mineral

Moonstone

Orthoclase (Potassium aluminum silicate - KAlSi3O8)

AI-generated identification · may be incorrect

Hardness: 6-6.5 (Mohs scale); Color: White, cream, or blue-ish with a pearly or opalescent sheen (adularescence); Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56-2.59

Hardness: 6-6
Luster: Vitreous to pearly

Identified March 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the cooling and slow separation of two different types of feldspar (orthoclase and albite) within igneous rocks like pegmatites. This internal layering causes light to scatter, creating the stone's characteristic glow.

Uses & applications

Primarily used as a gemstone in jewelry (cabochons, rings, earrings) and as a popular specimen for crystal healing and mineral collectors.

Geological facts

Ancient Romans believed moonstones were formed from frozen moonbeams. It is the Florida State Gemstone (commemorating the Apollo moon landings) despite not being naturally occurring in the state.

Field identification & locations

Identify by its 'adularescence' (a glowing interior shine when tilted). It is commonly found in Sri Lanka, India, Myanmar, and Madagascar. In the field, look for a perthitic texture and the characteristic pearly sheen on cleavage planes.