Static energy minimization techniques have been used to elucidate the surface structures of magnetite crystals in pure and hydroxylated forms. Adsorption energy values in the presence of molecular water, dissociate water and simple carboxylic group molecule (formic acid) are calculated and we found that the carboxylic group do not adsorb strongly in most of the pure and hydroxylated surfaces in comparison to water. Since the associated calcium minerals are floated from magnetite using fatty acid collector, our calculations corroborate the flotation practice of removing these impurity minerals from magnetite.