Carnelian is a red to orange variety of chalcedony, a type of microcrystalline quartz. Its color ranges from light orange to a deep red and is due to the presence of iron oxide impurities. Carnelian is commonly found in sedimentary rocks and can form in botryoidal or fibrous structures. It has a Mohs hardness of 6 to 7, making it durable and suitable for use in beads, cabochons, and jewelry. Carnelian is found in various regions, including India, Brazil, and the United States. It has been used for thousands of years in carvings and signet rings.