A morphologically variable assemblage of stromatolites has been discovered in thin chert layers within the Fig Tree Group of the Swaziland Supergroup, South Africa. They are commonly low-relief, nearly stratiform, laterally linked domes. Rarer forms include pseudocolumns and crinkly stratiform stromatolites. The stromatolites grew on a substrate of altered komatiitic lava and sediments deposited on the lava surface, and in most places are covered by later komatiitic flows. Abundant fine-grained tourmaline included within the stromatolite laminae suggests that stromatolites formed in an environment dominated by boron-rich hot-spring emissions and evaporitic brines.