Mineral

Moonstone

Adularia (orthoclase) or Albite (plagioclase), a potassium aluminum silicate of the feldspar group

AI-generated identification · may be incorrect

Hardness: 6-6.5 on Mohs scale. Color: Typically white, gray, blue-white, or peach with a characteristic adularescence (a shimmering, billowy light effect). Luster: Vitreous to pearly. Crystal Structure: Monoclinic (orthoclase) or Triclinic (albite). Cleavage: Two distinct cleavage directions at nearly 90 degrees.…

Hardness: 6-6
Luster: Vitreous to pearly

Identified September 27, 2025More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, particularly pegmatites and some hydrothermal veins. The adularescence is caused by the intergrowth of two different feldspar species (orthoclase and albite) at a microscopic level, creating a lamellar structure that scatters light. Geological Age: Varies depending on geological formation.

Uses & applications

Primarily used as a gemstone in jewelry, especially cabochons to best display its adularescence. It is also collected by mineral enthusiasts.

Geological facts

Moonstone is famous for its unique optical phenomenon called 'adularescence,' which appears as a milky, bluish sheen that seems to float just beneath the surface of the stone. It has been associated with lunar deities and mystical properties for centuries. The most prized moonstones show a strong blue sheen over a colorless body.

Field identification & locations

To identify in the field, look for its distinctive adularescence and pearly luster. It's often found in granular or lamellar masses within feldspar-rich rocks. Common locations include Sri Lanka, India, Myanmar, Madagascar, the USA (Pennsylvania, Virginia), and Brazil. Collectors look for specimens with strong adularescence and clarity. Distinguishing it from other similar-looking minerals like opals can be done by checking its hardness and cleavage. Opal has no cleavage and a different optical effect (play-of-color or opalescence).

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