The inclusions in the quartz from 35 igneous rocks and 16 metamorphic rocks were studied in detail in thin sections. They were grouped into "regular, acicular, globular, and irregular inclusions" following a modified scheme proposed by Mackie in 1896. In this study, regular inclusions characterize the quartz of schists, irregular inclusions predominate in igneous quartz, and globular and acicular inclusions are most abundant in igneous quartz although they also occur in metamorphic quartz. Spectrographic analyses were rim on 35 samples of petrogenic quartz. Even clear colorless quartz is rich in elements other than silicon and oxygen. Probably ordinary rock-forming minerals in sub-microsopically fine particles are abundantly included in most petrogenic quartz.