Carnelian (also spelled cornelian) is a brownish-red mineral commonly used as a semi-precious gemstone. Similar to the carnelian is sard, which is generally harder and darker (the difference is not rigidly defined, and the two names are often used interchangeably). Both carnelian and sard are varieties of the silica mineral chalcedony colored by impurities of iron oxide.
It ranges in color from pale orange and yellow-orange to rich, near reddish-orange, to orangey-brown, even to an intense almost-black coloration and varies from semi-opaque to highly translucent. Iron is the source of its color and as a result, it can be easily heat-treated, (even by the sun’s heat alone,) to dark red tones as the iron is oxidized.
The term, "carnelian" is a 16th-century corruption of the 14th-century word "cornelian". Cornelian, cognate with similar words in several Romance languages, comes from the Mediaeval Latin corneous, itself derived from the Latin word cornum, the cornel cherry, whose translucent red fruits resemble the stone.
The red variety of chalcedony has been known to be used as beads since the Early Neolithic in Bulgaria. Carnelian was recovered from Bronze Age Minoan layers at Knossos on Crete in a form that demonstrated its use in decorative arts; this use dates to approximately 1800 BC. Carnelian was used widely during Roman times to make engraved gems for signet or seal rings. Sard was used for Assyrian cylinder seals, Egyptian and Phoenician scarabs, and early Greek and Etruscan gems. There is a Neo-Assyrian seal made of carnelian in the Western Asiatic Seals collection of the British Museum that shows Ishtar-Gula as a star goddess.
Most commercial carnelian comes from India, but it is mined worldwide. Gem-quality sources also include Brazil, Egypt, Indonesia, Rusia (Siberia), Germany, and Uruguay.