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 (Tanzanite), 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.