Can savannah monitors digest dirt?

I recently made a new cage for my sav and put dirt in it. I figured it would probably be a good idea for him to not eat any accidentally so i tried feeding him a mouse in a different container. He seems to be scared in the new container though and will not eat. I then put him back into his cage and he ate right away. While he swallows it he rubs it back and forth on the dirt as I'm sure anyone who answers this will know they do. I was just wondering if it would be a bad idea to keep feeding him in his cage on the dirt or if the dirt on the mouse would cause any problems when ingested?