Stromatolites By Matt Young May 15, 2017 11:00 MST Photograph by James Kocher. Photography contest, Honorable Mention. Stromatolites – digitate stromatolites from Biwabik formation (banded iron formation), Aurora, Minnesota. 1.9 Ga (billion years) old. Also known in lapidary circles as "Mary Ellen Jasper." Horizontal field of view ~4 cm.
