Ultramarine

Ultramarine is a blue pigment consisting primarily of a zeolite-based mineral containing small amounts of polysulfides. It occurs in nature as a proximate component of lapis lazuli. The pigment color code is P. Blue 29 77007. Ultramarine is the most complex of the mineral pigments, a complex sulfur-containing sodio-silicate (Na_8-10Al₆Si₆O₂₄S_2-4) containing a blue cubic mineral called lazurite (the major component in lapis lazuli). Some chloride is often present in the crystal lattice as well. The blue color of the pigment is due to the S₃− radical anion, which contains an unpaired electron.