Gravel

Gravel is a kind of rock. It is not a mineral because it is not pure. Instead, it is a mixture of minerals. Gravel is a kind of rock. It is not a mineral because it is not pure. Instead, it is a mixture of minerals. Gravel is usually a light-colored sedimentary rock made up of sand, small pieces of broken rock, and clay. It is used for construction, as a road or track surface, or as a filter material in construction.