mineral

Moonstone

Orthoclase (Potassium Feldspar) - (K,Na)AlSi3O8

Hardness: 6-6.5 on Mohs scale; Color: Colorless, white, or peach with a bluish/white schiller; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Two directions at 90 degrees; Specific gravity: 2.56-2.59

Hardness: 6-6
Color: Colorless, white, or peach with a bluish/white schiller
Luster: Vitreous to pearly

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed from intergrown layers of orthoclase and albite. As the mineral cools, the two minerals separate into stacked layers, creating the 'adularescence' effect. Commonly found in pegmatites and metamorphic rocks of various geological ages.

Uses & applications

Primarily used in jewelry (cabochons, rings, pendants) and for crystal collecting. It is the birthstone for June and highly valued in decorative arts.

Geological facts

The characteristic 'glow' of moonstone is called adularescence, caused by the diffraction of light as it hits thin, alternating layers of feldspar minerals. In ancient Rome, it was believed that moonstone was formed from frozen beams of moonlight.

Field identification & locations

Identify in the field by its pearly luster and floating blue or white internal sheen when rotated under light. Common locations include Sri Lanka, Myanmar, Madagascar, India, and the United States (New Mexico/Virginia).

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