gemstone
Black Sapphire
Corundum (Al2O3)
AI-generated identification · may be incorrectMohs hardness of 9; dark blue, black, or opaque body color with vitreous to adamantine luster; trigonal crystal system; no cleavage.
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Physical properties
Mohs hardness of 9; dark blue, black, or opaque body color with vitreous to adamantine luster; trigonal crystal system; no cleavage.
Formation & geological history
Forms in aluminum-rich metamorphic or igneous rocks like pegmatites and basalts through high-temperature crystallization.
Uses & applications
Extensively used in fine jewelry, rings, and pendants, as well as industrial abrasives and watch bearings.
Geological facts
Star black sapphires display a six-rayed star effect called asterism caused by microscopic rutile needle inclusions.
Field identification & locations
Identified by its extreme hardness, heavy heft, and typical hexagonal crystal habit; found globally in Australia, Thailand, and Sri Lanka.
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