Conchoidal, Uneven, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal to uneven
Sub-Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Ca 5(PO 4) 3(F,OH,Cl)Walter Schumann , Gemstones of the world (2001) More from other references
Cu2H2Si2O5(OH)4