ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Uneven
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
Mg 3Al 6(Si,Al,B) 5O 21(OH)Walter Schumann , Gemstones of the world (2001) More from other references
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)