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TrueFacet's Fine Jewelry and Watch Guide

All About Opal: The October Birthstone

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The primary birthstone for the month of October is a mineraloid that goes by the name of opal.

The Origins and Cultural Significance of Opal

It was believed the word “opal” was adapted from the Latin term opalus, though many modern references suggest it is adapted from the Sanskrit word úpala. 

In the Middle Ages, opal was sometimes considered a stone that provided the wearer with good fortune, good health, and love because it was believed that each gemstone color represented in opal’s spectrum allowed the stone to possess the powers and characteristics of them all. However, opal is also known to have a negative stigma attached to it. For example, there were countries in Europe that feared opals because they believed the stones possessed the “Evil Eye,” largely due to the fact that it looks like the eyes of animals and reptiles such as cats, snakes, and frogs, which were said to be used in spells cast by witches and warlocks.

Despite the negativity surrounding opals, there have been plenty of cultures that have credited the colorful gem with supernatural characteristics and healing powers. The ancient Greeks believed opals protected their owners from illnesses and even allowed them the ability of prophecy. Even some Arabic legends believe that opals had fallen from the heavens during lightning storms. 

Opals, unlike its birthstone predecessor sapphire, are for the most part not found all over the world. Most opals are mined in Australia, Ethiopia, Mexico, and parts of the United States (though smaller deposits have also been found in Brazil, Indonesia, Canada, Turkey, and other countries). In the United States, northern Nevada’s “Virgin Valley” opal fields produce a wide variety of precious fire opal, black opal, white opal, and lemon opal, with the largest producing mines of Virgin Valley being the Rainbow Ridge, Opal Queen, Royal Peacock, Bonanza, and WRT Stonetree/Black Beauty mines. 

Notable Opals

olympic australis opal

The Olympic Australis opal.

The largest and most valuable opal found to date is the Olympic Australis, found in 1956 at what is known as the “Eight Mile” opal field in the outback opal gemstone mining town of Coober Pedy in South Australia. Weighing roughly 17,250 carats, the Olympic Australis was named for the Olympic games which were held in Melbourne, Australia the same year the stone was discovered. Valued at $2,500,000 AUD, the gem currently resides in Sydney, at the offices of Altmann & Cherny Ltd.

The Properties and Hardness of Opals


Coming in at a 5.5 to 6 rating on the Mohs hardness scale, opal is much softer than many of the other birthstone gems and should be worn sporadically and stored carefully to avoid being damaged by other gems or jewelry.

Because of its colorful characteristics and wide array of prismatic displays of varying hues, opal can look appealing whether it is set in white, yellow, or rose-colored metals. Oval shaped opals are often seen as jewelry centerpieces surrounded by a halo of white diamonds, but Boulder opals and black opals in funky shapes look just as inviting set into high carat yellow gold and enhanced with colored gemstones that are reflected in the opals, themselves.