Topaz

Irradiation followed by heat-treatment produces most blue colors. Irradiation also produces yellow, orange, red, brownish, pinkish and greenish colors: often unstable, may fade upon direct exposure to sunlight. Coated entirely or partially: may show peeled coating at facet junctions, iridescence (reflecting light), spotty coloration. Some surface-treatments are removed only with acids (mostly green and blue) - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 5 Good imitations of topaz can be made by fusing strass with a certain amount of glass of antimony (antimony oxide) and with a trace of purple of Cassius (a compound containing gold) or with a little iron oxide. Purple of Cassius gives a darker, more reddish-yellow, and iron oxide a paler yellow. Such imitations may be distinguished from genuine stones by their single refraction, lower specific gravity, much lower degree of hardness, and by the entire absence of dichroism. - Precious Stones, Max Bauer, 1968, p 333 8Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references 3.49 to 3.57Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references PerfectHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references ConchoidalArthur Thomas, Gemstones (2009) 1.606 to 1.644Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references Biaxial/+Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references 0.008 to 0.011Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references 0.014Arthur Thomas, Gemstones (2009) Colourless, yellow, yellow-brown, reddish-brown, blue, green, pink, red, violetUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references Blue, color centers of unknown structure. Green, yellow and blue color centers. Yellow, color center of unknown nature. Orange ("imperial topaz"), yellow color center and Cr3+ in octahedral coordination. Pink, Cr3+ - in octahedral coordination. Reddish brown ("sherry topaz"), yellow and red color centers.W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011) TransparentUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references VitreousArthur Thomas, Gemstones (2009) Pink: weak - brown; Red: weak - yellow-brown; Yellow: weak - orange-yellowWalter Schumann, Gemstones of the world (2001) Colorless, blue: inert to yellow-(greenish); golden, brownish, pink: often yellow-orangyHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) OrthorhombicHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references Prisms with multi-faceted ends, often 8-sided in cross-section striations along length.Walter Schumann, Gemstones of the world (2001) More from other references Liquid inclusions, two- and three-phase inclusions, healing cracks, needle-like crystals - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 13 Topaz information at mindat.org Afghanistan  Blauwet (2004) Menzies (1995) D. Blauwet (2009) Brazil  Morteani et al. (2002) Mossman (2001) Mossman (2001) Morteani et al. (2002) Mossman (2001) Menzies (1995) Mossman (2001) Morteani et al. (2002) Morteani et al. (2002) Canada  Wilson (2007, 2010) China  B. Ottens (2009) B. Ottens (2009) Kazakhstan  Smith and Smith (1995) MadagascarE.Ya. Kievlenko, Geology of gems, 2003, p. 110 Madagascar, extraLapis English No.1, 2001, p. 46 Milisenda et al. (2001) Madagascar, extraLapis English No.1, 2001, p. 43 Milisenda et al. (2001) Mozambique  J. Marques (2009) Myanmar  Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Hughes (1997) Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Namibia  Cairncross (2005) Pakistan  Muhammad (2004) Muhammad (2004) Menzies (1995) Blauwet (2004) Muhammad (2004) Muhammad (2004) Muhammad (2004) Muhammad (2004) Blauwet (2004) Blauwet (2004) Muhammad (2004) Blauwet (2004) Blauwet (2004) Blauwet (2004) Muhammad (2004) Muhammad (2004) Muhammad (2004) Muhammad (2004) Einfalt (2002) Russia  [var: Imperial Topaz] Evseev (1994) P. Lyckberg (2009) Evseev (1994) E.Ya. Kievlenko, Geology of gems, 2003, p. 116 E.Ya. Kievlenko, Geology of gems, 2003, p. 116 Sri Lanka  G. Zoysa (2009) G. Zoysa (2009) G. Zoysa (2009) Econ Geol (1981) 76:733-738 Tajikistan  Skrigitil (1996) Ukraine  Evseev (1994) USA  Fisher (2002, 2008) Fisher (2002, 2008) E.Ya. Kievlenko (2003) Geology of gems, p. 70 U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia. Vietnam  Pham et al. (2004) Pham et al. (2004) Zimbabwe  L.F. Marsh and F. Mutugumbate (2009) L.F. Marsh and F. Mutugumbate (2009)