Subconchoidal, Uneven, Conchoidal, Uneven
ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Mn2+ Al(PO 4)(OH) 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006)
Be 2BO 3(OH)Ulrich Henn and Claudio C.