mineral

Polished brown moonstone (likely feldspar)

Orthoclase or plagioclase feldspar, approximately KAlSi₃O₈ or NaAlSi₃O₈–CaAl₂Si₂O₈

AI-generated identification · may be incorrect

Tumbled, opaque-to-translucent brown feldspar with dark inclusions; Mohs hardness about 6, vitreous to pearly luster, monoclinic or triclinic crystals, and two cleavage directions. Identification is tentative from the photograph; the visible banding is not enough to confirm moonstone.

Identified October 16, 2026More mineral →

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Physical properties

Formation & geological history

Feldspar crystallizes in igneous and metamorphic rocks; moonstone’s shimmer typically results from fine intergrowths formed during cooling. Such rocks span a wide range of geological ages.

Uses & applications

Used as a decorative or lapidary stone in cabochons, beads, and inexpensive jewelry; feldspar is also an important industrial mineral in ceramics and glass.

Geological facts

Moonstone’s characteristic sheen, called adularescence, is usually strongest as a moving blue or white glow; this specimen does not show a clear glow in the image.

Field identification & locations

Common sources include India, Sri Lanka, Madagascar, and Myanmar. Check for feldspar-like cleavage and, under a moving light, a floating sheen; dark material may be inclusions. A small tumbled piece typically sells for about $2–$15 USD.