Individuals born in October get to choose between two birthstones—tourmaline and opal. Each gem then unveils nearly limitless possibilities, as each one comes in a rainbow of shades and color combinations.
In fact, both of October’s birthstones came to earth through a journey involving rainbows, according to legend.
Between tourmaline (whose color depends on trace elements in its chemical makeup) and opal (which diffracts light to show a play of multiple colors), October’s birthstones offer a full spectrum of gems to suit anyone’s personal tastes.
he 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 gem’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 gems 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 gem 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 gem with good luck. Though some recent superstitions claim that opals can be bad luck to anyone not born in October, this birthstone remains a popular choice.
Writers have compared opals to volcanoes, galaxies, and fireworks. Admirers gave extraordinary opals poetic names like Pandora, Light of the World, and Empress. In ancient Rome, this gem symbolized love and hope. The Romans gave it a name—opalus—that was synonymous with “precious stone.”
In 75 AD, the Roman scholar Pliny observed, “Some opali carry such a play within them that they equal the deepest and richest colors of painters. Others…simulate the flaming fire of burning sulphur and even the bright blaze of burning oil.” He marveled that this kaleidoscopic gem encompassed the red of ruby, the green of emerald, the yellow of topaz, the blue of sapphire, and the purple of amethyst.
Many cultures have credited opal with supernatural origins and powers. Arabic legends say it falls from the heavens in flashes of lightning. The ancient Greeks believed opals gave their owners the gift of prophecy and guarded them from disease. Europeans have long considered the gem a symbol of hope, purity, and truth.
Opal is considered an October birthstone. Some people think it’s unlucky for anyone born in another month to wear an opal. But that particular superstition comes from a novel written in the 1800s (Anne of Geierstein by Sir Walter Scott), and not from any ancient belief or experience. In fact, throughout most of history, opal has been regarded as the luckiest and most magical of all gems because it can show all colors. Once, it was thought to have the power to preserve the life and color of blond hair.