Introduction to granite rocks
Granites are igneous, intrusive, felsic rocks that are widely found. The texture of granite is medium to coarse, rarely with some crystals larger than the mass of the ground forming a rock called porphyry. Granites are in different colors such as pink, dark gray, green, yellow, red, or sometimes even black and gold, depending on their mineralogy and chemistry. Sometimes the granites are found in circular depressions surrounded by a series of hills that are formed by metamorphic hornfels. Granites are often massive and lack internal structures. They are resistant, hard and their use for construction purposes has become widespread. 2.75 g / cm3 is the average density of granite. If you look at the word ‘granite’, it comes from the Latin word ‘granum’ which is a grain, referring to its coarse-grained constitution.
According to a scientific diagram, granites are classified for coarse-grained plutonic rocks – granitoids and are named based on the percentage of quartz, alkaline feldspar – sanidine, orthoclase, or microcline. Rocks like granite that are saturated silica can have a feldspathoid like nepheline. According to modern petrology, true granite contains alkali feldspars and plagioclase. When a granitoid lacks or almost lacks plagioclase, the rock is said to be alkaline granite. If the granitoid contains less than 10% orthoclase, then it is called tonalite. Amphibole and pyroxene are common in tonalite. Granites that have biotite and muscovite micas are called binary or two-micas granite. Typically, two-mica granites are low in plagioclase and higher in potassium; Type A or type S granites. Rhyolite is a volcanic equivalent of plutonic granite.
Currently, Earth is the only place where granites are known to form a major part of the continental crust. Granites often occur as relatively small population masses, less than 100 km² and also in batholiths that are associated with orogenic mountain ranges. Smaller dikes of granite compositions are known as aplites and are often associated with granite intrusion margins. In some places, together with the granites, masses of very coarse-grained pegmatite are produced. Granites have been introduced into the earth’s crust during all geological periods as earthquakes, although most have occurred in the Precambrian era. Granite rocks are widely distributed throughout the Earth’s continental crust, and it is the most abundant basement rocks that underlie the relatively thin sedimentary layer of the continents.
Despite being quite common throughout the world, the places with the most commercial granite quarries are in Norway, Sweden: Bohuslän, Finland, North of Portugal in Chaves, Spain mainly in Galicia and Extremadura, India, Brazil and several others Southern African countries. , like Angola, Namibia, South Africa and Zimbabwe. Today, granites are widely used in the manufacture of luxury flooring, kitchen tables, office tables, bathrooms, and bathtubs.