Mount Hasan has produced volcanic rocks with compositions ranging from basalt to rhyolite but the dominant components are andesite and dacite which define an older tholeiitic and a younger calc-alkaline or alkaline suite. These rocks in turn include amphibole, apatite, biotite, clinopyroxene, garnet, ilmenite, mica, olivine, orthopyroxene, plagioclase, pyroxene in the form of augite, bronzite, diopside, hypersthene and salite, and quartz. The older volcanic stages have produced basaltic andesite while dacite appears only in the most recent stage. Obsidian also occurs in the most recent stage although it is not an important component while most of the rocks are porphyritic. The basaltic family includes both basaltic andesite and alkali basalts with augite, clinopyroxene, garnet, hornblende, hypersthene, olivine, orthopyroxene, oxides and plagioclase.