Micromorphology of weathering biotite and its secondary products

biotite weathering is second in a series on the weathering of individual minerals. The series was started by Delvigne et al. (1979) with an article on weathering olivine. Papers on the weathering of muscovite and chlorite are in preparation. The paper is mainly concerned with the transformations taking place in biotite during its weathering as observed in thin sections with the light microscope. To explain these transformations, however, reference has to be made