Opal is a hydrated amorphous silica, meaning it naturally contains a significant amount of H2O, from a minmum of 3% up to 21% by weight. The internal structure of gem quality Opal causes it to diffract light, causing a play of color, which can display virtually all colors from blue, to pink, green, yellow, white and black. When examined under a microscope, Opal has microscopic spheres that create the play of color called opalescence.

Opal is formed by the slow seep of silicon-rich water seeped into voids left by fossils, volcanic vughs and any cracks that this pressurized liquid could deposit itself. Each gem-quality opal is made up of millions of tiny silica spheres that are arranged in a fairly regular pattern. Much of the silicon-rich deposits came from organic material like diatoms, a tiny form of algae.  This material from into a gem like material that slowly hardened and formed into veins of opal. When viewed under a microscope, scientists discovered that when these spheres are smaller they produce violet, indigo and blue colors. Later spheres created yellow, orange and red colors. The more uniform the structure of the spheres, the higher quality of color-play produced.

Opal was first mined commercially at Listow Downs in Queensland starting in 1875 and later in New South Wales, Australia. Black Opal comes exclusively from Lightening Ridge, NSW, Australia and is the most expensive form of opal on average. It generally has a body color that is blue to dark grey or black, with striking plays of color. Other localities in Australia produce a huge variety of different types of opal including precious white opal from Andamooka, crystal opal from Coober Pedy and boulder opal from several localities.

There are two main sources for gem-quality opal, Australia and Ethiopia. Until 10 years ago, Australia was still the dominant supplier of rough but Ethiopia has become an important source of Opal, sometimes called Welo Opal, named after the province of Ethiopia. Welo produces variety of beautiful opals including precious opal, fire opal and black opal.

Although the vast majority of Opals today come from either Australia or Ethiopia, Opal discovered from other localities have been used by ancient cultures for thousands of years. Our modern name for Opal comes from the Greeks, who called it ‘Opallos’, meaning ‘change of color’. Elder, the Roman philosopher famously wrote of Opal, “for in them you shall see the living fire of the ruby, the glorious purple of the amethyst, the sea green of the emerald, all glittering together in an incredible mixture of light.”

Famously, Mark Antony of Rome (83-30 B.C.) wanted to purchase a large precious Opal owned by the Roman senator Nonius to gift to Queen Cleopatra. Nonius was offered a small fortune, the equivalent of $500,000 in todays money, but he declared “the Opal was his life”. Rather than part with his precious Opal he left behind his family and all of his possessions and fled Rome into exile!

The ancient Arabian tribes believed that Opals were stones of strong magic that had fallen from the heavens and were infused with lightening bolts of the Gods.

Australian Aborigines held Opal in high regard as a sacred stone of “dreamtime” and called it the ‘Rainbow Serpent’. The great Creator placed the colors of the rainbow into a stone for man to use. As the Creator walked a path of rainbows, each step left opal stones in the great footprints left behind. 

Archeological finds in North America reveal that Opal was mined in the Virgin Valley, Nevada. Opal artifacts found there date back at least 10,000 years. In Central America, around 850 A.D. the Aztecs begin to use Opal in jewelry and special shamanic rituals. The Aztecs called Opal “Stone of the bird of paradise”.

In ancient India, they believed Opal was the Rainbow Goddess manifested in the physical form. It was a symbol of Love ruled by the planet Venus and was called “the Queen of Gems”. Because many merchants brought precious Opal to ancient Greece and Rome, it was thought to originate from the Indian subcontinent, but it is more likely that they acquired them in trade in the middle east along their journeys.

In the middle ages, Opal continued to play an important role in the gem world, with myths that it could make the wearer invisible, bestowed protection. It was called “the eye stone” and was thought to improve eye sight and sharpen one’s vision. However, from the times of the Black Plague, Opal fell out of favor. It was rumored that Opal could lead to catching the plague. This association with bad luck prevailed for many centuries.

The most important source for Opals for hundreds of years was the Czech Republic and Slovakia. Dating as far back to Roman times, Opals were mined there. By the early 1900’s the quality and supply from Europe was superseded by the incredible stones coming out from “down under”, in Australia.

In the late 1800’s new finds in Australia begin to bring incredible new stones to the European market. At first, because the stones were so rich in color-play, many gem dealers thought they were fakes! Slowly, the world begin to take notice and its rise to fame was still somewhat gradual. The new finds in Australia created miner towns, where sudden influxes of prospectors seeking their fortunes saw more and more gem quality rough enter the market. By the 1900’s their value skyrocketed as Opal begin to be used by many famed jewelers in new Art Deco designs.