Ancient crystal-filled rock has been hiding dinosaur secret for 140 years

The agate specimen was originally stored in the Natural History Museum's mineralogy collection, but researchers think the gem grew inside a 67 million-year-old titanosaur egg.  (Image credit: Trustees of the Natural History Museum, London)

A beautiful crystal stored away in a mineral collection 135 years ago was harboring an even rarer treasure: The shell of a 67-million-year-old titanosaur egg.

The encrusted egg originates from a volcanic plain in central India, prompting researchers to think that a lava flow smothered the nest shortly after the dinosaur laid it. The embryo decayed, while layers of solidified volcanic rock preserved the shell. Over the eons, silica-rich water seeped inside the shell and crystalized to form a light pink and white agate mineral.