The solid crust of the Earth is rock. The soil itself is made up largely of rock which has been broken down by weathering. Beneath the Earth's solid crust are pockets of molten rock, called magma. Certain hard substances formed from the remains of animals and plants are also called rock. Coal, which is composed of plant material, is an example.
Limestone contains the shells and skeletons of sea creatures and limy masses built by plants.
The Uses Made of Rock Food is grown in soil, which is weathered rock. One kind of rock is eaten every day. This is salt, a rock composed of the mineral halite. Granite, limestone, sandstone, slate, and marble are rocks known as building stones. Buried treasure lies in the rocks.