Remember the pics of how they panned for gold? Well, after the poop is smooshed up run water in the bag at high velocity to separate stone from stool.Pour the stuff into a strainer or stretch a net over a pie pan and continue watering and shaking til you are extremely sure there is no stone unturned. If you could be really gross, convince your neighbors that you have a sack of rough that might contain some valuable stones and enlist their help.
OMG, I am truly gross. LOL