Ore is natural rock or sediment that contains one or more valuable minerals concentrated above background levels, typically containing metals, that can be mined, treated and sold at a profit. The grade of ore refers to the concentration of the desired material it contains. The value of the metals or minerals a rock contains must be weighed against the cost of extraction to determine whether it is of sufficiently high grade to be worth mining, and is therefore considered an ore. A complex ore is one containing more than one valuable mineral.
Minerals of interest are generally oxides, sulfides, silicates, or native metals such as copper or gold. Ore bodies are formed by a variety of geological processes generally referred to as ore genesis, and can be classified based on their deposit type. Ore is extracted from the earth through mining and treated or refined, often via smelting, to extract the valuable metals or minerals. Some ores, depending on their composition, may pose threats to health or surrounding ecosystems.
The word ore is of Anglo-Saxon origin, meaning lump of metal.
In most cases, an ore does not consist entirely of a single ore mineral but it is mixed with other valuable minerals and with unwanted or valueless rocks and minerals. The part of an ore that is not economically desirable and that can not be avoided in mining is known as gangue. The valuable ore minerals are separated from the gangue minerals by froth flotation, gravity concentration, electric or magnetic methods, and other operations known collectively as mineral processing or ore dressing.
Mineral processing consists of first liberation, to free the ore from the gangue, and concentration to separate the desired mineral(s) from it. Once processed, the gangue is known as tailings, which are useless but potentially harmful materials produced in great quantity, especially from lower grade deposits.
Main article: Mineral resource classification
An ore deposit is an economically significant accumulation of minerals within a host rock. This is distinct from a mineral resource in that it is a mineral deposit occurring in high enough concentration to be economically viable. An ore deposit is one occurrence of a particular ore type. Most ore deposits are named according to their location, or after a discoverer (e.g. the Kambalda nickel shoots are named after drillers), or after some whimsy, a historical figure, a prominent person, a city or town from which the owner came, something from mythology (such as the name of a god or goddess) or the code name of the resource company which found it (e.g. MKD-5 was the in-house name for the Mount Keith nickel sulphide deposit).
Main article: Ore genesis
Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis. The following is a general categorization of the main ore deposit types:
Magmatic deposits are ones who originate directly from magma
These are ore deposits which form as a direct result of metamorphism.
These are the leading source of copper ore. Porphyry copper deposits form along convergent boundaries and are thought to originate from the partial melting of subducted oceanic plates and subsequent concentration of Cu, driven by oxidation. These are large, round, disseminated deposits containing on average 0.8% copper by weight.
Hydrothermal deposits are a large source of ore. They form as a result of the precipitation of dissolved ore constituents out of fluids.
Laterites form from the weathering of highly mafic rock near the equator. They can form in as little as one million years and are a source of iron (Fe), manganese (Mn), and aluminum (Al). They may also be a source of nickel and cobalt when the parent rock is enriched in these elements.
Banded iron formations (BIFs) are the highest concentration of any single metal available. They are composed of chert beds alternating between high and low iron concentrations. Their deposition occurred early in Earth's history when the atmospheric composition was significantly different from today. Iron rich water is thought to have upwelled where it oxidized to Fe (III) in the presence of early photosynthtic plankton producing oxygen. This iron then precipitated out and deposited on the ocean floor. The banding is thought to be a result of changing plankton population.
Sediment Hosted Copper forms from the precipitation of a copper rich oxidized brine into sedimentary rocks. These are a source of copper primarily in the form of copper-sulfide minerals.
Placer deposits are the result of weathering, transport, and subsequent concentration of a valuable mineral via water or wind. They are typically sources of gold (Au), platinum group elements (PGE), sulfide minerals, tin (Sn), tungsten (W), and rare-earth elements (REEs). A placer deposit is considered alluvial if formed via river, colluvial if by gravity, and eluvial when close to their parent rock.
Main article: Mining
The extraction of ore deposits generally follows these steps. Progression from stages 1–3 will see a continuous disqualification of potential ore bodies as more information is obtained on their viability:
With rates of ore discovery in a steady decline since the mid 20th century, it is thought that most surface level, easily accessible sources have been exhausted. This means progressively lower grade deposits must be turned to, and new methods of extraction must be developed.
Main article: Environmental effects of mining
Some ores contain heavy metals, toxins, radioactive isotopes and other potentially negative compounds which may pose a risk to the environment or health. The exact effects an ore and it's tailings have is dependent on the minerals present. Tailings of particular concern are those of older mines, as containment and remediation methods in the past were next to non-existent, leading to high levels of leaching into the surrounding environment. Mercury and arsenic are two ore related elements of particular concern. Additional elements found in ore which may have adverse health affects in organisms include iron, lead, uranium, zinc, silicon, titanium, sulfur, nitrogen, platinum, and chromium. Exposure to these elements may result in respiratory and cardiovascular problems and neurological issues. These are of particular danger to aquatic life if dissolved in water. Ores such as those of sulphide minerals may severely increase the acidity of their immediate surroundings and of water, with numerous, long lasting impacts on ecosystems. When water becomes contaminated it may transport these compounds far from the tailings site, greatly increasing the affected range.
