Mineralization (silification, carbonatization and phosphatization) of cyanobacteria was studied in nature and laboratory. The increase in concentration of silica, phosphates, carbonates, and calcium leads to a sequence of morphological changes of cyanobacteria: (1) Formation of slime sheath, (2) formation of isolated globules of minerals on the slime sheath, (3) mineralization of slime sheaths of viable cells, and (4) mineralization of trichomes of dead cells.