1. Sedimentary Igneous Metamorphic

2.  They are formed by agency of water, wind and ice.  They are found in the form of particlesof various sizes and shapes.  They are of different layers.  They are formed mechanically, chemically and organically.  Examples>limestone, sand stone and chalk.

3.  They are formed by cooling of the moltem matter of the earth.  They are mostly found at the great depth of the earth but some times also found on the surface of the earth due to volcanic erruption.  They are found in crystals form.  Examples> granite, basalt, gemstone, gotonite.

4.  They are igneous and aqueous rocks formed by changes in heat and pressure.  They are of two types 1. Contact metamorphism> which are directly related to volcanic activity. For example lime stone convert into marble. 2. Regional metamorphism> it is associated with countain building movement. For example rocks convert into gemstone with massive and compact character.