ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Uneven
Sub-Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
(Mn2+ ,Fe2+ ,Mg,Ca) 2(PO 4)(F,OH)Michael OâDonoghue , Gems, Sixth Edition (2006)
Cu2H2Si2O5(OH)4