Description
A very hard, naturally occurring mineral composed of aluminum oxide. Corundum is mined in Australia, South Africa, Zimbabwe, India, Russia, Rhodesia, Turkey, the United States and Canada (Ontario). The transparent to translucent stones are typically gray or brown with some deeply colored varieties. Transparent corundum stones have been used as gemstones since at least Hellenistic times. Rubies are transparent red corundum gems while transparent blue stones are called sapphires. Transparent yellow corundum is called Oriental topaz, the violet color is called Oriental amethyst and the green, Oriental emerald. Impure corundum, commonly called emery, also contains hematite, magnetite, silica and/or magnesia. Emery is used as an abrasive. Artificial corundum has been produced on a very small scale by the Verneuil process.
(Corundum should not be confused with Carborundum)
Synonyms and Related Terms
emery (black); adamantine spar; ruby (red); sapphire (blue); Oriental topaz (yellow); Oriental amethyst (lavender); Oriental emerald (green); korund (Dan., Ned., Pol.); Korund (Deut.); corindon (Esp., Fr., Port.);
| Al2O3 |
| 1302-74-5 |
| 8.9-9.0 |
| 3.96-4.05 |
| 1.761-1.769 |
Other Properties
Hexagonal crystal system with tabular, prismatic or pyramidal crystals.
Luster = vitreous to adamantine. Fracture = conchoidal. Streak = white
Fluorescence = orange to strong red. Heat treated stones may fluoresce green.
Natural stones contain microscopic mineral and fluid inclusions not seen in synthetic stones. Synthetic stones may have gas bubbles.
Hazards and Safety
Inhalation of dust may cause irritation. Fire retardant.
Additional Information
Mineralogy Database: Corundum
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Last updated on: 7/6/2009 9:14:06 AM
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