This is just a wild guess so take it for what it's worth....if it is native related it could be either something used for starting a fire...(spinning a dry branch back and forth to light up some dry grass) or possibly pushing a needle through leather or rawhide to sew native garments.
Either of those sound at least plausible for using that worked stone.
Interesting piece. Seeing it is broken on the end it would be just a guess for me. Id of kept it though, nice find
Guessing id say a broken pendant by the material which looks soft.
maybe a weight for a fishing net? again just guessing. interesting find. I enjoy finding items that take a while to identify. Sorry I couldn't be of more help.
I think you and Mainjman nailed it! It is rough like a whetstone and I'm pretty sure I could sharpen a blade with it. Any reasonable idea as to whether this would be native? The area it was found in was very close to a major native trading area and I have found other native pieces here...