Jasper, an aggregate of microquartz and/or chalcedony and other mineral phases, 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. The mineral aggregate 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.