The planet we live in has many layers to it. These layers are divided according to their chemical properties and other related properties. The cores of the planet, the inner core and the outer core are both made of iron and nickel but the crust mainly consists of silicate rock. The region called the mantle also mainly contains silicate rocks. It is in these two regions that rocks are formed and re made. The process that each rock has to go through changes according to the type of rock. Basically there are three different types of rocks called the igneous, sedimentary and metamorphic. All three types of rock go through three different processes to form.
Igneous rocks are formed when heated magma cools itself and solidifies. This also occurs during volcanic eruptions when lava is spewed out during the eruption. Sometimes the magma reaches closer to the surface of the earth and solidifies gradually into rocks giving birth to rocks like granite and gabbro. Rocks formed in this manner are extremely hard. Rocks formed by slow cooling also result in bigger crystals than rocks that have been rapidly cooled down. Granite is used for construction purposes due to its high properties. Pumice is another product of this type of formation and is highly valued in the cosmetics industry.
Sedimentary rocks are formed when rock debris from mountains and rock formations get washed down into major water bodies and are coupled together with sand and other similar particles. The sediments settle at the bottom of the water body and undergo a process called sedimentation. As time passes by, the layers keep increasing. The layers that are the bottom harden due to the immense pressure exerted downwards on them by the new layers. This process is referred to as compaction. The salt elements found on the water end up helping to glue together the pieces of rock. After they harden they form sedimentary rocks. Examples include limestone and sandstone. Limestone has been used in the construction field commonly to make limestone walls or limestone are most durable and appealing stones.
Metamorphic rocks are the rarest rock type out of the available three types. They are basically igneous and sedimentary rocks that have been put through severe heat and exposed to immense pressure. The rock beds under the surface of the earth move constantly. This movement pushes rocks closer and puts them under a lot of pressure. As time goes on, the pressure and heat they are exposed to causes them multiple chemical changes to occur which transforms the rocks to metamorphic rocks. Examples of this type of formation are slate and gneiss.