Ore
An
ore is a volume of
rock containing components or
minerals in a mode of occurrence which renders it valuable for mining. An ore must contain materials which are:
* valuable
* in concentrations which can be profitably
mined, transported, milled, and processed.
* able to be extracted from waste rock by
mineral processing techniques.
Ore deposits are mineral deposits defined as being economically recoverable. Mineral deposits may include those bodies of mineralisation which are uneconomic resources, of too low a grade or tonnage or
technically impossible for extraction of the contained metal.
What is valuable to mine is generally considered in terms of purely economic considerations. However,
cultural,
strategic or
social goals of
nations,
tribes and individuals may render
economically unfeasible bodies of rock valuable for extraction, for instance
ochre, some
clays and ornamental stones which are of religious, cultural or sentimental value to a population. Here, value is placed on the rock in non-economic terms
Rare samples of ore in the form of exceptionally beautiful
crystals, exotic layering (when sectioned or polished) or metalic presentations such as large nuggets or chrystaline formations of metals such as
gold or
copper may command a value far beyond their value as mere ore or raw metal for subsequent reduction to utilitarian purposes.
Ore is thus an economic entity, not a physical entity. Fluctuations in
commodity prices will determine what rock is considered valuable and hence
ore, and what rock is not valuable and is considered
waste. Similarly, the costs of extraction may fluctuate, for example with fuel costs, rendering mining unprofitable and turning ore into waste.
The
grade or contained
concentration of an ore mineral, or metal, as well as its form of occurrence, will directly affect the costs associated with mining the ore. The cost of extraction must thus be weighted against the contained metal value of the rock and a 'cut-off grade' used to define what is ore and what is waste.
Ore minerals are generally
oxides,
sulfides,
silicates, or "native" metals (such as
copper) that are not commonly concentrated in the Earth's
crust or "noble" metals (not usually formng compounds) such as
gold. The ores must be processed to extract the metals of interest from the waste rock and from the ore minerals.
Ore bodies are formed by a variety of
geological processes. The process of ore formation is called
ore genesis.
*
Argentite: Ag
2S
*
Barite: BaSO
4*
Bauxite Al
2O
3 for production of
aluminum*
Beryl: Be
3Al
2(SiO
3)
6*
Bornite: Cu
5FeS
4*
Cassiterite: SnO
2*
Chalcocite: Cu
2S for production of
copper*
Chalcopyrite: CuFeS
2*
Chromite: (Fe,Mg)Cr
2O
4 for production of
chromium*
Cinnabar: HgS for production of
mercury*
Cobaltite: (Co,Fe)AsS
*
Columbite-
Tantalite or
Coltan: (Fe,Mn)(Nb,Ta)
2O
6*
Galena: PbS
*
Gold: Au, typically associated with
quartz or as
placer deposits
*
Hematite: Fe
2O
3*
Ilmenite: FeTiO
3*
Magnetite: Fe
3O
4*
Molybdenite: MoS
2*
Pentlandite:(Fe,Ni)
9S
8*
Scheelite: CaWO
4*
Sphalerite: ZnS
*
Uraninite (pitchblende): UO
2 for production of metalic
uranium*
Wolframite: (Fe,Mn)WO
4*
Mineral resource classification*
Economic geology*
Ore genesis
