A reddish brown semiprecious stone used for beads, seal stones, and jewelry in antiquity. The Indus Valley civilization, Greeks, and Romans valued the stone. It is a translucent variety of the silica mineral chalcedony. Carnelian is usually found in volcanic rocks, such as the Deccan Traps of western India. Engraved cornelians in rings and signets have offered information about manners and customs of ancient Greeks and Romans.