mineral

Moonstone

Orthoclase (KAlSi3O8) or Albite (NaAlSi3O8)

Hardness: 6-6.5 on Mohs scale; Color: Milky white to translucent with a blue or white internal sheen; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56-2.59

Hardness: 6-6
Luster: Vitreous to pearly

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in plutonic igneous rocks (pegmatites) through the cooling of magma. As it cools, the intergrowth of orthoclase and albite separates into stacked layers, creating its signature optical effect.

Uses & applications

Primary use is in the jewelry industry as a semi-precious gemstone. It is also used by collectors and in metaphysical practices.

Geological facts

The visual phenomenon seen in moonstone is called 'adularescence,' caused by light scattering between microscopic layers of different feldspars. It is the Florida State Gemstone (commemorating the Moon landing) and is associated with June birthdays.

Field identification & locations

Identify by its characteristic billowy light effect (schiller) when rotated. Found commonly in Sri Lanka, India, Myanmar, and Madagascar. In the field, look for a pearly luster and a distinct 'stair-step' cleavage pattern characteristic of feldspars.

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