mineral
Corundum
Aluminium oxide, Al2O3
AI-generated identification · may be incorrectHardness of 9 on the Mohs scale, commonly brown or purplish-gray in rough form, with a vitreous to adamantine luster and trigonal crystal system.
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Physical properties
Hardness of 9 on the Mohs scale, commonly brown or purplish-gray in rough form, with a vitreous to adamantine luster and trigonal crystal system.
Formation & geological history
Forms in metamorphic and igneous rocks, particularly in aluminum-rich and silica-deficient environments like marbles and pegmatites.
Uses & applications
Used primarily as an industrial abrasive and in gemstone jewelry as ruby and sapphire.
Geological facts
Corundum is the second-hardest natural mineral on Earth, surpassed only by diamond.
Field identification & locations
Identified easily by its extreme hardness which can scratch quartz and its barrel-shaped crystal habit; found globally in metamorphic terranes and alluvial deposits.
