Uneven-Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Conchoidal, Uneven, Irregular, Conchoidal, Management Team (2012)
The chief constituent Lapis Lazuli is Lazurite, with the following chemical formula: (Na,Ca)8Al6Si6O24(S,SO)4
Na(Li 1.5Al 1.5)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012) Formula given for elbaite.