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From Wikipedia, the free encyclopedia

Manganese ore – psilomelane (size: 6.7 × 5.8 × 5.1 cm)
Manganese ore – psilomelane (size: 6.7 × 5.8 × 5.1 cm)
Lead ore – galena and anglesite (size: 4.8 × 4.0 × 3.0 cm)
Lead ore – galena and anglesite (size: 4.8 × 4.0 × 3.0 cm)
Gold ore (size: 7.5 × 6.1 × 4.1 cm)
Gold ore (size: 7.5 × 6.1 × 4.1 cm)
Cart for carrying ore from a mine on display at the Historic Archive and Museum of Mining in Pachuca, Mexico
Cart for carrying ore from a mine on display at the Historic Archive and Museum of Mining in Pachuca, Mexico

An ore is a natural occurrence of rock or sediment that contains sufficient minerals with economically important elements, typically metals, that can be economically extracted from the deposit.[1] The ores are extracted at a profit from the earth through mining; they are then refined (often via smelting) to extract the valuable element, or elements.

The ore grade, or 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 weighed against the metal value contained in the rock to determine what ore can be processed and what ore is of too low a grade to be worth mining. Metal ores 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 elements 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 a particular ore type. Most ore deposits are named according to their location (for example, the Witwatersrand, South Africa), or after a discoverer (e.g. the Kambalda nickel shoots are named after drillers), or after some whimsy, a historical figure, a prominent person, something from mythology (phoenix, kraken, serepentleopard, etc.) 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).

Classification

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

Granite related hydrothermal

Magmatic deposits

Volcanic-related deposits

A cross-section of a typical Volcanic hosted massive sulfide|volcanogenic massive sulfide (VMS) ore deposit
A cross-section of a typical Volcanic hosted massive sulfide|volcanogenic massive sulfide (VMS) ore deposit

Metamorphically reworked deposits

Carbonatite-alkaline igneous related

Sedimentary deposits

Magnified view of banded iron formation specimen from Upper Michigan. Scale bar is 5.0 mm.
Magnified view of banded iron formation specimen from Upper Michigan. Scale bar is 5.0 mm.

Sedimentary hydrothermal deposits

Astrobleme-related ores

Extraction

Some ore deposits in the world
Some ore deposits in the world
Some additional ore deposits in the world
Some additional ore deposits in the world

The basic extraction of ore deposits follows these steps:

  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 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. 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 US and Japan.[citation needed]

Important ore minerals

See also

References

  1. ^ Guilbert, John M. and Charles F. Park, Jr. (1986) The Geology of Ore Deposits, W. H. Freeman, p. 1. ISBN 0-7167-1456-6

Further reading

DILL, H.G. (2010) The “chessboard” classification scheme of mineral deposits: Mineralogy and geology from aluminum to zirconium, Earth-Science Reviews, Volume 100, Issue 1-4, June 2010, Pages 1-420

This page was last edited on 14 May 2019, at 02:20
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