I
Italy
pietra serena, here,little useless, for flooring. (Tuscan stone).
just some stairs, or window sills, because it is combined with the oldest areas of the country.
Soft material, very absorbent, quick adhesive is better, less risk of stains. Just a damp wall and the stone absorbs and crumbles. Just to make an example, it's "tough" like carrara marble.
I saw a bunch of jobs, ruined by humidity.
Sorry if I speak to you clearly and say what I see here ..
Sorry again and you hope to succeed in the work.