Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Uneven-Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.
The chief constituent Lapis Lazuli is Lazurite, with the following chemical formula: (Na,Ca)8Al6Si6O24(S,SO)4