Black Opal

Black Opals are valuable gems in the game which may be found. This item appears in Baldur's Gate (game), Baldur's Gate: Enhanced Edition, Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition.

In-game description
"Black Opal has a greenish hue with black mottling and gold flecks. Usually found in ancient hot springs, the gem is tumbled smooth and cut cabochon. The phrase in the north "Black as an opal" is used as a subtle form of praise for kind-hearted rogues and the like."