure contamination was
minimised, that drying out or inclusion of excess moisture was avoided, and that the full
sample was taken. Any variations or sub-sampling in the field must be recorded (e.g. gas
desorption samples, geotechnical samples).
The process of how samples are taken in the field and stored prior to analysis can have a
marked impact on results and should be recorded. Outline the procedure for bagging,
identifying and sealing individual samples, and for compiling samples for storage and
transportation (i.e. use of poly sacks, drums, refrigerated containers, etc.).
Sub-sampling of coal bore core is normally undertaken at the coal laboratory. Describe
laboratory sub-sampling and pre-treatment procedures.
Define the QAQC measures that are undertaken to maximise sample representivity. Clearly
document where such procedures are unknown in historical data
Describe any size treatment procedures (e.g. drop shatter, dry sizing, wet tumble), the size
interval percentages, the top size analysed and the influence of top size and core size (i.e.
diameter and mass) on the usefulness of the result. Clearly document where such procedures
are unknown in historical data.
Discuss whether the coal analyses are fit for purpose. Are the analyses sufficient to
determine the potential coal products and support an assessment of the marketability of the
coal products?
For geophysical tools, spectrometers, handheld XRF instruments, etc., the parameters used
in determining the analysis including instrument make and model, reading times,
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Criteria
Verification of
sampling and
assaying
JORC Code explanation
calibrations factors applied and their derivation, etc.
Nature of quality control procedures adopted (e.g. standards, blanks, duplicates, external
laboratory checks) and whether acceptable levels of accuracy (i.e. lack of bias) and
precision have been established
The verification of significant intersections by either independent or alternative company
personnel.
The use of twinned holes.
Documentation of primary data, data entry procedures, data verification, data storage
(physical and electronic) protocols.
Discuss any adjustment to assay data.
Location of data
points
Data spacing and
distribution
Orientation of
data in relation to
geological
structure
Accuracy and quality of surveys used to locate drill holes (collar and downhole surveys),
trenches, mine workings and other locations used in Mineral Resource estimation.
Specification of the grid system used.
Quality and adequacy of topographic control.
Data spacing for reporting of Exploration Results.
Guidance - Coal
QAQC protocols by the laboratory in relation to verification of sampling results should be well
understood and appropriate documentation provided that supports verification of analysis,
either by duplicate testing or round robin analysis. A determination of accuracy between
different laboratories and the precision in results should be established.
Twinning borehole locations to verify the reliability of historical drilling results should be clearly
reported and discussed fully. Adjustments made to laboratory results should be reported on a
sample basis with calculations applied clearly documented. The process of data entry and
storage should be well documented.
Twinning borehole locations to verify the reliability of historical drilling results should be clearly
reported and fully discussed.
The process of data entry and storage should be well documented.
Adjustments made to laboratory results should be reported on a sample basis with
calculations applied and justification clearly documented. Discuss any adjustments to sample
thicknesses based on reconciliation with interpreted downhole geophysical log depths.
Ensure the correct thickness and mass values were used by the laboratory, especially for any
compositing of samples, and have been recorded in databases used for Coal Resource
assessment.
Establish and report the accuracy of survey control both at surface (boreholes and other
Points of Observation) and downhole.
Confirm the same grid system has been used across the data set or clearly describe where
discrepancies occur and why.
A discussion should be provided on the density and distribution of boreholes (both core and
non-core). The discussion should include the average depth of boreholes in relation to the
depth range of the target coal seams in the deposit. Reports should include appropriately
scaled plans depicting borehole locations relative to other features with symbols reflecting the
purpose of the borehole.
Whether the data spacing and distribution is sufficient to establish the degree of geological
and grade continuity appropriate for the Mineral Resource and Ore Reserve estimation
procedure(s) and classifications applied.
Whether sample compositing has been applied.
Whether the orientation of sampling achieves unbiased sampling of possible structures and
the extent to which this is known, considering the deposit type.
Although most coal deposits in Australia are oriented sub-horizontally, with boreholes drilled
vertically to shallow depths, an assessment of seam dip to the borehole orientation should still
be made to determine that no bias has been introduced. Discuss what methods have been
used to check borehole verticality (e.g. downhole verticality logs) and how they have been
utilised in the geological model.
If the relationship between the drilling orientation and the orientation of key mineralised
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Criteria
Sample security
JORC Code explanation
structures is considered to have introduced a sampling bias, this should be assessed and
reported if material.
