Reposting with a photo...
I was given a really lovely peice of marble countertop today, from a house that is to be demolished. It's white with just a light spray of black veining through it and about 4'x3' in size. It wasn't attached to anything, the house owners don't know where it came from as the tenants brought it in and then left it when they were evicted.

But....it is FILTHY!! The tenants destroyed the house with their filth, they kept all manner of pets in the house including pigs.
I'd like to use it in my tiny bathroom when I renovate later this summer and will need to have it cut for the sink and to size. Perhaps rehoned? Meanwhile...how do I clean it enough just for storage and that someone will be willing to handle it in the future? :-)

I've attached a photo of it but upon getting it home and closer examination, the "back" of it appears to be in better condition than the front. Still dirty, but doesn't appear to have the same kind of staining.
I think this was a wall panel, not a countertop peice. The really black mark at the top would be cut off when sizing to my bathroom cabinet.

Is there any hope for this peice of marble? I f nothing else, I will have a very ritzy potting bench top in my greenhouse! But I would rather use it for my bathroom.