Moonbar Gem

Moonbar Gems 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
"Moonbar is a pearly white, opaque gemstone, usually pale blue with green and gold mottling. Related in type to fire and black opals, but is only slightly more common."