Rocks Can Be Classified In How Many Groups?

Rocks are basically classified into three main types, which are as follow:

--Igneous rocks.
--Sedimentary rocks.
--Metamorphic rocks.

Igneous rock form when magma cools down and crystallize ,the molten magma that originates at the depth of 200 kilometers with in the earth. Lava is just similar to magma except is the case as most of the gases are escaped from it. The rocks which forms due to solidification of lave classified as extrusive or volcanic.

The magma which is not able to come to surface and crystallize at the depth that type of rock are known as intrusive or plutonic rock. Example of igneous rock is granite, gabbro.
Sedimentary is a Latin word which means settling . It means which solid material settle out of fluid. According to geologist earth is composed of only 5 % by volume of sedimentary rocks. By their varied nature they contains indication of past environment in which their particles were deposited and in some case it gives clue of some mechanism. Example of sedimentary rocks is shale, limestone, dolomite, and chert.

Metamorphic rocks: The word derived from Latin which means changed form .rock which changes in lithology, texture or chemical composition.Examples of metamorphic rocks are:
--quartzite.
--marble.
--slate schist.
--gneiss.

--Igneous rocks.
--Sedimentary rocks.
--Metamorphic rocks.

Rocks can be classified into three main groups:
--Sedimentary rocks.
--Metamorphic rocks.
--Igneous rocks.
Sedimentary rocks (they are formed by wind and water): they are actually formed while the layers of sediment (dregs: which can be mud, dirt, sand, gravel and different minerals) are settled to the bottom of the ocean in addition to after that compacted and compressed or we can say pressed together over millions of years. Sedimentary rocks are located where oceans or bodies of water once existed or still exist. Examples are the limestone, the sandstone, the chalk, the coal, the rock salt, the shale, the dolomite, and the conglomerate.
Igneous rocks (volcanoes): igneous rocks are created when molten rock or lava within the Earth pushes throughout the crust (similar to in a volcanic eruption) and then cools down. These types of rocks are located where volcanoes do exist. Examples of such rocks are the quartz, the pumice, the granite, the basalt, the obsidian
Metamorphic rocks: metamorphic rocks are produced when sedimentary or igneous rocks experience metamorphosis or simply we can say change which is caused by pressure, stress, high temperature, and water acting on the rocks. These types of rocks are located deep within the earth where heat and pressure have a very great affect. Examples can be the marble, the slate, the gneiss, the schist, the quartzite and the eclogite