Andalusite

It is reported that olive-green material from Brazil changes to pinkish when heated (Sinkankas, 1972), while brown material is reported (Smith et al, 1978) to fade above 800�C to colorless. Irradiation could conceivably reverse these changes (Nassau, 1984 7.5Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references 3.05 to 3.21Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references BrittleWalter Schumann, Gemstones of the world (2001) GoodWalter Schumann, Gemstones of the world (2001) More from other references UnevenArthur Thomas, Gemstones (2009) YesArthur Thomas, Gemstones (2009) 1.627 to 1.650Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references Biaxial/-Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references 0.007 to 0.013Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references Orange/brown stones - strong trichroism: yellow - olive green - reddish brown; Yellow stones - strong: yellow - olive-green - red-brown; Green stones - strong: yellow - olive green - red-brownHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references 0.016Arthur Thomas, Gemstones (2009) Green, yellowish-green, brown, pink, colourlessUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references Green and brown, pleochroism Fe2+ -O- Ti4+ charge transfer. Dark green, Mn3+ in octahedral coordinationW. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011) Transparent,Translucent,OpaqueUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references VitreousArthur Thomas, Gemstones (2009) Weak; green, yellow-greenWalter Schumann, Gemstones of the world (2001) Inert to moderate green to yellowish greenHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references The brownish greenstones from Brazil often show greenish yellow under X-rays.Michael O?Donoghue, Gems, Sixth edition (2006) OrthorhombicHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references Prismatic habit with vertically striated prisms which are nearly square in section and capped with pyramidsMichael O?Donoghue, Gems, Sixth edition (2006) More from other references A result of contact metamorphism of argillaceous sediments, also in regionally metamorphosed schists. Rare in granites and pegmatites, which however afford the largest crystals. Detrital in some sandstones.Anthony et al., Handbook of mineralogy (2003) Andalusite information at mindat.org Australia  [var: Chiastolite] Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 381 Brazil  Madagascar  Madagascar - extraLapis English No.1, p. 92 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 Sri Lanka  USA  [var: Chiastolite] Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 382 U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.