cleaning headstones

What can i use other than a metal brush and (http://maplered.com) alot of elbow grease to clean an old headStone (http://g603.net) (150 years old) whitish in color. Is there a chemical, bleach i could use. Can i use this same method on a shiny black Stone (http://g603.net) also. Don't know what kind of Stone (http://g603.net) s these are but the black one is obviously newer.