Uneven-Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
Fibrous, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references
The chief constituent Lapis Lazuli is Lazurite, with the following chemical formula: (Na,Ca)8Al6Si6O24(S,SO)4
AlAl6O3BSi3O18