What is this?

It looks like a couple of "cave pearls" which are concretions formd in cave waters where there is a bit of turbulence so the tuff does NOT crystalize along the ceilings or floors like stalagmites.
These are all of a bunch of cave formed uniques called "Speleothems"

They are kinda common in certain spring fed streams that intersect cavernous areas. There are big masses of them in certain streams in W Va , Va, NC , Ky and Ark.