Rock Specimens on the Lawn, Copper Harbor Conglomerate, 1100 North University Building, 1100 N University Ave, University of Michigan, September 22, 2020

https://lsa.umich.edu/earth/about-us/about-our-building/rock-specimens-on-the-lawn.html

Copper Harbor Conglomerate

'Late Precambrian of the Upper Penininsula of Michigan; dominantly rhyolite cobbles (which is curious because the Keeweenawan succession is approx. 99% basalts, and only 1% thin rhyolites); green minerals are copper sulfates and/or copper carbonates formed by the weathering of metallic copper. The original metallic copper was metasomatic, implaced by a convection driven solution related to regional metamorphism. Native copper + hematite were primary. Iron oxidizes before copper. (Rocks lack dellafosasite (CuFe2O4), which indicates copper didn't oxidize).'