There’s something quintessentially Australian about opal. Jonica Newby heads to Lightning Ridge to uncover the secrets hidden deep within the stones.
I’d never thought deeply about opal until I glimpsed my first one in the wild. “Oh, oh, there, LOOK!” I exclaimed in excitement. I swear my eyes started doing that big swirly cartoon thing. “You’ve got the fever,” chuckled my companion. “I do, I do,” I squeaked. “Can we get it out?”
It was 2024, my first visit to the legendary outback opal town of Lightning Ridge, and local miner Tim Warhurst had invited me into his mine. After traversing a flat red landscape dotted with little piles of mining rubble, I’d dubiously eyed the narrow hole, tested my arm strength on a 40ft shuddering ladder, followed my headtorch through a maze of rough tunnels and caverns supported by tree trunks – when a flash of blue set fire to my brain. Tim grabbed a pickaxe and kindly dug it out for me.
Opal fever, apparently, is real. “You can’t sleep, you’re a bit excited,” admits Tim. “Never lick it because you’ll get addicted,” warns another miner. (Too late – I licked mine – it’s what the miners do to bring out the colour.) And that addiction can be so powerful casual visitors end up moving here. Just ask palaeontologist Jenni Brammall, who came 28 years ago, looking for opalised fossils – and stayed.
“I remember the first time I saw opal glittering in a mine wall, I was enchanted, just seeing that dance of colour and light. That night, as I shut my eyes, I saw the colours of opal on the inside of my eyelids. And that was it – I was gone,” she laughs.
These stones have fire. Which is why, after a lifetime of taking opals for granted as common tourist trinkets, I’m now ablaze with questions. Why does 95% of the world’s precious opal come from Australia? Why is it so different to other gems with its dancing colours? And why does it make such amazing fossils?
When you stare at an opal, you look into a time tunnel that shoots you back 100 million years to a land of dinosaurs and volcanoes and a newly discovered “lost age” of egg laying mammals. Twist one way for a pre-European view of powerful rainbow-stones, another for the colourful backcountry lives of the miners.
In some ways, the story of opal is the story of Australia. And it’s never had a home worthy of the tale. Until now.
Outback opal cathedral
Which is why I’ve made the decision in mid-2025 to drive back to Lightning Ridge.
This is a grand dream born 30 years ago – of a big, bold, architecturally outstanding, world-class museum and research hub here in the outback. It’s the other reason Jenni Brammall stayed. While the project is a community-wide effort, it’s been her job as chief executive of the Australian Opal Centre to nurse it to life – and she’s about to show me the near completed building.
The building nestles into a low-slung landscape of white dirt and red gravel smattered with trees, old caravans, and little rubble mounds; tell-tale signs of opal mining. Surprisingly, there are no big mining companies here. Opal is still dug by individuals working their own claims – a goldrush lifestyle little changed in 100 years.
And just like the mines, what we see from the surface is a fraction of what lies beneath. “So as we pass through this underground entry tunnel you’ll hear a soundscape,” Jenni explains, “of Yuwaalaraay language, other voices, wind, a mining pick, birds, water.”
We emerge into a truly breathtaking space. We’re on a mezzanine; a ceiling rippled by skylights hangs high above us.
“It’s like an outback cathedral,” says Jenni, “for treasures of national significance. And I love that it’s built into the earth, and embedded with pebbles of this landscape that are part of our geological heritage.”
But the architecture is second to the true drawcard; the fossils and opals themselves.
Time travel to the Cretaceous
Jenni bypasses a fabulous set of opal dentures (local residents do love a colourful statement) to unwrap a dazzling relic of Australia’s deep past.
“This is one of the supreme hero pieces of the collection. Apart from the fact that it’s a glowing green opalised shark tooth, what’s interesting is that this was a freshwater environment and this shark lived in saltwater. What was it doing here? One theory is it swam upriver from the inland sea – maybe to breed or drop parasites that couldn’t tolerate fresh water.”
