100-million-year-old pearl fossil found in ancient seabed in Australian outback

Lauren Liebhaber, Miami Herald on Aug 27, 2025

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Over 100 million years ago, long before the extinction of land-dwelling dinosaurs, there lived a group of massive clams called Inoceramus.

With some species having shells up to 6.5 feet wide, they were “among the largest to have ever lived,” according to experts. As a result, these giant bivalves produced “very large pearls.”

At just over three-quarters of an inch in diameter, experts have now confirmed that a “very rare” and “most impressive” fossil discovered in the Australian outback is the largest fossil pearl ever found in the country, according to a news release shared with McClatchy News Aug. 26 by University of Queensland professor Gregory Webb.

In 2019, a traveling “fossicker,” or a person who hunts for precious stones, discovered a “very round stone” in Kronosaurus Korner — a fossil quarry and marine fossil museum in the remote town of Richmond in Queensland.

Today, central Queensland is arid, land-locked and desert-like. But millions of years ago, the area was covered by the Eromanga Sea, according to the release.

Many extinct marine species called the Eromanga Sea home, including the Kronosaurs, one of the “largest and most ferocious” marine reptiles, experts said.

Recognizing the rarity of the find and suspecting it might be a pearl, Kronosaurus Korner museum curator Michelle Johnston sought the help of Webb to verify her hunch.

Webb enlisted his colleague Dr. Joseph Bevitt at the Australian Nuclear Science and Technology Organisation “to carry out the very tricky investigation,” according to the release.

In order to investigate the internal structure of the suspected pearl without damaging it, the team used a machine called a Dingo neutronCT scanner.

“The results of that study have not yet been published, but it is safe to say that the sample is indeed a pearl, and the largest fossil pearl to be identified so far in Australia,” experts said.

“Ancient clams dealt with small irritants by making pearls just as modern clams do,” according to experts. “But for the ancient ones, we can see how they dealt with many other kinds of stress, including the kinds that finally killed them.”