UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Uneven
Ca 2(Mg,Al) 6(Si,Al,B) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Mn2+ ,Fe2+ ,Mg,Ca) 2(PO 4)(F,OH)Michael OâDonoghue , Gems, Sixth Edition (2006)