How do i verbs and polish an antique marble clock covering? it has spots of whiteish type

it has spots of whiteish type
Answers:    If heat up water beside a mild detergent doesn't work, try a little baking soda on a moisten cloth. If that doesn't work you may have to revert to a extremely light rubbing near a little bit of brass cleaner. (Be incredibly careful to rub especially lightly so you impose no damage.)