mineral

Black Spinel

Magnesium Aluminum Oxide (MgAl2O4)

Hardness: 8.0 on Mohs scale; Color: Jet black, opaque; Luster: Vitreous (glassy) to sub-metallic; Crystal structure: Isometric (cubic); Cleavage: Indistinct; Specific Gravity: 3.54 - 3.63

Hardness: 8
Color: Jet black, opaque
Luster: Vitreous (glassy) to sub-metallic

Identified January 23, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 8.0 on Mohs scale; Color: Jet black, opaque; Luster: Vitreous (glassy) to sub-metallic; Crystal structure: Isometric (cubic); Cleavage: Indistinct; Specific Gravity: 3.54 - 3.63

Formation & geological history

Formed through regional or contact metamorphism of limestone and dolostones. Often found in magnesium-rich igneous rocks and as water-worn pebbles in alluvial deposits. Age varies by deposit but found in Precambrian to Cenozoic formations.

Uses & applications

Primarily used as a gemstone in high-end and fashion jewelry due to its high hardness and brilliant luster. Often used as an affordable alternative to black diamond or black sapphire.

Geological facts

Black spinel is often referred to as 'the great imposter' because it was historically mistaken for other stones. It is one of the few natural gemstones that occurs in a true black color without treatment.

Field identification & locations

Identify in the field by its high hardness (it will scratch glass and quartz) and lack of magnetism compared to magnetite. Commonly located in Sri Lanka, Thailand, Cambodia, and Myanmar. For collectors, look for its characteristic octahedral crystal shape.