Uneven, UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven-Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
(Na,Ca) 8Al 6Si 6O 24(SO 4,S,Cl) 2Ulrich Henn and Claudio C.
The chief constituent Lapis Lazuli is Lazurite, with the following chemical formula: (Na,Ca)8Al6Si6O24(S,SO)4