Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Be3Al2SiO6
Al 4(Ta,Nb) 3(O,OH,F) 14Ulrich Henn and Claudio C.