It is a noun that also can be descriptive (I think). You would use it to describe a buildup on old wet stone, as in a castle dungeon or old underground passage. It's not limestone, not apatite, not stalagmite or stalagtite. I would be infinitely thankful if anyone can dredge it up. I need it. I need it so badly.
That is what a Google search finds. Efflorescence is a crystaline deposit on surfaces of masonry, stucco or concrete. It's a new term to me but this does seem to fit the OP question.
Calcite is in caves from the calcium dripping down within water. However, I don't think you even need word. You can honestly just call it something along the lines of "wet stone" and go on to describe it for what it is
