I like to rather describe the properties of good stone rather than what stone it is. Will open your eyes a little more to what is around you.
The properties of good axe stone is:
- Hard
- Can take a sharp, strong edge (homogenous)
- Workable (possible to either/and flake, grind or peck)
- Preferably, find a river cobble that is closely resembling the shape you want to achive. That will save you A LOT of work.
You should however seriously consider making an antler axe instead. Easier and is less prone to breaking. It doesn't hold up it's edge as well though. I have made one of red deer antler and I like it very much.