Extraordinarily, all the opalised fossils from Lightning Ridge have been dated to a narrow time band during the Cretaceous period 96-100 million years ago.
Glowing pearlescent yabby buttons, lungfish bones, crocodile teeth, turtle bones and exquisite pinecones in rippling greens and purples catapult us back to a lush Gondwanan Eden. To a land of vast rivers plummeting from 4km-high mountains which rimmed the continent, slowing here onto a massive floodplain before flowing into the distant sparkle of the inland Eromanga Sea.
“This foot bone is from perhaps our most famous dinosaur; Lightning Claw,” says Jenni. “It doesn’t have a scientific name yet, but we believe it’s a new species of megaraptor.” It had massive claws on its forefeet and a metre-long skull with razor-sharp teeth.
Lightning Ridge is the only major dinosaur site in NSW, so its scientific significance is immeasurable. And it blows my mind that these fossils are opal – many common grey potch, but others streaked with flashing gemstone.
“This is Fostoria, a large herbivorous iguanodontid dinosaur, maybe 5m long. It got around on its hind legs and had a beak-like structure it probably used to pluck leaves and ferns. These bones were found by the Foster family, hence the name. And the species name dhimbangunmal is a beautiful gift from the Yuwaalaraay language. It’s a literal translation of ‘sheepyard’ after the opal field it came from.”
Next, the less mighty but deliciously named Weewarrasaurus. “This was a small herbivorous dinosaur related to Fostoria. It was about the size of a dog, might’ve made a cute pet. Weewarra was the name of the place it was found – [it means] ‘standing fire’. Again, the language of the people who lived here for tens of thousands of years is coming through, which is wonderful.”
While the dinosaur bones are big and flashy – some literally – what excites me most is a tiny grey bone in the next cabinet. This bone is from a monotreme – whose only living relatives today are the echidna and the platypus. And they’re turning our understanding of mammal evolution on its head.
In 2024, palaeontologists described and named 3 entirely new ancient monotreme species, based on opalised fossils from Lightning Ridge. It brought to 6 the total number of 100-million-year-old monotremes discovered here, of which 5 were from separate families – as different as cats to horses – suggesting many more species once existed. It’s an entire lost era: the Age of Monotremes.
Far from the earliest mammals all being tiny, shrew-like creatures cowering until dinosaurs vanished, 100 million years ago, Lightning Ridge teemed with egg-laying mammals, large and small. There was platypus-like Dharragarra, a pig-sized Stirtodon, tiny Parvopalis, and Opalios the “echidnapus”.
Opals truly are a time traveller’s treasure trove. Which raises the question – why?
An opal-hearted country
The most famous line in Dorothea Mackellar’s iconic ode to Australia is “I love a sunburnt country”. Less known is her final stanza:
“An opal-hearted country, A wilful lavish land
“All you who have not loved here, You will not understand.”
Mackellar understood that opal lies literally at the heart of the Australian story – a quintessentially Australian gem found only in the Red Centre. Yet astonishingly, no one really had a good scientific explanation why – which shocked French geologist Dr Patrice Rey when he became Professor of Geology at the University of Sydney.
“It’s the national gemstone, most of the world’s precious opal comes from here and we don’t know how it forms? I was embarrassed for the nation,” he laughs.
Patrice had caught the opal bug as a French schoolboy after watching a documentary on Coober Pedy. “Even if you don’t find opal, you get an underground house and a swimming pool!” While he might never be an outback treasure hunter, perhaps he could crack opal’s secret planetary recipe.
It took years until the final clue came, perversely, from another planet entirely: Mars. “Opaline silica was discovered on Mars. So I started wondering; what do Mars and central Australia have in common?”
Unlike most gems, which are crystal, opal consists of nanoglobules of silica. It’s the diffraction of light by these tiny spheres that creates opal’s mesmerising play of colour.
