The nature, structure, and kinetics of formation of the adsorbed layers of oleate on fluorite in basic solutions have been examined by means of infrared external reflection spectroscopy. The adsorption of oleate on fluorite was found to be a very dynamic process which fails to reach equilibrium, Different steady states can be achieved. The surface composition and structure depend on competitive processes taking place at the interface, such as fluorite dissolution and interaction with water, and adsorption of oleate ions and other oleate aggregates from solution. Fluorite immersed in oleate basic solution shows surface phenomena dependent on an initial oleate concentration if other solution conditions (pH, agitation, etc.) are constant. Three characteristic regions of adsorption can be distinguished. In diluted solutions, below 10(-5) M, a steady state is reached. The amount of calcium oleate surface species does not exceed 0.3 of a statistical monolayer. At concentrations between 10(-5) and 10(-4) M the most dynamic interactions between fluorite and oleate aqueous solutions were observed. The adsorbed amount shows a maximum. The level of the maximum (up to 20 statistical monolayers) and the adsorption kinetics are strongly related to the initial oleate concentration. There is clear evidence that the thicker coverage is produced by a nucleation and growth mechanism. First nuclei are formed on the fluorite surface through tridimensional condensation before the monolayer is completed. Dissolution of the produced surface calcium oleate with an increase of adsorption time is caused by the Ostwald ripening that transfers the calcium and oleate from the fluorite surface to solution, where fine particles of calcium oleate are formed. At higher than 10(-4) M oleate concentration the total adsorbed amount of oleate does not exceed a monolayer coverage after a long adsorption time. A steady state is reached, and micelles are formed in solution, at concentrations lower than the cmc of sodium oleate due to the adsorption of calcium ions on the micelles, lowering significantly the calcium and oleate concentrations in solution. This prevents the formation of thick tridimensional patches on the fluorite surface. Adsorption kinetics is also very sensitive to other changes, such as solution hydrodynamics (agitation) or addition of external calcium lions or/and solid calcium oleate! to the oleate solution.