For more than a century, the landscape of Lightning Ridge, Australia, has been transformed by opal fever. For miles in all directions, this flat, desert-dusty land of cactus and brush is dotted with thousands of holes, with small piles of mine tailings next to them. Lightning Ridge—formerly Wallangulla, approximately 500 miles north-northwest of Sydney—is the black opal capital of the world.

Since its discovery in the late 1800s, this dark-bodied iridescent gemstone has ridden a roller coaster of availability. Sometimes the miners are “on opal,” finding enough to keep them busy and their clients happy for months. Other times there’s little opal to be found. For the professionals, it’s a daily job, a lifelong quest. For others, it’s a vacation, a retirement hobby they can leave after a few weeks or months of digging in someone’s old claim and then go back to the city and enjoy life with modern conveniences.

It’s a hard life digging a 50-foot hole on your 2,500 square meters (the size of a proper claim is 50 by 50), searching underground for a big strike of seam opal or nobbies. Seam opal follows the layers of earth, providing thin to thick tablets of opal. When thick enough, seam opal can be carved into designs or undulating free-forms. Nobbies, on the other hand, are small, rounded chunks of opal that can be turned into pieces that display opal’s characteristic iridescence through 360 degrees.

For those uncertain of value, the Lightning Ridge Opal Advisory Board (also called the pricing board) meets every Saturday to examine and value any opal. Several members of the trade along with professional valuers (licensed appraisers) establish a median value and present that to the owner of the opal. This value can be used to protect the seller’s interest, or can be used simply as a starting point for negotiation. The pricing board establishes value, not price.

Truly fine black opal has vibrant colors unlike that of any other gem. Lightning Ridge black opal produces an ever-changing display of spectral colors that has been compared to a miniature three-dimensional fireworks display set against the backdrop of a midnight sky.

While by definition black opal possesses iridescent colors against any dark background, the finest Lightning Ridge black opal has a pure pitch-black background. Some exceptional pieces are naturally backed in black, while others have 360-degree iridescence, front and back, side to side, top and bottom, with the spectral colors and contrasting black embedded throughout the opal.

That pitch-black background is the key to Lightning Ridge opal’s beauty and value. The blackness produces a higher contrast ratio, i.e., the ratio between the blackest blacks and the whitest whites. It’s the same characteristic TV salesmen tout when discussing high-definition television. The greater the ratio, the better the color.

Similarly, the contrast aspect of brilliance in the finest cut diamonds derives from the contrasting superblack reflections and the vivid reflections of fire and brilliance. This contrast, often due to obstruction of light by the observer’s head, results in brilliant spectral colors called the diamond’s fire.

So, to achieve the highest contrast on television, in a diamond, or in an opal, the blacks have to be really black, with the saturation levels of all other colors as vivid as possible. In television, it’s called high-contrast high definition. In diamonds, it’s called the Ideal cut. In Lightning Ridge, opal experts smile and call it the real thing.