Semi-Black Opal (Test Stone F) Lightning Ridge Black Opal Semi-black opal with shifting green and orange fire.
Black Opal (Test Stone E) Lightning Ridge Black Opal Deep-toned black opal with stronger blue-green play-of-colour.
Crystal Opal (Test Stone D) Lightning Ridge Black Opal Soft-toned crystal opal with gentle flashes of green, blue and yellow.