The measures taken to ensure sample security.
Audits or reviews
The results of any audits or reviews of sampling techniques and data.
Guidance - Coal
Describe how samples are uniquely identified in the field and in the lab, and how sample
receipt at each stage of transportation and transfer is recorded. The chain of custody should
be reviewed to ensure that sample swapping has not occurred between the field, the lab and
the final database input. Report how this has been carried out.
Section 2 Reporting of Exploration Results (Criteria listed in the preceding section also apply to this section.)
Criteria
Mineral tenement
and land tenure
status
Exploration done
by other parties
JORC Code explanation
Type, reference name/number, location and ownership including agreements or material
issues with third parties such as joint ventures, partnerships, overriding royalties, native
title interests, historical sites, wilderness or national park and environmental settings.
The security of the tenure held at the time of reporting along with any known impediments
to obtaining a licence to operate in the area.
Acknowledgment and appraisal of exploration by other parties.
Geology
Deposit type, geological setting and style of mineralisation.
Drill hole
Information
A summary of all information material to the understanding of the exploration results
including a tabulation of the following information for all Material drill holes:
•
easting and northing of the drill hole collar
•
elevation or RL (Reduced Level – elevation above sea level in metres) of the
drill hole collar
•
dip and azimuth of the hole
•
down hole length and interception depth
•
hole length.
If the exclusion of this information is justified on the basis that the information is not
Material and this exclusion does not detract from the understanding of the report, the
Competent Person should clearly explain why this is the case.
In reporting Exploration Results, weighting averaging techniques, maximum and/or
Data aggregation
Guidance - Coal
Describe the tenement with reference to its type, name/number, size, location, ownership and
expiry. Consider and report other agreements with Government Departments, local Councils,
landholders, overlapping tenure holders, community groups, and other land users. Comment on
any current or planned competing land use by Government, public or private interests or
exclusion zones.
Clearly document any previous exploration by Government or companies. Describe the
exploration history of the area to provide useful insights to its future potential. Indicate what
information or data is used in the current interpretation of the coal deposit and its reasonable
prospects.
The geological setting both on a regional and local setting should be described. Geological
maps, stratigraphic profiles and seam stratigraphy should be provided to support this
description.
Tabulations of all Points of Observation (Quantity and Coal Quality) used in the estimate should
be presented in the report or references to previous reports containing this data should be
provided. Details of the Point of Observation that should be included to enable its orientation
and sample length to be established are: borehole name; geographic location and grid; collar
height and datum; spatial position (x, y, z); total depth; borehole verticality; sample value(s); and
sample basis as required.
The combination of samples prior to testing should be recorded by reference to original sample
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
methods
Relationship
between
mineralisation
widths and
intercept lengths
Diagrams
minimum grade truncations (eg cutting of high grades) and cut-off grades are usually
Material and should be stated.
Where aggregate intercepts incorporate short lengths of high grade results and longer
lengths of low grade results, the procedure used for such aggregation should be stated
and some typical examples of such aggregations should be shown in detail.
The assumptions used for any reporting of metal equivalent values should be clearly
stated.
These relationships are particularly important in the reporting of Exploration Results.
If the geometry of the mineralisation with respect to the drill hole angle is known, its nature
should be reported.
If it is not known and only the down hole lengths are reported, there should be a clear
statement to this effect (eg ‘down hole length, true width not known’).
Appropriate maps and sections (with scales) and tabulations of intercepts should be
included for any significant discovery being reported These should include, but not be
limited to a plan view of drill hole collar locations and appropriate sectional views.
Balanced
reporting
Where comprehensive reporting of all Exploration Results is not practicable,
representative reporting of both low and high grades and/or widths should be practiced to
avoid misleading reporting of Exploration Results.
Other substantive
exploration data
Other exploration data, if meaningful and material, should be reported including (but not
limited to): geological observations; geophysical survey results; geochemical survey
results; bulk samples – size and method of treatment; metallurgical test results; bulk
density, groundwater, geotechnical and rock characteristics; potential deleterious or
contaminating substances.
The nature and scale of planned further work (eg tests for lateral extensions or depth
extensions or large-scale step-out drilling).
Diagrams clearly highlighting the areas of possible extensions, including the main
Further work
numbers and reported. It must be stated if compositing was on a length or mass basis.
Exclusion of material from composited lengths should be defined and supportable. Inclusion of
partings or waste material should be noted.
Compositing of sample types should be clearly described for each coal quality variable.
