Gemstones of the world (2001)
Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Microcline: KAlSi3O8 Oligoclase: (Na,Ca)Al1-2Si3-2O8
PbSO 4Michael OâDonoghue , Gems, Sixth edition (2006) More from other references