Granite is igneous rock. It is light in color, but the grain can be medium or coarse. The rock is composed mainly of alkali feldspar and quartz and is easily recognizable by the visible grains of the various dark minerals. Granite rocks are the most common of all crystalline rocks found on the surface of the earth. They are found all over the world, usually in great masses called batholiths that often extend over thousands of miles. This is a popular material form use in monuments and buildings because of its hardness, durability and the range of colors.

Composition of Granite

Granite is composed mainly of potash, feldspar and quartz. The color of the rock varies from gray to red and is usually determined by the amount of the potash feldspar. If there is a lot of glassy crystals in granite, it will tend to have a bluish color. Dark minerals, such as hornblende, biotite mica and muscovite mica can sometimes be found in granite. Some types of rock that are commonly called granite contain different amounts of plagioclase feldspar. Rocks that contain about one-fifth of the amount of potash feldspar relative to the amount of plagioclase feldspar is really granodiorite, rather than granite. Rocks that have the same composition as granite, but have a very large amount of crystals are known as pegmatite.

Where Granite is Found

Granite is found on every continent of the earth, especially in places where the earth has been worn away by erosion. It often forms the core of mountains that forceful pressures within the earth have pushed upward. Sometimes bodies of granite are found in large outcroppings of rocks that are found in chimney like and overhanging rock formations. The Appalachian Mountain range in the United States is composed mostly of granite. It is also found in the Ozark Mountains, the Black Hills, and the front range of the Rocky Mountains. Granite is also produced in many states such as Georgia, California, Virginia, Minnesota, South Dakota and the Carolinas.

How Granite is Formed

Geologists have two different theories about how granite was formed. One theory says that granite formed directly from molten lava. The other theory states that it was formed as a result of the alterations of other rocks and that granite is metamorphic rock, rather than igneous rock.

Uses of Granite

Granite has been used a building material for thousands of years. In ancient Egypt, the obelisks were built from granite. Today, granite is used in building monuments, curbs for roads, tombstones, and as a structural element in buildings.