I`m kinda new to the knapping area, but I`m pretty sure that you can use shale like that for a ground point, but I`d expect it to snap if used on anything harder than a hay bale or flesh, it`s brittle & won`t take the abuse of substantial impact like stump shooting. I`ve made some ground points for show & using on wallhanger arras w/ some beads & feathers danglin` off`n `em.
You might also give a thought to making the bases a little thinner so that they are easier to haft.
Lobo