Last time we were in Utah, I bought a slab of Dinosaur Poop.

It is petrified and gets its color from minerals in the ground surrounding it.

This is the other side of the slab.  I’ve been doing a little studying so I hopefully can spot it when out rockhounding (that and meteorites).  If you would like to know more about Coprolite, a great source for all things poo is: http://webecoist.com/2010/08/10/coprolites-a-few-words-on-prehistoric-turds/