mineral

Moonstone (Feldspar)

Orthoclase/Albite ((K,Na)AlSi3O8)

Hardness: 6-6.5 Mohs scale; Color: Milky white to translucent with a blue or pearly sheen; Luster: Vitreous to pearly; Crystal Structure: Monoclinic/Triclinic; Cleavage: Two perfect directions at nearly 90 degrees; Specific Gravity: 2.56-2.59

Hardness: 6-6
Color: Milky white to translucent with a blue or pearly sheen
Luster: Vitreous to pearly

Identified March 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the cooling of underground magma. As the magma cools, two types of feldspar (orthoclase and albite) intermix. As the mineral cools further, these two separate into thin, alternating layers, causing light to scatter (adularescence). Found in pegmatites and metamorphic rocks.

Uses & applications

Primarily used in jewelry (cabochons) and as a birthstone (June). Highly valued by gemstone collectors for its unique optical effects.

Geological facts

The shimmering light effect is called adularescence. In ancient Rome, it was believed moonstone was formed from solidified beams of moonlight. It is the state gem of Florida to commemorate the moon landings, despite not actually being found there naturally.

Field identification & locations

Identify in the field by the distinct billowy blue or white light floating across the surface when tilted. Common locations include Sri Lanka, India, Myanmar, Madagascar, and parts of the United States like New Mexico and Virginia.

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