mineral
Moonstone (Grey)
Feldspar (variety Orthoclase/Adularia) with the formula (K,Na)AlSi3O8
Hardness: 6-6.5 on Mohs scale; Color: Greyish-white with subtle adularescence (sheen); Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions.
- Hardness
- 6-6
- Color
- Greyish-white with subtle adularescence (sheen)
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-6.5 on Mohs scale; Color: Greyish-white with subtle adularescence (sheen); Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions.
Formation & geological history
Formed in igneous and metamorphic rocks, specifically within pegmatites and hydrothermal veins. The shimmering effect is caused by the intergrowth of two types of feldspar that separate as the mineral cools.
Uses & applications
Primarily used in jewelry for beads, cabochons, and decorative carvings. It is highlly valued as a birthstone and for metaphysical collections.
Geological facts
The optical phenomenon shown in moonstone is called adularescence, which occurs when light scatters between internal layers of orthoclase and albite. It has been used in jewelry since ancient civilizations, including the Romans and Greeks.
Field identification & locations
Identified by its distinctive internal glow or 'sheen' when rotated under light. Found commonly in Sri Lanka, India, and Madagascar. Surfaces of moonstone are prone to scratching, so it should be handled with care.
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Schist
Schist
Metamorphic
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
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Mineral/Rock