The science of Topaz
Pure topaz is colorless and transparent but is usually tinted by impurities; typical topaz is wine, yellow, pale gray, reddish-orange, or blue brown. It can also be made white, pale green, blue, gold, pink (rare), reddish-yellow or opaque to transparent/translucent.
Orange topaz , also known as precious topaz, is the traditional November birthstone, the symbol of friendship, and thestate gemstone for the US state of Utah.
Imperial topaz is yellow, pink (rare, if natural) or pink-orange. Brazilian Imperial Topaz can often have a bright yellow to deep golden brown hue, sometimes even violet. Many brown or pale topazes are treated to make them bright yellow, gold, pink or violet colored. Some imperial topaz stones can fade on exposure to sunlight for an extended period of time.
Blue topaz is the US state Texas' gemstone. Naturally occurring blue topaz is quite rare. Typically, colorless, gray or pale yellow and blue material is heat treated and irradiated to produce a more desired darker blue.
Mystic topaz is colorless topaz which has been artificially coated giving it the desired rainbow effect.
Topaz throughout History
The name "topaz" is derived (via Old French: Topace and Latin: Topazus) from the Greek Τοπάζιος ( Το pázi ο s) or Τοπάζιον ( Το pázi ο n), the ancient name of St. John's Island in the Red Sea which was difficult to find and from which a yellow stone (now believed to be chrysolite: yellowish olivine) was mined in ancient times; topaz itself (rather than topazios ) wasn't really known about before the classical era.
Pliny says that Topazos is a legendary island in the Red Sea and the mineral "topaz" was first mined there. The word topaz might be related to the Arabic word which meant "the subject of the search" or Sanskrit word "tapas" meaning "heat" or "fire."
Nicols, the author of one of the first systematic treatises on minerals and gemstones, dedicated two chapters to the topic in 1652. In the Middle Ages, the name topaz was used to refer to any yellow gemstone, but in modern times it denotes only the silicate described above.