mineral

Moonstone

Orthoclase (Potassium aluminum silicate - KAlSi3O8)

Hardness: 6.0-6.5 (Mohs), Color: Colorless to white with a blue or white adularescence (sheen), Luster: Vitreous to pearly, Crystal Structure: Monoclinic, Cleavage: Two directions at 90 degrees, Specific Gravity: 2.56-2.59

Hardness: 6

Identified March 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks. The characteristic 'glow' (adularescence) is caused by the intergrowth of two types of feldspar (orthoclase and albite) that separate as the mineral cools, causing light to scatter.

Uses & applications

Primarily used as a gemstone in jewelry (rings, pendants, earrings) and for crystal healing/collecting. High-quality specimens with strong blue sheen are highly sought after by lapidaries.

Geological facts

Ancient Romans believed moonstone was formed from frozen beams of moonlight. It is the Florida State Gemstone (commemorating the Moon landings) even though it is not naturally found there.

Field identification & locations

Identify by its distinctive 'billowy' light that moves across the surface as the stone is turned. It is commonly found in Sri Lanka, India, Madagascar, and Myanmar. In the field, look for feldspar-rich pegmatites.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

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Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral