Scott, I made a friend during my trip to ND last year who heat treats his Knife River Flint. The point in the photo was made from one of the pieces I traded him for. These two photos are of an unfinished piece I'm working on that was raw. It was tough and I was having trouble with cortex so I tried using the formula below. As soon as the rock got to 350° I cut the heat off and let it cool down. Made it slick and a lot easier to work. Rick B
Borrowed from another site:
Knife River Flint (ND)
I have had success with flakes and THIN spalls with 25°F/Hr to 350°F, when 350°F is reached, bring down temp. 25°F/Hr. Lower grades cook better than high grade.