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This article is about the mineral named zoisite. For the Sailor Moon character, see Shitennou.

Anyolite (left) & tanzanite
CategorySilicate mineral
Chemical formulaCa2Al3(SiO4)(Si2O7)O(OH)
ColorGray, yellow, blue, green.
Crystal habitCrystals flattened in an acicular manner, may be fibrously curved
Crystal systemOrthorhombic
CleavagePerfect {010} imperfect {100}
FractureUneven to conchoidal
Mohs Scale hardness6.5
LusterVitreous, pearly on cleavage surfaces
Refractive index1.69-1.70
Optical Propertiesbiaxial positive
PleochroismPresent, dichroism or trichroism depending on color.
StreakWhite or colorless
Specific gravity3.10-3.38
Major varieties
tanzaniteGem-quality zoisite, blue-purple
anyoliteOften found intergrown with ruby
chrome zoisiteGreen, uncommon

Zoisite is a calcium aluminium hydroxy sorosilicate belonging to the epidote group of minerals. Its chemical formula is Ca2Al3(SiO4)(Si2O7)O(OH). Zoisite is named after the Slovene 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. Transparent material is fashioned into gemstones while translucent-to-opaque material is usually carved into sculptural works. The latter is sometimes shot through with ruby crystals, which are completely opaque and unsuited to use as gems, yet are well colored and contrast strikingly against the green matrix of the zoisite.

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 in hardness 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.

Sources of zoisite include Tanzania (tanzanite), Kenya (anyolite), Norway (thulite), Switzerland, Austria, India, Pakistan, and Washington in the USA.

See also


  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7
  • Mineral Handbook, 2001, Mineral Data Publishing
  • Webmineral data
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Zoisite". A list of authors is available in Wikipedia.
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