Hi love2 clean,
Interesting. First off, you might want to check if it's something on the surface of the stone like a sealer. Ask the customer... If a sealer is applied incorrectly there might be a residue- almost like a gummy film or wax. It might even make the stone feel rough. Granite itself is a difficult surface to etch. It would take a highly corrosive material such as drano to actually etch the stone. The best cleaner to use on stone is a ph balanced cleaner.(a ph balance of 7) Try to stay away from waxes and polishes this will only add to the problem.