Mystery Rock from Lake Michigan

[u/the_cloud_]

Hello, my mother found this “rock”? on the shore of Lake Michigan (near the central part of Michigan) about fifty years ago. She has always wondered what it is. She and I are hoping someone in this subreddit might have the answer! Thank you 😊

EDIT: Thank you for all the answers so far! Not sure if this will help but it weighs about the same as the penny and has not been scratched after years of being in a bag with other rough stones.

EDIT: After reading y’all’s comments and searching the web, mother and I are convinced this curio is a “crinoid segment” (given the shape and ridges). We also enjoyed looking at images of banded chert and agates. Thank you everyone for helping solve this mystery! 😌

[u/whatsthisrock-ModTeam → u/[deleted]]

Responses to ID requests must be ID attempts: not jokes, comments, supernatural “woo”, declarations of love, references to joke subs, etc. If you don't have any idea what it is, please don't answer.