Although surface chemistry fundamentals of semisoluble minerals have been studied by many researchers, detailed understanding of these systems is still incomplete. In situ Fourier transform infrared internal reflection spectroscopy (FT-IR/IRS) techniques have recently been used to successfully describe the adsorption of carboxylates at semisoluble mineral surfaces. The wetting characteristics of these adsorbed films, however, require further consideration. In this regard, the hydrophobicity and stability of transferred Langmuir-Blodgett (LB) monolayers of fatty acids at fluorite and calcite surfaces have been studied by contact angle measurements with water and diiodomethane. Generally, it was found that the transferred LB monolayers of fatty acids at a calcite surface are unstable whereas such monolayers transferred onto a fluorite surface are stable, as revealed from advancing and receding contact angle measurements. These results are believed to be due to incomplete reaction of the fatty acid monolayer at the calcite surface. In addition it was found that a closely packed well-ordered stearate monolayer similar to that of a transferred LB monolayer can be formed at fluorite surfaces by spontaneous adsorption and self-assembly from aqueous solutions.