2013 Conference of the International Medical Geology Association (25–29 August 2013)

Paper No. 2
Presentation Time: 2:50 PM


WILLIAMS, Lynda B., School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404, Lynda.Williams@asu.edu

Healing clays are comprised of alteration minerals dominated by nano-scale crystals and aggregates. They heal by physical or chemical processes as the clays react with fluids and cells (bacteria or tissue). A purely physical electrostatic attraction between a mineral surface and a cell wall can be strong enough to impede metabolic functions (nutrient intake or toxin efflux), or cause cell lysis. Some clay minerals (e.g. kaolins) are attracted to epithelial cells, of the stomach lining and can form a protective coating, or may adsorb bacteria and toxins to be excreted from the digestive tract.

Clays may be stable in a mammalian system, but undergo ion exchange when exposed to body fluids. Smectite is common in ‘healing clays’ and has a large surface area (800 m2/g) that impacts the fluid chemistry. Common exchange cations in smectite include Na, K, Ca, Mg and Fe, which can be released into fluids becoming bioavailable nutrients that promote healing. More complex chemical reactions may occur when clays undergo re-equilibration with body fluids. Oxidation reactions are common and generate heat; therefore healing may be promoted topically by excretion of toxins through sweat.

Antibacterial clays are a unique group that causes chemical alterations to bacterial cells. The dominant clay is illite-smectite that buffers the fluid pH and Eh away from circum-neutral. Under these conditions, metal oxides or sulfides produce chemical products (e.g., hydrogen peroxide and radicals) that decompose certain biomolecules. Fortunately, mammalian cells have a complex vascular system that can endure the chemical attack, while pathogens cannot tolerate the rapidly changing chemical conditions imposed as clays approach a new equilibrium. The mineralogy, chemistry and physical properties of ‘healing clays’ collected worldwide will be presented and classified according to their impact on human health. Evaluating the healing process requires a geochemical approach to predicting chemical reaction paths and products along with evaluation of microbial defenses to new chemical conditions introduced by the clay, and the response of mammalian tissues.