Need an Opinion -- Ground Stone?

[MarkDz]

I found this stone in PA, on a riverbank in an area with lots of Native American activity. I think the groove looks like it may be human-made, but other aspects of this (the odd shape of the rock and the partial and misaligned groove on the opposite side) make me think it's just a really odd "geofact."
I'd appreciate any opinions, good or bad.

 

[old digger]

Looks like a naturally weathered rock.

 

[MarkDz]

Thanks, Old Digger... You're probably right.

 

[rock]

If they had found it they probably would of used it. Would of made a good net weight but I would guess they would of grooved the other side to secure it better.