I was heading up to a high point in a cornfield in Acton, and happened to step over this on the way.
In this next picture, the working edge is to the lower right. The nicely fluted scallops out of the rock are produced by percussive flaking and this is a material I do not know the name of. It certainly does not come from Acton.
I was trying to figure out how to hold it.
Opposite from the sharp edge, the squared off butt end is clearly not functional. Perhaps this rock was a fragment broken off from something larger, like an axe head. But it was re-worked. Or maybe it started out this way.
By studying where the rock was smoothed out, after a while it became clear how it was held and, it could have been held quite tightly while in use on some slippery task. There was even some dried blood still on it - believe it or not, dried blood can persist for 10K years and I read a book once how re-crystallizing the hemoglobin allows determining the species of animal the blood came from. So there is more that could be learned from this rock.