Structure and swelling of fibrous and granular saponitic clay from Orrock Quarry, Fife, Scotland

Abstract

AbstractVeins of intimately associated fibrous and granular saponitic clay occur in a basalt quarry at Orrock, Fife, Scotland. Preliminary X-ray diffraction studies suggested that both fibrous and granular forms consisted of pure saponite but chemical and thermal studies showed the presence of subsidiary amounts of interstratified chlorite. The fibrous clay, which is strongly oriented around the a axis but with a uniform distribution of the b and c poles, consists mainly of highly-crystalline laths with minor amounts of turbostratically-ordered particles. The granular clay consists of turbostratically-ordered particles only. The swelling behaviour of both types of clay in water and in ethylene glycol is similar to that of pure saponite. With glycerol, only the granular clay swells completely but the fibrous clay behaves similarly if first subjected to grinding or chemical pre-treatment. These observations are accounted for on the basis that the fibrous clay has better order than the granular form, thus enabling the interlamellar constituents to participate more fully in layer-to-layer bonding.