Zoisite is named for the famed collector Sigmund Zois. Discovered in Austria in 1805 in the Sau-Alp mountains, zoisite was not always considered gem material. A green specimen with hornblende inclusions and, more importantly, large opaque ruby inclusions, was discovered in 1954 making zoisite interesting for ornamental objects and some gem usage.
A major variety of zoisite is tanzanite, a blue or violet colored gem, discovered in 1967.
Another variety of zoisite is Thulite, an opaque red stone often confused with rhodonite.
|Gemological Information for Zoisite|
|Color||Blue to Violet, Brown, Green-Yellow and Pink|
|Refractive Index||1.691 to 1.700|
|Durability||Fair to Poor|
|Hardness||6 to 7|
|Similar Stones||Rhodonite, Hydrogrossular Garnet, Sapphire, Benitoite, Spinel, Iolite|
|Country of Origin||Tanzania, Austria, Germany, Italy, Mexico, Switzerland, U.S.|
|Warm Soapy Water||Safe|
|Chemical Attack||Hydrochloric and Hydrofluoric Acids Attack|
|Heat Sensitivity||Jeweler's Torch may Fuse|
Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 262-264.
Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 160.