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Topaz fact file | |
| Crystal Structure:orthorhombic Chemical Composition:fluosilicate of aluminum Hardness:5-6 MOHS | Refractive Index:colorless and blue topaz – 1.610 to 1.617 yellow and brown topaz – 1.630 to 1.637 Colors:Many colors including pink, blue, lavender, yellow, orange, orange-yellow, brownish yellow, yellow-brown, red, and colorless |
Topaz, the November birthstone along with Citrine, has all the colors of the setting sun – Brown, yellow, orange, sherry, red and pink.
It is said to cure insomnia, asthma, and hemorrhages. Topaz crystals may become quite large and finished gems weighing several thousands of carats are seen in many museum collections.
Name
Topaz may have derived its name from the Island of Topazios in the Red Sea but some authorities think the name may have come from the Sanskrit word “topas” that means “fire.”
Physical and Chemical Properties
Chemical composition
Topaz is an fluosilicate of aluminum Topaz has a specific gravity of about 3.50 to 3.57. Light shades (pink, yellow, etc.) usually occupy the lower range and darker shades (blues) usually occupy the higher range, as do colorless stones. Many of the blue topazes are derived from colorless stones that have been heat-treated so that is one reason why colorless stones have a higher specific gravity. The refractive index of topaz ranges from about 1.610 to about 1.617 in colorless and blue to about 1.630 to about 1.637 in yellow and brown stones. The fairly low refractive index and the fairly high specific gravity are an unusual characteristic as refractive index usually varies upward with the specific gravity. The anomalous, low refractive index of topaz may be due to the presence of the very large fluoride ion in the crystal lattice. Topaz is an extremely hard silicate mineral containing fluorine and hydroxl and is formed by fluorine-bearing vapors created during the crystallization of igneous rocks (rocks formed from a molten state).
Colors
Topaz comes in many colors including pink, blue, lavender, yellow, orange, orange-yellow, brownish yellow, yellow-brown, red, and colorless. Although most commonly found as yellow or blue in color, topazes also may be transparent, brown, and most rarely pink or red. Their colors can be unstable and change according to temperature. “Brazilian rubies” or “burnt topazes” are often yellow topazes that have been exposed to moderate heat to turn pink or red. Often confused with citrine quartz, yellow topazes tend to have more orange or pinkish tones. Irradiating clear topazes can create a blue tone in the gem.
Healing Properties and Interesting Information
Where Found
Topaz has been found in granitic pegmatite (coarsely crystalline hydrothermal deposits) and in cavities in rhyolitic welded ash flow tuffs. Topaz is almost always found in the form of large, well-developed crystals. Most gem topaz is mined directly from the host rock or from nearby sediment derived from the host rock. Because of its poor toughness, this november birthstone is rarely found in gravel deposits that have been removed any distance from the source area. Most gem topaz that reaches the United States has been found in Brazil where it is mined from deeply weathered pegmatites. Sri Lanka in the Indian Ocean and the Ural Mountains in Russia were important Old World sources and Scotland and Ireland were lesser sources for these stones. In North America, Mexico has been an important topaz source and California, Colorado, Utah, Maine, and New Hampshire have also produced topaz. Brazil boasts the largest topazes. They are also found in Pakistan, Russia, Nigeria, Zaire, Mexico, Northern Ireland, England, Sri Lanka, and the United States (California and Utah).
History, mythology
Topazes have been used to cure bad vision and to ward off death. During the spread of the Bubonic plague (1347-1400) the clergy touched topazes to people’s sores. They were also ground into a powder and added to wine to prevent asthma and insomnia. Topazes are believed to bring intelligence, long life, beauty, and loyalty.
Buying and Caring tips
Tips for Buying Topaz Jewelry
Prices for these gemstone range between $5 and $100 per carat for a one-carat stone. Topaz has many lower priced imitators that include synthetic corundum and synthetic spinel as well as citrine quartz; the latter often sold under the misleading name of “Brazilian Topaz.” More recently, colorless quartz crystals that are coated with a monomolecular layer of gold have been substituted for blue topaz. These stones have been sold under several trade names such as Aqua-AuraTM. Topaz is usually easily separated from its imitators by refractive index—few materials fall into this range, except tourmaline which is so strongly doubly refractive that one will observe doubled back facets when looking through the table of the stone with a small magnifier (about 6 to 10 power). Topaz rarely comes in the same shades as tourmaline either.
Tips to take care of Topaz Jewelry
Give topaz the same care you would an emerald. Although it is hard, it cleaves. A sudden temperature change or impact can cause a break. Clean with a soft, damp cloth, warm water and a soft brush. Do not use mechanical cleaners. Avoid chemicals and heat that dissolve oils used during cutting and processing to conceal inclusions.