An occurrence of phlogopite and its transformation to vermiculite by weathering

Summary. The characteristics of a phlogopite and its weathering product, vermiculite, have been studied by X-ray, infra-red, electron-microscope, and chemical methods. Inclusions within these minerals have been identified as thin films rich in iron oxide (which impart a schiller effect), spinel (which may exist in a preferred orientation), and serpentine. The orientation relationship between the fresh mica and its weathering product has been established by single-crystal methods. The mechanism of transformation from a l-layer to a 2-layer polytype is discussed. A SOIL sample containing the material used in the present investiga- tion was submitted to the Macaulay Institute for identification of a gold-coloured mineral that was abundant both in the soil and on the surfaces of rock particles included in that soil. The sender did not include details of the exact locality of the occurrence but the parent rock has been identified as scyelite, an ultrabasic rock that was named b