Brittle, Metallic, Brittle, Metallic
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Na 2ZrSi 3O 9 · 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006)
MgAlBO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references