Conchoidal, Uneven, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal to uneven
Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Ca 5(PO 4) 3(F,OH,Cl)Walter Schumann , Gemstones of the world (2001) More from other references
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.