Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
MgCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2Ulrich Henn and Claudio C.