About two billion years ago, micro-organisms in the ancient oceans gathered sunlight to make energy and in due course, turned into fossilised rocks called stomatolites. The oxygen appeared as bubbles in their microbial mats. These organisms, according to Swedish palaeobiologist Therese Sallstedt and colleagues, helped form sedimentary phosphate minerals called phosphorite globally during the Proterozoic Eon. Some of it is preserved as phosphorite within both the Vindhya and Aravalli sedimentary r