In its oxide or silicate form, silicon is used to make concrete, bricks, glass, ceramics, and soap. Silicon metal is also the base material for making silicones used in such products as synthetic oils, caulks and sealers, and anti-foaming agents.
Intrusive igneous rocks crystallize below Earth's surface, and the slow cooling that occurs there allows large crystals to form. Examples of intrusive igneous rocks are diorite, gabbro, granite, pegmatite, and peridotite. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals.
Part 1 Classifying igneous rocks by where they are formed. Intrusive Igneous Rocks â¢ Igneous rocks that form below the Earthâs surface are called intrusive igneous rocks (or plutonic). â¢ The word âplutonicâ comes from Pluto, the name for the Roman god of the underworld.