gemstone
Sapphire
Al2O3 (Corundum)
AI-generated identification · may be incorrectMohs hardness of 9; deep blue color; adamantine to vitreous luster; trigonal crystal system; specific gravity of 4.0.
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Physical properties
Mohs hardness of 9; deep blue color; adamantine to vitreous luster; trigonal crystal system; specific gravity of 4.0.
Formation & geological history
Forms in aluminum-rich metamorphic or igneous rocks like pegmatites and marbles under high temperatures and pressures.
Uses & applications
Extensively used in high-end fine jewelry, watch crystals, and industrial abrasive or optical applications.
Geological facts
Sapphire is the precious variety of corundum in any color except red, which is designated as ruby.
Field identification & locations
Easily identified by its extreme hardness of 9 and distinct barrel-shaped hexagonal crystal habit; found worldwide, notably in Madagascar, Sri Lanka, and Australia.
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