Gemstones of the world (2001)
Uneven, Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Uneven, Subconchoidal, Brittle, Metallic, Brittle, Metallic
Microcline: KAlSi3O8 Oligoclase: (Na,Ca)Al1-2Si3-2O8
Zn 2(AsO 4)(OH)Michael OâDonoghue , Gems, Sixth edition (2006)