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

This is the primary school student’s first time fossicking for thunder eggs, but he knows what he’s looking for.

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

He is one of scores of children who have spent the school holidays fossicking for gemstones and thunder eggs in central Queensland.

What are thunder eggs?

Although thunder eggs are found throughout Australia, Mt Hay has one of the country’s largest deposits that formed 120 million years ago.

It’s an odd name to give a rock, but it’s thought to originate from a Native American legend that described thunder eggs as dropping from the sky during thunderstorms.

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

A star-shaped pattern forms in the middle and can be filled with agate or sometimes with more coarsely crystalline materials like amethyst.
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Source
ABC News