mineral

Moonstone (Feldspar)

Orthoclase (KAlSi3O8) or Albite (NaAlSi3O8)

Hardness: 6.0–6.5 (Mohs scale); Color: Colorless to white, gray, or peach with blue/white adularescence; Luster: Vitreous to pearly; Crystal structure: Monoclinic or Triclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56–2.59

Hardness: 6
Luster: Vitreous to pearly

Identified March 30, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic environments, specifically within pegmatites. The characteristic 'glow' (adularescence) is caused by the intergrowth of two types of feldspar that separate as the mineral cools.

Uses & applications

Primarily used as a gemstone in jewelry (cabochons, beads) and highly valued by mineral collectors for its optical effects.

Geological facts

Ancient Romans believed moonstones were formed from frozen rays of moonlight. It is the Florida State Gemstone, designated to commemorate the Moon landings, despite not being naturally found there.

Field identification & locations

Identify by its 'adularescence' (a billowy light effect across the surface) and two-directional cleavage. Common locations include Sri Lanka, India, Myanmar, and Madagascar. In the field, look for glassy luster and the specific play of light.

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