International Opal Fields

Mexican Opal, Welo Opal, and Indonesian Opal Specimens at the Brisbane Opal Museum

About International Opal

Across the last three centuries, opals have become intrinsically associated with the continent of Australia. With the strongest, highest quality opal ever mined consistently being unearthed in the country’s vast outback, Australia has become the world’s most prolific, and famous, source of the gemstone. It is estimated that 95% of all the opal in the world was mined in Australia.

But what about the other 5% of opal? It is a little known fact outside of the industry that precious opal, in various types and forms, has been mined all around the world. Some of the most well known international opal mines can be found in parts of Indonesia, Ethiopia, Slovakia, the United States, and Mexico. International opal, though not of the same calibre as Australian opal, is beautifully unique, and is sought after by collectors from around the globe.


Precious opal has been mined in Indonesia since 1995. It mostly comes from the region of Banten, which is situated slightly outside of Jakarta. The Indonesian opal mines are shallow and flood easily, meaning it is only possible for diggers to work during the dry season (July-December). The host stone of Banten opal is a greyish - brown clay called kaolinite. As a result, most Indonesian opal has a jet black body tone, though crystal opal and fossilised wood specimens have also been mined. Although fairly stable, Banten opal is still considerably softer than the Australian variety. However, the small flashes of colour-play juxtapose magnificently against the opal’s midnight hued body tone. Across all the Indonesian islands, Banten opal is made into and sold as costume jewellery and specimens, with an opal market beginning to emerge in Jakarta.


Ethiopia is the second largest supplier of international opal, after Australia. Opal was first discovered in the African nation in 1994, and was a booming business by 2013. The most stable, colourful Ethiopian opal comes from a valley in the Wollo Province. It is commonly referred to as “Welo Opal”.

Rather than the vertical, underground opal mines that most are accustomed to seeing, Welo opal is mined from horizontal caves in the valley’s mountains. The Welo opal was formed when pores in volcanic minerals were flooded with silica rich water. The result is an incredible variety of precious opal, with crystal, light, orange, grey, and black body tones. The most famous type of Ethiopian opal is called “Precious Fire Opal”. This is opal with a yellow or red body tone that exhibits bright, multi-hued play-of-colour.

Ethiopian opal jewellery and specimens have become highly sought after in the last decade. While most of these opals are sold naturally, many hit the market having been smoked, dyed, or sugared to deepen the stone’s body tone and enhance it’s play-of-colour. This makes Welo opal the perfect choice for costume jewellery such as dangly earrings or a beaded string of necklaces. 


Mexican fire opal, or, more simply put, Mexican opal, have warm yellow, orange, and red body tones, with large flashes of colour across the surface of the stone. Similar to many other types of international opal, Mexican opal is volcanic. It is believed that the opals formed in the pores and seams of volcanic rock that were exposed to extreme heat and pressure. Interestingly, fire opal is mined at ground level, from deposits in volcanic soil. The mining mostly occurs in the Mexican state of Queretaro. Like Australia, opal is Mexico’s national gemstone.

The discovery of Mexican opal dates back to the ancient Mayan and Aztec civilisations, who referred to the gem as quetzalitzlipyollitli (the stone of the bird of paradise). When the Spanish conquistadors arrived in Central America, they discovered several Aztec graves where the deceased had been buried with fire opal jewellery, artwork, and figurines. 

Mexican opals are too small to be sold as specimens. Instead, they are used to make simple jewellery, such as strings of beaded necklaces and bracelets. This is because fire opal is too delicate and brittle to be set in more elaborate jewellery designs. Despite its fragility, Mexican opal is incredibly unique. It is the only type of international opal that doesn’t require cutting or polishing, as it is naturally faceted.


Also known as “Hungarian Opal”, Slovakian opal is the oldest form of international opal known to mankind. Opal was first mined in eastern Europe thousands of years ago by ancient Romans. It was the only major source of opal in the world until the late 1800s, when the gemstone was discovered in Australia. The introduction of Australian opal into the international market quickly led to the decline of Slovakian opal, with the largest of the mines, Dubnik, shutting down in the 1880s.

Slovakian opal is believed to be volcanic in nature, and has a solely white body tone, with flashes of blue and dark red. It was beloved by royalty across continents, including Cleopatra, Napoleon, and the emperors of Austro-Hungary. However, the European opal mining industry never fully recovered after its collapse, and no significant deposits of the gemstone have been mined for over a century. The Dubnik mine, which is now almost completely underwater, has found a second life as a popular tourist spot for scuba divers. 

United States

In the early 1900s, rumours of a colourful gemstone were spread across the American Southwest by cowboys and ranchers. This led to the 1905 discovery of precious opal in the US state of Nevada. The opal field was named Virgin Valley and contained five different mines: Opal Queen, Bonanza, Rainbow Ridge, Stonetree, and Royal Peacock. Virgin Valley is famous for it’s rare “Nevada Black Crystal Opal” and “Virgin Valley Brown Bottleglass”, also known as “Root Beer Opal”. 

Virgin Valley opals were formed from bentonite, which is a volcanic ash based clay. Silica rich water seeped into cracks in the bentonite, and, in some instances, petrified wood, and hardened into precious opal. Because of the Virgin Valley opals’ softer host stones, it is unstable, dry, and cracks or crazes soon after being mined. Most Virgin Valley opal has a lifetime of 25 years above ground before it begins to weather away. As a result, Virgin Valley opal is not used for jewellery making purposes. However, the international opal specimens are quite popular on the collector’s market. 


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