Sixty years ago, in 1965, the fascinating thunderegg was declared Oregon’s state rock.

People come to Oregon from all over the world to hunt for thundereggs, the seemingly unremarkable egg-shaped rocks that hide beautiful patterns of agate, opal, jasper and other gemstones.

Oregon’s thundereggs formed up to 60 million years ago, when gas bubbles were encased in molten lava. The water and minerals that filled in those holes form surprisingly beautiful shapes and colors.

In 2013, “Oregon Field Guide” followed a group of rock hounds as they dug for “dull, brown, bumpy and round” shapes in the high desert of Central Oregon, later cutting them open to see what they could find in these ancient treasures.

It’s one of the most popular “Oregon Field Guide” stories ever, produced by Vince Patton and filmed by Nick Fisher.

News Source : https://www.opb.org/article/2025/05/10/oregon-field-guide-thundereggs-oregon-state-rock-60-year-anniversary/