Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a common rock, is a combination of the minerals quartz , feldspar and biotite. The Earth 's outer solid layer, the lithosphere, is made of rock.
Rock has been used by humankind throughout history . The minerals and metals in rocks have been essential to humancivilization .
Three majorgroups of rocks are defined: igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is an essential component of geology .