In the Earth's crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon). Because of its strong affinity to oxygen, however, it is almost never found in the elemental state; instead it is found in oxides or silicates. Feldspars (KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8), the most common group of minerals in the Earth's crust, are aluminosilicates. Native aluminium metal can be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes. It also occurs in the minerals beryl, cryolite, garnet, spinel and turquoise.Template:Inote Impurities in Al2O3, such as chromium or cobalt yield the gemstones ruby and sapphire, respectively.Template:Inote Pure Al2O3, known as corundum, is one of the hardest materials known.Template:Inote
Although aluminium is an extremely common and widespread element, the common aluminium minerals are not economic sources of the metal. Almost all metallic aluminium is produced from the ore bauxite (AlOx(OH)3-2x). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions. Large deposits of bauxite occur in Australia, Brazil, Guinea and Jamaica but the primary mining areas for the ore are in Ghana, Indonesia, Jamaica, Russia and Surinam.Template:Inote Smelting of the ore mainly occurs in Australia, Brazil, Canada, Norway, Russia and the United States.Template:Inote Because smelting is an energy-intensive process, regions with excess natural gas supplies (such as the United Arab Emirates) are becoming aluminium refiners.
Manganese makes up about 1000 ppm (0.1%) of the Earth's crust, making it the 12th most abundant element there. Soil contains 7–9000 ppm of manganese with an average of 440 ppm. Seawater has only 10 ppm manganese and the atmosphere contains 0.01 µg/m3. Manganese occurs principally as pyrolusite (MnO2), braunite, (Mn2+Mn3+6)(SiO12), psilomelane (Ba,H2O)2Mn5O10, and to a lesser extent as rhodochrosite (MnCO3).
The most important manganese ore is pyrolusite (MnO2). Other economically important manganese ores usually show a close spatial relation to the iron ores. Land-based resources are large but irregularly distributed. Over 80% of the known world manganese resources are found in South Africa and Ukraine, other important manganese deposits are in Australia, India, China, Gabon and Brazil. In 1978 it was estimated that 500 billion tons of manganese nodules exist on the ocean floor. Attempts to find economically viable methods of harvesting manganese nodules were abandoned in the 1970s.
Manganese is mined in South Africa, Australia, China, Brazil, Gabon, Ukraine, India and Ghana and Kazakhstan. US Import Sources (1998–2001): Manganese ore: Gabon, 70%; South Africa, 10%; Australia, 9%; Mexico, 5%; and other, 6%. Ferromanganese: South Africa, 47%; France, 22%; Mexico, 8%; Australia, 8%; and other, 15%. Manganese contained in all manganese imports: South Africa, 31%; Gabon, 21%; Australia, 13%; Mexico, 8%; and other, 27%.
For the production of ferromanganese, the manganese ore are mixed with iron ore and carbon and then reduced either in a blast furnace or in an electric arc furnace. The resulting ferromanganese has a manganese content of 30 to 80%. Pure manganese used for the production of non-iron alloys is produced by leaching manganese ore with sulfuric acid and a subsequent electrowinning process.
- Main article: Silver mining
Silver is found in native form, as an alloy with gold (see also: electrum), and in ores containing sulfur, arsenic, antimony or chlorine. Ores include argentite (Ag2S), chlorargyrite (AgCl) which includes horn silver , and pyrargyrite (Ag3SbS3). The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from Peru, Mexico, China, Australia, Chile, Poland and Serbia. Peru and Mexico have been mining silver since 1546 and are still major world producers. Top silver-producing mines are Proaño / Fresnillo (Mexico), Cannington (Queensland, Australia), Dukat (Russia), Uchucchacua (Peru) and Greens Creek mine (Alaska).
The metal is primarily produced through electrolytic copper refining, gold, nickel and zinc refining, and by application of the Parkes process on lead metal obtained from lead ores that contain small amounts of silver. Commercial-grade fine silver is at least 99.9% pure, and purities greater than 99.999% (five 9s) are available. In 2007, Peru was the world's top producer of silver, closely followed by Mexico, according to the British Geological Survey.Template:Clarify
- ↑ 1.0 1.1 1.2 Template:Greenwood&Earnshaw2ndTemplate:Inote
- ↑ "Aluminum Mineral Data". Retrieved on 2008-07-09.
- ↑ Guilbert, John M. and Carles F. Park (1986). The Geology of Ore Deposits, Freeman. pp. 774–795. ISBN 0-7167-1456-6.
- ↑ 4.0 4.1 4.2 4.3 Emsley, John (2001). "Aluminium". Nature's Building Blocks: An A-Z Guide to the Elements. Oxford, UK: Oxford University Press. p. 24. ISBN 0198503407, http://books.google.com/books?id=j-Xu07p3cKwC&pg=PA24.
- ↑ Bhattacharyya, P. K.; Dasgupta, Somnath; Fukuoka, M.; Roy Supriya (1984). "Geochemistry of braunite and associated phases in metamorphosed non-calcareous manganese ores of India". Contributions to Mineralogy and Petrology 87 (1): 65–71. doi:10.1007/BF00371403.
- ↑ 6.0 6.1 6.2 Corathers, Lisa A. (2009). "Mineral Commodity Summaries 2009: Manganese" (PDF). United States Geological Survey. Retrieved on 2009-04-30.
- ↑ Cite error: Invalid
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- ↑ Wang, X; Schröder, Hc; Wiens, M; Schlossmacher, U; Müller, We (2009). "Manganese/polymetallic nodules: micro-structural characterization of exolithobiontic- and endolithobiontic microbial biofilms by scanning electron microscopy.". Micron (Oxford, England : 1993) 40 (3): 350–358. doi:10.1016/j.micron.2008.10.005. ISSN 0968-4328. PMID 19027306.
- ↑ United Nations Ocean Economics and Technology Office, Technology Branch, United Nations (1978). Manganese Nodules: Dimensions and Perspectives, Springer. ISBN 9789027705006.
- ↑ Corathers, Lisa A. (June 2008). "2006 Minerals Yearbook: Manganese" (PDF). Washington, D.C.: United States Geological Survey. Retrieved on 2009-04-30.
- ↑ Corathers, L. A.; Machamer, J. F. (2006). "Manganese". Industrial Minerals & Rocks: Commodities, Markets, and Uses (7th ed.), SME. pp. 631–636. ISBN 9780873352338, http://books.google.com/books?id=zNicdkuulE4C&pg=PA631.
- ↑ Zhang, Wensheng; Cheng, Chu Yong (2007). "Manganese metallurgy review. Part I: Leaching of ores/secondary materials and recovery of electrolytic/chemical manganese dioxide". Hydrometallurgy 89: 137–159. doi:10.1016/j.hydromet.2007.08.010.
- ↑ Cite error: Invalid
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- ↑ "Top silver producers". Infomine.com. Retrieved on 2009-04-05.