Characterisation of outcrop and reservoir rock by a wide range of analytical techniques is presented, with the aim to understand mineral-organic interfaces. It is demonstrated that despite silicate rock being dominated by silicates, the exposed surfaces of the rock is not reflected in the bulk composition. This leads to a range of mineral surfaces and functional groups at the surface that drive adsorption and subsequently wettability on real rock. The second part of this thesis considers exposing model minerals to crude oil. It is found that different species from crude oil adsorb onto certain minerals to a varying extent. Key findings show that asphaltenes contribute to larger organic species adsorbed. However, this is not the case for muscovite mica, where the contact angle determining layer can be removed and identified by high resolution mass spectrometry. Finally, to facilitate the detailed understanding of complex systems, a model system investigated. Adsorption of stearic acid on the calcite surface in toluene was investigated via depletion isotherms, neutron reflectometry, sum-frequency generation and X-ray reflectometry. Stearic acid is shown to adsorb from toluene and can be removed and reapplied. However, in the presence of excess water, stearic acid can be removed from the surface to form calcium stearate.