Petrified Potato

I think this is a potato that became petrified somehow. It weighs as much as a rock - it feels like solid stone. But you can see areas such as the one where I've put a note on it and it looks like the outer skin was peeled away before it became petrified.

Taken on August 11th, 2015, with my Sony Alpha SLT-a77V DSLR.