Formula: (CaCa)(AlAlAl)O[Si2O7][SiO4](OH)

Colour: Colourless, purple, greyish-white, grey, yellowish-brown, yellow, pink, green

Lustre: Vitreous, Pearly

Hardness: 6 – 7

Specific Gravity: 3.15 – 3.36

Crystal System: Orthorhombic

Name: Originally named saualpite for the locality Saualpe in Carinthia, Austria, where it occurs in eclogites. The name zoisite was introduced by A.G. Werner in 1805 to honour Sigmund Zois, Baron von Edelstein (1747-1819), Austrian scholar who financed mineral-collecting expeditions. It was from Baron Zois that Werner obtained the holotype specimen from Saualpe (found by mineral dealer Simon Prešern in 1804).

Type Locality: Prickler Halt, Eberstein, Sankt Veit an der Glan District, Carinthia, Austria

Dimorph of: Clinozoisite

Zoisite is a calcium aluminum silicate hydroxide. It is characteristic of regional metamorphisms and of hydrothermal alterations of igneous rocks. It is also found in quartz veins and pegmatite. Formerly assigned to the Epidote Group. Since Zoisite is the orthorhombic polymorph of Clinozoisite, zoisite is no longer considered a member of this group, according to the new nomenclature of the Epidote Supergroup.  Tanzanite is the dark blue variety of zoisite, colored by vanadium, sometimes mistaken for sapphire. A massive pinkish-red variety is called thulite.