gemstone

Black spinel bead strand

Spinel, magnesium aluminum oxide (MgAl₂O₄)

AI-generated identification · may be incorrect

Likely faceted, polished black spinel beads; hardness 7.5–8 Mohs, vitreous luster, typically opaque to translucent, cubic crystal structure, no cleavage, and specific gravity about 3.5–4.1. The dark appearance may also represent treated or imitation material, which cannot be confirmed visually.

Identified September 20, 2026More gemstone →

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Physical properties

Formation & geological history

Natural spinel forms in metamorphic marble and aluminous rocks, commonly during regional metamorphism; gem-quality deposits occur in Myanmar, Sri Lanka, Vietnam, Tanzania, and Madagascar. Geological ages vary by deposit, often from Precambrian to younger metamorphic events.

Uses & applications

Used for jewelry, beads, cabochons, and ornamental carving; black spinel is a durable, relatively affordable gemstone. It is not generally used as a construction stone.

Geological facts

Spinel is an oxide mineral and a frequent ruby and sapphire-associated mineral; its name derives from the Latin spina, meaning “thorn,” referring to sharp crystal forms. Black spinel can resemble black diamond, obsidian, or synthetic glass.

Field identification & locations

Field identification requires hardness testing, loupe examination, and ideally refractive-index or specific-gravity testing; natural spinel commonly shows octahedral crystals, while beads are machine-faceted. Common sources include Southeast Asia, East Africa, and Sri Lanka.