Category  :  Silicate mineral
Hardness  :  8
Gravity  :  3.49–3.57
Reflection  : 1.64 / 1.63
                    1.62 / 1.61
Color  :  Clear (if no impurities), blue, brown, orange, gray, yellow, green, pink and reddish pink.
Chemical formula  :  Al2SiO4(F,OH)2
Crystal system  :  orthorhombic
Major varieties  :  Pink Topaz, Blue Topaz, Colourless Topaz

Orange topaz, also known as precious topaz, is the traditional November birthstone, the symbol of friendship, and the state gemstone for the US State of Utah.

Imperial topaz is slightly pinkish- to reddish-orange color. This variety is the most sought-after and highly valued of the topaz gems. Some imperial topaz fades when exposed to sunlight for an extended period of time.

Blue topaz is the Texas state gemstone. Topaz very rarely occurs blue naturally. Typically, colorless, gray or pale yellow material is heat treated and irradiated in order to turn it blue.

Mystic topaz is colorless topaz which has been artificially treated with a thin film/coating giving it the desired rainbow effect, and is not a naturally occurring topaz.

Topaz is commonly associated with silicic igneous rocks of the granite and rhyolite type. It typically crystallizes in granitic pegmatites or in vapor cavities in rhyolite lava flows like those at Topaz Mountain in western Utah. It may be found with fluorite and cassiterite. It can be found in the Ural and Ilmen mountains, Afghanistan, Sri Lanka, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico, Flinders Island and the United States.

Some clear topaz crystals from Brazilian pegmatites can reach boulder size and weigh hundreds of pounds. Crystals of this size may be seen in museum collections. The Topaz of Aurungzebe, observed by Jean Baptiste Tavernier measured 157.75 carats.

Colorless and light-blue varieties of topaz are found in Precambrian granite in Mason County, Texas within the Llano Uplift. There is no commercial mining of topaz in that area.

Pink Topaz

The color is pink with a distinctive yellowish or orange shade, but is more often a definite light to medium pink, tending to red or violet in deeper color stones. The most common cut is the oval or pear shape, but many other old or antique faceted cuts are seen, as is the step cut. When the color is fairly intense, it is one of the most valuable of the second level of gemstones.

Blue Topaz

It has a definite, uniform sky-blue color, usually without any overtones. Often pale, it can be bright or very rarely an intense blue. Furthermore, they are usually wholly or almost free of inclusions. The most common cut is the oval, with a crown and pavilion consisting of very many lozenge-shaped facets, but all the mixed cuts, plus the step cut, are used.

Colourless Topaz

These stones easily acquire good luster and are only disappointing on the rare occasions when they are given the brilliant cut, prompting comparison with diamonds, which have a very different luster and “fire”. In large stones the mineral’s weak birefringence can be detected with the aid of a lens, the facet edges appearing double when seen through a flat facet of the stone.

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