Mars Black is one of the few non-carbon pigments. It is an artificial mineral pigment made from iron metal. Named for the god of war, Mars Black is very opaque, with approximately three times the tinting strength of Ivory Black. Mars Black is often the choice of the Neo-Expressionists and others who want make black opaque marks in thick wet paintings. It also is the leanest black and dries more quickly than Ivory.
Although I've never used Mars Black, I may give it a try. I like the fact that is nontoxic and fast drying. I would also like to try it for its warm color compared to Ivory Black.