Zeta potential measurements of rare earth element enriched apatite from Jacupiranga, Brazil under water and collector conditions. Zeta potential measurements can be used to indicate the surface behaviour of a mineral under different reagent conditions. Mineral surface behaviour is important in processing and extracting minerals from their host ore, which can be energy intensive. Apatite is a phosphate mineral which can become enriched with rare earth elements. Rare earth elements are important in a wide range of products from iPhones to wind turbines.