need help identifying this rock? crystal?

[rockquestion]

Found this in Cheboygan Michigan. I can't figure out what it is. it's about 6LB's and looks like a brain or coral?
anyone shed some light?
Thanks !!

 

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[DDancer]

Looks that you have a worn down mass of chalcedony, the brainy looking portion is called a mammilary or botryoidal formation. Seeing as you found it in Michigan there's a likely hood that it was worn down from a glacial movement. Chalcedony is hard stuff. Neat looking though.

 

[rockquestion]

Thank you DDancer! much appreciated

 

[RustyGold]

Excellent find!