Vermiculite surface morphology

A study of the surface morphology of vermiculites from several different sources by the electron microscope has indicated that, unlike the smooth surfaces of micas, the vermiculite surfaces show micromorphological structural variations such as small humps, prominent crystaUo~aphic steps on the basal cleavage planes, marginal rolling of the layers and layer buckling. The production of layer buckling may result from the inhomogeneity of interlayer population caused by the introduction of hydrated cations replacing potassium during weathering. The (110) steps on the surface of the cleavage can be observed and these are visualized as nuclei for weathering in addition to the particle edges. The surface morphology of vermiculites i closely related to the nature of the inter-layer cation. When treated with potassium or ammonium salts, the surfaces assume smooth morphology, the K and NH 4 ions occupying interlayer sites and collapsing the mineral. When treated with Na or Li salts, the complex surface morphology persists, and in some cases is enhanced, possibly by the slow exchange of residual potassium from the interlayer. On this basis, the presence of unweathered mica cores have been identified in natural vermiculites which show varying amounts of residual K~O content. It is possible to offer an explanation from structural considerations for the complex mor-phology of the vermicuhte surfaces including the curling of the layers on depletion of potassium. The morphological features of vermiculites have been produced on biotite mica by leaching with salt solutions