[Rockhounds] "D'ever Wonder?" - Wondering about mountain leather

[Mr EMan]

Mountain leather is a hydrated weathering product of amphibole.
The mineral name is Palygorskite. Most often it resembles a wad of crumpled up paper akin to discharge lint from your washing machine. To most it looks like litter and is easily overlooked.  It can also be called "Mountain Cork" and come in pads or sheets as well.

Try Googleing images of "Mountain Leather, Mountain Cork", or Palygorskite. Visit <mindat.org>. etc. 

It comes from one or more amphiboles/chain silicates? e.g tremolite.  IIRC, Its parent source rock can be from a pegmatite or the hornfels zone where a dolomite/carbonate has been invaded by a pegmatite. 

I have found specimens in the Franklin Marble District of NJ and in SE Pennsylvania.   I think it is one of the obligatory specimens to own because it is so "un-mineral" looking and impresses newbies with the marvelous differences that are found in the mineral world.

Eman