Thunder Eggs May Not Be Gems, But They’re Worth Millions For Generations Of Children


After an hour of energetic digging in the scorching sun, Kaleb has collected a decent number of rocks and he hopes some will reveal hidden treasure.

It’s the first time the elementary student has been looking for thunder eggs, but he knows what he’s looking for.

“You know it’s a thunder egg because it’ll have this bubbly kind of thing on it,” Kaleb says.

Kaleb with two of the many Thunder Eggs he unearthed during his morning digs at Mount Hay.(ABC Capricorn: Inga Stünzner)

He is one of dozens of children who have spent the school holidays searching for gems and thunder eggs in central Queensland.

The hands of a boy hold a pickaxe for digging in the earth
Thunder Eggs have a knobby exterior, but can be beautiful on the inside.(ABC Capricorn: Inga Stünzner)

It’s almost time for the moment of truth.

A short distance from the dig site, Don Kayes takes the small round rock and cuts it carefully with a diamond saw.

The sound is deafening, but as the rock falls in two, the intricate brown and dark blue patterns are revealed.

Close up hands cutting a thunderegg on a diamond saw
Thunder Eggs can be the size of your thumbnail and contain incredible beauty.(ABC Capricorn: Inga Stünzner)

“You found some good ones,” Kayes told Kaleb.

“Look, this one has a piece of agate,” he remarks.

Mr Kayes runs a thunder egg and gemstone fossil park at Mt Hay, a 30-minute drive west of Rockhampton, and the reaction on Kaleb’s face is why he’s been doing it ever since decades.

Close up of a small Thunderegg cut in half to reveal a brown dolphin shape.
Mt Hay’s Thunder Eggs were formed 120 million years ago.(ABC Capricorn: Inga Stünzner)

“That’s enough, isn’t it?

wide-eyed girl smiles while showing cut thunder egg
The look on children’s faces when they see the inside of their thunder egg is priceless.(ABC Capricorn: Inga Stünzner)

Explore close to home

Since the COVID-19 pandemic, most visitors have been locals exploring their own backyards.

“In the past two years, especially during school holidays, I don’t think I’ve ever seen her so busy,” says Mr Kayes.

Don Kayes stands before a large polished thunder egg inside his shed.
Don Kayes found this 45kg thunder egg when he came across it in 1984.(ABC Capricorn: Inga Stünzner)

Many are return visitors who have brought their children and are now bringing their grandchildren.

“The family I just cut for, he came here about 32 years ago when he was a kid, and here he is, bringing his kid to Fossick today.”

What are Thunder Eggs?

Although thunder eggs are found throughout Australia, Mt Hay has one of the largest deposits in the country which was formed 120 million years ago.

It’s a strange name to give a rock, but it’s thought to come from a Native American legend that describes thunder eggs as falling from the sky during thunderstorms.

a pile of gray round stones in a bucket
What secret treasures hide these rocks?(ABC Capricorn: Inga Stünzner)

They’re fascinating enough that the Australian Museum in Sydney has hundreds on display – and most come from Mount Hay, says Ross Pogson, who manages the collection.

Although there are deposits found in parts of New South Wales, Queensland had the right volcanic conditions hundreds of millions of years ago for Thunder Eggs to form.

They form in rhyolite, a slow molasses-like lava, and silica-carrying water seeps through the cavities, leaving deposits.

“You get a star-shaped pattern in the middle and that can be filled with agate or sometimes coarser crystalline materials like amethyst,” says Pogson.

Thunder Eggs Exposed
Unique centers of thunder eggs.(ABC Capricorn: Inga Stünzner)

lucky dip

Thunder Eggs may not be worth much in monetary value. The appeal is more in what they reveal.

“You can’t tell what’s inside a thunder egg by looking at it,” Pogson says.

A little girl looks forward to a newly revealed Thunderegg.
Don Kaye says the smiles on children’s faces are priceless.(ABC Capricorn: Inga Stünzner)

“When you open it, there may be nothing or there may be a beautiful banded agate pattern, or there may even be a dip in the middle with beautiful clear quartz or amethyst crystals.”

For Mr. Kayes, it never gets old.

“It’s a surprise,” he said.

A man sits in front of a rock cutting machine
Don Kayes’ father started digging at Mt Hay 60 years ago and started the business in 1974.(ABC Capricorn: Inga Stünzner)

“It’s a lucky dip, this surprise package. It doesn’t look like much on the outside, a bit like a rounded rock, but the beauty it can have inside is quite incredible.”

As for Kaleb, he was satisfied with his morning’s work and quite surprised with the results.

“I didn’t expect them to look as good as they do.”


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