Large 2.4 BYA Stromatolite - Rare Girvanella Form

Precambrian stromatolite is the oldest of all fossils, and with much labor (cutting and polishing), it is most beautiful. The banding that commonly appears in stromatolite is a record of the growth patterns of colonies of microorganisms, principally photosynthetic prokaryotes (e.g, cyanobacteria). The colors that are often expressed are the result of the interaction of biological and sedimentary processes, together with subsequent chemistry and mineral exchange.

This stromatolite is at once, ancient (Precambrian), beautiful, and unusually colored. Coming from the Chocolay Group in an area know as the Chocolay Hills located southeast of Ishpeming, Michigan, it dates to the Lower Proterozoic, some 2.2 to 2.4 Billion years old. This stromatolitic carbonate has been hand-polished to a mirror finish on one side exhibits intricate banding and a spectrum of colors close to orange, lavender, and various tans, among others - rather like butterscotch in areas.

This particular specimen is a cross section that has three individual bacterial colonies with an unsymmetrical spherical form called Girvanella (sometimes called algal balls, though this is misleading nomenclature). This form is diminishingly rare within the formation -- very rarely are specimens found containing multiple and large Girvanella forms.