Figure 6. Microbial colonisation and microcolony formation associated with Microfacies 1 sinter. (1) Irregularly lobed, coccoidal cells, and associated EPS. (2) Close-up of a conical microcolony. (3) Preferential silicification on the uppermost portion of a microcolony. (4) Colonisation of a silica substratum (yellow arrow) by a succession of partially silicified biofilm. Red arrows indicate acicular, aluminum, and oxygen-rich minerals (as determined by EDS) of unknown phase.