Scientists narrow down how Witwatersrand gold deposits formed .
Feb 2, 2015 . The richest gold ore in Witwatersrand is found in thin layers rich in carbon, plating fibres of ancient microbial life forms. (Photo: James St. John.lavas (uppermost part of photograph) at the Vaal Reefs mine in the Klerksdorp Gold Field, Witwatersrand, South Africa. Hammer for scale. Photograph by Cliff D.