OCTOBER BIRTHSTONES

Lightning Ridge Collection

The name “opal” originates from the Greek word opallios, which meant “to see a change in color.” The Roman scholar Pliny used the word opalus when he wrote about this gemstone’s kaleidoscopic “play” of colors that could simulate shades of any stone.

Opal’s characteristic “play-of-color” was explained in the 1960s, when scientists discovered that it’s composed of microscopic silica spheres that diffract light to display various colors of the rainbow. These flashy gemstones are called “precious opals;” those without play-of-color are “common opals.”

Dozens of opal varieties exist, but only a few (like Fire Opal and Boulder Opal) are universally recognized. Opals are often referred to by their background “body color”—black or white.

Opal’s classic country of origin is Australia. Seasonal rains soaked the parched Outback, carrying silica deposits underground into cracks between layers of rock. When the water evaporated, these deposits formed opal. Sometimes, silica seeped into spaces around wood, seashells and skeletons, resulting in opalized fossils.

Since opal was discovered in Australia around 1850, the country has produced 95 percent of the world’s supply. Opal is also mined in Mexico, Brazil, Honduras, Ethiopia, the Czech Republic and parts of the U.S., including Nevada and Idaho.

The water content of opal can range from three to 21 percent—usually between 6 and 10 in gem-quality material. This, combined with hardness of only 5.5 to 6 on the Mohs scale, makes opal a delicate gemstone that can crack or “craze” under extreme temperature, dehydration, or direct light.

Wearing opal is well worth the extra care, though. For centuries, people have associated this gemstone with good luck. Though some modern superstitions claim that opals can be bad luck to anyone not born in October, this birthstone remains a popular choice.

Lika Behar Collection

According to Arabic legend, opals fell from the sky in bolts of lightning. Australian aborigines, meanwhile, believed that the creator came to Earth on a rainbow, leaving these colorful stones where his feet touched the ground.

In 75 AD, the Roman scholar Pliny compared opals to volcanoes and vibrant paintings, noting that their dancing “play” of color could simulate shades of any gemstones.

During the Middle Ages, people believed that the opal possessed the powers of each gemstone whose color appeared in its sheen, making it a very lucky stone.

But Sir Walter Scott’s 1829 book, Anne of Geierstein, transformed opal’s lucky perception. The story featured an enchanted princess who wore an opal that changed colors with her moods. A few drops of holy water extinguished the stone’s magic fire, though, and the woman soon died.

People began associating opals with bad luck. Within a year after publication of Scott’s book, opal sales in Europe fell by 50 percent.

Discoveries of opal deposits in Australia revived opal’s image after 1850 and began producing 95 percent of the world’s supply, and many of its finest opals.

The world’s largest and most valuable opal, “Olympic Australis,” came from Coober Pedy, Australia in 1956, during the Olympic Games in Melbourne. Valued at $2.5 million in 2005, this gemstone measures 11 inches long and weighs 17,000 carats (7.6 pounds).

After scientists discovered the spherical silica structure of opal in the 1960s, they figured out how to synthesize it in 1974.

Since then, opal has gained more popularity through recent discoveries in Ethiopia. Material mined in the Shewa Province in 1994 wasn’t desirable because it was dark and tended to crack easily. But deposits in the Wollo Province, discovered in 2008, brought vivid play-of-color displays to the market.

Le Vian

Opal has been a good luck charm for centuries—though recent superstitions consider it lucky only for people born in October, and unlucky to anyone else.

However, opal’s kaleidoscopic play-of-color can suit many changing moods and tastes to make this gemstone appropriate for anyone. It is also the traditional gift to celebrate 14th wedding anniversaries.

Like diamonds, opals can be evaluated by color, clarity, cut and carat weight. But these unique gemstones also have several additional conditions to consider.

Color is the key factor of opal quality: both the background “body color” and the flashing “play-of-color.” Dark backgrounds provide more contrast against vivid play-of-color, making black opal more highly valued than milky white varieties.

Pattern is another factor unique to opal. Descriptive names like “stained glass,” “peacock,” “rolling fire,” and “Chinese writing” distinguish opal patterns. Gemologists typically prefer large, concentrated patches over small specks.

