It can be cleaned, resealed and polished...that's all intensive labor to do so. It will not be able to be polished until it is grouted, otherwise the machine will break the edges.

It can be cleaned with Oxalic Acid...by a pro only by flushing and wet vaccuming. This may help with mineral staining from debris and earth sediment. Surface stains can be removed by a poultice too.

The pros are the same type as the installers for Terrazzo floors in Banks and Airports---they are NOT janitor type tradesmen. It may or may not be worth testing an area first before totaling. If there is a slim chance of transfer red staining from flood it will come from beneath the floor where it is set in mortar and cleaning may not guarantee this long term. Otherwise remove and replace because it will end up being 6 one way and half a dozen the other way in costs. Both will make substantial messes. Home Depot got rid of pallets for $1.79 sf pre-polished not to long ago.

Hope this helps.