Quartz
Quartz, most common of all minerals is composed of silicon dioxide, or silica, SiO2. It is an essential component of igneous and metamorphic rocks. The size varies from specimens weighing a metric ton to minute particles that sparkle in rock surfaces. The luster in some specimens is vitreous; in others it is greasy or glossy. In pure form, quartz is colorless, but it is commonly colored by impurities.