mineral

Black Spinel

Magnesium Aluminum Oxide (MgAl2O4)

Hardness: 8.0 on Mohs scale. Color: Jet black, opaque. Luster: Vitreous (glassy) to splendent. Crystal structure: Isometric/Cubic. Cleavage: Indistinct. Specific gravity: 3.6 - 4.1.

Hardness: 8
Color: Jet black, opaque
Luster: Vitreous (glassy) to splendent

Identified March 10, 2026More mineral →

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Physical properties

Hardness: 8.0 on Mohs scale. Color: Jet black, opaque. Luster: Vitreous (glassy) to splendent. Crystal structure: Isometric/Cubic. Cleavage: Indistinct. Specific gravity: 3.6 - 4.1.

Formation & geological history

Formed in metamorphic rocks such as marble or as a primary mineral in mafic igneous rocks. It is often found in alluvial deposits. They can be hundreds of millions of years old based on the host rock's metamorphic history.

Uses & applications

Primarily used in jewelry as a durable and affordable alternative to black diamonds or black sapphires. It is also a sought-after specimen for mineral collectors due to its high luster.

Geological facts

Black spinel is often referred to as the 'great impostor' of the gem world because it was historically mistaken for other stones (like the 'Black Prince's Ruby' in the British Crown Jewels, which is actually red spinel). The black variety is completely natural and rarely requires treatment to achieve its deep color.

Field identification & locations

Identify in the field by its high hardness (it will scratch glass and quartz) and lack of magnetism (unlike magnetite). Commonly found in Myanmar, Sri Lanka, and Thailand. For collectors, look for well-defined octahedral crystals.