Mineral resource classification
is the systematic organization of information on ores
and other mineral deposits which contain economic value. The process guides governmental and industrial planning on how to manage the resources.
Not all mineralisation meets these criteria. The specific categories of mineralization in an economic sense are:
- mineral occurrences or prospects which are of geological interest but may not be of economic interest
- mineral resources, include those which are potentially economically and technically feasible, and those which are not
- ore reserves, must be economically and technically feasible to extract
The common terminology for mining, "ore deposit", by definition must have an 'ore reserve', and may or may not have additional 'resources'.
Classification, because it is an economic function, is governed by statutes, regulations and industry best practice norms. There are several classification schemes worldwide, however the Canadian CIM classification (see NI 43-101) and the Australasian Joint Ore Reserves Committee Code (JORC Code) are the general standards.
Mineral occurrences, prospects
These classifications of mineral occurrences are generally the least important and least economic. They included are all known occurrences of minerals of economic interest, including obviously uneconomic outcrops and manifestations. However, these are often mentioned in a company prospectus
because of "proximity
"; a concept that something valuable may be found near these occurrences because it has been in the past due to a similar geological environment. Often, such occurrences of mineralisation are the peripheral manifestations of nearby ore deposits.
"Ore deposit" is a term applied specifically to those economic mineral occurrences which could be mined at a profit after consideration of all factors impacting a mining operation.
Mineral resources are those economic mineral concentrations which have undergone enough scrutiny to quantify their contained metal to a certain degree. None of these resources are ore
, because the economics of the mineral deposit may not have been fully evaluated.
Indicated resources are simply economic mineral occurrences which have been sampled (usually by drilling) to a point at which an estimate of their contained metal and grade has been made. Generally this is very approximate and subject to sampling errors and uncertainties.
Measured resources are indicated resources which have undergone enough further sampling that a 'competent person' (which is defined by the norms of the relevant mining code; usually a geologist) has declared them to be an acceptable estimate of the grade, tonnage and occurrence of the mineral occurrence.
Resources may also be portions of a mineral occurrence which are attached to reserves, but are not
- sufficiently drilled out to qualify as Reserve status
- too deep to economically extract
- too deep to technically extract
- too low of grade to economically or technically extract
- contaminated, or refractory in nature
- have not yet met all of the criteria for Reserve status
Mineral reserves are the resources which are known to be economically feasible for extraction. Reserves are either 'Probable Reserves
or Proven Reserves
, in a similar manner to resources, above. Generally the conversion of resources into reserves requires;
- knowledge of the geology of the deposit sufficient that it is predictable and verifiable
- consideration of metallurgy, including plans for extraction, mineral processing
- calculation and design of open pit or underground mine plans based on ore models
- quantification of geotechnical risk; basically, managing the geological faults, joints and fractures in the ground so the mine does not collapse
- consideration of technical risk; essentially, statistical and variography to ensure the ore is sampled properly
- scrutiny of the assay data to ensure the accuracy of the information supplied by the laboratory
This is required because ore reserves are bankable. Essentially, once a deposit is brought up to reserve status, it is an economic entity and an asset upon which loans and equity can be drawn - generally in order to pay for its extraction (hopefully, at a profit).