Think about all of these you have been posting and the likelihood they are artifacts. Do you look at other posts and notice how very very rarely actual hardstone artifacts are found and posted? Take some time and study pictures of actual artifacts and you'll start to develop a better eye for what they look like, particularly in your area. In the mean time, keep up the hunt, you'll be finding artifacts soon.
Your stone is naturally well shaped to use as a grinder but it is too rough to have been used for that purpose.
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These three stones are pretty ordinary on one side but when flipped over the tell-tale smoothness from use is evident. The stone on the right is a little iffy, but I have learned over the years to know the difference between river smooth (top side) and polished smooth from use (bottom side). I have watched enough Native Americans using a stone like that to smooth the outside of pots they are working on to be somewhat sure it was used for that purpose. It was found at a site with several pottery shards so context helps a lot with figuring out wether or not you have a good find.
Crowfriend what is the one on the left used for if you dont mind me asking? I have found some like that and I keep them. I have 4 or so and found in different areas. I thought maybe they were used like a hammer stone used in the flaking of flint tools but not sure. Id like some info on them please, thanks rock