Zoisite This article is about the mineral named zoisite. For the Sailor Moon character, see Shitennou. Zoisite Anyolite (left) & tanzanite General Category Sorosilicate - epidote group Chemical formula Ca2Al3(SiO4)(Si2O7)O(OH) Strunz classification VIII/C.23-100 Dana classification 58.2.1b.1 Identification Color White, gray, greenish brown, greenish gray, pink, blue, purple Crystal habit Crystals flattened in an acicular manner, may be fibrously curved and striated. Massive to columnar Crystal system Orthorhombic - Dipyramidal Cleavage Perfect {010} imperfect {100} Fracture Uneven to conchoidal Mohs Scalehardness 6 to 7 Luster Vitreous, pearly on cleavage surfaces Streak White or colorless Diaphaneity Transparent to translucent Specific gravity 3.10-3.36 Optical properties biaxial positive Refractive index nα = 1..696 - 1.700 nβ = 1.696 - 1.702 nγ = 1.702 - 1.718 Birefringence 0.006-0.018 Pleochroism X = pale pink to red-violet; Y = nearly colorless to bright pink or deep blue; Z = pale yellow to yellow-green References [1][2][3] Major varieties Tanzanite Gem-quality zoisite, blue-purple Thulite Pink Zoisite is a calcium aluminium hydroxy sorosilicate belonging to the epidote group ofminerals. Its chemical formula is Ca2Al3(SiO4)(Si2O7)O(OH). Zoisite is named after theSlovene scientist Baron Sigmund Zois von Edelstein (Žiga Zois), who realized that this was an unknown mineral when it was brought to him by the mineral dealer Simon Prešern, who had discovered it in the Saualpe mountains (Svinška planina) of Carinthia in 1805. Zoisite was first known as saualpite, after its type locality. Zoisite occurs as prismatic, orthorhombic (2/m 2/m 2/m) crystals or in massive form, being found in metamorphic and pegmatitic rock. Zoisite may be blue to violet, green, brown, pink, yellow, gray, or colorless. It has a vitreous luster and a conchoidal to uneven fracture. When euhedral, zoisite crystals are striated parallel to the principal axis (c-axis). Also parallel to the principal axis is one direction of perfect cleavage. Zoisite is somewhat higher than 6 inhardness and its specific gravity is between 3.10 - 3.38, depending on the variety. Zoisite streaks white and is said to be brittle. Clinozoisite is a more common monoclinic polymorph of zoisite. Transparent material is fashioned into gemstones while translucent-to-opaque material is usually carved. A metamorphic rock known as anyolite consists of green zoisite with blacktschermakite and ruby crystals.[4][5] Sources of zoisite include Tanzania (tanzanite), Kenya (anyolite), Norway (thulite),Switzerland, Austria, India, Pakistan, and Washington in the USA.