Zoisite

Tanzanite bracelet

Description

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.)

IR spectrum of zoisite from RRUFF

Raman spectrum of zoisite from RRUFF

Physical and Chemical Properties

• Orthorhombic system with long, striated, prismatic crystals
• Cleavage is very good lengthwise
• Luster = vitreous to pearly
• Streak = white
• Fracture = uneven to conchoidal
• Birefringence = 0.008 - 0.013
• Fluorescent, especially thulite
• Pleochroism = Strong; usually blue, purplish red and greenish yellow

Composition	Ca2(AlOH)Al2(SiO4)3
Mohs Hardness	6.0 - 6.5
Density	3.25-3.37 g/ml
Refractive Index	1.685 - 1.725
Birefringence	0.006 - 0.018

Resources and Citations

• Gem Identification Lab Manual, Gemological Institute of America, 2016.
• Mineralogy Database: Zoisite
• G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 435
• Encyclopedia Britannica, http://www.britannica.com Comment: "zoisite" [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
• Wikipedia: http://en.wikipedia.org/wiki/Zoisite (Accessed Mar. 1, 2006)