Weathering Studies: 2. A Note on the Conversion of Phlogopite to Septechlorite

An examination of a partly weathered single crystal of phlogopite (with a low iron content) has been carried out. The only weathering product found is a two-layer clay mineral of the "septechlorite" or antigorite type. Electron microscopic observation shows the absence of epitaxial relations between the two phases. The importance of the iron content of a mica as a controlling factor in its weathering is illustrated.