Resources Definitions
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Excerpt from The Toronto Stock Exchange/Ontario Securities Commission Mining Standards Task Force Report of January 1999

  • Inferred resource
  • Indicated resource
  • Measured resource
  • Possible reserve
  • Probable reserve
  • Proven reserve
  • 4.3.1.1 Resources/reserves

    Mineral Resources: Mineral resources include base and precious metals, coal and industrial minerals, and are defined as follows:

    Mineral Resource: "a deposit or concentration of natural, solid, inorganic or fossilized organic substance in such quantity and at such grade or quality that extraction of the material at a profit is currently or potentially possible."

    Mineral resources are subdivided according to the degree of assurance of existence, as follows:

    Measured Resource: "the estimated quantity and grade of that part of a deposit for which size, configuration, and grade have been very well-established by observation and sampling of outcrops, drill holes, trenches, and mine workings."

    Indicated Resource: "the estimated quantity and grade of part of a deposit for which the continuity of grade, together with the extent and shape, are so well-established that a reliable grade and tonnage estimate can be made."

    Inferred Resource: "the estimated quantity and grade of a deposit, or a part thereof, that is determined on the basis of limited sampling, but for which there is sufficient geological information and a reasonable understanding of the continuity and distribution of metal values to outline a deposit of potential economic merit."

    Reserves: A reserve ("ore reserve", in the case of metallic deposits) is derived from mineral resources and is defined as:

    Reserve: "that part of a resource which can be legally mined and at a profit under economic conditions that are specified and are generally accepted as reasonable. Economic viability must be demonstrated by at least a preliminary feasibility study based on Indicated and Measured Resources."

    Reserves are subdivided into categories of Proven, Probable, and Possible:

    Proven Reserve: "the estimated quantity and grade of that part of a Measured Resource for which the size, grade and distribution of values, together with technical and economic factors, are so well-established that there is the highest degree of confidence in the estimate. The term should be restricted to that part of a deposit being mined, or being developed and for which there is a mining plan."

    Probable Reserve: "the estimated quantity and grade of that part of an Indicated Resource for which the economic viability has been demonstrated by adequate information on engineering, operating, and legal factors, at a confidence level that will allow positive decisions on major expenditures."

    Possible Reserve: "the estimated quantity and grade of that part of an Inferred Resource that are determined from limited sample data for which geology, grade continuity, and operating parameters are based, to a large extent, on reasonable extrapolations, assumptions, and interpretations. A Possible Reserve does not stand alone, and must be an extension or addition to probable or proven reserves. Also, a Possible Reserve may not be used in an economic analysis or feasibility study."


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