Dry grinding of pyrophyllite (Hillsboro, USA) has been studied by X-ray diffraction (XRD), specific surface area measurements (BET) and scanning electron microscopy (SEM). At the beginning of the grinding process, some effects such as delamination, gliding and folding of the layers, and decrease in particle size were detected by SEM and XRD, resulting in a large increase in specific surface area, up to a maximum of ~ 60 m 2 . g-1. Marked changes in the structure take place between 30 and 32 mins grinding. Longer grinding times increase the degree of disorder and SEM and specific surface area data suggest that aggregation occurs. XRD results indicate that some residual order persists in the degraded structure.

This investigation was made possible through the financial support of the Consejo Superior de Investigaciones Científicas and Junta de Andalucía, research project No. 613-125. Thanks are extended to the Ministerio de Educación y Ciencia for a grant to one of the authors (P.J.S.S.) to enable him to make this investigation.

12 pages, 5 figures, 1 table, 34 references.

Peer reviewed