mineral

Black Spinel

Magnesium Aluminum Oxide (MgAl2O4)

Hardness: 8.0 on Mohs scale; Color: Jet black, opaque; Luster: Vitreous to sub-adamantine; Crystal Structure: Isometric/Cubic (often octahedrons); Cleavage: Indistinct; Specific Gravity: 3.54-3.63.

Hardness: 8
Color: Jet black, opaque
Luster: Vitreous to sub-adamantine

Identified June 29, 2026More mineral →

Explore Black Spinel in the encyclopedia →

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 to sub-adamantine; Crystal Structure: Isometric/Cubic (often octahedrons); Cleavage: Indistinct; Specific Gravity: 3.54-3.63.

Formation & geological history

Formed through contact metamorphism where magmatic intrusions interact with limestone or dolomite. Also found in igneous rocks like basalt. These are often primary deposits or found as water-worn pebbles in alluvial deposits.

Uses & applications

Primarily used in jewelry as a more affordable, durable alternative to black diamonds or black sapphires. Used in faceted stones, beads, and cabochons.

Geological facts

Black spinel is often called the 'Master of Re-energization'. It was historically confused with black tourmaline or onyx, but its superior hardness and brilliance distinguish it as a high-quality gemstone.

Field identification & locations

Identify in the field by its high hardness (it will scratch glass and quartz) and its lack of perfect cleavage. Commonly found in Thailand, Sri Lanka, Myanmar, and Australia.