Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Conchoidal
(Mg,Fe2+ ) 9(SiO 4) 4(F,OH)) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Mg,Fe,Zn)Al 6BeO 12Ulrich Henn and Claudio C.