Australian Opals


Although opal can be been found all around the world, there are only a few major sources of this precious stone. Australian opals account for 95% of the world’s supply. Unique geological formations in Australia have favored the formation of this sedimentary stone.

This freeform oval cabochon cut opal from Lightning Ridge, Australia, displays blue, green, and teal fire, or play of colors. Long thought to be the result of iridescence, opal’s fire is actually the result of diffraction.  “Crystal Seam Opal.”  ©Dan Stairs Custom Gemstones.  Used with permission.
This freeform oval cabochon cut opal from Lightning Ridge, Australia, displays blue, green, and teal fire, or play of colors. Long thought to be the result of iridescence, opal’s fire is actually the result of diffraction. “Crystal Seam Opal.” ©Dan Stairs Custom Gemstones. Used with permission.

The Great Artesian Basin

The process began about 140 million years ago. At that time, much of central Australia was covered by an inland sea, abundant with silica-rich sands. This sea eventually receded and formed what is now known as the Great Artesian Basin.

Great Artesian Basin

Around 30 to 40 million years ago, heavy weathering began to dissolve the silica. The holes that were formed in the rock began to collect silica-rich water. Over time, the silicates trapped in these spaces formed opals.

This freeform cabochon opal from Lightning Ridge, Australia, shows a wonderful red, green, gold, and blue rolling ribbon-like broadflash. “Opal.” ©Dan Stairs Custom Gemstones.  Used with permission.
This freeform cabochon opal from Lightning Ridge, Australia, shows a wonderful red, green, gold, and blue rolling ribbon-like broadflash. “Opal.” ©Dan Stairs Custom Gemstones. Used with permission.

While the Great Artesian Basin is vast, there are only a few sites in this area that are sources of opal. (As any miner will tell you, good quality opal is rare even in the best of areas).

Australian Opal Fields

The Beginning of the Australian Opal Trade

The modern history of opal mining in Australia began in July of 1889. Tullie Cornthwaite Wollaston took 60 brilliant pieces of opal rough mined in Queensland to London. Despite initial rejections from gem dealers, after Wollaston sold the stones to an international jewelry firm, the demand for Australian opals grew steadily worldwide.

“Mr. Tullie Cornthwaite Wollaston (opal dealer), ca. 1920.” Public Domain.
“Mr. Tullie Cornthwaite Wollaston (opal dealer), ca. 1920.” Photographer unknown. Public Domain.

Select Sources of Australian Opals

Today, most black opal (stones with a dark gray to blue-black background) comes from Lightning Ridge, New South Wales, and Mintabie, South Australia. Some black opal is also found in the fields around Coober Pedy, South Australia.

“8ct. Lightning Ridge Black Opal” by Daniel Mekis is licensed under CC By-SA 3.0
“8ct. Lightning Ridge Black Opal” by Daniel Mekis is licensed under CC By-SA 3.0

Coober Pedy and Mintabie are also rich sources of light and white opal (stones with a white or light background).

“Rainbow Shield Mintabie Opal Pendant” by Dpulitzer is licensed under CC By-SA 4.0
“Rainbow Shield Mintabie Opal Pendant” by Dpulitzer is licensed under CC By-SA 4.0

Boulder opal, a thin seam of precious opal on an ironstone matrix, is found at a number of locations in Queensland. Smaller finds are coming from Andamooka, South Australia.

“Discovered in 1989, this is one of the largest (2765 carats) and finest quality boulder opals ever mined.  This opal is unique not only for its size but also for its quality -- every color of the spectrum is visible which is extremely rare, even in the finest of opals.”  “Opal, Opalville Mine, Queensland, Australia” by Wikipedia Loves Art participant “Assignment_Houston_One” is licensed under CC By-SA 2.5
“Discovered in 1989, this is one of the largest (2765 carats) and finest quality boulder opals ever mined. This opal is unique not only for its size but also for its quality — every color of the spectrum is visible which is extremely rare, even in the finest of opals.” “Opal, Opalville Mine, Queensland, Australia” by Wikipedia Loves Art participant “Assignment_Houston_One” is licensed under CC By-SA 2.5

Yowah nuts are walnut-sized stones with opals in the center. They are found in Yowah, Queensland.

“Opal” (Yowah Nut) by Rob Lavinsky is licensed under CC By-SA 3.0
“Opal” (Yowah Nut) by Rob Lavinsky is licensed under CC By-SA 3.0