Different opal varieties have varying clarity standards. Crystal opals should be transparent, while opacity makes black opals more valuable. A cloudy, milky haze lowers any opal’s value, and may indicate instability.

Due to high water content, opal can easily crack or “craze” under extreme temperatures, dehydration, or direct light. Crazed opal sells at much lower prices, and is more susceptible to fracture. Even high-quality opal demands delicate care.

Fine opals are often cut into irregular shapes to emphasize play-of-color. When possible, opals should be cut cabochon with rounded domes. But most opal comes in thin layers, which are commonly mounted on another dark stone like onyx or obsidian (as a doublet) and sometimes capped with clear glass or plastic (as a triplet) to make this fragile gemstone more wearable.

Opals may be treated with wax, oil, smoke, plastic or other additives to enhance luster. Identifying enhancements or synthetic materials may require specialized lab equipment, so it’s best to work with an American Gem Society jeweler who understands the criteria that determine opal’s value.

Gregg Ruth

Egyptian legend tells that tourmaline found its famed array of colors when, on its journey up from the Earth’s center, it passed through a rainbow. Because of its colorful occurrences, tourmaline has been confused with other gemstones throughout history.

In the 1500s, a Spanish conquistador found green tourmaline in Brazil—which he mistook for emerald. His error held until the 1800s, when mineralogists finally identified tourmaline as its own mineral species.

Variations of the name “schorl” may have been used to describe black tourmaline even before 1400. The name comes from a village in Saxony, Germany, (now called Zschorlau) near a mine with black tourmaline deposits.

The Dutch East India Company brought Sri Lankan tourmaline to Europe for centuries before traders realized it was the same mineral as schorl.

American tourmaline deposits caused the gemstone’s spike in popularity. In 1876, mineralogist George Kunz launched a craze when he sold green tourmaline from Maine to Tiffany & Co.

In the early 1890s, tourmaline was reported in California—where Native Americans had, for centuries, given certain colors of the gemstone as funeral gifts.

At that point, China represented the biggest market for tourmaline. The Chinese Empress Dowager Cixi was particularly fond of pink tourmaline, and she purchased large quantities of it from deposits in San Diego County.

The Chinese market was so critical to tourmaline, in fact, that when the Chinese government collapsed in 1912, it took tourmaline trade down with it.

Brazilian tourmaline discoveries in the 1980s and 90s reignited interest in this gemstone, because material mined in Paraíba displayed such striking neon greens, radiant blues, and vivid violets. This region has produced the world’s finest, most valuable specimens of tourmaline—including the world’s largest, weighing 191.87 carats.

Omi Privé

No two tourmaline gemstones are exactly alike, which makes this a one-of-a-kind gift for any individual—especially someone celebrating an October birthday or an eighth wedding anniversary.

With a wide variety of colors, qualities, and sources available, there’s tourmaline to suit a range of styles and budgets. Like diamonds, tourmaline is evaluated by the criteria of: color, clarity, cut, and carat weight.

In general, darker toned tourmaline that appears black is priced lower than brightly colored material. Rubellite tourmaline, in shades of pink or red, is one of this gemstone’s most desirable colors.

Green and blue tourmaline are also popular, though the most striking shades of these colors come from Brazil’s exotic and rare Paraíba tourmaline. Prices can run $10,000 per carat, making this the most valuable variety of tourmaline.

Inclusions are common in tourmaline, because liquid inclusions and crystals can get trapped during formation. It’s not uncommon for red or pink tourmaline to display visible inclusions, but inclusions can lower the value of other colors, depending on their visual impact.

Some tourmaline material, especially rubellite, undergoes heat treatment to improve color. Other tourmaline is clarity-enhanced to remove inclusions, which can significantly lower the value. 

Because tourmaline forms in slender, columnar crystals, many finished gemstones have long, irregular shapes.

Tourmalines tend to absorb light differently down the length of a crystal, versus than across it. This optical property is called “pleochroism,” which means they appear different colors from different directions—so the cut is critical.

Tourmaline can come in a range of sizes, but Paraíba tourmaline is rare in sizes larger than one carat. But with these stones, color is more highly valued than size, so a small, brightly colored gemstone is preferred over a large, dark one.

With such a wide range of tourmaline options available—from the common, inexpensive schorl to the highly-valued Paraíba—the price of these gemstones can vary greatly.