mineral
Prehnite
Prehnite (Ca2Al2Si3O10(OH)2)
Hardness of 6 to 6.5 on the Mohs scale, pale green to yellow-green color, vitreous to pearly luster, crystal system is orthorhombic, distinct cleavage, specific gravity is 2.80 to 2.95.
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Physical properties
Hardness of 6 to 6.5 on the Mohs scale, pale green to yellow-green color, vitreous to pearly luster, crystal system is orthorhombic, distinct cleavage, specific gravity is 2.80 to 2.95.
Formation & geological history
Forms in hydrothermal veins and cavities in mafic volcanic rocks, often associated with zeolites, calcite, and datolite.
Uses & applications
Popular as a gemstone, tumbled stone, and collector mineral specimen, often cut into cabochons.
Geological facts
Prehnite was the first mineral to be named after a military person, having been discovered in South Africa by Hendrik von Prehn in 1783.
Field identification & locations
Can be identified in the field by its characteristic pale translucent apple-green color and botryoidal or tumbled aggregate form, commonly found in South Africa, Australia, and the USA.
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