Good old birch polypore, which on it's own won't take a spark very well.
http://en.wikipedia.org/wiki/Polypore
As Mors (and many others) spell out, if you boil birch polypore in hard wood ash it will then take a spark. This is correct. I boiled (simmered is more like it) this batch for round about 20 hours, dried it and then pounded it out. Bingo Bango it will now take a spark like crazy. A little labor intensive but it does in fact work. If nothing else it is something to file away in the brain bucket. Good old Ötzi liked it enough to carry a batch.
Seeing is believing.

Just as a polypore note: in a earlier picture on this thread you can see a chunk of this stuff that I drilled a small divot into and then placed a coal. This chunk smoldered long enough to easily transport a "fire" from Point A to B.


