Hello, Does anyone have experience using black fossil marble slab for bread baking? I have found an inch thick marble slab which perfect dimensions make one think that it might have been used for baking before. And at some earlier point in its life it used to be a part of a kitchen countertop. It is polished on one side and rough on the other. Is there a way to say that this marble slab is safe for the oven, that is, has not been treated with solvents or sealants? Would appreciate any suggestion. Thanks, h.