A carbuncle is an archaic name given to any red cabachon cut gemstone. The name applied particularly to red garnet. The word occurs in four places in most English translations of the Bible. Each use originates from the Vulgate's Latin translation of the Septuagint's Greek term Anthrax - meaning coal, in reference to the colour of burning coal; in this sense, a carbuncle is usually taken to mean a gem, particularly a deep-red garnet, unfaceted and convex. In the same place in the masoretic text is the Hebrew word בָּרְקַת בָּרְקַת or bâreqath bâreqath (baw-reh'-keth, baw-rek-ath'); however, the Hebrew definition is less definite and the precise color of the gems is not known.
Exodus 28:17 and 39:10 both refer to the carbuncle's use as the third stone in the breastplate of the Hoshen.
Ezekiel 28:13 refers to the carbuncle's presence in the Garden of Eden.
Isaiah 54:12 uses carbuncle to convey the value of the Lord's blessing on His faithful servants:
"And I will make thy windows of agates, and thy gates of carbuncles, and all thy borders of pleasant stones."