Chemical Formula: (AlF)2
Composition: 33.3% Silica, 56.5% Alumina, 17.6% Fluorine
: 3.50 to 3.57
Refractive Index: 1.610-1.638
Double Refraction: +.008 to +.010
Colors: colorless, yellow, red-brown, light blue, pink, blue
Topaz, believed to be named after an island in the Red Sea, which is now called Zebirget and formerly called Topazos, is a semi-precious gemstone found in a variety of different colors all over the world. Some colors of topaz are only found in certain locations over the world. In general, topaz can be found in Minas Gerais, Brazil, Siberia, Burma, Sri Lanka, Pikes Peak, Colorado, Saxony and in several other places. It is often found near clutches of gneiss or granite, and sometimes near crystals of quartz or aquamarine. Imperial topaz, found only in Brazil, is the birthstone for the month of November.
Topaz is a hard gemstone, with a hardness of 8 on Mohs' scale. Only three gems, corundum, diamond and chrysoberyl are higher on Mohs' scale than topaz. Because of topaz's high hardness, it's great for jewelry as it won't get scratched very easily. The stone itself can range greatly in size. Some topazes have been found that are the size of the head of a pin. Others, such as one unearthed in 1901 from Saetersdalen, Norway weighed in at a whopping 137 pounds. Another large topaz, tipping the scales at 100 pounds, was pulled out of the Ukraine in 1965.
While the stone is mostly composed of the compound, silica, and the elements aluminum and fluorine. Other compounds and elements can be found in the crystal; the most important "extra" compound is water. The amount of water in the stone can range up to 2.5% of the total composition. While this does not seem like a lot of water, topazes with higher water contents often contain that water as hydroxyl, chemical formula OH. This hydroxyl isomorphically replaces the fluorine in the gem. While topazes that contain no hydroxyl have been found, none have been discovered which contain no fluorine.
Topaz is known for its distinct cleavage (Cleavage in the geologic sense does not refer to breasts but instead to how the stone breaks when struck, say, by a hammer). Topaz has only one direction of cleavage, parallel to the basal plane. The gem breaks away evenly, and crystals broken off from the crystal matrix almost always have a smooth shining face. This distinct cleavage is useful because a large stone, such as the humungous ones mentioned in the previous paragraph, can easily be broken up in to smaller stones for jewelry or other uses. However, the cleavage also allows for the creation of small fissures, which can detract from the beauty, value, and lustre of the gem. Avoiding these small fissures can be hard to do. The stone cannot be dropped or even jarred. Great care, lots of time, and a steady hand are required to cut the stone without creating any fissures.
Because of the wide color variation found in topaz, they are often mistaken for any of a number of other gems. They are commonly confused with Apatite, Citrine, Ruby, Zircon, Beryl, Flourite, Diamond, Sapphire and several others. The Braganza Topaz, a famously large stone found in the Portuguese crown was long thought to be a 1640 carat diamond. It is actually a large colorless topaz. Colorless topaz, such as the Braganza, was once called Slaves' Diamond, as it is a cheaper version of the real thing, and looks very similar to an actual diamond. Because topaz is often mistaken for other gems, and gems such as citrine and heat-treated amethyst are sometimes called Gold Topaz or Madeira Topaz, true topaz is often called Precious Topaz to avoid confusion.
Topaz, like most gemstones, was thought to have curative powers by ancient peoples. The thirteenth century hindu physician, Naharari, thought that topaz could be used and a cure for flatulence. He also claimed that and many who wore the stone would receive long life, intelligence and beauty. Another story from that area of the world tells how a powerful necromancer who had fallen in battle. Alongside the dying necromancer lay a wounded soldier, complaining of thirst. The necromancer gave the soldier his topaz, and told him to place it to his heart. According to the story, the soldier's thirst was immediately quenched, and he was healed enough to leave the battlefield. The next day, the soldier returned to the battlefield and searched for the corpse of the necromancer, but he was unable to find it.
Precious Stones, by Dr. Max Bauer. Charles E. Tuttle Company: Rutland Vermont and Tokyo, Japan, 1969
Gemstones of the World, by Walter Schumann. Sterling Publishing Co., New York, 1979
Simon and Schuster's guide to Rocks and Minerals, Simon and Schuster Inc. New York, 1978
The Magic of Jewels and Charms, Dr. George Frederick Kunz. J.B. Lippincott company, Philadelphia and London, 1915