A variety of chalcedonic (see chalcedony) silica (SiO2) which is reddish-brown, opaque, and cryptocrystalline. It may be banded to give ‘Egyptian jasper’ (‘ribbon jasper’). A contact metamorphosed (see thermal metamorphism) shale may also be baked to give ‘porcelain jasper’ which may be similar in appearance but has a different composition.