Abstract: Now more than one century after the publication of works of V.I. Vernadsky and Ya.V. Samoilov, important role of the biogenic factor in the sedimentary ore genesis has become an undeniable fact for all geologists. Discussions at present are concerned mainly with creative nature of the activity of organisms in the formation of specified mineral resources. In the collective monograph of Russian geologists “Biomorphic Structures of Bauxites” published in 2004, based on studying several tens of deposits with a vast age (Late Proterozoic to Quaternary) range and geographic setting (Africa, Eurasia, Australia, and America), active participation of different microbial communities in the bauxite formation was demonstrated. Accomplishment of SEM studies of ores from the Eva bauxite deposit (Guinea-Bissau), an object little known in Russia, continues research works in this field initiated by E.L. Shkol’nik. © 2019, Pleiades Publishing, Inc.