How Much Is an Opal Worth?

Opal is priced on entirely different criteria from other gemstones, because its value comes from play of color, the shifting spectral flashes produced by silica spheres diffracting light. Two opals of identical size and origin can differ in price by a hundred times based on how bright, complete, and directionally stable that play of color is. The type hierarchy runs black opal at the top, then boulder opal, then crystal, then white or milky opal at the bottom. Black opal from Lightning Ridge in New South Wales is the most valuable, because a dark body tone makes the color flashes appear far more vivid. Ethiopian Welo opal entered the market in quantity after 2008 and offers bright color at much lower prices, though it is hydrophane, meaning it absorbs water and can temporarily lose transparency or crack. Doublets and triplets, which are thin opal slices backed and capped with other materials, look impressive but are worth a small fraction of solid stones.

Play of color is the dominant variable and is assessed on brightness, the range of colors present, and whether the color holds from all viewing angles. Red is the rarest and most valuable flash color, followed by orange, then green, then blue, which is the most common. Body tone, graded on a scale from N1 for black to N9 for white, matters enormously because darker bodies make color appear more vivid. Pattern has its own hierarchy, with named patterns like harlequin, rolling flash, and Chinese writing commanding premiums over random pinfire. Solid versus doublet or triplet is a fundamental split that many buyers miss, and doublets are worth a small fraction. Origin matters, with Lightning Ridge black opal at the top. Finally, stability is a real concern: Ethiopian hydrophane opal can craze and crack, and any visible crazing eliminates most of the value.