Note:  Do not rely on this information. It is very old.

Jasper

Jasper, an opaque, impure, non-crystalline form of silica, generally red from iron peroxide or brown from its hydrous form. These colours occur in bands in ribbon jasper. Bloodstone or heliotrope (q.v.) ought apparently to be classed with the opaque jaspers rather than with the translucent chalcedonies. The jasper of the ancients seems to have been green and translucent, a prase, chrysoprase or plasma.