mineral

Moonstone

Orthoclase Feldspar (composed of alternate layers of orthoclase and albite), (K,Na)AlSi3O8

Hardness: 6.0-6.5 on Mohs scale; Color: Colorless to white/bluish with a milky sheen; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56-2.59

Hardness: 6
Color: Colorless to white/bluish with a milky sheen
Luster: Vitreous to pearly

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed from molten rock (magma) that cools slowly. As it cools, the intergrowth of orthoclase and albite separate into stacked layers, which causes the light to scatter, creating the 'adularescence' effect. It is typically found in pegmatites and metamorphic rocks worldwide.

Uses & applications

Primarily used as a gemstone in jewelry (rings, pendants, earrings). It is also highly valued by mineral collectors for specimens showing strong blue or rainbow schiller.

Geological facts

The shimmering light effect is called adularescence, named after Mt. Adular in Switzerland, a famous source for the stone. It was once believed by the Romans to be formed from frozen beams of moonlight.

Field identification & locations

Identify in the field by its distinct pearly luster and floating blue or white light as the stone is turned (adularescence). It is commonly found in Sri Lanka, India, Myanmar, and Madagascar. For collectors, look for high transparency and a strong blue sheen.

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)]

mineral

Epidote

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

mineral