Black Oval Cabochon Opal. Lightning Ridge, New South Wales, Australia. Photo Bonhams

Even within the category of black opals, some are more sought-after than others. The present stone is such a piece—surpassed by few other opals in terms of its vibrancy of color—a true 5/5 for vividness and presence of color. Distinctive also is its "flagstone" pattern play-of-color: dominated by broad patches of electric blue, purple, green and orange at the edges and centering on a "windmill" pattern of predominantly fiery red and orange to the center. This is a world-class opal of fine quality for the discerning collector. Weighing approximately 9.90 carats and measuring 18.0 x 14.5 x 5.0mm. Sold for US$ 76,900

Bonhams. 11 Dec 2012 13:00 PST California, Los Angeles. The World of Opals, The Splendor of Gold including the Margie and Robert E. Petersen Collection of Gold Nuggets