Spectacular Black (Dark Brown) Nevada Opal. Royal Peacock Mine, Virgin Valley, near Denio, Nevada © 2002-2010 Bonhams 1793 Ltd Weighing 25.48 carats and measuring 19.5 x 28.0 x 7.5mm - Estimate: $10,000 - 15,000 Note: Some of the most stunning black opals...