Exclusion of material from composited lengths should be defined and supportable. Many
analyses by their nature cannot be validly composited (eg caking properties).
An assessment should be made to determine whether any sample and analysis result is
representative of the deposit and over what area it is valid. This will be recorded as the
confidence category for that data point.
A selection of contour and isopach plans should be provided at legible scales with data posting
for each seam or seam grouping, depicting structural orientation, thickness and critical coal
quality variables. Strip ratio contour plans should be presented for open cut coal deposits.
Plans should also include tenure boundaries, location and areal extent of each confidence
category, any boundary between open cut and underground (if applicable), the factors used to
limit the estimates, the Points of Observation (with the coal quality holes for that seam clearly
differentiated) and any Supportive Data on which the Coal Resource estimates for that seam
were based. Cross sectional diagrams at a scale that clearly demonstrates how geological
continuity has been established across the deposit area should be included. Type borehole
profiles providing greater detail combined with wireline logs should be considered in reporting to
demonstrate the geology.
When reporting exploration data the report must be balanced providing detail on all material
issues. The report should provide an unbiased view of the information collected and
interpretations without being misleading. A Coal Resource report should contain a tabulation
indicating the depth and thickness ranges for each seam or working section, and the range of
values for key analytical results (e.g. proximate analysis results, energy, caking properties,
yield).
Documentation of other types of observations should include washability and clean coal test
work, gas testing, geotechnical and spontaneous potential tests.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
geological interpretations and future drilling areas, provided this information is not
commercially sensitive.
Section 3 Estimation and Reporting of Mineral Resources - (Criteria listed in section 1, and where relevant in section 2, also apply to this section.)
Criteria
Database
integrity
Site visits
Geological
interpretation
Dimensions
Estimation and
modelling
techniques
JORC Code explanation
Guidance - Coal
Measures taken to ensure that data has not been corrupted by, for example, transcription or keying Comment on the process of collecting and storing exploration data from both the
errors, between its initial collection and its use for Mineral Resource estimation purposes.
field and the laboratory. Attention should be given to transcription methods and
QAQC procedures used to ensure the integrity of all data. Discuss control
procedures used for transfer and distribution of data.
Data validation procedures used.
Comment on any site visits undertaken by the Competent Person and the outcome of those visits.
If no site visits have been undertaken indicate why this is the case.
Confidence in (or conversely, the uncertainty of) the geological interpretation of the mineral deposit.
Nature of the data used and of any assumptions made.
The effect, if any, of alternative interpretations on Mineral Resource estimation.
The use of geology in guiding and controlling Mineral Resource estimation.
The factors affecting continuity both of grade and geology.
The factors affecting continuity both of quality and geology.
The extent and variability of the Mineral Resource expressed as length (along strike or otherwise), plan The size, orientation, thickness and depth of the deposit should be documented
width, and depth below surface to the upper and lower limits of the Mineral Resource.
and presented visually to enable the reader of a report an accurate
understanding of the deposit geometry. The subcrop of each seam should be
clearly defined.
The nature and appropriateness of the estimation technique(s) applied and key assumptions, including State whether computer software applications were used to model and estimate
treatment of extreme grade values, domaining, interpolation parameters and maximum distance of Coal Resources.
extrapolation from data points. If a computer assisted estimation method was chosen include a
description of computer software and parameters used.
The availability of check estimates, previous estimates and/or mine production records and whether the Checking the Coal Resource estimate against previous estimates or alternative
Mineral Resource estimate takes appropriate account of such data.
methods should be undertaken and the documentation should reflect this.
The assumptions made regarding recovery of by-products.
Estimation of deleterious elements or other non-grade variables of economic significance (e.g. sulphur
for acid mine drainage characterisation).
In the case of block model interpolation, the block size in relation to the average sample spacing and the See Section 5.8 of the 2014 Coal Guidelines.
search employed.
Any assumptions behind modelling of selective mining units.
Any assumptions about correlation between variables.
Description of how the geological interpretation was used to control the resource estimates.
Discussion of basis for using or not using grade cutting or capping.
The process of validation, the checking process used, the comparison of model data to drill hole data,
and use of reconciliation data if available.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Moisture
Whether the tonnages are estimated on a dry basis or with natural moisture, and the method of
determination of the moisture content.
Cut-off
parameters
Mining factors or
assumptions
The basis of the adopted cut-off grade(s) or quality parameters applied.
