Mineral Exploration Definitions ~ Mining Geology

Mineral is a homogeneous inorganic substance that occurs naturally, usually in crystalline form with a definite chemical composition.

The common rock-forming minerals (RFM) are quartz, orthoclase feldspar (KAlSi3O8), plagioclase feldspar (CaNaAlSi3O8), albite, mica group such as muscovite and biotite.

The common ore-forming minerals (OFM) are hematite (Fe2O3), cassiterite (SnO2), chalcopyrite (CuFeS2), sphalerite (ZnS), galena (PbS), baryte, gypsum (CaSO4), apatite, etc.

Rock is an assemblage of mineral(s) formed under natural process of igneous, sedimentary and metamorphic origin. The common rocks are basalt, granite, quartzite, sandstone, limestone, marble and mica-schist.

Rock and Minerals

Ore This concept has undergone radical changes over the years. The Institution of Mining and Metallurgy, UK, currently defines “Ore as a solid naturally occurring mineral aggregate of economic interest from which one or more valuable constituents may be recovered treatment.

Ore

Ore deposit is a natural concentration of one or more minerals within the host rock. It has a definite shape on economic criteria with finite quantity (tonnes) and average quality (grade). The shape varies according to the complex nature of the deposit such as layered, disseminated, veins, folded and deformed. It may be exposed to the surface or hidden below stony barren hills, agricultural soil, sand, river and forest.

Ore Minerals maybe classed as primary (Hypogene) or econdary (supergene).

Hypogene minerals were deposited during the original period of rock formation or mineralization.

Supergene minerals were formed during a later period of mineralization, usually associated with weathering and other near-surface proccesss, leading to precipitation of the secondary minerals from descending solutions “meteoric waters”.

Ore Deposits and Minerals

Protore is an altered rock mass or primary mineral deposit having uneconomic concentration of minerals. It may be further enriched by natural processes to form ore. These are low-grade residual deposits formed by weathering, oxidation, leaching and similar alteration. The protore can turn into an economic deposit with advance technology and/or increase of price. It can be exploited for kaolin, iron and nickel due to sufficient enrichment of the respective metals.

Protore

Prime commodity” is the principal ore mineral recovered from the mines.

Associated commodities” are the associated minerals recovered as by-products along with the main mineral.

Trace elements” In general all ore deposits contain number of valuable “trace elements” that can be recovered during processing of ore.

"The prime commodity of a zinc lead- copper-silver mine is zinc, and the associated commodities are lead and copper. The expected value-added trace elements are cadmium, silver, cobalt and gold. The value of all prime commodity, by-products and trace elements are considered collectively for valuation of the ore/mine."

Prime Commodity, Associated Commodity and Trace Element

Ganague minerals is the associated minerals or rocks, having no significant or least commercial value, are called “gangue” minerals. Pure chalcopyrite having 34.5% Cu metal in copper deposit and sphalerite with 67% Zn metal in zinc deposit are hosted by quartzite/mica-schist and dolomite respectively. The constituent minerals of quartzite, mica-schist and dolomite are called the gangue minerals. A list of common gangue minerals are Quartz - Barite- Calcite - Clay minerals All types - Dolomite - Feldspar All types - Garnet All types - Gypsum - Mica All types - Pyrite – Pyrrhotite.Quartz - Barite- Calcite - Clay minerals All types - Dolomite - Feldspar All types - Garnet All types - Gypsum - Mica All types - Pyrite – Pyrrhotite.

The raw ore is milled before the separation of the ore minerals from the gangue by various beneficiation processes. The concentrate is fed to the smelter and refinery to produce 99.99% metal.

Tailing is the rejects of the process plant which are composed of the gangue minerals. Tailings are used as support system by backfilling of void space in the underground mines. Alternatively, it is stored in a tailing pond and is treated as waste. High-value metals can be recovered by leaching from tailing in future. Tailing of Kolar gold mine, India, historically stored at tailing dam, is being considered to recover gold by leaching without any mining cost.