The Carbuncle belongs to the same species of stone as the Garnet, the latter being cut with facets, while the former is cut en cabochon, or with a rounded surface. It is found in India, Ceylon, Brazil, and the Cape, and has been described by mediaeval writers (including Chaucer and Mandeville) as giving forth light in darkness, whilst in old legends a large Carbuncle is said to have served Noah as a lamp.

Shakespeare also refers to the light that comes from this stone, and these descriptions may have arisen from the fact that many very sensitive or psychic people are able to see a certain luminous effect surrounding the gem. It was a very popular stone with the Ancient Hebrews, who knew it as Baraketh, or flashing stone, which is derived from Barak, meaning lightning. Camillus Leonardus recommends it as a safeguard from poison, and in infectious illnesses, for repressing extravagance, and for mightily increasing the popularity and prosperity of its wearer.

During the Middle Ages it was believed to protect its owners from the plague, also to banish sadness, dispel evil thoughts, repress sensuality, reconcile differences between friends, and attract success to all undertakings, as well as to cure indigestion and sore throat if suspended round the neck.

According to Pliny there are male and female stones, the deep red being masculine and the lighter-coloured feminine, a belief also held with regard to other gems.

Amongst the tribes of Northern India and Africa it was believed to protect from wounds in battle, an idea also common amongst the Arabs.