mineral
Moonstone
Orthoclase (KAlSi3O8) with Albite inclusions
Hardness: 6-6.5 Mohs. Color: White or grayish with a pearly or opalescent adularescence. Luster: Vitreous to pearly. Crystal structure: Monoclinic. Specific gravity: 2.56-2.59.
- Hardness
- 6-6
- Color
- White or grayish with a pearly or opalescent adularescence
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-6.5 Mohs. Color: White or grayish with a pearly or opalescent adularescence. Luster: Vitreous to pearly. Crystal structure: Monoclinic. Specific gravity: 2.56-2.59.
Formation & geological history
Formed in igneous pegmatites and metamorphic rocks. The characteristic sheen (adularescence) is caused by the intergrowth of two types of feldspar (orthoclase and albite) that separate as the magma cools, creating thin layers that scatter light.
Uses & applications
Primarily used in jewelry as a gemstone, especially in rings, pendants, and earrings. It is also a popular collector's mineral and used in metaphysical practices.
Geological facts
The Roman historian Pliny the Elder wrote that moonstone's appearance changed with the phases of the moon. It was highly popular during the Art Nouveau period and is the Florida State Gemstone (commemorating the Apollo moon landings).
Field identification & locations
Identify by the billowy blue or white light (adularescence) that moves across the surface when rotated. Found commonly in Sri Lanka, India, Myanmar, and Madagascar. Look for the characteristic pearly sheen in feldspar-rich areas.
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