Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references, Brittle
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
SiO2 · nH2O
Al 4(Ta,Nb) 3(O,OH,F) 14Ulrich Henn and Claudio C.