Uneven-Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Conchoidal, Brittle
The chief constituent Lapis Lazuli is Lazurite, with the following chemical formula: (Na,Ca)8Al6Si6O24(S,SO)4
Ca(Mg 3)MgAl 5(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012)