From the website:
The first fossils of half-billion-year-old clusters of soft-shelled eggs have been found preserved in a strange new way in south China — some of the eggs were even caught in the act of dividing.
The three-dimensional clusters of petrified eggs from invertebrate animals that lived in a sea 501 million to 510 million years ago are preserved in silica — glass essentially. Jih-Pai Lin, an Ohio State University paleontologist, explained this is a totally unexpected way for soft eggs to fossilize and survive for eons.