It was in the package of a box of mussels.
Asker: Danny, 44 years old
Answer
Dear Danny
It is a stone that was not so long ago in the sea and on which oysters and bryozoa were attached during their lives. These animals always need a hard stable surface to attach themselves to via lime secretion. The stone itself, a flint, was rounded quite strongly at an earlier stage in the surf zone. Based on the mussel-like shape, I suspect that it came along by accident when filling the box with mussels.
Answered by
Prof. dr. Robert Speijer
Geology – Paleontology – Paleoclimatology. You study geology in Leuven!
Catholic University of Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.