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."