An opaque, impure type of massive fine-grained quartz that typically has a tile-red, dark-brownish-red, brown, or brownish-yellow color. The color of the reddish varieties of jasper is caused by admixed, finely divided hematite, and that of the brownish types by finely divided goethite. Jasper has been used since ancient times as an ornamental stone, chiefly of inlay work, and as a semiprecious gem material. Under the microscope, jasper generally has a fine, granular structure, but fairly large amounts of fibrous or spherulitic silica also may be present.