Guido defines them as follows:
Resource.
A concentration of naturally occurring material in such form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible. Location, grade, quality, and quantity are known or estimated from specific geologic evidence. To reflect varying degrees of geologic certainty, resources can be subdivided into Measured, Indicated and Inferred.
Measured -- Quantity is computed from dimensions revealed in outcrops, trenches, workings, or drill holes. Grade and/or quality are computed from the result of detailed sampling. The sites for inspection, sampling, and measurement are spaced so closely and the geologic character is so well defined that size, shape, depth and mineral content of the resource are well established.
Indicated -- Quantity and grade, and/or quality, are computed from information similar to that used for Measured Resources, but the sites for inspection, sampling, and measurement are farther apart or are otherwise less adequately spaced. The degree of assurance, although lower that for Measured Resources, is high enough to assume geologic continuity between points of observation.
Inferred -- Estimates are based on geologic evidence and assumed continuity in which there is less confidence that for Measured or Indicated Resources. Inferred resources may or may not be supported by samples or measurements but the inference must be supported by reasonable geo-scientific data.
Reserve.
A Reserve is that part of the Resource that meets minimum physical and chemical criteria related to the specified mining and production practices, including those for grade, quality, thickness, depth; and can be reasonably assumed to be economically and legally extracted or produced at the time of the determination. The feasibility of the specified mining and production practices must have been demonstrated or can be reasonably assumed on the basis of tests and measurements.
Proven Reserve -- That part of a Measured Resource that satisfies the conditions to be classified as a Reserve.
Probable Reserve -- That part of an Indicated Resource that satisfies the conditions to be classified as a Reserve. |
