Rocks are naturally formed, consolidated material composed of grains of one or more minerals. Geologists group rocks into three categories depending on their origin: igneous, sedimentary and metamorphic.
is defined as a naturally occurring, crystalline solid of definite chemical
composition and a characteristic crystal structure.
Igneous rocks are formed from solidification of molten material. Sedimentary rocks are formed by the accumulation of fragmental material derived from preexisting rocks of any origin as well as the accumulation of organic material or precipitated material. Metamorphic rocks occur as a result of high pressure, high temperature and the chemical activity of fluids changing the texture and (or) mineralogy of preexisting rocks.