Further work on the importance of nanobacteria in geology by R. L. Folk and co-workers includes study of calcium carbonate Bahama ooids,[18] silicate clay minerals,[19] metal sulfides,[20] and iron oxides.[21] In all these chemically diverse minerals, the putative nanobacteria are approximately the same size, mainly 0.05 to 0.2 μm. This suggests a commonality of origin. At least for the type locality at Viterbo, Italy, the biogenicity of these minute cells has been supported by transmission electron microscopy (TEM).[22] Slices through a green bioslime showed entities from 0.4 down to as small as 0.09 μm with definite cell walls and interior dots resembling ribosomes; and even smaller objects with cell walls and lucent interiors with diameters of 0.05 μm.[23] Culturable organisms on earth are the same 0.05 μm size as the supposed nanobacteria on Mars.[24]