Jasper, an aggregate and/or 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. Jasper breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals , and snuff boxes of jasper is typically 2.5 to 2.9. A green variety with red spots, known as heliotrope (bloodstone) , is one of the traditional birthstones is a banded-iron-formation rock that often has distinctive bands of jasper.