Chris,
The floor sealant/impregnator will have to be removed, and the stone allowed to dry-out before before any cleaning/re-sealing takes place.
Check out a manufacturer called `Lithofin`.........they sell a range of products for natural stone based materials, I believe a product called `Lithofin Wexa`, (alkaline cleaner) should do the trick, but I would ask there advice first on your problem!