Yes Sir George...
I could only get tiny little flakes off that Ryolite with Indirect Percussion.
Was able to get some pretty Robust points out of it with my heavier gear.
At the moment I'm down to Obsidian only as I have worked my way through that heated rock you send home with me.
In truth I'm giving it a rest as I broke off an obsidian point in my thumb last Saturday and have yet to get all of IT outa me...
Plus breaking rock was kinda consuming me there for a while, letting everything else fall behind.
So I'm back to bending wood.
-gus