 Nontronite forms from the weathering of biotite and basalts, precipitation of iron and silicon rich hydrothermal fluids and in deep sea hydrothermal vents.Some evidence suggests that microorganisms may play an important role in their formation.Microorganisms are also involved in reduction of structural iron in nontronite when soils undergo anoxia, and the reduced form of the clay appears to be highly reactive towards certain pollutants, perhaps contributing to the destruction of these compounds in the environment.