mineral

Moonstone

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

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

Hardness: 6
Luster: Vitreous to pearly

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous or metamorphic environments where alternating layers of orthoclase and albite feldspar precipitate out of a cooling magma or during recrystallization. These layers create the light-scattering effect known as adularescence.

Uses & applications

Primarily used in jewelry as a gemstone, particularly in cabochon cuts. Also popular as a healing crystal, collector's specimen, and the state gem of Florida (to commemorate the moon landing).

Geological facts

Moonstone has been used in jewelry for centuries, including by the Romans who believed it was born from solidified rays of the moon. It was highly popular during the Art Nouveau period with designers like René Lalique.

Field identification & locations

Identify by its 'glow' or shimmer that moves across the stone as it is turned. Common locations include Sri Lanka (best quality), India, Myanmar, Madagascar, and parts of the United States. Collectors should look for even color distribution and transparency.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

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

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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)

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