I think what can fool folks here is the fact that it's likely in an unfinished stage of production, as well as the appearance of poor quality lithics common to New England pieces. If you don't know our regional rhyolites, it can look like a rock, more so if the piece is still a stage and not finished. If I had to guess type, the type of shoulders and the lobate shape stem suggests Adena related, but normally the stem would not be that short on an Adena related piece. Another possibility would be a Lagoon point, but that's questionable as well because the shoulders are almost always much weaker in Lagoons. Still a piece of prehistory, and hence still a nice find, IMHO....
Edit: here is an example of a poor New England lithic, argillite of a type that is argillaceous slate(in contrast, Pa argillite is argillaceous shale), showing the original cobble cortex and a minimum of reduction or flaking. In this instance, it's actually a finished piece, as this is an end pick, which was a tool used in steatite quarrying in southern New England. But, I have to imagine it could easily be judged as "just a rock" if one is simply not used to seeing lithics as poor as this....
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