Topaz, also called "Saxon diamond" (from the Saxons) with the orthorhombic crystallization system, is a mineral from the category of precious stones with the chemical composition Al2SiO4(OH, F)2. Hydroxyl ions (-OH) can combine with different concentrations of fluorides, which determines the large number of varieties of topaz. Topaz by gamma ray irradiation, electron bombardment. or heating changes its color to greenish-brown or reddish. Although it has a hardness of 8, it has a good cleavage (splits easily) which makes it difficult to process.
It occurs in the characteristic form of prismatic crystallization or as a gritty mass. Often associated with beryl, tourmaline and apatite in an acid igneous rock of granite or pegmatite, it can also be found in gneiss metamorphic rocks (Brazil). Other places where topaz has been found are the Czech Republic, Norway, Sweden, Japan, Mexico, USA, Sri Lanka, Burma and Pakistan. In the past, topazes were found on the territory of Germany, Saxony, on the Snail Mountain in Vogtland, from there come polished topazes from the time of August the Great, today they are kept in the "Green Chamber" in Dresden and the English crown.
Topaz is frequently used as a valuable gemstone. The largest topaz found to date is a 271 kg crystal, and the largest processed (polished) topaz weighs 4.2 kg.
According to the accounts of the Roman naturalist Plinius, the name of the mineral comes from the island "Topazos" in the Red Sea. In fact, no topaz was found there, but olivine with which it was confused. Another source of the name comes from a Sanskrit writing tapas meaning "fire". In 1740 there was a topaz fixed in the Portuguese crown, it being called "Diamond of Braganza" believing that it is really a diamond.
Swiss Blue Topaz is obtained by treating white topaz, it does not exist in nature in the form in which it is known. All varieties of blue topaz are obtained through this kind of technical procedure for processing white topaz.
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