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 in the world come from the Royal Peacock mines in Virgin Valley, Nevada. Discovered in 1912, in an isolated area thirty miles southwest of Denio at an elevation of 5,000 to 6,000 feet, the Royal Peacock mine is located in the southern end of Virgin Valley. The Wilson family purchased the mines in 1944 and commenced excavation; ten to thirty feet of overburden is stripped off with heavy equipment to expose the opal bearing clay. The present specimen was collected as a nodule over five years ago at this famed mine and was fashioned as an oval cabochon by an Arizona lapidary. An important American gemstone, this cabochon represents the finest Virgin Valley black (dark brown) opal available on the market. Rarely found in sizes this substantial and certainly not with this vibrant a hue; the gem has an even, translucent dark brown body color known by mineral hobbyists as "root beer". The play-of-color for this material is superb and evenly distributed across the entire opal with flashes of mainly orange, red and green with touches of violet. This gem is worthy of consideration by any opal collector, particularly those interested in American gemstones.

Bonhams & Butterfields. The Nature of Opals, 10 Nov 2010. 220 San Bruno Avenue, San Francisco www.bonhams.com