Corundum

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Corundum
Several corundum crystals.jpg
General
Category Oxide meeneral – Hematite group
Formula
(repeatin unit)
Alumeenium oxide, Al
2
O
3
Strunz clessification 4.CB.05
Dana clessification 4.3.1.1
Creestal seestem Trigonal
Creestal cless Hexagonal scalenohedral (3m)
H-M seembol: (3 2/m)
Space group R3c
Unit cell a = 4.75 Å, c = 12.982 Å; Z = 6
Identification
Colour Colourless, gray, broun; pink tae reid, orange, yellae, green, blue, violet; mey be colour zoned, asteriated mainly gray an broun
Creestal habit Steep bipyramidal, tabular, prismatic, rhombohedral creestals, massive or granular
Twinnin Polysynthetic twinnin common
Cleavage Nane – pairtin in 3 directions
Fractur Conchoidal tae uneven
Tenacity Brittle
Mohs scale haurdness 9 (definin meeneral)[1]
Skinkle Adamantine tae vitreous
Streak White
Diaphaneity Transparent, translucent tae opaque
Speceefic gravity 3.95–4.10
Optical properties Uniaxial (–)
Refractive index nω = 1.767–1.772
nε = 1.759–1.763
Pleochroism Nane
Meltin pynt 2044 °C
Fusibility Infusible
Solubility Insoluble
Alters tae Mey alter tae mica on surfaces causin a decrease in haurdness
Ither chairacteristics Mey fluoresce or phosphoresce unner UV licht
References [2][3][4][5]
Major varieties
Sapphire Ony colour except reid
Ruby Reid
Emery Black granular corundum intimately mixed wi magnetite, hematite, or hercynite

Corundum is a creestalline form o aluminium oxide (Al
2
O
3
) teepically conteenin traces o airn, titanium, vanadium an chromium.[2][3]

References[eedit | eedit soorce]

  1. "Mohs' scale of hardness". Collector's corner. Mineralogical Society of America. Retrieved 10 January 2014. 
  2. 2.0 2.1 Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1997). "Corundum". Handbook of Mineralogy (PDF). III(Halides, Hydroxides, Oxides). Chantilly, VA, US: Mineralogical Society of America. ISBN 0962209724. 
  3. 3.0 3.1 Corundum. Mindat.org
  4. Corundum. Webmineral
  5. Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, pp. 300–302 ISBN 0-471-80580-7