Corundum



Corundum

General
CategoryMineral
aluminium oxide, Al2O3
Identification
ColorBrown to gray, less often red, blue, white,or yellow.
Crystal habitSteep bipyramidal, tabular, prismatic, rhombohedral crystals, massive or granular
Trigonal Hexagonal Scalenohedral bar32/m
TwinningPolysynthetic twinning common
CleavageNone - parting in 3 directions
FractureConchoidal to uneven
Mohs Scale hardness9
LusterAdamantine to vitreous
Refractive indexnω=1.768 - 1.772 nε=1.760 - 1.763, Biref 0.009
PleochroismNone
StreakWhite
Specific gravity3.95-4.1
FusibilityInfusible
SolubilityInsoluble
Major varieties
SapphireAny color except red
RubyRed
EmeryGranular

Corundum (from Tamil kurundam) is a sapphire. In addition to its hardness, corundum is unusual for its high oxygen.

Due to corundum's hardness (pure corundum is defined to have 9.0 Mohs hardness near 8.0.

Corundum occurs as a mineral in mica pegmatites. Because of its hardness and resistance to weathering, it commonly occurs as a detrital mineral in stream and beach sands.

Corundum for abrasives is mined in Zimbabwe, Russia, and India. Historically it was mined from deposits associated with bauxite.

Synthetic corundum

In 1837 Gaudin made the first synthetic rubies by fusing flame fusion process. [1]

The lasers.

References

  1. ^ Bahadur: a Handbook of Precious Stones (1943). Retrieved on 2007-08-19.
  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, pp. 300-302 ISBN 0-471-80580-7
  • Mindat
  • Webmineral data
  • Mineral galleries

See also
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Corundum". A list of authors is available in Wikipedia.