Rare Indonesian Hyrdophane Opal. Rangkasbitung, Banten Province, West Java, Indonesia  © 2002-2010 Bonhams 1793 Ltd

Weighing approximately 23.0 carats and measuring 23.0 x 22.5 x 9.75mm. Sold for $2,745

It is a little known fact that Indonesia produces some of the most beautiful opals in the world – although still in very small quantities. The opals are all of volcanic origin and just about every type of opal can be found including milky white, crystal white opals, boulder opal (but not with an ironstone matrix as in Queensland), jelly opals and black opals (known as "Java Black").

The present free-form opal, obtained directly from the miner, displays a light golden brown body color and brilliant harlequin pattern play-of-color in hues of red, green, yellow and orange. Known as hydrophane opal, this type of opal has little or no play of color when wet, but is perhaps the brightest of all opals in the world after cutting, polishing and being thoroughly dried. Hydrophane opals also exist in Australia but they are just the opposite – dull when dry but with a beautiful play of color when wet.

Footnote: An article about this find of Javanese opals, entitled "Fireworks at Midnight", By Irwan Holmes, appeared in Lapidary Journal, June 1986.

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