An ore reserve, more formally termed a Mineral Reserve under codes such as JORC and NI 43-101, is the economically mineable portion of a Measured or Indicated Mineral Resource that has been demonstrated, through detailed technical and economic studies, to be viable for extraction under realistic operating conditions, including consideration of mining, metallurgical, infrastructure, legal, environmental, and marketing factors. Reserves are reported in two confidence categories: Proven Reserves, corresponding to the highest confidence Measured Resources, and Probable Reserves, corresponding to Indicated Resources or lower-confidence Measured Resources. The conversion of a resource into a reserve requires the application of modifying factors, such as cut-off grade, mining dilution, recovery rates, and a positive economic outcome based on current or reasonably projected commodity prices. Reserve figures for bauxite, gold, iron ore, and diamonds all follow this same conceptual framework, though the specific technical studies differ: bauxite reserves depend heavily on alumina-to-silica ratios affecting refining economics, gold reserves depend on metallurgical recovery and processing costs, iron ore reserves depend on product quality specifications demanded by steelmakers, and diamond reserves depend on average stone value derived from bulk sampling programs.
