A method for determining a mineralogical composition of a geological formation sample includes measuring a mineralogical composition of the sample and measuring an elemental composition of the sample. The mineralogical composition is processed to compute a predicted elemental composition of the sample based on known elemental compositions of predetermined minerals. The measured mineralogical composition is corrected to obtain a corrected mineralogical composition which is in turn processed to compute a corresponding corrected predicted elemental composition of the sample. The measured elemental composition is compared with the predicted elemental compositions to obtain error indicators. The error indicators are compared and evaluated to selected and output one of the measured or corrected measured mineralogical compositions.