Ore

An ore is a volume of rock containing components or minerals in a mode of occurrence that renders it valuable for mining. An ore must contain materials that are

• valuable
• in concentrations that 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.

Rare samples of ore in the form of exceptionally beautiful crystals, exotic layering (when sectioned or polished) or metallic presentations such as large nuggets or crystalline 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 native copper) that are not commonly concentrated in the Earth's crust or "noble" metals (not usually forming 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.

Ore deposits

An ore deposit is an accumulation of ore. This is distinct from a mineral resource as defined by the mineral resource classification criteria. An ore deposit is one occurrence of the particular ore type. Most ore deposits are named according to either their location (for example the Witswatersrand, South Africa), or after a discoverer (eg; the kambalda nickel shoots are named after drillers), or after some whimsy, an historical figure, a prominent person, something from mythology (phoenix, kraken, etc) or the code name of the resource company which found it (eg; MKD-5 is the in-house name for the Mount Keith nickel mine).

Classification of ore deposits

Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis. The classifications below are typical

Hydrothermal epigenetic deposits

• Mesothermal lode gold deposits, typified by the Golden Mile, Kalgoorlie
• Archaean conglomerate hosted gold-uranium deposits, typified by Elliot Lake, Canada and Witwatersrand, South Africa
• Carlin type gold deposits, including;
• Dolomite-hosted jasperoid replacement subtype
• Epithermal stockwork vein deposits

Granite related hydrothermal

• IOCG or iron-oxide copper-gold, typified by the supergiant Olympic Dam Cu-Au-U deposit
• Porphyry copper +/- gold +/- molybdenum +/- silver deposits
• Intrusive-related copper-gold +/- (tin-tungsten), typified by the Tombstone, Arizona deposits
• Hydromagmatic magnetite iron ore deposits and skarns
• Skarn ore deposits of copper, lead, zinc, tungsten, etcetera

Nickel-cobalt-platinum deposits

• Magmatic nickel-copper-iron-PGE deposits including
• Cumulate vanadiferous or platinum-bearing magnetite or chromite
• Cumulate hard-rock titanium (ilmenite) deposits
• Komatiite hosted Ni-Cu-PGE deposits
• Subvolcanic feeder subtype, typified by Noril'sk-Talnakh and the Thompson Belt, Canada
• Intrusive-related Ni-Cu-PGE, typified by Voisey's Bay, Canada and Jinchuan, China

• Lateritic nickel ore deposits, examples include Goro and Acoje, (Philippines) and Ravensthorpe, Western Australia.

Volcanic-related deposits

• Volcanic hosted massive sulfide (VHMS) Cu-Pb-Zn including;
• Examples include Teutonic Bore and Golden Grove, Western Australia
• Besshi type
• Kuroko type

Metamorphically reworked deposits

• Podiform serpentinite-hosted paramagmatic iron oxide-chromite deposits, typified by Savage River, Tasmania iron ore, Coobina chromite deposit
• Broken Hill Type Pb-Zn-Ag, considered to be a class of reworked SEDEX deposits

Carbonatite - alkaline igneous related

• Phosphorus-tantalite-vermiculite (Phalaborwa South Africa)
• Rare earth elements - Mount Weld, Australia and Bayan Obo, Mongolia
• Diatreme hosted diamond in kimberlite, lamproite or lamprophyre

Sedimentary deposits

• Banded iron formation iron ore deposits, including
• Channel-iron deposits or pisolite type iron ore
• Heavy mineral sands ore deposits and other sand dune hosted deposits
• Alluvial gold, diamond, tin, platinum or black sand deposits
• Alluvial oxide zinc deposit type: sole example Skorpion Zinc

Sedimentary hydrothermal deposits

• SEDEX
• Lead-zinc-silver, typified by Red Dog, MacArthur River, Mt Isa, etc
• Stratiform arkose-hosted and shale-hosted copper, typified by the Zambian copperbelt.
• Stratiform tungsten, typified by the Erzgebirge deposits, Czechoslovakia
• Exhalative spilite-chert hosted gold deposits
• Mississippi valley type (MVT) zinc-lead deposits
• Hematite iron ore deposits of altered banded iron formation

Astrobleme-related ores

• Sudbury Basin nickel and copper, Ontario, Canada

Extraction

The basic extraction of ore deposits follows the steps below;

1. Prospecting or Exploration to find and then define the extent and value of ore where it is located ("ore body")
2. Conduct resource estimation to mathematically estimate the size and grade of the deposit
3. Conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work.
4. Conduct a feasibility study to evaluate the financial viability, technical and financial risks and robustness of the project and make a decision as whether to develop or walk away from a proposed mine project. This includes mine planning to evaluate the economically recoverable portion of the deposit, the metallurgy and ore recoverability, marketability and payability of the ore concentrates, engineering, milling and infrastructure costs, finance and equity requirements and a cradle to grave analysis of the possible mine, from the initial excavation all the way through to reclamation.
5. Development to create access to an ore body and building of mine plant and equipment
6. The operation of the mine in an active sense
7. Reclamation to make land where a mine had been suitable for future use

Trade

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.

Iron ore is traded between customer and producer, though various benchmark prices are set yearly 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. The London Metal Exchange aims to add uranium to its list of metals on warrant.

The World Bank reports that China was the top importer of ores and metals in 2005 followed by the USA and Japan.

As compared with 2005-2006, at the end of 2007 - beginning of the year 2008 the Iron ore prices on FOB/CIF terms increased considerably, at least at 50-55%. The prices were increased after CVRD, which is the world's biggest iron ore producer, has agreed to increase its contract prices, continuing its previleged position on this market.

Price FOB Brazil reached 141-144 U$D/MT CIF Europe came up to 185-188 U$D/MT.

Important ore minerals

See also

• Mineral resource classification
• Economic geology
• Ore genesis