gemstone

Moonstone

Orthoclase feldspar (potassium aluminum silicate, KAlSi3O8)

Mohs hardness: 6.0-6.5; Color: White, colorless, gray, peach, blue adularescence; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56-2.58

Hardness: 6
Color: White, colorless, gray, peach, blue adularescence
Luster: Vitreous to pearly

Identified August 2, 2026More gemstone →

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Physical properties

Formation & geological history

Formed within igneous rocks like granites and syenites, as well as in pegmatites and metamorphic rocks, through the cooling and exsolution of alternating layers of orthoclase and albite.

Uses & applications

Primarily used in jewelry, such as rings, necklaces, and earrings, as a popular lapidary gemstone.

Geological facts

Moonstone exhibits a unique optical phenomenon called adularescence, which is a billowy, moonlight-like sheen caused by light scattering between microscopic layers of different feldspars.

Field identification & locations

Identified by its characteristic floating blue or white sheen under light. Commonly found in Sri Lanka, India, Madagascar, Myanmar, and the United States.

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