Metallurgical
factors or
assumptions
Environmental
factors or
assumptions
Bulk density
Classification
Assumptions made regarding possible mining methods, minimum mining dimensions and internal (or, if
applicable, external) mining dilution. It is always necessary as part of the process of determining
reasonable prospects for eventual economic extraction to consider potential mining methods, but the
assumptions made regarding mining methods and parameters when estimating Mineral Resources may
not always be rigorous. Where this is the case, this should be reported with an explanation of the basis of
the mining assumptions made.
The basis for assumptions or predictions regarding metallurgical amenability. It is always necessary as
part of the process of determining reasonable prospects for eventual economic extraction to consider
potential metallurgical methods, but the assumptions regarding metallurgical treatment processes and
parameters made when reporting Mineral Resources may not always be rigorous. Where this is the case,
this should be reported with an explanation of the basis of the metallurgical assumptions made.
Assumptions made regarding possible waste and process residue disposal options. It is always
necessary as part of the process of determining reasonable prospects for eventual economic extraction
to consider the potential environmental impacts of the mining and processing operation. While at this
stage the determination of potential environmental impacts, particularly for a greenfields project, may not
always be well advanced, the status of early consideration of these potential environmental impacts
should be reported. Where these aspects have not been considered this should be reported with an
explanation of the environmental assumptions made.
Whether assumed or determined. If assumed, the basis for the assumptions. If determined, the method
used, whether wet or dry, the frequency of the measurements, the nature, size and representativeness of
the samples.
The basis of moisture analysis and its application is critical when reporting a Coal
Resource estimate. Coal Resource tonnages are typically reported on an in situ
moisture basis, yet regardless of the basis applied, it should be clearly described
and not assumed to be understood. Coal Resource qualities are typically
reported on an air dry basis. Conversion from one basis to another should be
clearly detailed in any report.
Document the constraints applied to any parameter (e.g. thickness, depth, ash)
to define the areal extent of a Coal Resource and the reason it has been used.
General assumptions that provide detail on how reasonable prospects were
determined must be documented. This may include but not be limited to those
factors outlined in Section 6 of the 2014 Coal Guidelines.
Although Coal Resource tonnages are normally reported in situ, clarification is
required on whether the coal could be sold as raw product or would require
beneficiation. It should be stated what product is expected, the key quality
parameters of the product that can be obtained and how these were determined.
If washing of the coal is required then a discussion of the likely yield and how it
has been determined should be reported. If full scale testing has not been
undertaken or a full suite of analyses has not been conducted then the impact
and how it would influence the reasonable prospects should be discussed.
Discuss the presence of deleterious minerals and trace elements (e.g. pyrite,
arsenic) in the coal and waste rock (where data allow) that have the potential for
acid mine drainage or to otherwise pollute the environment.
Coal Resources are generally estimated using relative density results that are
modified to provide an estimate of in situ tonnage. The in situ moisture
assumptions used in the determination of in situ density should be disclosed.
The basis of density data utilised to determine and report coal tonnage should be
clearly documented.
The bulk density for bulk material must have been measured by methods that adequately account for
void spaces (vugs, porosity, etc), moisture and differences between rock and alteration zones within the
deposit.
Discuss assumptions for bulk density estimates used in the evaluation process of the different materials.
The basis for the classification of the Mineral Resources into varying confidence categories.
Whether appropriate account has been taken of all relevant factors (i.e. relative confidence in
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
Audits or reviews
Discussion of
relative accuracy/
confidence
tonnage/grade estimations, reliability of input data, confidence in continuity of geology and metal values,
quality, quantity and distribution of the data).
Whether the result appropriately reflects the Competent Person’s view of the deposit.
The results of any audits or reviews of Mineral Resource estimates.
Where appropriate a statement of the relative accuracy and confidence level in the Mineral Resource
estimate using an approach or procedure deemed appropriate by the Competent Person. For example,
the application of statistical or geostatistical procedures to quantify the relative accuracy of the resource
within stated confidence limits, or, if such an approach is not deemed appropriate, a qualitative
discussion of the factors that could affect the relative accuracy and confidence of the estimate.
The statement should specify whether it relates to global or local estimates, and, if local, state the
relevant tonnages, which should be relevant to technical and economic evaluation. Documentation
should include assumptions made and the procedures used.
These statements of relative accuracy and confidence of the estimate should be compared with
production data, where available.
AUSTRALIAN GUIDELINES FOR THE ESTIMATION
AND CLASSIFICATION OF COAL RESOURCES
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