Brittle, Metallic
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
CaCuAlSi 2O 6(OH) 3Michael OâDonoghue , Gems, Sixth Edition (2006)
CaZrBAl 9O 18Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references