Deposits are classified based on the level of geological knowledge and economic feasibility, and is used as a guide for industrial planning and financing. Mineral deposits can be classified into three main groups:
- Mineral prospects
A mineral prospect has the least level of confidence and refers to a deposit of geological interest that may not be of economic value.
- Mineral resources
A mineral resource is a mineral concentration which is known, estimated and interpreted from specific geological evidence and knowledge and with reasonable prospects for economic extraction.
- Ore reserves
An ore reserve is an economical minable part of a mineral resource where appropriate assessments and studies have been carried out to show that the deposit can be mined at a profit after consideration of all factors impacting a mining operation.
There are several classification systems worldwide, however the Canadian CIM classification (see NI 43-101) and the Australasian Joint Ore Reserves Committee Code (JORC Code) are defined as standards. The JORC-code classifies resources and reserves in more detailed sub-groups:
- An inferred mineral resource is a deposit which has been sampled (usually by drilling) to a point at which an estimate of its grade and tonnage is made at low confidence. Generally this is very approximate and subject to uncertainties.
- An indicated mineral resource is a deposit in which tonnage, density; shape, physical characteristics, grade and mineral content can be estimated with a reasonable level of confidence. However, the continuity of the deposit is not verified.
- A measured mineral resource is an economic deposit with a high level of geological confidence and confirmed geological continuity. The deposit has undergone enough sampling that a 'competent person' (which is defined by the JORC-code) has declared it to be an acceptable documented resource estimate.
- A probable ore reserve is the economically minable part of an indicated, and in some circumstances, a measured mineral resource. The level of confidence is sufficient as a basis for decision on developing a deposit.
- A proven ore reserve is an economically minable part of a measured mineral resource and therefore holds the highest level of geological confidence. The deposit is also proved minable in terms of economic, mining, metallurgic, marketing, legal, social and governmental factors.