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Zoisite

Originally named saualpite for the locality Saualpe in Carinthia, Austria, where it occurs in eclogites (mafic metamorphic rock). The name zoisite was introduced in 1805 to honor Sigmund Zois, an  Austrian scholar who financed mineral-collecting expeditions. 

ï   Mineral: Zoisite

ï   Chemistry: Ca2Al3[Si2O7][SiO4]O(OH)  common impurities Fe,Mn,Mg,Cr,Ti,Ca,Na,V,Sr,H2O

ï   Class: Sorosilicate 

ï   Crystal system: Orthorhombic

ï   Color: Colorless, greyish-white, grey, yellowish-brown, yellow, pink, green, greenish brown, 

greenish gray, pink, blue, purple

ï   Refractive index:  1.696 to 1.718

ï   Luster: Vitreous, pearly on cleavage surfaces

ï   Specific gravity: 3.15 - 3.36

ï   Mohs Hardness: 6 - 7

ï   Cleavage: Perfect {010} imperfect {100}

ï   Fracture: Irregular/Uneven, Conchoidal

There are several varieties of Zoisite - Tanzanite, Thulite and Anyolite.  Tanzanite is probably the best known being 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.  Anyolite is better known as "Ruby in Zoiste".  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.  


Ruby in fuchsite can be mistaken for ruby in zoisite.  The fuchsite is also a green mineral only much softer (2-3) and typically lighter in coloration then zoisite.  Additionally, the ruby in fuchsite can exhibit blue kyanite alteration rims around the ruby crystals, which does not occur with the ruby in zoisite. 

Zoisite can occur as prismatic orthorhombic crystals or in massive form.  Euhedral crystals are striated parallel to the principal axis (c-axis).  Zoisite is fairly common in regionally metamorphosed calcareous shales and sandstones, and in amphibolites resulting from the regional metamorphosis of basic igneous rocks.  It is also occasionally found in low-grade thermally metamorphosed impure limestone and skarns.  Hydrothermal alteration of calcium-rich plagioclase (sassuritization) can also form zoisite.


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.

Some of the locales from which specimens of Zoisite (including Anyolite, Tanzanite & Thulite) are available at Taos Rockers include:

New Mexico

India 

Kenya

Tanzania


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"






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

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