Uranium ores and those containing other radioactive elements may pose a significant threat if leaving occurs and isotope concentration increases above background levels. Radiation can have severe, long lasting environmental impacts and cause irreversible damage to living organisms.
Main article: History of mining
Metallurgy began with the direct working of native metals such as gold, lead and copper. Placer deposits, for example, would have been the first source of native gold. The first exploited ores were copper oxides such as malachite and azurite, over 7000 years ago at Çatalhöyük . These were the easiest to work, with relatively limited mining and basic requirements for smelting. It is believed they were once much more abundant on the surface than today. After this, copper sulphides would have been turned to as oxide resources depleted and the Bronze Age progressed. Lead production from galena smelting may have been occurring at this time as well.
The smelting of arsenic-copper sulphides would have produced the first bronze alloys. The majority of bronze creation however required tin, and thus the exploitation of cassiterite, the main tin source, began. Some 3000 years ago, the smelting of iron ores began in Mesopotamia. Iron oxide is quite abundant on the surface and forms from a variety of processes.
Until the 18th century gold, copper, lead, iron, silver, tin, arsenic and mercury were the only metals mined and used. In recent decades, Rare Earth Elements have been increasingly exploited for various high-tech applications. This has led to an ever-growing search for REE ore and novel ways of extracting said elements.
Ores (metals) are traded internationally and comprise a sizeable portion of international trade in raw materials both in value and volume. This is because the worldwide distribution of ores is unequal and dislocated from locations of peak demand and from smelting infrastructure.
Most base metals (copper, lead, zinc, nickel) are traded internationally on the London Metal Exchange, with smaller stockpiles and metals exchanges monitored by the COMEX and NYMEX exchanges in the United States and the Shanghai Futures Exchange in China. The global Chromium market is currently dominated by the United States and China.
Iron ore is traded between customer and producer, though various benchmark prices are set quarterly between the major mining conglomerates and the major consumers, and this sets the stage for smaller participants.
Other, lesser, commodities do not have international clearing houses and benchmark prices, with most prices negotiated between suppliers and customers one-on-one. This generally makes determining the price of ores of this nature opaque and difficult. Such metals include lithium, niobium-tantalum, bismuth, antimony and rare earths. Most of these commodities are also dominated by one or two major suppliers with >60% of the world's reserves. China is currently leading in world production of Rare Earth Elements.
The World Bank reports that China was the top importer of ores and metals in 2005 followed by the US and Japan.
For detailed petrographic descriptions of ore minerals see Tables for the Determination of Common Opaque Minerals by Spry and Gedlinske (1987). Below are the major economic ore minerals and their deposits, grouped by primary elements.
|Metal ore minerals||Aluminum||Al||Alloys, conductive materials, lightweight applications||Gibbsite (Al(OH)3) and aluminium hydroxide oxide, which are found in laterites. Also Bauxite and Barite|| '|
|Antimony||Sb||Alloys, flame retardation||Stibnite (Sb2S3)|||
|Beryllium||Be||Metal alloys, in the nuclear industry, in electronics||Beryl (Be3Al2Si6O18), found in granitic pegmatites|||
|Bismuth||Bi||Alloys, pharmeceuticals||Native bismuth and bismuthinite (Bi2S3) with sulphide ores|||
|Cesium||Cs||Photoelectrics, pharmaceuticals||Lepidolite (K(Li, Al)3 (Si, Al)4O10 (OH,F)2) from pegmatites|||
|Chromium||Cr||Alloys, electroplating, colouring agents||Chromite (FeCr2O4) from stratiform and podiform chromitites|||
|Cobalt||Co||Alloys, chemical catalysts, cemented carbide||Smaltite (CoAs2) in veins with cobaltite; silver, nickel and calcite; cobaltite (CoAsS) in veins with smaltite, silver, nickel and calcite; carrollite (CuCo2S4) and linnaeite (Co3S4) as constituents of copper ore; and linnaeite|
