“Can you identify the rocks that will make a suitable cutting edge?”
Rocks that have a fracture point.
How about this one. Given a green sapling, 1.5 inches in diameter, 5 ft long, your sharp rock and a fire... how do you make a hasty, field expedient spear out of it that will bring down a feral pig?
Assume we will give it to a brawny young man that isn't too bright and will poke a feral pig with a spear and maybe live through it.
/johnny