gemstone
Sapphire
Corundum (Al2O3)
AI-generated identification · may be incorrectMohs hardness of 9, distinct blue color from iron and titanium impurities, vitreous to adamantine luster, trigonal crystal system with no true cleavage.
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Physical properties
Mohs hardness of 9, distinct blue color from iron and titanium impurities, vitreous to adamantine luster, trigonal crystal system with no true cleavage.
Formation & geological history
Forms in aluminum-rich, silica-deficient metamorphic or igneous rocks like pegmatites and marble, often concentrated in alluvial secondary deposits.
Uses & applications
Valued extensively as a precious gemstone in fine jewelry, and utilized industrially for watch crystals, bearings, and scientific optics.
Geological facts
Sapphire is the second hardest natural mineral on Earth, surpassed only by diamond. Famous deposits include Kashmir, Madagascar, and Sri Lanka.
Field identification & locations
Identify by its extreme hardness, barrel-shaped hexagonal crystal habit, and heavy feel. Commonly found in gem gravels and stream beds.
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