Uneven-Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
Splintery, Granular, Splintery, Granular, Gemstones (2009)
The chief constituent Lapis Lazuli is Lazurite, with the following chemical formula: (Na,Ca)8Al6Si6O24(S,SO)4
Ca 2(Mg,Fe) 5(OH) 2Walter Schumann , Gemstones of the world (2001) More from other references