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I found this rock by the shore of Lake Ontario. It's light weight and it was grouped with some other rocks with the same patterns.

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closed as off-topic by Gimelist, uhoh, Fred, BillDOe, arkaia Aug 28 at 2:17

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions about rock identification requests are off-topic. For more information, see the announcement on meta." – Gimelist, uhoh, Fred, BillDOe, arkaia
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Not OT IMHO - as edited, it's not asking what the rock is, it's asking what the circular features are. $\endgroup$ – Semidiurnal Simon Aug 27 at 20:46
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Your rock contains crinoid stem fossils.

Wikipedia has a good summary of crinoids

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