If the damage is not too bad , you can copper wire brush the loose crumble then seal it with a breathable Matt sealant ( for a natural look) . If the damage is too bad then you can call a restorer in to try to restore the affected area , keeping in mind the texture and colour matching to the existent natural stone is key .

The other solution is to cut off the affected areas and replace the stone ( that could be more costly) . Hope this helps

Replace with new stone or cut back and coat with Lithomex

没有取代石头和石头重嵌wi工作th limemorte

Hi, I would never recommend a sealant or Matt paint for natural stone, you could try and descale the areas you have described depending on how bad the deterioration is. Replacement is obviously if it’s too far gone, I would only ever recommend a lime wash for natural stone as a form of protection, hope this helps