Hey buddy...I have no clue either. As I never recalled seeing anything like that growing up,just a bunch of sand,mud,clay,n gravel beds. And I spent my share o time in the woods. Was this found not to far from your house? Im perplexed you even found something like that where you live. I wouldn't be if it was from further up north or in da u.p. eh
Anyways,yeah if you don't find out,hit some thin spalls off of it and heat treat it and see if it'll flake for ya. Its hard to tell from photos but it kinda looks like it might,or might not...not sure...hard to tell.
Maybe locate a local geologist and show them.