jewelry topaz gemstones violet semi precious stones jewlery blue gem stones topaz gems

        Topaz is actually a fairly common gemstone and is worn around the world in its blue avatar. However, naturally occurring blue topaz is extremely rare and the many varieties of blue topaz set in inexpensive jewellery around the world is actually irradiated material. Until the 1950s though; topaz was generally known as a yellow or golden colored gemstone.

        Topaz has been used in jewellery for centuries. The name itself is said to derive from the Sanskrit word Tapas meaning fire or from the island of topazios (Zabargad) where peridot was found. It is believed to be one of the gemstones on the breastplate of Aaron. The ancient Egyptians associated its color with the golden glow of their mighty Sun God Ra.

        This made topaz a very powerful amulet in their estimation and they believed that it protected the faithful from harm. The ancient Romans too associated the gem with their Sun God Jupiter.

        There are many legends associated with topaz. The Greeks believed that it had the power to increase strength and even make its wearer invisible in times of danger. It was also believed that the stone would change color in the presence of poisoned food and drink, a very important quality to possess in ancient times. It was said to dispel enchantment and improve eyesight. Its mystical and curative powers were believed to wax and wane with the phases of the moon. Ground topaz mixed with wine was used in the treatment of asthma, insomnia and haemorrhages.

        Topaz was a popular talisman with the Europeans of the Middle Ages who believes that it protected the wearer from having bad dreams, calmed passions and ensured faithfulness. There is a story that Lady Hildegarde, wife of Theodoric, the Count of Holland, presented a topaz to a monastery in her native town. The gem emitted such a bright light at night that prayers could be read without the aid of candles in the chapel where it was kept. Of course, one would expect that the monks would already have known the prayers by heart so the story can be dismissed as the stuff of legends. It serves to point to the past popularity of this gem though which is in stark opposition to its current position as a low-end gemstone. In fact in the 19th century when pink topaz was discovered in the Ural Mountains, the Czar of Russia restricted the gems from those mines for the exclusive use of the Imperial Topaz. Today the term imperial is reserved for pink, orange and red topaz.

        Topaz commonly occurs in colorless or brown. Rare varieties include golden, pink, red, purple and green. There is some naturally occurring blue topaz but it is extremely rare. These natural colored topazes can be classified as fine gems. The color of some natural topaz, most notably Siberian topaz, can change when exposed to sunlight or heat. Brown topaz can be bleached by sunlight and yellow topaz turns pink or purple-red when exposed to moderate heat. A Parisian jeweler discovered this latter phenomenon in 1750 and used it to create the first artificially enhanced pink topaz. Today nearly all the pink topaz being sold in jewellery has been heat treated to turn it pink.

        Topaz is a silicate and often occurs in deposits of granite associated with other minerals. It is also commonly found as rounded pellets in alluvial deposits. The most notable occurrences are in Brazil, Pakistan, Nigeria, Australia, Tasmania, Sri Lanka, Russia, USA, Mexico, China and Burma.

        A chain like structure of connected irregular octahedrons controls the structure of topaz. These octahedrons have one aluminum atom in the middle surrounded by four oxygen atoms. Above and below the aluminum are the hydroxide or fluoride ions. The chains of octahedrons are held together by individual silicate tetrahedrons but it is the octahedrons that give topaz its crystalline shape. Why this information is important is that in spite of being one of the hardest minerals and the hardest silicate mineral, toting up 8 on Moh's scale, it has a perfect cleavage that is perpendicular to the chains and is caused by the planes that break the weaker aluminum-oxygen, aluminum-hydroxide and aluminum-fluoride bonds. None of the stronger silicon-oxygen bonds cross these planes.

        Topaz crystals can consequently reach huge sizes and weigh as much as several hundred pounds. Topaz's crystal habits also make it a very attractive mineral specimen due to its high luster, nice color and well formed multifaceted crystals. The largest uncut stone, a specimen found in Brazil weighing almost 600 pounds is on display at the American Museum of Natural History in New York City.

        Its crystalline formation also allows the gem to hold an electric charge for up to thirty hours. In fact, you can charge topaz by the simple act of rubbing it between your fingers. Some Brazilian stones get a charge just by holding the ends between your fingers. Heating the gem and allowing it to cool slowly builds an electrified charge greater than any achieved with other stones and the topaz will retain the electrical energy for more than a day after cooling down.

        Topaz from most sources is reasonably clean. Thus eye clean stones are both desirable and available. The exceptions are pink and red topaz, which are usually found only in small sizes and are often included. In fact, fine pinks and reds of more than five carat size are very rare and orange stones in sizes of more than twenty carats are also uncommon.

        Topaz contains up to 20% water and fluorine and the relative proportions of these impurities are what cause the color in the natural stones. Crystals with more water are yellow to brown, while those with more fluorine are typically blue to colorless. Except in some red and pink stones where trace quantities of Chromium act as a chromophore, the color in topaz is due to color center which is thy they are good candidates for color change through irradiation and heating.

        Topaz as mentioned earlier is rarely sold unenhanced and the most common enhancement technique used is irradiation to turn the stones blue. Shy, Swiss and London Blue are all shades of blue achieved by irradiation. The most widely used techniques are explained below. The most widely used techniques are explained below. The first method is the Gamma Ray Treatment where exposure to a gamma ray source (usually cobalt 60 is used) will produce both blue and yellow color center resulting in a brownish or brownish - green color in most of the stones. Subsequent heating removes the less stable yellow color center without affecting the blue. Such treatment, though it was once very commonly used is no longer popular today as it is not capable of producing the darker, purer blues that are in the highest demand and that can be created by other techniques.
Source: Bangkok Gems & Jewellry Magazine VOL.18 NO.3 October 2004
http://www.gemsgateway.com

ID : NB1174 Type : Topaz Piece/lot : 1 pc(s). Weight : 6.23 ct(s). Price/lot : $ 482.50	ID : NB1180 Type : Topaz jewelry Piece/lot : 1 pc(s). Weight : 2.95 ct(s). Price/lot : $ 192.50	ID : NB1409 Type : Topaz gems Piece/lot : 1 pc(s). Weight : 3.63 ct(s). Price/lot : $ 192.50	ID : NB1410 Type : Topaz gemstone Piece/lot : 1 pc(s). Weight : 8.46 ct(s). Price/lot : $ 165.00
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