mineral

Moonstone

Orthoclase Feldspar (formula: (K,Na)AlSi3O8)

Hardness: 6.0–6.5 on the Mohs scale; Color: Colorless to white with a blue or white schiller; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56–2.59

Hardness: 6
Color: Colorless to white with a blue or white schiller
Luster: Vitreous to pearly

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks. Its unique adularescence is caused by the intergrowth of two types of feldspar (orthoclase and albite) that separate into thin, alternating layers as the mineral cools.

Uses & applications

Primarily used in jewelry as a gemstone, typically cut into cabochons to enhance its optical effects. It is also a popular collector's mineral.

Geological facts

Moonstone is the Florida State Gemstone (to commemorate the moon landing) despite not being found there naturally. It is the birthstone for June and has been used in jewelry since ancient civilizations, who believed it was made of solidified moonbeams.

Field identification & locations

Identify by its 'adularescence'—a milky, bluish glow that appears to move across the surface as the stone is turned. It is commonly found in Sri Lanka, India, Myanmar, and Madagascar. In the field, look for feldspar crystals with a pearly luster and internal flashes.

Other mineral specimens

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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)

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