Rock (geology)

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids. The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, and petrology is an essential component of geology. Rocks are classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. These indicators separate rocks into igneous, sedimentary and metamorphic. They are further classified according to particle size. The transformation of one rock type to another is described by the geological model called the rock cycle.