Topaz: Properties and Types
Topaz is a precious crystal belonging to the silicate mineral. It is made up of fluorine and aluminum. The gem is usually prismatic and crystalizes in the orthorhombic system. Topaz is transparent and colorless but it has traces of impurities that give it a variety of tints. The gem commonly occurs in yellow, reddish – orange, blue-brown, wine and pale-gray. It can also be pale green, gold, reddish – yellow, sherry and pink. The pink Topaz is extremely rare, and Pakistan is one of the few locations where the gem occurs naturally. It occurs in nature in igneous rocks of rhyolite and granite. It crystallizes either in vapor cavities (rhyolite lava flows) or in granatic pegmites. The sherry colored Topaz is majorly mined in Minas Gerais, Brazil. In this region, Topaz occurs in conjunction with quartz and the aquamarine gem. The brown – yellow sapphire from Thailand and Sri Lanka is called “oriental topaz” and is often mistaken for a Topaz. The hardness of the gemstone is 8 in the mohs scale which makes it the hardest silicate mineral.
Orange Topaz: It is the November Birthstone and called “the precious topaz”. It is the gemstone of the state Utah in USA, and symbolizes friendship.
Blue Topaz: It is a naturally occurring specimen and is extremely rare. The typical colors it comes in are pale or gray yellow, colorless and blue (that is normally heat treated to obtain a darker shade). It is the state gem of Texas State in USA. The intense cobalt blue Topaz is normally obtained by treating a blue Topaz.
Imperial Topaz: This type normally comes in three colors: pink (easily available as heat-treated specimen), yellow and pink-orange. The Imperial Topaz from Brazil comes in golden brown or bright yellow hue and in rare cases it occurs in violet color. The pale or brown specimens are generally heat treated to obtain a pink, golden, bright yellow or violet color. Imperial Topaz can be sensitive to sunlight and causes the gem to fade when exposed to the sun for a long time.
Mystic Topaz: It is relatively new in the gemstone market. This type is artificially coated with color to give it a rainbow look. This type of Topaz is generally colorless. Other gemstones are also sometimes used to create the mystic Topaz gemstone.