Why We Love This Gemstone
The name “opal” originates from the Greek word opallios, which meant “to see a change in color.”
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 rainbow 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.