Topaz

Topaz of any type is a good jewelry stone and it is historically one of the most important gemstones. With its relatively high refractive index and hardness of eight (Mohs scale), with no special sensitivity to chemicals it can be used, with appropriate care (should be protected from hard knocks), in any jewelry application. Topaz comes in many colors, including clear, brown, yellow, orange, red, pink and blue. The blue topaz, with a pale to medium blue color created by irradiation, can be found in very large sizes at affordable prices. The fine golden-yellow variety, known as Imperial Topaz, is relatively scarce. Topaz colors are rarely vivid. The most common color is yellow with a red tint; the most valuable is pink to reddish. The coloring agents are iron and chromium. The name topaz is most probably derived from an island in the Red Sea, "Topazos", today called Zabargad, the ancient source of peridot. In former times all golden-brown and sometimes also green gemstones were called topaz, which caused sufficient confusion such that today real topaz is referred to as precious topaz. Topaz is the birthstone for those who are born in the month of November.

Topaz comes in many colors, including clear, brown, yellow, orange, red, pink and blue. The blue topaz, with a pale to medium blue color created by irradiation, can be found in very large sizes at affordable prices. The fine golden-yellow variety, known as Imperial Topaz, is relatively scarce. Topaz colors are rarely vivid. The most common color is yellow with a red tint; the most valuable is pink to reddish; the most popular is blue. The coloring agents are iron and chromium. Natural blue topaz is rare. Found in all major deposits and also in England (Cornwall), Northern Ireland and Scotland. Most of the blue topazes are enhanced colorless topaz gemstone. Champagne topaz is one of the very few naturally colored varieties of topaz in a light to medium shade of brown, primarily found in Mexico. The most sought after of all natural topaz is the Imperial topaz. Its rich golden color is generally not enhanced by any kind of treatment. The most important deposit was found in Minas Gerais, Brazil. A natural pink topaz is very rare and costly. The vast majority of pink topazes are heat-treated yellow stones that turn pink. The most valuable variety of topaz can be found in Brazil, Pakistan and Russia.

Topaz is a very hard gemstone but it can be split with a single blow, a trait it shares with diamond. As a result it should be protected from hard knocks. The fine golden-yellow variety, known as Imperial Topaz, is relatively scarce. The most common color is yellow with a red tint; the most valuable is pink to reddish. The most popular color is blue. Topaz shows pleochroism, the appearance of several colors in one and the same stone which means, depending on the perspective, a yellow topaz appears lemon-honey, straw-yellow: a red topaz dark red, yellow, pink-red: a blue topaz light and dark blue. Topaz is transparent to translucent. One should look for an eye clean gemstone. Colored topazes get usually a step- or scissor-cut. The cutting style for weakly colored stones is the brilliant cut. A topaz with disordered inclusions is cut in a cabochon.

Brazil (Minas Gerais) is the most important supplier for topaz. Other deposits are in Afghanistan, Australia, China, Japan, Madagascar, Mexico, Myanmar, Namibia, Nigeria, Pakistan, Russia, Sri Lanka, Ukraine, United States and Zimbabwe. Natural light blue topaz is also found in England (Cornwall), Northern Ireland and Scotland.

Blue topaz begins as colorless or very lightly tinted natural topaz crystals, which are then irradiated to change the color to blue and heated to stabilize the change. Neutron bombardment in a nuclear reactor produces the deep slightly greenish or grayish "London Blue", while electron bombardment in a linear accelerator results in the light aqua-like blue known as "Sky Blue". Combinations of both treatments produce the highly saturated "Swiss" and "Electric" blues. If neutron bombardment has been used, there is residual radioactivity, and the gems must be held, up to a year, before they have "cooled" enough to be worn. In general, blue topaz is modestly priced. Due to the expenses of reactor time the London Blue color is short in supply and climbs in value. In early 1998, a new type of enhanced topaz made its appearance, the surface-enhanced topaz, with colors described as blue to greenish-blue or emerald green. The vast majority of pink topazes are heat-treated yellow stones that turn pink.

Perhaps the most famous topaz is a giant specimen set in the Portuguese Crown, the "Braganza", which was first thought to be a diamond. There is also a beautiful topaz set in the Green Vault in Dresden, one of the world's important gem collections. Topaz can be found in astonishing big sizes. In 1964 blue topazes were found in the Ukraine, each weighing about 100 kg. The Smithsonian Institution in Washington D.C. displays cut topaz of several thousand carats each. A faceted topaz weighing 22,892.50 carats, making it the largest cut yellow topaz in the world.

Topaz Gemology
Species: Topaz
Color: Colorless, yellow, orange, red-brown, light to dark blue, pink-red, red, violet, light green
Chemical composition: Al2SiO4(F2OH)2 fluor containing aluminum silicate
Crystal system: Orthorhombic, prisms with multi-faceted ends, often eight-sided in cross-sections along length
Hardness: 8 (Mohs scale)
Specific gravity: 3.49 - 3.57
Refractive index: 1.609 - 1.643
Birefringence: +0.008 to + 0.016
Absorption spectrum: Pink: 682
Fluorescence: Pink: weak; red-brown: weak; yellow brown: weak

The Egyptians believed that topaz was colored with the golden glow of the mighty Sun God Ra. This made topaz a very powerful amulet that protected the faithful against harm. The Romans associated topaz with Jupiter, their God of the Sun. In ancient times it was believed that topaz helps to improve the eyesight. The Greeks trusted topaz's supernatural power to increase strength and make its wearer invisible in times of emergency. Topaz was also said to change color in the presence of poisoned food or drink. Its mystical curative powers changed with the phases of the moon. It was said to cure insomnia, asthma, and hemorrhages.

In Antiquity, as well as in the Middle Ages one believed that the cosmos reflects in the gemstones. The topaz is assigned to planet Venus.
Topaz is the birthstone for those who are born in the month of November.