Field views of the sample location and petrographic thin section of 3.33 Ga JC retrieved from the BGB, South Africa. Panel (A): field outcrop sites, showing black chert with flaser bedding outlined by the gray tuff (arrows). Panel (B): showing details of the carbonaceous, matt black chert from which the thin section was made. Panel (C): a photomicrograph of the sampled thin section, CM in the form of biofilms and clots are distributed throughout a silica matrix.