Granite is a course-grained intrusive igneous rock formed by the crystal arrangements of quartz, feldspar, mica, and traces of other minerals. Granite is a plutonic rock which usually forms deep inside the Earth’s crust from the crystallization of molten magma. Based on their chemical properties and mineral content, granite can acquire a pink to gray color. Granite is most commonly found in the continental plates along mountain ranges in circular depressions. The physical characteristics of granite, including its hardness and coarseness make it very usable in the construction industry.
How are igneous rocks formed?
Molten magma can crystallize into several types of igneous rocks. Magma does not solidify into a single type of rock, but into distinct types. When magma solidifies, it forms distinct minerals, which crystallize when the right temperature is reached. When the temperature drops, crystals rearranged one after another. When crystals are forming inside a magma chamber, they may be denser than the surrounding liquid. This causes them to sink to the bottom of the chamber and form different crystal formations. As the cooling and crystallization progresses, distinct types of crystal formations with different chemical compositions are created.
Igneous rocks are usually formed from the cooling or hardening of magma within the Earth’s crust. Granite is an intrusive igneous rock usually formed at subduction zones near continental plate limits, therefore, granite is known as a plutonic rock. Granite is formed at temperatures needed to melt rock of at least 700 °C. Tens of kilometers inside the Earth, the pressure and friction produced in a subduction zone melt large quantities of rock. Granite may be formed either by the melting of rocks or in lesser amounts by fractional crystallization of basaltic magma. Melted rock ascends gradually to the surface; however, to become surface rock, this rock must go through the process of erosion.
How is granite used?
Because of their characteristic pink or gray color, granite is used as a building material in the construction industry. Many granitic stones are used for building purposes, since they are usually strong and durable. In some places, granite is utilized to build gravestones and memorials; however, some granite stones have been reported as being radioactive, raising concerns about health issues. There is some concern about the safety in the use of granite countertops and related building materials. According to solidsurfacealliance.org, almost all granite stones contain concentrations of radioactive minerals, and granite may emit radiation as these minerals decay.
Where is granite found?
Granite and other igneous rocks are abundant in the Earth’s crust. More than 95% of the Earth’s crust consists of igneous rocks formed from lava ejections. Granite often forms rounded hills scattered over a hillside, and is major component of the mountain ranges of the world. Granite is usually found at convergent plate boundaries where part of the ocean lithosphere submerges underneath a continental plate boundary. The process generates enough pressure and melting points to create granite. Fractionation created all the world’s volcanic arcs and continents. The implication being that most of the earth’s crust is made of igneous rock.
Granite was widely used in ancient times. The Red Pyramid in Egypt is named after the reddish hue of its stones, which is made of granite stones. The Great Pyramid of Giza contains within an enormous granite sarcophagus. In India, many structures and life-size animal statues were carved using granite stones. According to jmu.edu, the Earth began with a composition similar to the one seen in the Moon, and from that beginning, all other rocks have evolved through a series of fractionation. From this theory, it is thought that the parent rock present at the time of the Earth’s formation gave rise not only to igneous rocks, but sedimentary and metamorphic rocks, as well.