mineral

Moonstone

Orthoclase (KAlSi3O8), a variety of potassium feldspar

Hardness: 6-6.5 (Mohs scale), Color: Colorless to white/bluish-white, Luster: Vitreous to pearly, Crystal Structure: Monoclinic, Cleavage: Perfect in two directions, Specific Gravity: 2.56-2.59

Hardness: 6-6

Identified February 15, 2026More mineral →

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Physical properties

Hardness: 6-6.5 (Mohs scale), Color: Colorless to white/bluish-white, Luster: Vitreous to pearly, Crystal Structure: Monoclinic, Cleavage: Perfect in two directions, Specific Gravity: 2.56-2.59

Formation & geological history

Formed from intergrowths of orthoclase and albite. As the cooling occurs after formation in igneous environments (mostly pegmatites), the two feldspars separate into stacked layers, creating the optical effect known as adularescence.

Uses & applications

Primarily used in jewelry as gemstones (cabochons), talismans, and as a popular specimen for collectors due to its unique optical properties.

Geological facts

Moonstone is the state gem of Florida to commemorate the moon landing, despite not being found on the moon. It has been used in jewelry since ancient Roman times and was highly popular during the Art Nouveau period.

Field identification & locations

Identify in the field by its distinct adularescence (a milky blue or white sheen that glows from within). It is commonly found in Sri Lanka, India, Myanmar, and Madagascar. Look for the 'shiller' effect when rotated under light.

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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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