Zoisite

Mineral formula: Ca₂Al₃[Si₂O₇][SiO₄]O(OH) ; dimorph of clinozoisite

Crystal system: orthorhombic

Crystal habit: Prismatic crystals, columnar to compact, massive

Cleavage: perfect on {010} imperfect on {100}

Fracture: irregular / uneven, conchoidal

Color: colorless, purple, greyish-white, white, gray, yellowish-brown, yellow, pink, green

Luster: vitreous, pearly, dull when fine-grained

Diaphaneity: transparent, translucent

Moh’s scale hardness: 6 - 7

Streak: white

Specific gravity: 3.15 – 3.36

Named after: Originally named saualpite for the locality Saualpe in Carinthia, Austria, where it occurs in eclogites. The name zoisite was introduced by A.G. Werner in 1805 to honor Sigmund Zois, Baron von Edelstein (1747-1819), Austrian scholar who financed mineral-collecting expeditions.

Type locality: Prickler Halt, Ladinger Spitze - Speikkogel area, Eberstein, Sankt Veit an der Glan District, Carinthia, Austria

Geological occurrence: Medium grade regionally metamorphosed rocks, eclogites, blueschist facies metamorphic rocks.

Energetic properties: Melody, in her book Love Is In The Earth, says of Zoisite: "Zoisite can provide for decomposition of negativity and for transmutation of the negative energies to positive force-fields...It can also be used to dispel laziness and idleness.  It allows for direct connection, via the mental processes, to the celestials latitudes...this can facilitate advancement in all areas of ones life"

The mineral zoisite occurs in many forms and color. One of the best known is tanzanite; a transparent blue to blue-violet zoisite (colored by vanadium) used as a gem stone. Thulite is an opaque pink zoisite (containing trivalent manganese), also used in jewelry as a pink cabochon and in sculptures.

Zoisite also occurs intergrown with ruby ("Ruby in Zoiste"), also known as anyolite. It is a rock composed of green zoisite, red corundum crystals (ruby) and occasionally black crystals of the amphibole pargasite. Anyolite is used to produce cabochons, tumbled stones, ornamental objects and sculptures, or sold as specimens.

Zoisite and Clinozoisite share the identical chemical composition but have a different crystal structure (dimorphs). Zoisite is the orthorhombic form while clinozoisite is the monoclinic form (and therefore classified in the epidote group). The physical properties of these two distinct minerals are extremely similar and are therefore virtually indistinguishable from each other when in massive form. 

There is no industrial use of zoisite. Most deposits of zoisite are relatively small.

Zoisite has been documented in hundreds of localities. A few of those locales of special interest to mineral collectors include the Arusha district of Tanzania (tanzanite), Kenya (anyolite), Gandegg in Switzerland, Norway (thulite) and the northern areas of Pakistan.  In the United States, thulite deposits found in Taos County, New Mexico, northeastern Washington state and numerous locales in California have attracted the interest of collectors as well.

References:  mindat.org; wikipedia.org; Collector's Guide to the Epidote Group - Robert J Lauf; Love is in the Earth - Melody; and geology.com