Technical Abstract: Despite widespread consumption of earth among animals, its role in health maintenance remains an enigma. It has been hypothesized that animals consume earth for supplementation of minerals and protection against toxins. Unfortunately, most studies have only determined the total elemental composition of earth, which does not reflect the actual amount of bioavailable minerals. The aim of this study was to evaluate the actual bioavailability of iron in geophagic earth consumed by chacma baboons using a technique that simulates alimentary digestion and adsorption. Our results indicate that despite variation in absolute iron concentration of geophagic earth, actual iron bioavailability is low. These results suggest that iron supplementation may not be the primary motivation for geophagy in this population. We encourage more research to determine the role earth geophagy plays in health maintenance.