Ruby in Zoisite Specimen.
Ruby in Zoisite Specimen.

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.

Gemological Information for Zoisite

Color:Blue to Violet, Brown, Green-Yellow and Pink
Crystal Structure:Orthorhombic
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

Zoisite Care

Ultrasonic Cleaning:Never
Steam Cleaning:Never
Warm Soapy Water:Safe
Chemical Attack:Hydrochloric and Hydrofluoric Acids Attack
Light Sensitivity:Stable
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.
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