It's porous and reactive to acids and bases. In my case I spilled toilet bowl cleaner, a strong base, on my untreated marble, and it made permanent spill marks. With time on my hands this COVID winter I did some rubbing and it looks much better. If you get marble floors put in, have them sealed with a permanent sealer. It still may wear off, especially on a countertop or heavy traffic area.
Lustro Italiano Etch Remover
Etch rubbing.
Final product coated with Rejuvenate Floor Restorer