Scanning electron microscopy (SEM) images of the Colloidal Pool colloids (images are a combination of backscatter and secondary electrons). The colloids are a mixture of clay particles, hydrated silica, alunite, and diatoms. (a) Image shows how hydrated silica (the whispy, lighter colored precipitate) uses larger particles, such as dust, clay, or things like pine needles that may fall into the pool, as substrates for precipitation. (b) Magnified image of hydrated silica precipitations on clay particles. (c) Highly magnified image of a diatom showing detailed shell structure. (d) Image that shows the platy habit of clay particles and several diatoms. Scale bars are on each image.
Figure designed by Lauren Harrison, USGS.