|Copper||Cu||Alloys, high conductivity, corrosion resistance||Sulphide minerals, including chalcopyrite (CuFeS2; primary ore mineral) in sulphide deposits, or porphyry copper deposits; covellite (CuS); chalcocite (Cu2S; secondary with other sulphide minerals) with native copper and cuprite deposits and bornite (Cu5FeS4; secondary with other sulphide minerals)
Oxidized minerals, including malachite (Cu2CO3(OH)2) in the oxidized zone of copper deposits; cuprite (Cu2O; secondary mineral ); and azurite (Cu3(CO3)2(OH)2; secondary)
|Gold||Au||Electronics, jewellery, dentistry||Placer deposits, quartz grains|||
|Iron||Fe||Industry use, construction, steel||Hematite (Fe2O3; primary source) in banded iron formations, veins, and igneous rock; magnetite (Fe3O4) in igneous and metamorphic rocks; goethite (FeO(OH); secondary to hematite); limonite (FeO(OH)nH2O; secondary to hematite)|||
|Lead||Pb||Alloys, pigmentation, batteries, corrosion resistance, radiation shielding||Galena (PbS) in veins with other sulphide materials and in pegmatites; cerussite (PbCO3) in oxidized lead zones along with galena|||
|Lithium||Li||Metal production, batteries, ceramics||Spodumene (LiAlSi2O6) in pegmatites|||
|Manganese||Mn||Steel alloys, chemical manufacturing||Pyrolusite (MnO2) in oxidized manganese zones like laterites and skarns; manganite (MnO(OH)) and braunite (3Mn2O3 MnSiO3) with pyrolusite|||
|Mercury||Hg||Scientific instruments, electrical applications, paint, solvent, pharmeceuticals||Cinnabar (HgS) in sedimentary fractures with other sulphide minerals|||
|Molybdenum||Mo||Alloys, electronics, industry||Molybdenite (MoS2) in porphyry deposits, powellite (CaMoO4) in hydrothermal deposits|||
|Nickel||Ni||Alloys, food and pharmaceutical applications, corrosion resistance||Pentlandite (Fe,Ni)9S8 with other sulphide minerals; garnierite (NiMg) with chromite and in laterites; niccolite (NiAs) in magmatic sulphide deposits|||
|Niobium||Nb||Alloys, corrosion resistance||Pyrochlore (Na,Ca)2Nb2O6(OH,F) and columbite ((FeII,MnII)Nb2O6) in granitic pegmatites|||
|Platinum Group||Pt||Dentistry, jewellry, chemical applications, corrosion resistance, electronics||With chromite and copper ore, in placer deposits; sperrylite (PtAs2) in sulphide deposits and gold veins|||
|Rare-earth elements||La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y||Permanent magnets, batteries, glass treatment, petroleum industry, micro-electronics, alloys, nuclear applications, corrosion protection (La and Ce are the most widely applicable)||Bastnäsite (REECO3F; for Ce, La, Pr, Nd) in carbonatites; monazite (REEPO4; for La, Ce, Pr, Nd) in placer deposits; xenotime (YPO4; for Y) in pegmatites; eudialyte (Na15Ca6(Fe,Mn)3Zr3SiO(O,OH,H2O)3
(Si3O9)2(Si9O27)2(OH,Cl)2) in igneous rocks; allanite ((REE,Ca,Y)2(Al,Fe2+,Fe3+)3(SiO4)3(OH)) in pegmatites and carbonatites
|Rhenium||Re||Catalyst, temperature applications||Molybdenite (MoS2) in porphyry deposits|||
|Silver||Ag||Jewellery, glass, photo-electric applications, batteries||Sulfide deposits; Argentite (Ag2S; secondary to copper, lead and zinc ores)|||
|Tin||Sn||Solder, bronze, cans, pewter||Cassiterite (SnO2) in placer and magmatic deposits|||
|Titanium||Ti||Aerospace, industrial tubing||Ilmenite (FeTiO3) and rutile (TiO2) economically sourced from placer deposits with REEs|||
|Tungsten||W||Filaments, electronics, lighting||Wolframite ((Fe,Mn)WO4) and scheelite (CaWO4) in skarns and in porphyry along with sulphide minerals|||
|Uranium||U||Nuclear fuel, ammunition, radiation shielding||Pitchblende (UO2) in uraninite placer deposits; carnotite (K2(UO2)2(VO4)2 3H2O) in placer deposits|||
|Vanadium||V||Alloys, catalysts, glass colouring, batteries||Patronite (VS4) with sulphide minerals; roscoelite (K(V,Al,Mg)2 AlSi3O10(OH)2) in epithermal gold deposits|||
|Zinc||Zn||Corrosion protection, alloys, various industrial compounds||Sphalerite ((Zn,Fe)S) with other sulphide minerals in vein deposits; smithsonite (ZnCO3) in oxidized zone of zinc bearing sulphide deposits|||
|Zirconium||Zr||Alloys, nuclear reactors, corrosion resistance||Zircon (ZrSiO4) in igneous rocks and in placers|||
|Non-metal ore minerals||Fluorospar||CaF2||Steelmaking, optical equipment||Hydrothermal veins and pegmatites|||
|Graphite||C||Lubricant, industrial molds, paint||Pegmatites and metamorphic rocks|||
|Gypsum||CaSO42H2O||Fertilizer, filler, cement, pharmaceuticals, textiles||Evaporites; VMS|||
|Feldspar||Fsp||Ceramics, glassmaking, glazes||Orthoclase (KAlSi3O8) and albite (NaAlSi3O8) are ubiquitous throughout Earth's crust|||
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