While polished stromatolite is often very pretty, seldom are such traces of rich green color manifest. This unique fossil is also very ancient, dating back to the boundary of the Archean and the Proterozoic in Precambrian time. This was a time on Earth when environments were still hostile to life as we know it. It was a time when bacteria reined, and those Prokaryotic bacteria (no cell nucleus) that produced their energy through photosynthesis were ubiquitous and were oxygenating the Earth's atmosphere. This was near the peak of stromatolite formations on Earth. This stromatolite is the oldest microfossil of Wisconsin and occures below the banded iron formations.