Industry experts recommend that natural stone floors should be sealed every 5 to 7 years after they've been installed.

When cleaning your natural stone countertops, use products specifically designed for granite and stone. These products should be pH neutral, free from ammonia and phosphate, and leave a streak-free finish.

Granite and marble are natural stones but have different origins. Granite forms deep within the earth's mantle under high temperatures and is a very hard, resistant stone made of crystallized minerals. Marble forms from sediment (like animal skeletons, shells, plant matter, and silt) at the bottom of bodies of water. Over millions of years, this sediment solidifies into stone. Made of calcium, marble is sensitive to acids such as vinegar and citrus beverages.

Since natural stones are porous, water, oils, and chemicals can penetrate your countertop. Therefore, light to medium-colored stone countertops might need resealing every 3 to 5 years with a quality penetrating sealer. Dark-colored stones may not need sealing, depending on the type. You can wipe down and dry your counter as needed without damaging it.

Natural stones like granite and marble can have veins, pits, pores, and fissures on their surfaces. These are not defects, and in fact, they can enhance the beauty of your stone’s surface.

For routine maintenance and spills you catch quickly, warm, soapy water is the best for the job—make sure to rinse well, sop up any standing water, and thoroughly dry the surface. Also, note that acid is a kryptonite for marble. Do your best to keep things like wine and lemon juice (or even cleaners containing vinegar) away from the surface. And if they do spill, tend to them as quickly as possible. For marble floors, start with a dust mop; you want to avoid anything abrasive on the surface, and dirt and sand being dragged around by a vacuum could do more damage than you intend.

There's hope if you don't catch a spill quickly (hello, red wine spilled at a lasts-until-2 am dinner party). For most organic food stains, the Marble Institute recommends cleaning with a solution of 12% hydrogen peroxide and a few drops of ammonia; if you spill anything oil-based, like a vinaigrette, and the stain has set, attack it (gently) with a liquid cleanser that contains "household detergent, mineral spirits, or acetone."

Source: https://www.architecturaldigest.com/story/how-to-clean-marble