Corundum

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Corundum
Several corundum crystals.jpg
General
CategoryOxide meeneral – Hematite group
Formula
(repeatin unit)
Alumeenium oxide, Al
2
O
3
Strunz clessification4.CB.05
Dana clessification4.3.1.1
Creestal seestemTrigonal
Creestal clessHexagonal scalenohedral (3m)
H-M seembol: (3 2/m)
Space groupR3c
Unit cella = 4.75 Å, c = 12.982 Å; Z = 6
Identification
ColourColourless, gray, broun; pink tae reid, orange, yellae, green, blue, violet; mey be colour zoned, asteriated mainly gray an broun
Creestal habitSteep bipyramidal, tabular, prismatic, rhombohedral creestals, massive or granular
TwinninPolysynthetic twinnin common
CleavageNane – pairtin in 3 directions
FracturConchoidal tae uneven
TenacityBrittle
Mohs scale haurdness9 (definin meeneral)[1]
SkinkleAdamantine tae vitreous
StreakWhite
DiaphaneityTransparent, translucent tae opaque
Speceefic gravity3.95–4.10
Optical propertiesUniaxial (–)
Refractive indexnω = 1.767–1.772
nε = 1.759–1.763
PleochroismNane
Meltin pynt2044 °C
FusibilityInfusible
SolubilityInsoluble
Alters taeMey alter tae mica on surfaces causin a decrease in haurdness
Ither chairacteristicsMey fluoresce or phosphoresce unner UV licht
References[2][3][4][5]
Major varieties
SapphireOny colour except reid
RubyReid
EmeryBlack 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