Ore deposit

Large copper ore deposits are found in the U.S., Chile, Zambia, Zaire, Peru, and Canada. The most important copper ores are the sulfides, the oxides, and carbonates. From these, copper is obtained by smelting, leaching, and by electrolysis. 

Important ore deposits are found in Zaire, Morocco, and Ganada. The U.S. Geological Survey has announced that the bottom of the north central Pacific Ocean may have cobalt-rich deposits at relatively shallow depths in water close to the the Hawaiian Islands and other U.S. Pacific territories. 

Sources. Iron ore deposits were formed by many different processes, eg, weathering, sedimentation, hydrothermal, and chemical. Iron ores occur in igneous, metamorphic, and sedimentary deposits. Normally, as-mined iron ore contains 25 to 68% iron. 

The Utah deposit is located in southwestern Utah near Cedar City. The iron ore deposits are of contact metamorphic origin. The cmde ore contains 35 to 65% iron, primarily in the form of magnetite and goethite. Mining is done by the open pit method. The cmde ore is cmshed, screened at —75 mm (—200 mesh size) and shipped as lump ore containing 54% iron. The ore is rescreened at the steel mill to produce lump ore (10—64 mm) for the blast furnace and sinter feed (0—10 mm) for the sinter plant. 

Other countries that have large iron ore deposits include Brazil (Carajas and Quaddlatero Ferrifero deposits), AustraUa (Pilbara deposits), Ukraine (Krivi Rog deposit), Russia (Kursk deposit), Venezuela (Cerro BoHvar deposit), India (Bihar-Orissa, Hospet, Kudremukh, and Goa deposits). South Africa (Sishen and Thabazimbi deposits), and Sweden (Kimna, Svappavaara, and Malmberget deposits). A Hst of world iron ore production and reserves in 1992 by country is shown in Table 3. 

F. W. Fraser and C. B. Belcher, "Mineralogical Studies of the Groote Eylandt Manganese Ore Deposits," Proceedings Mustralasian Institute of Minerals and Metallurgy tFo. 254, June 1975. 

Worldwide reserves of manganese in ore deposits are estimated (ca 1994) at 1.8 x 10 and potential resources are 1.1 x 10 t (11). The world s supply of commercial manganese ore comes from AustraUa, Bra2H, Gabon, and the RepubHc of South Africa. 

Mercury ore deposits occur in faulted and fractured rocks, such as limestone, calcareous shales, sandstones, serpentine, chert, andesite, basalt, and rhyolite. Deposits are mostiy epithermal in character, ie, minerals were deposited by rising warm solutions at comparatively shallow depths from 1—1000 m (6). 

AH metals come originally from natural deposits present in the earth s cmst. These ore deposits result from a geological concentration process, and consist mainly of metallic oxides and sulfides from which metals can be extracted. Seawater and brines are another natural source of metals, eg, magnesium (see Chemicals frombrine Magnesium and magnesium alloys Ocean raw materials). Metal extracted from a natural source is called primary metal. 

Table 1 gives the average metal content of the earth s cmst, ore deposits, and concentrates. With the exceptions of the recovery of magnesium from seawater and alkaU metals from brines, and the solution mining and dump or heap leaching of some copper, gold, and uranium (see Uranium and uranium compounds), most ores are processed through mills. Concentrates are the raw materials for the extraction of primary metals. 

Table 1. Metal Content of Igneous Rocks, Ore Deposits, and Concentrates, wt %...

Mining of the ore deposit constitutes a significant cost, especially in hard rock mining. Mining costs vary considerably from ore to ore and from a few cents to well over 100/t mined. Underground mining is the most expensive hydrauHc mining of sedimentary deposits is the least expensive. 

The economic importance of an ore deposit itself is largely affected by mineral or metal prices. Mine closures and reopenings are a common event in the mineral iadustry for this reason. Economics can also be affected by the ore composition, for example, by unacceptable levels of penalty elements ia the ore. The assessment of overall economics of exploiting a given ore deposit is similar to that for any large-scale industry. The various cost components are those associated with equipment, labor, utiUties, contingencies, operation and production, transportation, working capital, suppHes, maintenance. 

R. Edwards and K. Atkinson, Ore Deposit Geology, Chapman Hall, London, 1986. 

Geochemical Nature and Types of Deposits. The cmst of the earth contains approximately 2—3 ppm uranium. AlkaHc igneous rock tends to be more uraniferous than basic and ferromagnesian igneous rocks (10). Elemental uranium oxidizes readily. The solubiHty and distribution of uranium in rocks and ore deposits depend primarily on valence state. The hexavalent uranium ion is highly soluble, the tetravalent ion relatively insoluble. Uraninite, the most common mineral in uranium deposits, contains the tetravalent ion (II). 

Estimated world production capacity for elemental phosphoms is shown in Table 5 (6). Three elemental phosphoms production sites remain operational in North America (14), although Rhc ne Poulenc has announced its intention to cease production in late 1995. The remaining plants have survived owing to the availabiUty of economical electric power in the Northwest and proximity to phosphate ore deposits, resulting in lower cost phosphoms. The capacity of these producers in 1995 was estimated to be 264,000 metric tons. U.S. production capacity peaked at approximately 622,000 metric tons in 1970. 

Rl accomplishes this task correctiy in a fraction of the time it would take for human technicians. The savings in this case are in terms of the number of orders processed, which ultimately translates to doUars. As a final example, consider Prospector, another classic expert system built in the 1970s (4). This computer program, designed to detect commercially viable ore deposits based on geological data, correctiy identified a molybdenum ore deposit worth about 100 million. 

Vorkommen, n. occurrence, etc. (see vorkommen) presence, existence (of ores) deposit. Vor-kondensator, m. preliminary condenser, -kost, /. provisions first course, -kracken,... 

The depletion of domestic high-grade ore deposits has made the United States vulnerable... 

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