The black opal is a natural solid stone usually possessing an opaque body but can also be crystal, the body color ranges from dark grey to black, and from which the background the overlying spectral colors are enhanced. This occurs because the dark background of the opal absorbs the otherwise scattered white light which is developed in lighter varieties of opal and which invariably dilutes and diffuses the color play. Consequently, the visual impact and brilliance of the spectral colors are much enhanced.
Usually, even the most valuable black opals have an uppermost layer containing the gem color play overlaying the dark base beneath, which is generally devoid of color and may have a thin color bar on black potch.
Black opal is the rarest and most valuable of all opal. It is most sought after because the dark background enhances the brilliance of the diffracted colors. High quality stones are very rare and are easily distinguished by their dark body color. The darker the body and brilliance of fire the more valuable the gem stone. The majority of black opal comes from lightning Ridge, New South Wales, Australia.