Knoll uses a process they describe as a "transparent polyester coating" to achieve the fabulous shine and pretty good durability of their marble topped furniture (like the Saarenin and Florence Knoll tables.)
Our marble table has held up remarkably well over the twelve years that we've owned it, but the coating is beginning to bubble up and crack in a few places. Where this happens, it becomes opaque.
Knoll was not particularly helpful when I called them with this question. Perhaps they would prefer that we just buy a new table, or maybe I didn't reach the right person.
In any event, hope someone here has a thought. Since the finish is a big part of the attraction of the table, I'd like to find someone who can remove the old coating and apply a new one.