Structure defects in palygorskite

Abstract

It is well established that palygorskite has an amphibole-like, double-chain structure. The linked tetrahedral groups forming continuous sheets are divided into ribbons of various widths due to alternation of the direction of tetrahedra which run parallel to the fibre axis (Brindley, 1980). This alternation of the chains leaves a series of holes of well-defined size which are filled with water molecules (channel water). Based on microscopic observations of cleavage surfaces (Bailey, 1980), the mineral appears to be built up of regular stacking of planes parallel to (h00) and (hk0) which form predominantly the surface of the laths parallel to the c-axis. This is further supported by the enhanced X-ray reflections from these planes. Some degree of structural disorder might be expected to result from the progressive elimination of the channel water on heating. In addition, the weak interchain bonding in palygorskite is likely to result in a shift of the layers parallel to the fibre axis.