Copper-included Proterozoic Stromatolites (Dr. B. Phillips Coll.)

Item Description

The younger Copper Harbor Conglomerate lies above the Portage Lake Volcanics, the primary copper and silver source of the famed Keweenaw Peninsula Copper Country. The Copper Harbor Conglomerate is lower Oronto Group, upper Mesoproterozoic, 1.085-1.093 billion years old. It is well-known for stromatolites. Stromatolites are layered mounds, columns, and sheet-like sedimentary rocks that were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe (Wikipedia). The stromatolites were deposited in shallow ephemeral lakes under arid to semi-arid conditions. This sculptural sawed and polished nodule hosts striking undulating stromatolite layers, that are included with native copper. A rich and showy large example from Copper Country from the Dr. Barratt Phillips Collection.