A few years ago I got a Gorilla brand granite mortar and pestle. I seasoned it as directed and got quite a bit of use out of it, then I stopped cooking for a while and it got kind of...well, gross. It's possible that I spilled something on it, but portions of the bowl and exterior are a darker color now. I guess I'm afraid with the relatively porous granite that it's full of rancid garlic effluvium. Does anyone know how to clean this thing? Should I just pitch it?