Uneven-Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
Gemstones (2009), Flexible Flexible fragments.
The chief constituent Lapis Lazuli is Lazurite, with the following chemical formula: (Na,Ca)8Al6Si6O24(S,SO)4
Al 2Si 4O 10(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references