Unlike most other commodities, coal is not a solid mineral, but a complex natural raw material formed under specific sedimentary environments and requiring specific conditions of burial for its formation. Comprehensive characterisation can require the determination and analysis of over 25 different parameters, both physical and chemical. These parameters determine the utilisation of the coal, and govern whether the coal can be sold unprocessed (raw) or only after suitable beneficiation has produced a saleable product. Certain of these parameters have unique properties, needing very particular analyses and resulting in coal with highly specific niche uses.
As with the Reporting Codes for Australia, Canada and the United States of America, South Africa has developed coal-specific guidelines for estimating and reporting Coal Resources and Coal Reserves. The guidelines also contain definitions of terms and methodologies used exclusively for coal. The first edition of the guideline was published by the South African Bureau of Standards in 2004 as South Africa National Standard 10320:2004 Edition 1 South African guide to the systematic evaluation of coal resources and coal reserves. This document is under revision and it is anticipated the second edition - South Africa National Standard 10320:2017 Edition 2 Systematic evaluation of coal exploration results, inventory coal, Coal Resources and Coal Reserves (“SANS 10320”) – is expected to be published shortly (2018). Public reporting of Coal Resources and Coal Reserves follows the SAMREC Code: Clauses 1 to 47 of the Code apply (as does Table 1), while specific provision for coal reporting is made in Clauses 48 to 59. Clause 49 states that SANS 10320 must be taken into consideration when preparing public reports on Coal Resources and Coal Reserves. Note that inventory coal may not be publicly reported, and coal exploration results may not be included in public Coal Resource or Coal Reserve statements.
Publicly reported Coal Resources are classified as Inferred, Indicated or Measured Coal Resources based on increasing geoscientific confidence and may only be reported on a Mineable Tonnes in-situ (MTIS) basis. This means that the tonnage estimate has been reduced by factors accounting for losses due to unobserved geological conditions as well as the theoretical height at which the deposit is proposed to be mined. In addition, the tonnage estimate must be reported on an in-situ density basis, which itself must be reported on an in-situ bed moisture basis. This is achieved by applying the Preston and Sanders (1993) change of moisture basis methodology. The applicable coal qualities must be stated for each resource category, as must the moisture content and moisture reporting basis.
Publicly reported Coal Reserves are classified as Probable or Proved Coal Reserves and must be reported on both a Run of Mine and a Saleable Coal Reserve basis. Indicated Coal Resources can only be converted into Probable Coal Reserves, while Measured Coal Resources can be converted into either Probable or Proved Coal Reserves, depending on the quantity, quality and distribution of the available data and the confidence in that data. The Coal Reserve tonnage estimates must be modified to account for dilution and contamination and for losses expected during mining. The Modifying Factors must also be considered and these factors should be clearly stated, along with the specific mining and coal processing methods and the reference point at which Run of Mine and Saleable Coal Reserves are defined. The applicable coal qualities must be stated for each reserve category, as must the moisture content and moisture reporting basis. Raw Saleable Coal Reserves must be reported on an as received basis for a specified total moisture content and the saleable product coal quality reporting basis must be stated. For beneficiated Saleable Coal Reserves, the practical product yield (on an air-dried basis) and the basis of the predicted yield to achieve those reserves must be stated. In each case, the specific particle size and target coal quality at which the practical product yield is obtained must be specified and different mining methods (surface and underground) and different coal product types must be reported separately.
(This article was previously published on the SAMCODES website in March 2017,
and re-issued in November 2019.)