The three main types, or classes, of rock are sedimentary, metamorphic, and igneous and the differences among them have to do with how they are formed. Sedimentary rocks are formed from particles of sand, shells, pebbles, and other fragments of material. Together, all these particles are called sediment.
Also know, how do you identify a rock or mineral?
A rock is a solid, inorganic, naturally-formed substance without a particular atomic structure or chemical composition. It's probably easier to just remember that rocks are made up of two or more minerals.
How can you tell if a rock is a sedimentary rock?
One way to tell if a rock sample is sedimentary is to see if it is made from grains. Some samples of sedimentary rocks include limestone, sandstone, coal and shale. Igneous rocks form when magma from inside the Earth moves toward the surface, or is forced above the Earth's surface as lava and ash by a volcano.