Conchoidal, Uneven, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal to uneven
Conchoidal, Brittle
Ca 5(PO 4) 3(F,OH,Cl)Walter Schumann , Gemstones of the world (2001) More from other references
(Mn2+ ,Fe2+ ,Mg)(Fe3+ ,Mn3+ ) 2O 4Anthony et al , Handbook of mineralogy (2001)