Any ideas what this might be?

[BadAdze]

My neighbors daughter found this while hiking. This is in Northwest Missouri, if im not mistaken. Any clue as to what it is?

 

[GatorBoy]

My guess is its fossilized mud or clay with evidence of an air bubble or worm or some other creature in it. Its neat..but natural.

 

[BadAdze]

Thanks man, was thinking myself that it looked too natural, its super smooth like it may have been in a creek or something like that.

 

[rock]

Id say natural also. Still a nice looking rock though.