mineral
Black Moonstone
Potassium Aluminum Silicate (KAlSi3O8)
Hardness: 6-6.5 (Mohs scale), Color: Dark grey to black with silver/white chatoyancy, Luster: Vitreous to pearly, Crystal Structure: Monoclinic, Cleavage: Two directions at 90 degrees
- Hardness
- 6-6
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Physical properties
Hardness: 6-6.5 (Mohs scale), Color: Dark grey to black with silver/white chatoyancy, Luster: Vitreous to pearly, Crystal Structure: Monoclinic, Cleavage: Two directions at 90 degrees
Formation & geological history
Formed in plutonic and metamorphic rocks from the cooling of magma. As it cools, the intergrowth of orthoclase and albite creates the characteristic schiller effect (adularescence).
Uses & applications
Primarily used in jewelry as cabochons, beads, and tumbled stones for collectors; also highly popular in metaphysical and spiritual practices.
Geological facts
Black Moonstone is a variety of Feldspar. While traditional moonstone is white/blue, this dark variety contains inclusions of ilmenite or other minerals that give it its dark hue and silvery flash.
Field identification & locations
Identify by its dark color combined with a silver-grey flash that moves as the stone is turned. Commonly sourced from Madagascar and India. Look for the 'shiller' effect under a single light source.
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Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
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