any ideas on this one?

[fuss]

I did not collect this one due to its size but might go back for it since it looked so interesting, I did no tests on it, so all i have are some snapshots. Wondering based on the interesting markings if a rough id is possible. located on the shoreline of Lake MI, WI side.









Thx
Fuss.

 

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[Eu_citzen]

Either amphibole or pyroxene I'd guess.