Well hot dang, A Hawkeye!
Where abouts in the state are you, gustav? I'm from a little town in the southeast corner, Fairfield.
And I am assuming you hunt artifacts. If you're a rockhound in Iowa I guess you got two choices. Geodes or artifacts.
Anyway, welcome to the board.

That material you are looking for comes from the mountains of NC. That's where the natives quarried the mica to trade. Some of the prehistoric quarry sites are recorded
but I have never explored any of them. I wouldn't be a bit surprised if material almost identical to what
you are looking for could easily be found in the vicinity today. It is not something people collect a lot of so it might be laying all around up there.
And another member of the board knows of a spot where he is finding a high grade serpentine called antigorite.
I'm not going to be able to get up to the mountains any time soon to poke around for any of what you're looking for, unfortunately,
but here in Wake County there is lots of good talc,ie; soapstone, with a lot of chlorite and mica in it.
Let me poke around the yard here and see what I can come up with.
In the meantime maybe one of our mountain members will reply.

Joe

Gustav, that looks very similar to the ultramafic rocks on my property Treasure Valley here in Western North Carolina.  It's green with gold flecks in it which I take to probably be mica. It is very hard however until it breaks down through weathering or whatever word the geologists use.