gemstone

Spinel

Magnesium aluminum oxide (MgAl2O4)

Hardness of 8 on the Mohs scale; color ranges from pink, red, blue, purple, to black (this specimen is a vibrant pink); vitreous luster; isometric (cubic) crystal system; octahedral crystal habit; poor or indistinct cleavage; specific gravity around 3.58 - 4.06.

Identified August 3, 2026More gemstone →

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Physical properties

Formation & geological history

Forms primarily in metamorphic environments such as contact-metamorphosed limestones and marbles, as well as in alluvial gravel deposits from weathering of parent rocks.

Uses & applications

Widely used as a gemstone in high-end jewelry due to its brilliance, durability, and wide range of colors; historically famous red spinels were often mistaken for rubies.

Geological facts

Many famous 'rubies' in the crown jewels of various nations, such as the Black Prince's Ruby and the Timur Ruby, are actually large red spinels.

Field identification & locations

Found globally in countries like Myanmar, Sri Lanka, Tanzania, and Vietnam. Identified by its characteristic octahedral crystal shape, hardness, and lack of birefringence as an isometric mineral.