Halloysite from the Eucla Basin, South Australia - comparison of physical properties for potential new uses

The tubular form of halloysite, a kaolin group mineral, is a natural nanotube that has attracted research interest in development of new products as fibre reinforcement in polymers and as micro-containers for controlled delivery of active agents. The principal source of commercial halloysite is from Northland, New Zealand, with large resources also available at the Dragon Mine, Utah, USA. These formed by hydrothermal activity. Physical characteristics of these halloysites are compared with those of halloysites from a potential new source in the Eucla Basin, South Australia, formed by the action of acid groundwater on finegrained sediments. Nitrogen adsorption and transmission electron microscopy show that the hydrothermal halloysites have a low specific surface area and are thicker and more varied in pore dimensions than the more regular, thinner tubes associated with the acid groundwater deposit. Tailoring the choice of clay to meet specific requirements should assist in optimising the performance of new products.John L. Keeling, Pooria Pasbakhsh and G. Jock Churchma