mississippi river

Map showing the size and location of the Northwest Angle relative to surrounding bodies of water and political divisions, including those demarcating Manitoba, Ontario, and Minnesota. Minnesota's Northwest Angle in Lake of the Woods is farther north than any other part of the contiguous United...

I recently found this on a large island in the Mississippi River in Iowa. It was on the exposed clay layer that is underwater a lot of the year, so there has been a lot of wear from sand. I’m pretty sure it is a celt but wanted to get the opinions of people on here who have more experience than me!