Jasper, an opaque form of quartz that contains iron oxide or iron hydroxide as an impurity. Jasper is usually red, brown, grayish green, or yellow. The stone is very hard and takes a high polish. It is used for inlays and for such ornamental objects as vases and decorative table tops. Showy or unusual forms of jasper are often used in jewelry. Ribbon, or riband, jasper is jasper in striped layers, or banded with rock crystal. Porcelain jasper is porcellanite, a dense, siliceous rock resembling unglazed porcelain. Brown or yellow jasper, also called Egyptian jasper, is usually streaked or clouded. Jasper occurs abundantly in veins and masses in many parts of the world.