Opals are more than just beautiful gems—they’re like rainbows you can wear! Their unique phenomenon, known as play-of-color, showcases an extraordinary display of flashing rainbow hues. This dazzling optical effect has made opals cherished for centuries. Even the name “opal” stems from the Greek word "opallios," meaning “to see a change in color.” But what makes these gems even more fascinating is their history and symbolism.

While opals were traditionally considered symbols of good luck, fortune, and hope, a strange rumor in the 1820s turned public opinion. It was said that opals were unlucky—unless you were born in October. How did this bizarre superstition take hold?

It turns out the source was a work of fiction. In 1829, Scottish novelist Sir Walter Scott published Anne of Geierstein, a book in which an opal, worn by one of the characters, is portrayed as demonically possessed. After coming into contact with holy water, the opal shatters. Despite the thrilling adventure of the novel, the portrayal of the opal spread misinformation, and the gem developed an undeserved reputation.

Before that fictional tale, opals had always been revered for their brilliant color play and symbolism of hope and good fortune. One famous opal necklace, featured in the Smithsonian’s collection, was even designed by the renowned Tiffany & Co. (Yes, that Tiffany!).

But What Causes Opals to Shine?

The breathtaking colors of opal are due to millions of years of natural processes. Formed from silica deposits in the earth’s crust, opals are most commonly found in Australia, thanks to the region’s unique weather patterns. During seasonal rains, water seeps into the ground, carrying dissolved silica deep below the surface. During dry periods, the water evaporates, leaving behind silica deposits. Over time, these deposits solidify into the precious opals we know today.

Interestingly, despite their solid appearance, opals still contain about 3% to 20% water. Because of this, gemologists recommend handling opals with care. To avoid "crazing," which is the development of tiny cracks that look like spiderwebs, it's essential to keep opals moist and protect them from excessive heat or light. Jewelry pieces like earrings, necklaces, or brooches are ideal ways to wear opals while keeping them safe from drying out.

Opals owe their play-of-color to their microscopic structure. When examined under a powerful electron microscope, the silica spheres that make up an opal are arranged in a three-dimensional grid. The size of these silica spheres determines the colors we see—the smallest spheres produce violet, while larger ones create red. This microscopic structure is why no two opals are exactly alike; each gem has its unique color display depending on the arrangement and size of its silica spheres.

A Fossilized Wonder

The same silica that forms opals can also preserve fossils, leading to remarkable opalized fossils. The Smithsonian Institution houses a collection of these opalized fossils, including a vertebra with remarkable play-of-color. Australia, the world’s leading source of high-quality opals, also displays fascinating opalized fossils, such as a pliosaur skeleton, at the National Opal Collection in Sydney .

Australia’s unique climate, with its silica-rich soils, rainy seasons, and subsequent dry spells, creates the perfect environment for opal formation. The town of Lightning Ridge in New South Wales is especially famous for producing some of the world’s most exquisite black opals, further cementing Australia's status as a hub for opal mining .

Final Thoughts

Opals are as fascinating as they are beautiful. With their stunning play-of-color and rich history, they’re truly one-of-a-kind gems. Whether you’re wearing opals for their beauty or their symbolic meaning of hope and good fortune, they’re sure to bring a little rainbow into your life.

So, next time you see an opal, remember: it's not just a stone, it’s a colorful piece of history millions of years in the making. And don’t worry—those old superstitions about bad luck? They’re just a relic of the past!