Quinoid polycyclic aromatic hydrocarbons (PAH quinones; PAHQs), which are known to cause adverse health effects, are partly formed by the atmospheric oxidation of their parent compounds, PAHs. However, the heterogeneous oxidation of PAHs by gaseous O3 on natural mineral substrates, such as desert dust aerosols, is poorly understood. This study examines the potential for the secondary formation of a representative PAHQ, 9,10-anthraquinone (AntQ), by the oxidation of anthracene (Ant) on mineral dust aerosols. Experiments with a flow reactor and analysis of the water content on the substrate surfaces showed that the decay rate of Ant with O3 was typically high when the surface water content on the substrates was increased. We showed through surface analysis by temperature-programed desorption using NH3 that the Ant–O2 reaction was accelerated on the acidic surfaces of the mineral dust, particularly on the clay minerals. Both processes led to AntQ formation, suggesting that chemical reactions on the surface of the mineral dust aerosols, including clay minerals, result in the unintended formation of toxic organic compounds in the atmosphere.