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corundum

corundum Mineral, Al2O3; sp. gr. 3.9–4.1; hardness 9; trigonal; the two main varieties blue and green, but can be yellow, or brown to almost black, and transparent; adamantine to vitreous lustre; crystals usually rough and barrel-shaped, tapering, and also flat and tabular; no cleavage, partings {0001}, {011T̄}; occurs in silica-poor rocks such as nepheline syenites and undersaturated (see SILICA SATURATION) alkali igneous rocks, in contact aureoles in thermally altered alumina-rich shales or limestones, in aluminous xenoliths found within basic igneous rocks in association with spinel, cordierite, and orthopyroxene, in metamorphosed bauxite deposits and in emery deposits, and in alluvial deposits because of its hardness and resistance to abrasion along with muscovite, hematite, and rutile. Flawless crystals are the gemstones blue sapphire, red ruby, and green oriental emerald. The main use of corundum is based on its hardness. It is made into grinding wheels and discs, emery paper, and powders for grinding and polishing.

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"corundum." A Dictionary of Earth Sciences. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"corundum." A Dictionary of Earth Sciences. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/corundum

corundum

corundum (kərŭn´dəm), mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in masses. It is transparent to opaque and has a vitreous to adamantine luster. The transparent gem varieties are colorless, pink, red, blue, green, yellow, and violet; the common varieties are blue-gray to brown. Emery is a common corundum, used as an abrasive and distinguished by its impurities of magnetite and hematite. The chief corundum gems are the ruby (red) and the sapphire (blue). Yellow, pink, green, and white stones are also called yellow, pink, green, and white sapphires. Corundum gems are also made synthetically. The chief sources of natural corundum are Myanmar, Sri Lanka, India, Thailand, Republic of South Africa, Tanzania, and the United States (North Carolina, Georgia, and Montana). Most of the emery is mined in Naxos and the other Cyclades and in Asia Minor.

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"corundum." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"corundum." The Columbia Encyclopedia, 6th ed.. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/corundum

corundum

corundum Translucent to transparent mineral, aluminium oxide (Al2O3). It is found in igneous, pegmatitic and metamorphic rocks, occurring as pyramidal or prismatic crystals in the rhombohedral class and as granular masses. It is the hardest natural substance after diamond. Gemstone varieties are sapphire and ruby. It is an industrial abrasive. Hardness 9; r.d. 4.

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"corundum." World Encyclopedia. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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corundum

co·run·dum / kəˈrəndəm/ • n. extremely hard aluminum oxide, used as an abrasive. Ruby and sapphire are varieties of corundum.

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"corundum." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"corundum." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/corundum-0

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corundum

corundum mineral allied to sapphire and ruby. XVIII. — Tamil kurundam = Telugu kuruvindam — Skr. kuruvinda- ruby.

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"corundum." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

"corundum." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (August 19, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/corundum-1

"corundum." The Concise Oxford Dictionary of English Etymology. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/corundum-1

corundum

corundumjeroboam, Noam, Siloam •brougham •residuum, triduum •continuum • Brabham • album •sachem • Beecham • Mitchum •Adam, macadam, madam, Madame •avizandum, fandom, memorandum, nil desperandum, random, tandem •tarmacadam •shahdom, stardom, tsardom •beldam, seldom •addendum, corrigendum, referendum •heirdom • sheikhdom • Gaeldom •thanedom • saintdom •Edom, freedom, Needham •chiefdom, fiefdom •queendom • heathendom •crippledom • officialdom • Wyndham •Christendom • kingdom • princedom •wisdom • fogeydom • yuppiedom •rodham, Sodom •condom •boredom, whoredom •thraldom • Oldham • popedom •dukedom •Carborundum, corundum •poppadom • pauperdom • martyrdom •reductio ad absurdum • serfdom •earldom

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"corundum." Oxford Dictionary of Rhymes. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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"corundum." Oxford Dictionary of Rhymes. . Retrieved August 19, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/corundum