These rocks are both classified as granitic, because they both are rich in quartz. Granite contains mostly potassium feldspars and has a low percentage of dark iron and magnesium minerals. In contrast, granodiorite contains more plagioclase (calcium and sodium) feldspar than potassium feldspar and has more dark minerals. Thus it is a darker color than granite. Chemical and x-ray analysis of granite and granodiorite can be used to “fingerprint” these rocks, telling their exact composition and where they may have formed.