gemstone

Moonstone

Potassium aluminum silicate (KAlSi3O8)

Hardness: 6-6.5 (Mohs scale); Color: Colorless to white/gray with blue or white schiller; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions.

Hardness: 6-6
Color: Colorless to white/gray with blue or white schiller
Luster: Vitreous to pearly

Identified July 13, 2026More gemstone →

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Physical properties

Hardness: 6-6.5 (Mohs scale); Color: Colorless to white/gray with blue or white schiller; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions.

Formation & geological history

Formed in plutonic igneous rocks (pegmatites) through the intergrowth of orthoclase and albite. As the cooling magma solidifies, the two minerals separate into alternating layers, causing the adularescence effect.

Uses & applications

Primarily used in jewelry (cabochons, beads, rings) and for spiritual or metaphysical collection.

Geological facts

The characteristic blue glow of moonstone is known as adularescence, named after Mt. Adular in Switzerland, an early source of the stone. It is the birthstone for June.

Field identification & locations

Look for the unique billowy internal light (schiller) that moves across the stone's surface as it is rotated. It is commonly found in India, Sri Lanka, Madagascar, and Myanmar.