This beautiful stromatolite exhibiting classic growth ring structure is from a locality that people generally associate with trilobites and other Paleozoic fossil, the Atlas Mountains of Morocco, except this fossil is 2 to 3 times older. Dating to the Mesoproterozoic, this 1.0 to 1.2 billion year old stromatolite has various shades of reddish brown to almost white in irregular, alternating bands. The unidentified prokaryotic bacteria responsible for this fossil is likely to be a species of cyanobacteria, the primitive organisms that largely produced Earth's atmospheric oxygen.

It would take another 600 million years after this stromatolite was formed before shelly animals appeared on earth.

The distinct alternating band structures within stromatolite could signify temporal variation growth patterns in a large global colony that resulted from changing conditions in the benthic environment.

The specimen has been polished to a mirror finish perpendicular to the growth lines.