As you know, mop n glow is a type of finish( WAX ). This will add shine to your floor.
If this is what your looking for, I recommend a finish made for slate, made by TEC. It comes in gloss or matte finishes. If you decide to use one of these finishes, I recommend you wash the floor down with vinegar and water before hand to remove any residues from the floor, left from the cleaners you have used.
If Larry responds he is the man to have more details.