Mineral resource classification

Mineral resource classification is the classification of mineral resources based on an increasing level of geological knowledge and confidence.[1] In an effort to achieve a standard set the classifications, representative bodies from Australia, Canada, South Africa, the USA and the UK reached a provisional agreement in 1997 on the definitions of each of the various mineral classifications. This was followed in 1998 to have these definitions incorporated into the International Framework Classification for Reserves and Resources - Solid Fuels and Mineral Commodities, developed by the United Nations Economic Commission for Europe(UN-ECE)[2].

Mineral deposits can be classified as:

  • Mineral resources that are potentially valuable, and for which reasonable prospects exist for eventual economic extraction.
  • Mineral reserves or Ore reserves are valuable and legally, economically, and technically feasible to extract

Classification, because it is an economic function, is governed by statutes, regulations and industry best practice norms. There are several classification schemes worldwide, the most commonly used are the Canadian CIM classification (see NI 43-101), the Australian Joint Ore Reserves Committee Code (JORC Code), the South African Code for the Reporting of Mineral Resources and Mineral Reserves (SAMREC)[3] and the “chessboard” classification scheme of mineral deposits by H. G. Dill.[4]

To ensure international standardization in the definitions of the various mineral classifications, an initiative was commenced by CRIRSCO to develop a template (largely based on the JORC Code) to assist countries in developing their own guidelines and regulations based upon global best practices. This template was recognized in the United Nations Framework Classification for Resources (UNFC) in 2009. [5]

Mineral resources

A 'Mineral Resource' is a concentration or occurrence of material of intrinsic economic interest in or on the earth's crust in such form, quality and quantity that there are reasonable prospects for eventual economic extraction. Mineral Resources are further sub-divided, in order of increasing geological confidence, into inferred, indicated and measured as categories.

Inferred Mineral Resource is the part of a mineral resource for which quantity, grade (or quality) and mineral content can be estimated with a low level of confidence. It is inferred from geological evidence and assumed but not verified geological or grade continuity. It is based on information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes which may be of limited or uncertain quality and it is also reliability.

Indicated resources are simply economic mineral occurrences that have been sampled (from locations such as outcrops, trenches, pits and drill holes) to a point where an estimate has been made, at a reasonable level of confidence, of their contained metal, grade, tonnage, shape, densities, physical characteristics.

Measured resources are indicated resources that have undergone enough further sampling that a 'competent person' (defined by the norms of the relevant mining code; usually a geologist has declared them to be an acceptable estimate, at a high degree of confidence, of the grade (or quality), quantity, shape, densities, physical characteristics of the mineral occurrence.

Mineral reserves and ore reserves

Mineral reserves (or ore reserves) are resources known to be economically feasible for extraction. Reserves are either Probable Reserves or Proved Reserves.

A Probable Ore Reserve is the part of indicated, and in some circumstances, measured mineral resources that can be mined in an economically viable fashion. It includes diluting material and allowances for losses which may occur when the material is mined. A Probable Ore Reserve has a lower level of confidence than a Proved Ore Reserve but is of sufficient quality to serve as the basis for decision on the development of deposit.

A Proved Ore Reserve is the part of Measured resources that can be mined in an economically viable fashion. It includes diluting materials and allowances for losses which occur when the material is mined.

A Proved Ore Reserve represents the highest confidence category of reserve estimate. The style of mineralization or other factors could mean that Proved Ore Reserves are not achievable in some deposits.

Generally the conversion of resources into reserves requires the application of various modifying factors, including:

  • mining and geological factors, such as knowledge of the geology of the deposit sufficient that it is predictable and verifiable; extraction and mine plans based on ore models; quantification of geotechnical risk—basically, managing the geological faults, joints, and ground fractures so the mine does not collapse; and consideration of technical risk—essentially, statistical and variography to ensure the ore is sampled properly:
  • metallurgical factors, including scrutiny of assay data to ensure accuracy of the information supplied by the laboratory—required because ore reserves are bankable. Essentially, once a deposit is elevated to reserve status, it is an economic entity and an asset upon which loans and equity can be drawn—generally to pay for its extraction at (hopefully) a profit;
  • economic factors;
  • environmental factors;
  • marketing factors;
  • legal factors;
  • political factors; and
  • social factors[3]

See also

References
  1. "The International Reporting Template" (PDF). CRIRSCO.com. CRIRSCO. November 2013. Retrieved 5 January 2017.
  2. Joint Ore Reserves Committee (2012). The JORC Code 2012 (PDF) (2012 ed.). p. 44. Retrieved 10 June 2020.
  3. Staff (2012). "Home". SAMCODE - South African Mineral Codes. Retrieved 27 May 2012.
  4. Dill, Harald G. (June 2010). "The "chessboard" classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium". Earth-Science Reviews. 100 (1–4): 1–420. doi:10.1016/j.earscirev.2009.10.011.
  5. United Nations Framework Classification for Resources (UNFC) (1 May 2015). Bridging document between the Committee for Mineral Reserves International Reporting Standards (CRIRSCO) Template and the United Nations Framework Classification for Resources (UNFC) (PDF). pp. 3–4.
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