ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Splintery, Brittle, Uneven
SiO 2 + H 2OUlrich Henn and Claudio C.
NaCa 2(Mg 4Al)Si 6Al 2O 22(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)