We have used quantum chemical ab initio methods to describe the adsorption interaction of two of the most commonly used anionic collectors (oleate and oleoyl sarcosine anions) on calcium mineral surfaces. Calcite and dolomite were selected to represent calcium mineral structures, since they are the main impurities in the calcium phosphate flotation process. The similarities and differences of the calcite and dolomite surfaces were studied by computing various possible binding modes of the collector molecules. Also, the possibility to enhance the selectivity of the collectors was studied by modifying the sarcosine anion structure. The nature of the interaction was found to depend mostly on the steric features of the active surface sites. As a result, both surfaces showed a similar behavior of the collector anions in the adsorption process.