Zoisite
Gemstone
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Zoisite, first known as saualpite, after its type locality, is a calcium aluminum hydroxy sorosilicate belonging to the epidote group of minerals. Its chemical formula is Ca₂Al₃O(OH).
Zoisite occurs as prismatic, orthorhombic crystals or in... Wikipedia
Chemical formula: Ca₂Al₃(SiO₄)₃(OH)
Hardness (Mohs hardness scale): 6 – 6.5
Refractive index: 1.69 – 1.7
Mohs scale: 6 to 7
Birefringence: 0.006–0.018
Category: Sorosilicate – epidote group