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This is a 2.2 billion year old, Pre-Cambrian stromatolite called Collenia undosa. It comes from the Biwabik Formation, Mary Ellen Mine, St. Louis County, Minnesota. The specimen measures 8 x 5.5 inches in size and is highly polished on both sides. This has proved very difficult to photograph and get an accurate colour balance. The pictures do not do justice to this piece.
Stromatolites are the mineralised result of a symbiotic relationship between bacteria and filamentous algae. Together these organisms played a significant paleobiological role contributing vast amounts of metabolised oxygen to the earth's early atmosphere. During the Pre-Cambrian the seas were saturated with free iron and the atmosphere had very low oxygen content. As stromatolites continued to cover the ancient shorelines oxygen was produced in ever increasing quantities. This caused the so-called "Rusting of the Seas" where free iron began to precipitate in enormous quantites. Whenever you visit places such as the iron-belts in Michigan, Wisconsin and Minnesota just remember that the iron is a result of this "rusting process." Hence, all of the steel mills and iron factories! Stromatolites existed in abundance during the early Palaeozoic and slowly declined in numbers due to environmental pressures such as reef boring organisms and shell crushing fish. Today, living stromatolites can only be found hypersaline environments.
Order # STCO 01
Price: £90 ($142 €128)