This work deals with the determination of the mineralogical composition of three quartzite samples, selected as case study to verify the viability and accuracy of various experimental techniques commonly used in geometallurgy and petrography for the determination of the mineralogical composition of rock samples. The investigated samples are from the North-Eastern side of the Denali National Park (Alaska Range, USA). The mineralogical phase abundance of the samples was determined by digitally assisted optical modal point counting, scanning electron microscopy (SEM) + energy dispersive spectroscopy (EDS) modal and digital image analysis, normative calculation from bulk chemistry calculation, and modal Rietveld X-ray powder diffraction. The results of our study indicate that the results provided by modal optical and SEM digitalized counting seem less accurate than the others. The determination with EDS mapping was found to be inaccurate only for one sample. Agreement was found between the X-ray diffraction estimates and bulk chemistry calculation. For both modal optical and SEM digitalized counting, the statistics was probably insufficient to provide accurate results. The estimates obtained from the various methods are compared with each other in the attempt to attain general indications on the precision, accuracy, advantages/disadvantages of each method.