Blue Agate Ordovician Stromatolite

This is yet another form of stromatolite that is at once beautiful and has interesting scientific characteristics. It derives its name, Brecciated Basal, from the fact that it originates at the base (Basal) of a large overlaying stromatolite structure. Brecciated (angularly broken) signified that, in fact, the original stromatolitic structures were shattered into irregular shapes, probably in a surf, and were then buried under the stromatolite colonies that subsequently grew above. Mineral replacement has been hard at work with a bluish gray silica predominating, making for an attractive creation through the interaction of biology and chemistry. The mineral replacement was likely formed by cold water precipitation, resulting in the crypto crystalline (blue agate) structure that yet retains the definitive imprints of growth of ancient microbial mats.

A final point of scientific interest is the age, Lower Ordovician, some two Billion years after stromatolite reached its peak on Earth, and during a time when stromatolite niches were disappearing because of competing metazoan and benthic life forms. The final major decline of stromatolite on Earth was a mere 50 million years after this stromatolite was formed.