Rocks are naturally occurring solids which consist of one or more minerals. Minerals are naturally occurring homogenous compounds or elements with a definite chemical composition. Magma forms very deep underground. Igneous rocks are often associated with volcanos.
Sedimentary rocks form from loose sediment or fragments that are cemented together and harden.
Clastic sedimentary rocks have broken fragments of rocks and minerals. Chemcal sedimentary rocks are formed from a precipitate or solution usually sea-water or a lake. Halite or salt is such a rock. Organic sedimentary rocks form from animal or plant remains. Limestone is a common organic.