The “rock” containing the amazing agate turns out to be a 60-million-year-old dinosaur egg

In 1883, a beautiful garnet mineral was recorded in the Natural History Museum’s mineralogy collection. About 15 cm (6 in) across, almost entirely spherical but unassuming, the specimen had remained in the collection for the past 175 years, until serendipity revealed it to be a dinosaur egg.

The specimen’s beautiful colors of pale pink and white on the inside caught the eye of Robin Hansen, one of the museum’s mineral curators who helped prepare the specimen when it was selected for display in 2018. Then a trip to a mineral exhibition in France helped reveal the rock’s significance.

“As I was looking around the display, a merchant showed me a miracle dinosaur egg, which was spherical, with a thin shell, and a dark agate in the middle,” Hansen recounts. statement. That was a lightening moment when I thought: ‘Wait a minute, this looks a lot like the one we just showed at the museum! “

The mineral was then examined by the museum’s dinosaur experts and they decided to run a CT scan of the specimen to see what clues they could uncover. Unfortunately, the density of the agate means that a CT scan can’t pick up any fine details. On the plus side, the team agreed that the thin layer around the agate resembles a shell, and they found that the outside of the specimen indicated that more than one object had been grouped together.

Furthermore, the specimen was collected in India and the size, shape and surface features were similar to those of other titanosaur egg specimens from China and Argentina. The egg is believed to date back to 60 million years ago when titanosaurs were the most common dinosaurs living in India. Titanosaurs, despite their enormous size, were thought to have laid clutches of about 30-40 eggs and not shared parental care with their offspring.

“This specimen is an excellent example of why museum collections are so important,” explains Hansen. “It was properly identified and cataloged as agate in 1883 using the scientific knowledge available at the time.”

“It is only now that we realize that this specimen had something extra special—opal filled this spherical structure, which turned out to be a dinosaur egg.”

The team believes this happened due to volcanic activity, which caused the egg to become covered with hard volcanic rock after the eruption. The internal structures would have eventually dissolved, and the silica-rich water would have forced its way through the rock into the egg cavity, forming the banded agate specimen we see today.

For more on the nests made by titanosaurs, check out our exclusive feature.