Jasper, a form of chalcedony, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions in what is basically a chert. The mineral breaks with a smooth surface, and is used for ornamentation or as a gemstone. It can be highly polished and is used for vases, seals, and snuff boxes. The specific gravity of jasper is typically 2.5 to 2.9.[3] Along with heliotrope (bloodstone), jasper is one of the traditional birthstones for March. Jaspilite is a banded iron formation rock that often has distinctive bands of jasper.