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Flawless Topaz Crystal

The Mineral topaz




Topaz is a well-known mineral, occurring in large and beautifully shaped and colored crystals. It naturally occurs in many colors, but rarely in pink, purple, and deep blue. Those colors are formed from lighter-colored stones that undergo irradiation and heat treatment. Topaz from certain localities may also turn pink or colorless upon heating. The color of some Topaz specimens, namely those from Siberia, fade upon prolonged exposure to light.

Topaz crystals in a matrix are rare and very much desired, since the perfect basal cleavage of Topaz causes it to separate from its base and form loose crystals. Precautions must be taken not to damage specimens, for pressure or improper faceting can cause a crystal to cleave and become ruined.

For additional information, see the gemstone section on Topaz.
Chemical Formula Al2SiO4(F,OH)2
Composition Aluminum fluoro-hydroxyl-silicate
Color Colorless, white, yellow, orange, brown, pink, light purple, gray, light blue, greenish blue, green. Occasionally multicolored.
Streak Colorless
Hardness 8
Crystal System Orthorhombic
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
Prismatic, tabular, and stubby crystals, usually striated and sometimes quite large. Crystals may contain numerous faces, and often have complex terminations. Also occurs columnar, massive, grainy, radiating, and as rounded, waterworn pebbles. Topaz may also be in the form of feldspar as a pseudomorph.
Transparency Transparent to opaque
Specific Gravity 3.4 - 3.6
Luster Vitreous
Cleavage 1,3 - basal
Fracture Subconchoidal
Tenacity Brittle
In Group Silicates; Nesosilicates
Striking Features Great hardness and perfect basal cleavage
Environment In igneous environments in granite pegmatites and in rhyolite. Occasionally in sedimentary alluvial deposits.
Rock Type Igneous
Popularity (1-4) 1
Prevalence (1-3) 2
Demand (1-3) 1

Topaz ON EBAY

VARIETIES
Topaz is often preceded by its color, for example Blue Topaz, Pink Topaz, Yellow Topaz, White Topaz, and Sherry Topaz.
 -  Highly valued yellow-orange to orange-pink form of Topaz from Ouero Prito, Brazil.
 -  A columnar variety of Topaz. May also refer to a yellow-white variety of Topaz.

USES
Topaz is a very popular gemstone. All colors are fashioned into gemstones, and the yellow-brown Imperial is especially valuable. Crystals, especially those still in a matrix, are greatly sought by mineral collectors.

NOTEWORTHY LOCALITIES
The most important Topaz deposits are in Brazil. Exceptionally large crystals come from many of the Brazilian pegmatite localities in Minas Gerais, especially at Itinga and Virgem da Lapa, in the Jequitinhonha valley. The famous golden orange-brown Imperial Topaz, as well as Topaz of pinkish tones, come from the famous occurrence in Minas Gerais at Ouero Prito. Other Brazilian occurrences are Mimoso do Sul, in Espírito Santo, which has produced very large crystals; and Brumado, in Bahia, which produces fine natural pink crystals.

The most classic locality of blue Topaz is Murzinka, Ekaterinburg, in the Ural Mountains of Russia. Multicolored yellow and blue Topaz comes from Nerchinsk, Transbaikalia, Russia; and transparent and often etched crystals from Volodarsk-Volynskii, Zhytomyr, Ukraine.

Glassy colorless and sherry crystals, some very large in size, come from the gem mines at Mogok, Burma (Myanmar). Excellent gem crystals are found in the Gaoligong Mts, Nujiang, Yunnan Province, China; and Goricho, Ghorkhi massiv, Mongolia. Large and outstanding thick crystals come from Pakistan in the Gilgit and Skardu Districts, in Baltistan, (especially the Shigar Valley, Shengus, and Dassu). Pink and purple Topaz with exceptionally deep color comes from Katlung, Khyber, Pakistan. White, rounded waterworn Topaz crystals are well-known at Killiecrankie Bay, Flinders Island, Tasmania, Australia.

Classic yellow Topaz crystals once came from the Schneckenstein, Klingenthal, Saxony, Germany; and odd-shaped radiating microcrystals from the Eifel Mountains of Germany. Topaz crystals have recently been found in the Strzegon Granite Quarries in Strzegom, Poland. Water-clear and colorless crystals of top quality come from Klein Spitzkopje, in the Erongo Region, Namibia; and a natural deep blue Topaz from the St Anne's Mine, Mwami, Zimbabwe. Very good Topaz crystals also come from the Jos Plateau, Plateau State, Nigeria.

In Mexico, a famous locality that produces multicolored Topaz with brownish-red tints is Tepetate, San Luis Potosí; along with the Veronica Mine, Copetillo; and Villa Garcia, Zacatecas.

In the U.S., the best and most well-known Topaz occurrence is the Thomas Range, Juab Co., Utah (especially Topaz Mountain and Maynard's Claim), where lustrous sherry colored crystals with good pointed terminations are associated with a rhyolite matrix. A new find of good Topaz crystals is the Zapot Mine, near Hawethorne, Mineral Co., Nevada, which produces rare green crystals. Topaz is found in the gem pegmatites of San Diegeo County, in localities such as the Little Three Mine in Ramona, and the Ware Mine in Oak Grove. Colorless Topaz come from the Pikes Peak area in El Paso Co., Colorado, particularly in Glen Cove, Devils Head, and Crystal Peak.  Fine colorless and light blue tabular crystals come from Mason Co., Texas (near Streeter, Katemcy, and Grit). Other localities include the Tarryall Mts, Park Co., Colorado; the Morefield Mine, Winterham, Amelia Co., Virginia; Trumbull, Fairfield Co., Connecticut; Moat Mountain, Carroll Co., New Hampshire; and South Baldface Mountain, Chatham, Carroll Co., New Hampshire.

COMMON MINERAL ASSOCIATIONS
Quartz, Microcline, Orthoclase, Albite, Tourmaline, Beryl, Fluorite, Garnet, Rutile, Cassiterite, Pyrophyllite

DISTINGUISHING SIMILAR MINERALS
Quartz (especially Citrine) - Slightly softer (7), lacks cleavage, forms in different crystal habits.
Chrysoberyl - Lacks cleavage, different crystal habits.
Beryl - Lacks cleavage, crystallizes hexagonally.
Apatite - Much softer (5), different crystals.
Danburite - Slightly softer (7)
Fluorite - Much softer (4), different crystals.
Barite - Forms in similar crystals but is much softer (3).
Euclase  - Different cleavage, otherwise hard to distinguish.


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