Coprolite

The poo-looking rock is indeed poo...at least it was during the Miocene epoch.

All animals poo, even animals that lived millions of years ago. When the droppings are well-preserved, the organic matter is slowly replaced by mineral deposits, and a permanent, fossilized replica of the poo is created called a coprolite.

Paleontologists use coprolites to study the diet of prehistoric creatures. Based on this information, this fossilized feces you received was most likely from a prehistoric turtle that lived between 5 to 23 million years ago in what is now Madagascar.