"Rock" Containing Stunning Agate Turns Out To Be 60-Million-Year-Old Dinosaur Egg

We hereby name it Eggate.


Eleanor Higgs


Eleanor Higgs

Creative Services Assistant

Eleanor is a content creator and social media assistant with an undergraduate degree in zoology and a master’s degree in wildlife documentary production.

Creative Services Assistant

White and pink bands of agate inside two half spheres

Not just a rock but agate formed inside a dinosaur egg. Image courtesy of © Trustees of the Natural History Museum, London

Back in 1883, a pretty agate mineral was registered to the Natural History Museum’s Mineralogy Collection. Around 15 centimeters (6 inches) across, almost completely spherical but otherwise unassuming, the specimen has remained in the collection for the last 175 years, until a chance finding revealed it to be a dinosaur egg.

The specimen's pretty colors of light pink and white interior caught the eye of Robin Hansen, one of the Mineral Curators at the museum who helped prepare the specimen when it was selected to go on display in 2018. Then a trip to a mineral show in France helped reveal the significance of the rock.


'While I was looking around the show, a dealer showed me an agatised dinosaur egg, which was spherical, had a thin rind, and dark agate in the middle," recounts Hansen in a statement. "That was the lightbulb moment when I thought: 'Hang on a minute, that looks a lot like the one we've just put on display in the Museum!'"

The mineral was then inspected by dinosaur experts at the museum who decided to run a CT scan on the specimen to see what clues they could unveil. Unfortunately, the density of the agate meant the CT scan could not pick out any finer details. On the plus side, the team agreed that the thin layer around the agate looked like a shell, and found that the outside of the specimen suggested that more than one object had been gathered together. 

Brown shell of the outside of the egg showing the indent where another egg could sit.
One side of the eggshell showing how another egg could have been laid next to it. Image courtesy of © Trustees of the Natural History Museum, London

Furthermore, the specimen was collected in India and the size, shape, and surface features are the same as those of other specimens of titanosaur eggs from China and Argentina. The egg is thought to date back to 60 million years ago when titanosaurs were the most common dinosaurs living in India. Titanosaurs, despite their massive size, were thought to have laid clutches of around 30-40 eggs and had no parental care involvement with their offspring.

"This specimen is a perfect example of why museum collections are so important," explained Hansen. "It was identified and cataloged correctly as an agate in 1883 using the scientific knowledge available at the time."


"It is only now that we have recognized that this specimen has something extra special – the agate has infilled this spherical structure, which turns out to be a dinosaur egg."

Dinosaur egg phot from above showing it as almost perfectly round brown showing how it fits together
The two halves of the egg put together showing the almost perfect sphere shape. Image courtesy of © Trustees of the Natural History Museum, London

The team think this occurred due to volcanic activity causing the egg to become encased in solidified volcanic rock after an eruption. The internal structures would have eventually decomposed, and the silica-rich water would have made its way through the rock and into the egg cavity, creating the banded agate specimen we see today. 

To find out more about the nests the titanosaurs would have made, check out our exclusive feature.


  • tag
  • geology,

  • animals,

  • dinosaurs,

  • extinct,

  • Palaeontology,

  • dinosaur egg