How do you keep clean a marble sink?

Marble like porcelain likes to retain water droplets on their surfaces; it is best to wipe out the sink after using it with a paper towel.

Now, IF your sink has water that pools around the drain ring...the ring isn't the correct size for the opening [it's too small], IF you don't want to 'change it out'...then dry out the sink ring area & apply a small amount of clear latex sealant around the ring [where the water 'puddles'] to fill in the extra space...let it dry the require amount of time, then use as normal. You will know when it's time to replace the worn sealant when it begins to peel away from the ring. Happy Plumbing!

Once I cleaned a terrazzo floor with the lanolin hand cleaner that car mechanics use to get grease off their hands. I wet the floor, applied a thick layer of cleaner, like cleansing cream on your face, let it sit for four hours, then wiped it off. I had to spray a little more water on the floor to keep it moist and I checked every hour to see how it was working. The cleaner melted away the YEARS of grime. I had several old towels that I used to wipe off the hand cleaner. I rinsed the towels in hot water in the bathtub and just kept wiping/rinsing the floor with clean water until the all the hand cleaner was removed from the floor. My landlord could not believe how clean it was!! Do a test in a small area to make sure the cleaner does not stain the marble. Hope this helps.

Thanks. I'll try this to see if it works and let you know.