Our entire earth is made up of rocks and minerals. The word Igneous comes from Latin word ignis which means "The Fire". Our earth has a hard crust outside and a liquid core inside. The crust is covered with soil, ice, water and sand. The rocks are seen in the form of mountains, canyons and riverbeds. Acccording to our geologists rocks are classifeid in to three categories namely: Sedimentary, igneous and metamorphic. When volcanos erupt magma rises above the earth's surface. This maga is called the lava.When magma cools Igneous rocks are formed on the earth surface. Magma lies some hundreds of thousands of kilometers  under the ground and flows through cracks and chambers of the inner earth. It sometimes takes millions of years to cool and form into rocks. The melting of magma is mainly caused either with an increase in temperature, or a decrease in pressure or with some changes in composition.

Igneous rocks are classified in two groups namely: intrusive and extrusive. Intrusive rocks are formed when the melted rock rises towards the surface, but could not reach the surface of the earth. The cooling and crystalization of magma below the earth surface forms Intrusive (Plutonic) igneous rocks. Examples of intrusive igneous rocks are Monzonite, Pegmatite, Garanite, Gabbro, Carbonatite and Dunite. Extrusive igneous rocks are formed at the surface of the crust as a result of partial melting of rocks with in the crust and mantle. These rocks are fine grained and solidify faster than intrusive rocks. Examples of extrusive igneous rocks are Pumice, Basalt, Obsidian and Andesite. The rocks that are formed between plutonic and volcanic rocks are called hypabyssal igneous rocks which are rarely found on the earth. The texture of extrusive igneous rocks (also called volcanic rocks) is  very fine grained. Intrusive igneous rocks are thick or thin and are huge irregular masses of rocks.

Igneous rocks contain crystals which are large enough to be seen with our eyes and these are called phaneritic.The crystals that are too small to observe with a naked eye are called aphanitic. The texture which includes the size, shape and orientation helps to determine if the rock is a tuff or simple lava. The basic classification of igneous rocks depends on the chemical or mineralogical parameters.

There are nearly some 700 different typres of igneous rocks rocks formed below the surface of the earth comprising of different properties and composition. The temperature of magma under the surface of the earth is around 1200 degrees C. Igneous rocks are the first rocks found on the earth.