mineral

Black Spinel

Magnesium Aluminum Oxide (MgAl2O4)

Hardness: 8 (Mohs scale); Color: Black, opaque; Luster: Vitreous (glassy) to submetallic; Crystal system: Isometric (octahedral crystals); Cleavage: None/Indistinct; Specific Gravity: 3.54-3.63

Hardness: 8 (Mohs scale)
Color: Black, opaque
Luster: Vitreous (glassy) to submetallic

Identified April 29, 2026More mineral →

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Physical properties

Hardness: 8 (Mohs scale); Color: Black, opaque; Luster: Vitreous (glassy) to submetallic; Crystal system: Isometric (octahedral crystals); Cleavage: None/Indistinct; Specific Gravity: 3.54-3.63

Formation & geological history

Spinel forms as a metamorphic mineral in limestone/dolomite through contact metamorphism. It is also found as a primary mineral in mafic igneous rocks and as water-worn pebbles in alluvial deposits. They can be hundreds of millions of years old.

Uses & applications

Primarily used in jewelry as a more affordable, durable alternative to black diamonds or black sapphires. It is also highly valued by gemstone collectors.

Geological facts

Black Spinel is known for its intense black color and lack of secondary hues. Historically, spinels were often confused with rubies or sapphires (such as the famous 'Black Prince's Ruby' in the British Crown Jewels, which is actually a red spinel).

Field identification & locations

Identify in the field by its high hardness (it will scratch glass), octahedral crystal shape, and lack of cleavage. Common sources include Thailand, Myanmar, Sri Lanka, and Vietnam.