Definition - What does Intrusive Rock mean?
Intrusive Rock is a kind of igneous rock which is formed when magma slowly cools and solidifies beneath the earth's surface. As the magma cools down slowly the rock is coarse-grained and the mineral grains can be identified easily with naked eye. The cooling of the magma in the earth's surface is much slower than on the surface hence it leads to formation of large crystals. The rock can be divided in accordance with its size, shape and relation to other formation in which it intrudes.
Petropedia explains Intrusive Rock
Intrusive Rocks have characteristic appearance which makes it easy to identify them. They are formed from the cooling magma deep in the earth's surface. The surrounding rocks within the surface insulate the magma and make it cool down very slowly. The slow cooling make the crystals or the rocks to be large in size as compared to the rocks formed above the surface; hence they can be identified easily by their large sizes. They are commonly used in building facades and kitchen counterparts. They are known as granite by the people who use them in the field of architecture and in building. Granite is considered to be the only specific kind of Intrusive Rock.