Sugilite

It has been noted by J.Call (unpublished observation) that dark purple sugilite can be lightened by heating at about 450�C; the product may have a banded appearance - Nassau (1984) May be mixed with chalcedony - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 5 5.5 to 6.5Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references 2.69 to 2.79Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references PoorArthur Thomas, Gemstones (2009) Sub-ConchoidalArthur Thomas, Gemstones (2009) 1.607 to 1.612Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references Uniaxial/-Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references 0.003 to 0.005Michael O?Donoghue, Gems, Sixth Edition (2006) More from other references WeakAnthony et al, Handbook of mineralogy (2001) Violet, purple-redUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) More from other references Purple, Mn3+ and Fe3+ presumably in octahedral coordinationW. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011) Translucent,OpaqueHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Opaque to semi-transparentMore from other references ResinousWalter Schumann, Gemstones of the world (2001) More from other references HexagonalHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) More from other references MassiveMichael O?Donoghue, Gems, Sixth Edition (2006) More from other references Sugilite occurs in an aegirine-bearing syenite stock in biotite granite in bedded manganese deposits.Michael O?Donoghue, Gems, Sixth Edition (2006) More from other references Sugilite information at mindat.org South Africa  Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 457 Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 457 Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 457