Uneven, UnevenArthur Thomas, Gemstones (2009)
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Cu 5(SiO 3) 4(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al 4(Ta,Nb) 3(O,OH,F) 14Ulrich Henn and Claudio C.