The beautiful pink and white agate, which has been in the Mineralogical Collection of London’s Natural History Museum since 1883, has turned out to be much more striking than one might have imagined, for some surprising reason. This specimen, about 15 centimeters in diameter, almost perfectly spherical but otherwise unremarkable, remained in the collection for the last 175 years until a chance find earlier this year revealed it to be a dinosaur egg.

The specimen’s attractive colors caught the attention of Robin Hansen, one of the minerals curators at NHM, who helped prepare the specimen when it was selected for display in 2018. A later trip to a mineral exhibition in France helped reveal its true nature.

“While looking at the exhibit, I was shown an agate dinosaur egg that was spherical, thin-shelled, and had dark agate in the middle,” Hansen told NHM’s Josh Davis. “Wait a minute, this looks a lot like what we just had on display at the museum!” I thought.

The mineral was then examined by the museum’s dinosaur curators, Professor Paul Barrett and Dr Susie Maidment, and they decided to CT scan the sample to see what clues they could reveal. Unfortunately the density of the agate meant that the CT scan was unable to detect any of the finer details. On the bright side, the team agreed that the thin layer around the agate resembles a shell, and found that the exterior of the specimen indicates that more than one object was collected.

Additionally, the specimen was collected in India and its size, shape, and surface features are identical to other Titanosaurus egg specimens from China and Argentina. The egg is believed to date from 60 million years ago, when titanosaurs were the most common dinosaurs that lived in India. Despite their enormous size, titanosaurs were thought to have laid around 30-40 eggs and did not provide parental care to their offspring.

“This example is a great example of why museum collections are so important,” Hansen explained. “It was accurately identified and cataloged as agate in 1883 using the scientific knowledge available at the time.”

“We only now realized there was something special about this sample; the agate filled this spherical structure, and it turned out to be a dinosaur egg.”

The team believes this was caused by volcanic activity that caused the egg to become embedded in solidified volcanic rock after the eruption. The internal structures will eventually decompose and silica-rich water will enter the egg cavity, creating the striped agate pattern we see today. Source