Siliceous sinter in the field and viewed via Scanning Electron Microscope

Left photo shows a loose piece of siliceous sinter that was precipitated around a photosynthetic microbial mat in the Lower Geyser Basin.  The microbial mat died when the outflow channel changed positions. In the upper right, a Scanning Electron Microscope (SEM) image of siliceous sinter, with sheaths of silica that had precipitated around the once-living phototrophic microorganisms, making a texture that looks like cooked spaghetti. In the lower right, a closeup SEM image of the broken ends of those ‘spaghetti’ pieces, showing the hollow inside where there once was a bacterial filament that was part of a photosynthetic mat. The original bacterial filaments were about 1 µm in diameter, or about the diameter of a human hair.