Black opal and diamond ring. Black opals are a particularly prized variety of opal, primarily found in Australia, and are so-called because their plays of colour flash dramatically against a dark background. This navette-shaped cabochon, carved from a single piece of black opal, throws out a kingfisher-like palette of deep indigo, azure and green colour flashes, in a display that illuminates the entire surface of the stone. The navette-shaped mount follows its outline beautifully, contrasting the deep body colour of the central stone with a light, sparkling border of circular-cut diamonds. Opals are relatively soft stones, but the secure collet setting of this opal allows it to cope perfectly with occasional wear.