Figure 18. Biotic characteristics and textures of Microfacies 4 sinter. (1) Clusters of interconnected diatoms (red arrows) distributed on the surface of the sinter rim. Yellow arrow points to gypsum. (2) Close-up of interconnected diatoms (numbered), with silica spheres (~250 nm) precipitating on test margins (red arrow). (3) Colonisation of sinter surface by spherical cells. (4) Spherical cell with silica precipitating on its surface (red arrow). (5) Vertically upright microcolony of bacilli on a diatom test. (6) Incorporation of spherical cells, including endospores, into sinter.