yep. still writing for venture vermont.
this year again, flintknapping is on the list.
now, i learned to do this in college, although i did not apparently learn to talk about it coherently.
anyway, for your striking stone you want something nice and hard and not fracture-y. i've using a granite against this here shale.
shale isn't ideal for it, but you can get it to fracture mostly reliably and it will make nice sharp edges, if not durable ones. you work with what you have.