Craving Minerals, Eating Rocks: Why do animals and humans eat rock dust?

Last October the Los Angeles Times released an article about research on tool-use among the wild bearded capuchin monkeys of Brazil. The article showcased two short videos of the monkeys smashing rocks against larger boulders – which was interpreted as intentional tool-making behavior. With a closer look, another strange behavior emerged. The monkeys occasionally licked the rocks in their paws. Several hypotheses were proposed to explain this behavior: the monkeys were licking off the minerals in the rock dust collected on the surface of the rocks; they were consuming lichen with antimicrobial properties; or, they were simply consuming ...