gemstone
Black Spinel
Magnesium aluminate, MgAl2O4
AI-generated identification · may be incorrectHardness of 8 on the Mohs scale, deep black color, vitreous to sub-metallic luster, isometric crystal system with octahedral habit, and conchoidal fracture.
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Physical properties
Hardness of 8 on the Mohs scale, deep black color, vitreous to sub-metallic luster, isometric crystal system with octahedral habit, and conchoidal fracture.
Formation & geological history
Forms through high-grade regional metamorphism and in mafic igneous rocks or contact metamorphic zones.
Uses & applications
Widely used in fine jewelry, especially as a durable substitute for black diamond or onyx in faceted beads and gemstones.
Geological facts
Black spinel is often mistaken for black tourmaline or black diamond due to its intense dark color and high refractive index.
Field identification & locations
Identified by its octahedral crystal form, high hardness, lack of cleavage, and vitreous luster; found globally in metamorphic rocks and alluvial gravels.
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