🔎 UNIDENTIFIED Stone tool?

[tomtector]

This has puzzled me for years. My assumption is a type of tool. Never able to positively identify it.
Photos were sent to the Wisconsin geological center and I was told it was just a rock concretion/formation. Any help to confirm or deny would be appreciated.
Thanks for looking!

 

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[Treasure_Hunter]

Natural stone formed by water erosion.

 

[Limitool]

I'm no expert at all.... but it doesn't appear to have been worked by man at all.