I'm not sure if this is a hammerstone, or a pestle.It's very heavy like iron ore, pretty cool.Also a nice quality broken point.It warrants more investigation finding these two near each other on the surface.
Wild guess on the point, a Marshall
By design that stone may well have been used as a Pestle, a small accompanying mortar might be called a " paint pot " Are you curious enough to take a file to it to confirm what material it is ?
Tks for th show