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.
Igneous rocks. Igneous rocks form from melted rock, called magma. On the surface of the Earth, igneous rocks usually occur in a cooled state, except where molten rock is erupting from an active volcano.Magma that flows out onto the Earth's surface is called lava. Rocks that crystallize quickly from cooling lava at or near the Earth's surface are called volcanic rocks-no surprise.gneous rocks form from melted rock, called magma. On the surface of the Earth, igneous rocks usually occur in a cooled state, except where molten rock is erupting from an active volcano.