Pend Oreille Mine, Boundary Dam, Metaline District, Pend Oreille Co., Washington, USA
It isn't often that I get to offer "world class" or "museum quality" examples of a given species.... of course, when I do, it's usually something odd like this (as opposed to a tourmaline...)
With that said, this is a very good specimen of "mountain leather" (not a used paper towel.) It is flexible, bendable, and I even had to lift a corner of it up to take the close-up photo of the calcite (you can see my fingers int he corner.) The piece is studded with tabular calcite crystals at various points, the largest reaching a couple cm.
Unusual, but very interesting....