Can you heat treat shale?

[Dante_F]

Ive messed around with some shale I found on some beaches in the Olympic peninsula and have been able to strike off fairly large flakes but when trying to drive small flakes it just grinds the stone, so far Ive just been using this technique to rough out stone axe head/celt preforms and grind them smooth but I was wondering if anyone has had any experience heat treating these rocks and how it may effect them. I dont expect it to make it top tier material but maybe it would knap and hold an edge a bit better with some heat to harden it up a bit? Any input is welcome!

[Outbackbob48]

Dante F, First let me say that I have no experience with heat treating shale. Here are some of my thoughts with this. Heat treating of most cherts makes them weaker not stronger also will bring out colors on some flints. Heat treating makes tough rock weaker so that  it is easier to knap. Also alot of black materials heat doesn't do anythink to, by this it doesn't hurt it but also doesn't help it. Oh I am assuming your shale is black. I quess  you will just need to build a fire and see what heat treating does to does to your shale, I know not very helpful, but that is my .02 worth on heattreating. Bob

[Deerhunter21]

I would knock a couple flakes off or test it with pieces that arent really suitable for knapping. Put one flake in your turkey roaster or whatever to 170 and gradually crank it up to 400 degrees and leave it there for 6-12 hours. then determine if its easier to knap or if its more brittle and harder to knap. turn the max heat down if its too brittle and turn it up if its still hard to work.

I dont heat treat much but thats what i would do. Trial and error you get it right!

[Dante_F]

Thank you for the advice OutbackBob, some of the shale I have is green, some gray and some beige, the beige being the softest and the green being the hardest. My goal with the shale or what I'm hoping to achieve is just to see of it will harden up some to make it hold an edge a bit better and maybe make bigger individual flakes for making tools.

DeerHunter, I already have a few good size flakes ive knocked off and will try to heat them at different temperatures individually to see what results I'll get

Thanks for the input!

[Hawkdancer]

 (lol)If it from the Roan Basin in western Colorado, very likely it will be black and go BOOM! .  I really couldn't resist!
Hawkdancer

[Allyn T]

From what I understand that isn't the right type of rock for knapping. Guy on Instagram called nwprimate grinds out points all the time and they seem to work well.