Stone Tools on the Beach

I am convinced there are stone tools along the beaches of Cape Cod, at least most of the ones on the Buzzard's Bay side. Going into the water at "Stoney" Beach in Woods Hole, I glance down cuz I figure one of these days I am going to find an arrowhead. This is about as close as I am going to get:

If you are used to looking for man-made flaking, those little graded ripples look quite unnatural. A few other views:

A nice smooth gray material like quartzite.

Probably some sort of knife.