Hard water deposits can be very damaging to natural stone. If you have hard water you should soften it. Chemical cleaners should be carefully evaluated prior to using for compatibility with the stone. Never use acidic type cleaners on marble or limestone. Exterior Areas Exterior stone will weather sooner or later so expect some cosmetic changes over time.
Polished surfaces show cosmetic changes rapidly in most exterior situations.
Acid rain and pollution will attack natural stones - some more readily than others. Carbonate based stones are most sensitive, siliceous stone less sensitive as a rule. The most economical stone surface to maintain is one that does not show cosmetic changes during normal use. Polished stone surfaces re very stable cosmetically if they are not subjected to abrasion and chemical attack. Non-polished surfaces are more practical in areas that are expected to be abraded, especially in high traffic areas.