O, the power of the pen. With just one strange plot twist in his 1829 bestseller, “Anne of Geierstein,” Sir Walter Scott destroyed the European opal market for nearly 50 years. And he did it just by having a character falsely accused of being a demoness die shortly after a chance drop of holy water fell on her opal and quenched its mysterious, fiery color. Convinced Scott was warning them that wearing opal could bring bad luck, suggestible readers stopped buying the gem. Within a matter of months, the opal market had crashed and prices were down more than 50 percent.
It took a remarkable find of black opal at Lightning Ridge in New South Wales, Australia, in 1877, to revive the market for this gem. Australia’s spectacular new opals took the world by storm. Indeed, there have been almost no opals found in the last 50 years to match what came from Lightning Ridge in its late nineteenth and early twentieth century heyday. No wonder dealers sometimes liken Lightning Ridge’s impact and significance to that of Kashmir for sapphire, a Himalayan source discovered around the same time, that set the standard for sapphire in the same way Lightning Ridge did for opal.
Lightning Strikes Once
Black opal is far rarer than white opal. In fact, there are only two active black opal localities in the world, both in Australia. Of the two, the older, Lightning Ridge, is said to be the only one to produce true black opal. The other, Mintabe, is known more for gray-to-grayish-black material. Some purists even protest calling Mintabe stones black opal. They do so on both geological and aesthetic grounds.
Traditionally, black opal was considered a variety of opal found in rock formations called nodules (or “nobbies” in the trade) as opposed to white opal, which is found in seams. But when Mintabe, whose opal is also found in seams, was discovered, this geology-based distinction began to blur- at least among dealers.
One can see why opal dealers insist that Mintabe’s dark- gray material be accorded full standing as black opal. If they had to restrict their definition to goods from fast-depleting Lightning Ridge, the future of this gem would be in grave doubt. For even when production from Lightning Ridge and Mintabe are pooled together, there is still far less black than white opal. Given its relative scarcity, black opal has never lent itself to volume jewelry use the way white opal has. As a result, black opal remains primarily a special order stone in this country. But the few who buy it here generally look for the same things the Japanese do: base color, hue mixture and color pattern.
Basics of Opal Beauty
When dealers evaluate black opal, they start with its base color. The darker the base- or what dealers call “potch”- of an opal, the more pronounced and vivid its color. That’s because an opal’s beauty is the product of the contrast between its color play and its background.
As for ideal color in black opal, most experts look for the predominance of red and then orange. “Stones that appear all or almost all red are the most coveted,” one dealer explains. “Increasing amounts of blue and green will reduce their value.”
But specific color isn’t all that connoisseurs want in a fine black opal. The pattern that they take is equally important. For years, the most prized pattern was what dealers call the “harlequin”: well-defined squares, rectangles, triangles or diamonds of color in both symmetrical and asymmetrical designs.
Today, unfortunately, the harlequin pattern is encountered only in older pieces. No new stones with this pattern have been mined in years. Failing to find stones with big blocks or even chunks of color, connoisseurs must content themselves instead with swirls. Often you’ll hear them describe the best patterns that can be hoped for in black opal today as stones that exhibit broad well-defined flashes of color (called “rolling flash” in the trade) that change kaleidoscopically as stones are turned in the hand. Yet even these patterns are far from plentiful.
Realistically, the top black opals that consumers are likely to be offered nowadays feature color patterns comprised, at their best, of lively pointillistic dots. As these dots get smaller and less vivid, they come to resemble what the trade calls “pin fire.” Such black opals are the most commonly found and least expensive.