mineral

Black Spinel

Magnesium Aluminum Oxide (MgAl2O4)

Hardness: 8.0 on Mohs scale; Color: Opaque black; Luster: Vitreous (glassy); Crystal Structure: Isometric/Cubic; Cleavage: Indistinct; Specific Gravity: 3.54-3.63

Hardness: 8
Color: Opaque black
Luster: Vitreous (glassy)

Identified March 18, 2026More mineral →

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Physical properties

Hardness: 8.0 on Mohs scale; Color: Opaque black; Luster: Vitreous (glassy); Crystal Structure: Isometric/Cubic; Cleavage: Indistinct; Specific Gravity: 3.54-3.63

Formation & geological history

Formed through contact metamorphism where magmas intrude into aluminous schists or limestones. The finest specimens are often found in metamorphic marbles or as water-worn pebbles in alluvial deposits.

Uses & applications

Primarily used in jewelry as a faceted gemstone. Due to its high hardness and brilliance, it is a popular, natural alternative to black diamond or black tourmaline.

Geological facts

Black Spinel was historically often mistaken for black diamond or magnetite. It is considered one of the rarest colors of spinel, despite being more affordable than the red or blue varieties.

Field identification & locations

Identified in the field by its high hardness (it cannot be scratched by steel) and lack of magnetism compared to magnetite. Found commonly in Thailand, Sri Lanka, Myanmar, and Tanzania. Collectors look for sharp facet edges and a high polish.