Pipe filling with organic mud from the Kromberg Formation (Onverwacht Group, Buck Reef Chert). Age ~ 3416Ma. Barberton greenstone belt, South Africa. This sample shows a vertical cut through the margin of the pipe: laminated chert layers are around the margin, while a black matrix rich in organic carbon fills the spaces between the angular fragments of the pipe filling. Sample from the collection of FSU Jena, collected with funds from the DFG (German Research Foundation).