gemstone
Black Sapphire
Corundum (Al2O3)
Hardness of 9 on the Mohs scale, dark black to very dark blue color, vitreous to adamantine luster, trigonal crystal system, specific gravity of 3.95-4.03, no true cleavage.
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Physical properties
Hardness of 9 on the Mohs scale, dark black to very dark blue color, vitreous to adamantine luster, trigonal crystal system, specific gravity of 3.95-4.03, no true cleavage.
Formation & geological history
Formed in metamorphic and igneous rocks, particularly in aluminum-rich and silica-poor environments like pegmatites, basaltic flows, and marble, over millions of years.
Uses & applications
Widely used in fine jewelry, rings, pendants, watch crystals, and industrial applications due to its extreme hardness.
Geological facts
Black sapphire is an opaque to sub-translucent variety of corundum. While it lacks the high transparency of blue sapphires, large and well-cut stones make striking and durable jewelry pieces.
Field identification & locations
Found globally in regions like Australia, Thailand, and parts of the United States. Easily identified by its extreme hardness which can scratch almost all other minerals except diamond.
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