My house was built in 1905 out of Basalt rock. We had put a swamp cooler in a window & it seems the water from the cooler seeped into the rock and then into the wall causing the paint and all the layers underneath to peel up. There was a couple spots of mold that I cleaned with bleach. But now I have this HUGE 6 foot patch that I have no clue how to patch. There is no drywall it looks like cement.