It is always a struggle to keep marble fireplace mantels looking as gorgeous as the day they were installed, but with these tips, you should be able to keep your fireplace shining like it always did. Remember that much of the maintenance is preventative, such as keeping scratches from ruining your marble surface. Marble can be a fairly difficult stone to keep fresh looking, mainly because it is highly porous and is soft. Too much water can damage marble and it is possible to also damage it with most household cleaners.
The best route to go with your marble surfaces is to use a little warm water with a soft sponge. A hard sponge can etch the marble and damage it. You should also use a little water and a sponge whenever any liquid touches the marble, especially colorized liquids like coffee or wine. Even strongly pigmented household items, such as spices or leafy greens, should be removed immediately upon touching the marble. Make sure nobody uses the mantel as a resting place for their drinks or for any sort of liquid container.
For heavy duty stains that absolutely require a solution, your best bet is hydrogen peroxide. Do not use vinegar based solutions because this will corrode the marble. That is absolutely the last thing you want to do. Corroded marble can be extremely difficult to restore. Use the hydrogen peroxide with a soft sponge and scrub gently over the top of the affected area.
If, in the course of its existence, your marble fireplace mantel does get a scratch; there is a routine to treat it. Start by gently cleaning the affected area with warm water and a soft cloth, being sure to gently treat the scratch. This method usually buffs out the lightest scratches. For more intense scratches, it is sometimes necessary to use finely grained sandpaper to treat the affected area. Be sure to only use fine grain sandpaper. If these methods do not work, you may have to consult a professional.