The world's first recorded opalised pearls discovered, at least 65 million years-old.

The "priceless" four-millimetre specimens were found in the Coober Pedy opal fields, an area famed for the colourful gems. Dr Ben Grguric from the SA Museum, where the pearls have gone on display, said opal miners Dale Price and Tanja Burk were sorting through a spoil heap when they made the discovery.

"The miners pick out anything that glows with ultraviolet light, because even a small chip of opal might be worth something if it's high quality with a high range of colours," Dr Grguric. "It turns out these resembled pearls."

He said opals formed when seas dried up and alkaline soil dissolved the silica in certain rocks, as well as bones and shells - and in this case, pearls. "A lot of the opal fossils, including bones and shells, were formed during the cretaceous period, which was an era earlier than 65 million years ago and the age of the dinosaurs," Dr Grguric said. Read the full story.