A rock is called a dense, coordinated ma ss of one or more naturally occurring minerals. In general, according to their composition cksareclassified into three major categories: igneous rocks, sedimentary rocks and metamorphic rocks

Igneous or volcanic rocks are formed by the hardening of magma. When magma or molten material solid underground, igneous rocks are divided into 2 groups. Interior igneous rocks which form in depths of earth such as Granite. If magma flows in earth surface or ocean, exterior rocks are formed such as Basalt.

Another classification are existed in base of amount of siliceous in rocks

Acidic rocks: rocks which contain more than 63% siliceous

Medium rocks: rocks which contain 52 to 63% siliceous

Basic rocks: rocks which contain 45 to 52% siliceous

Ultrabasic rocks: rocks which contains less than 45% siliceous

Sedimentary rocks

Typically, sedimentary rocks deposited by minerals which carried with water, wind, or ice settles on the surface of the earth or in the ocean.there rocks are always layered and the process of sedimentation comprises, layering and filling of the pores of the cement are done. In terms of how sedimentary rocks are formed, they are divided into five categories 

Trigenous Rocks : They are rocks that are made of particles and ingredients that have been created by the destruction of other rocks. Like sandstone, mudstone, clay

Siliceous Rock : They are rocks that contains a lot of siliceous in their chemical compositions like chert rocks

Carbonaters Rocks : In this group of rocks there are many calcium carbonate (calcite or dolomite mineral) like limestone

Evaporties Rocks These rocks are interaction by effective chemical interactions and have been called evaporative rocks, such as salt rock, gypsum and travertine

Organic rocks: this rocks contain of plants and animals which have calicoes shells like kokina  

Metamorphic rocks which under pressure and high temperature their chemical composition and texture changed into new rocks, different types of metamorphism are as follows:  

Zonal metamorphism: If there is a fault in the area. This fault at high depths due to high pressure and heat causes a metamorphism

Burial metamorphism:it caused by high sediment pressure

Hydrothermal metamorphism: This type of transformation is caused by the penetration of hot water into the rock

Proximity metamorphism:When a molten mass is placed next to the rocks it transforms the rocks around it, also known as the metamorphic zone.

Onyx is a type of metamorphic rock formed by the alteration of limestone by heat and pressure.

Rock cycles

The set of processes which the rocks are formed, broken and crushed and re-formed as new rocks, is called the rock cycle. These processes are dependent on factors such as pressure, temperature, time, and changes in the environmental conditions of the Earth's crust (outer hard layer). In several stages of the rock cycle, old rocks are crushed, new minerals are formed and new rocks are formed from old rock compositions.

Therefore, the rock that began its life as an igneous rock on the surface of the earth can enter the nature cycle after some time in the form of sedimentary rock, metamorphic rock or new igneous rock.