Like most Earth materials, rocks are created and destroyed in cycles. The rock cycle is a model that describes the formation, breakdown, and reformation of a rock as a result of sedimentary, igneous, and metamorphic processes. ... All igneous rocks start out as melted rock, (magma) and then crystallize, or freeze.
Sedimentary rocks form when mud and sand are deposited in layers on the Earth's surface. The layers are deposited in many environments including oceans, rivers and deserts. These layers of sand and mud are later buried. The weight of overlying layers compresses the mud and sand to form solid rock.
LIMESTONE: A sedimentary rock, it is used mainly in the manufacture of Portland cement, the production of lime, manufacture of paper, petrochemicals, insecticides, linoleum, fiberglass, glass, carpet backing and as the coating on many types of chewing gum. SHALE: A sedimentary rock, well stratified in thin beds.
There are three main types of sedimentary rocks:Clastic: your basic sedimentary rock. ... Chemical: many of these form when standing water evaporates, leaving dissolved minerals behind. ... Organic: any accumulation of sedimentary debris caused by organic processes.