I found these walking some fields a few miles from my house. They were in areas I have found a lot of pottery shards and a few points. There are no similar rocks anywhere nearby. Artifacts or rocks?
I think they could be Mano stones if there is no River close by...especially since they were found with other artifacts. Look for a flat well worn grinding stone (s) of the same material...could tie them together.
Those could very easily be hammerstones. Several of them appear to have the right type of wear and damage to be hammerstones but context has a lot to do with it. It they're hammerstones I'd also expect that you find a fair amount of flint debitage in the area.