gemstone
Moonstone
Orthoclase Feldspar ((K,Na)AlSi3O8)
Hardness: 6-6.5 Mohs; Color: Colorless to white with blue/white adularescence; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions
- Hardness
- 6-6
- Color
- Colorless to white with blue/white adularescence
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-6.5 Mohs; Color: Colorless to white with blue/white adularescence; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions
Formation & geological history
Formed in igneous and metamorphic rocks when two types of feldspar intergrow. As the magma cools, the two minerals separate into stacked layers, creating the light-scattering effect.
Uses & applications
Primarily used in jewelry (cabochons, rings, pendants) and as a birthstone for June. Also popular in metaphysical collections.
Geological facts
The optical phenomenon 'adularescence' is caused by light scattering between microscopic layers of albite and orthoclase. It is the state gem of Florida to commemorate the moon landing.
Field identification & locations
Look for a milky white appearance that displays a shimmering blue or white 'glow' when rotated under light. High-quality specimens are found in Sri Lanka, Myanmar, and Madagascar.
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