A study of the formation of goethite, hyrogoethite and hematite under the bacterial action indicates that the bacterial action includes the whole process of solution and adsorption, complexation, transformation and crystallization-nucleation. The action of bacteria on minerals is characterized by specialization. Bacterial action not only dissolves the original minerals and form new minerals but also produces the differences in microenvironments of organic chemistry, which can help to form new different minerals. This is called organic crystallization action. At the same time, bacterial action affects the crystalline structures and the surface properties of the minerals.