It turned out, both Mars and central Australia had an ideal source of silica – basalt, from ancient volcanoes. To become opal though, the silica needed exposure to acidic conditions; common on Mars, but rare on Earth because widespread limestone neutralises any acid. And this is where the penny dropped for Patrice. The Great Artesian Basin in Australia’s centre has very little limestone. And he had an idea for a source of acid; not a mineral process, but a biological one.
Anaerobic bacteria excrete pyrite, which in the presence of oxygen releases sulfuric acid. And where do anaerobic bacteria hang out? Muddy swamps. And there was only one place in all Earth’s history with that unique confluence of volcanoes, vast swamplands and little limestone; central Australia starting 130 million years ago.
Australia was still part of the super-continent of Gondwana then and sat much further south. It was too cold for coral reefs to grow – hence low limestone. Moving east, the continent passed over a subduction zone, sucking central Australia into a bowl shape, creating an inland sea surrounded by volcanoes and rivers which, unusually, flowed inland.
So picture our Weewarrasaurus. 100 million years ago, she dies by a river, is swept into a muddy lake and smothered in sediment. Anaerobic bacteria eat her soft flesh, excreting pyrite. Meanwhile, in this oxygen free environment, her bones are perfectly preserved as fossils.
But they are not yet opal. That requires an alchemic transformation so unlikely it’s a miracle it happened at all. From 97-60 million years ago, the subduction stops. The bowl bounces back up, the inland sea dries up. Oxygen begins to reach down through the rock layers toward the buried bones, reacting chemically with the pyrite, releasing sulfuric acid which dissolves the bones. Meanwhile, the acid also reacts with basalt-derived clay to create a silica gel – which slowly seeps into voids in the rocks – including the beautiful Weewarrasaurus fossils, gently replacing the dissolving bones, molecule by molecule.
“It turns out for precious opal to form, it needs a very narrow range of acidity,” says Patrice. “If the balance was exactly right between the amount of pyrite and clay, then the silica organised itself into perfect spheres, forming this beautiful gemstone.
“It seems impossible, basically, for this gemstone to exist,” marvels Patrice. “And yet it does.”
Rainbow stones
Before I leave Lightning Ridge, I have one more important opal story to hear. Auntie Brenda McBride is a Gamilaraay, Yuwaalaaray, Wailian woman; a local elder and long-term collaborator with the Australian Opal Centre. I ask her the word for opal in her language. “Yuluwirri” means rainbow”, she tells me, “so they’re rainbow stones.”
She knows two exquisite stories about how opal came to be. In one, a rainbow kept coming and putting her colours into the stones. In another; a pretty butterfly went to the Warrumbungles and her colours went into the earth and formed the opals underground.
These are powerful stones. “We can’t keep them because of the rainbow serpent,” she explains. “It’s taboo to us because it’s a snake. And a lot of people only hold their opal for a while and sell it off because they reckon if you keep it, a sickness was going to fall on the family.”
Aboriginal people have nevertheless long been prominent opal miners. Brenda mined opal with her dad. And remember the Foster family who found the magnificent sheepyard opal dinosaur, Fostoria dhimbangunmal? Greg Foster was Auntie Brenda’s nephew. “So they asked me to name it for them, so I named it dhimbangunmal – means sheepyard.” Auntie Brenda has given Indigenous names to several of the new opal fossil species, including Dhurrugarra, the ancient platypus from the Age of Monotremes.
Opal contains multitudes. And I’m so pleased these powerful stones will soon have the grand new outback cathedral home they deserve.
A few months after I get back from my first visit to Lightning Ridge, a package arrives. Before I’d left, opal miner Tim Warhurst gifted me the opal we’d found. A friend of Jenni Brammall’s gifted me the gemstone polish. And now, here it is in my home. A piece of rainbow, a butterfly’s wing, forged in the alchemic confluence of acid and ancient swamps and volcanoes. A gift from deep in my country – all the way across the ages – to me.
Dr Jonica Newby is an award-winning science reporter, author, TV presenter and director, best known for her two decades on ABC TV’s science program, Catalyst.