mineral

Moonstone

Orthoclase (KAlSi3O8) with inclusions of Albite (NaAlSi3O8)

Hardness: 6.0-6.5 Mohs scale; Color: Opalescent white, colorless, or grey; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56-2.59. It exhibits 'adularescence', a unique blue or white sheen.

Hardness: 6
Color: Opalescent white, colorless, or grey
Luster: Vitreous to pearly

Identified March 1, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic environments. It is a member of the feldspar group, specifically where two species of feldspar (orthoclase and albite) intergrow during cooling, creating thin alternating layers that scatter light.

Uses & applications

Primarily used in jewelry for rings, earrings, and pendants; it is also a popular specimen for gemstone collectors due to its optical effects.

Geological facts

Ancient Romans and Greeks believed moonstone was created from solidified rays of the moon. It is the Florida State Gemstone (commemorating the Moon landing) and a birthstone for June.

Field identification & locations

Identify in the field by its distinct adularescence (a 'billing' or floating light effect) and typical monoclinic feldspar cleavage. Found commonly in Sri Lanka, Myanmar, India, and Madagascar.

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