Splintery, Brittle, Uneven
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
NaCa 2(Mg 4Al)Si 6Al 2O 22(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references