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An epidote type mineral used as an ornamental stone. Zoisite was named for Baron Zois van Edelstein (1747-1819). It is a lustrous transparent to translucent stone whose color may be grayish-white, peach, pink (thulite), blue (tanzanite) or green. Zoisite has been quarried in Tanzania, Austria, Switzerland, Norway (Telemark), Italy (Piedmont), Germany, Scotland, Mexico and the U.S.(Tennessee, Massachusetts, Pennsylvania).

Synonyms and Related Terms

thulite (pink); tanzanite (blue); zoisita (Esp.); zoisyt (Pol.); zoisite (Port.); Zoisit (Deut.); zoisiet (Ned.)

Other Properties

Orthorhombic system with long, striated, prismatic crystals. Cleavage is very good lengthwise.

Luster = vitreous to pearly. Streak = white. Fracture = uneven to conchoidal.

Fluorescent, especially thulite.

Composition Ca2(AlOH)Al2(SiO4)3
Mohs Hardness 6.0 - 6.5
Density 3.25-3.37
Refractive Index 1.685 - 1.725

Additional Information

Mineralogy Database: Zoisite

Sources Checked for Data in Record

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 435
  • Encyclopedia Britannica, http://www.britannica.com Comment: "zoisite" Encyclopædia Britannica [Accessed December 11, 2001]. (color photo)(tech info)
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979

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