Opal gemstones captivate us, mainly because of their unique optical characteristics. Opals often exhibit a spectrum of colors called “play-of-color,” which is observed in various kinds of lighting. The Roman naturalist, Pliny the Elder, referred to opal’s play-of-color in the 1st Century A.D., when he wrote: “For in them you shall see the living fire of ruby, the glorious purple of the amethyst, the sea-green of the emerald, all glittering together in an incredible mixture of light.”

Opal is an October birthstone. Every opal is unique in appearance, which makes them desirable for anyone who craves individual expression.

Opal Facts

  • Opals can have fiery play-of-color, but they can also be colorless, opaque, translucent or transparent.
  • Opal has a hardness of 5.0-6.5 on the Mohs Hardness Scale. Due to their relative softness, opals are rarely faceted.
  • The majority of the world’s precious opal comes from Australia, where it is the national stone. Other sources include Brazil, Ethiopia, Madagascar, Mexico and Peru.
  • Opals are mainly cut as cabochons or fashioned as beads.

Opal Treatment

  • Opals may be treated to enhance their color or appearance. Any treatments should be disclosed to the consumer.

Synthetic Opal

  • The discovery of the ordered spherical structure of precious opal led to its synthesis in the 1970s. Information about any stone known to be synthetic – made in a lab rather than mined – should be disclosed to the buyer.

Opal Care & Cleaning

  • To minimize scratching and wear, store each piece of fine jewelry separately in a soft cloth or padded container.
  • Opals should not be subjected to heat, chemicals, temperature and air pressure changes, because they are somewhat delicate.
  • The best way to clean opal jewelry is with warm, sudsy water and a tightly woven microfiber or other soft cloth. Always avoid ultrasonic machines and steam-cleaning.
  • Take all your fine jewelry to a professional jeweler at least twice a year for a thorough cleaning and inspection.
  • See our full guide to jewelry care and cleaning.

Content © GIA. Image © Robert Weldon/GIA

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