Come to central Illinois, you can find all the chert you you can carry in some fields. Most all of it I've found will make a spark. I'm not an expert on arrow heads, but I've found a few made of chert (I think) from the tractor when I was a kid. No tractor cabs back then, so we watched for arrow heads for something to do. They really showed up good in the spring after it rained. If the Indians could knap it, it will spark. My 2 cents worth on it.