Carnelian

Known as the stone of artists because it stimulates creativity, carnelian is a variety of chalcedony  acclaimed by many cultures, from ancient Egypt to ancient Rome through India and China.
Recognizable by its  translucent fiery-orange color, the Egyptians called it “sunset stone“. The Romans widely used carnelian for the realization of signet rings because the hot wax does not adhere to this stone. This is why we find many rings set with a carnelian engraved with inscriptions meant to bring luck and protection to their owner.
Finally, the story says that the seal of Muhammad was an engraved carnelian, set on silver.