Granite is a type of common, felsic, intrusive igneous rock. Granite is medium to coarse in texture, occasionally with a few individual crystals larger than the soil mass that form a rock known as porphyry. Granites can be pink to dark gray or even black in color, depending on their chemistry and mineralogy. Granite outcrops tend to form towers and rounded clumps. The granites sometimes occur in circular depressions surrounded by a series of hills, formed by the metamorphic halo, or hornfels.
Granite is an igneous rock and is formed from magma. Granitic magma has many potential origins, but it must intrude on other rocks. Most granite intrusions are emplaced deep within the crust, typically more than 1.5 km and up to 50 km deep within the thick continental crust. The origin of granite is controversial and has given rise to various classification schemes. Classification schemes are regional; there is a French scheme, a British scheme and an American scheme. This confusion arises because classification schemes define granite by different means. In general, the “alphabet soup” classification is used because it classifies according to the genesis or origin of the magma.
Ancient uses of granites
Granite is almost always massive (lacks internal structures), hard, and strong, and has therefore gained widespread use as a building stone. The Red Pyramid of Egypt, named for the light crimson hue of its exposed granite surfaces, is the third largest pyramid in Egypt. The Menkaure Pyramid was built with limestone and granite blocks. The Great Pyramid of Giza contains a huge granite sarcophagus made of “Aswan Red Granite”. The mostly ruined Black Pyramid, dating to the reign of Amenemhat III, once held a polished granite pyramidion, or capstone, now on display in the main hall of the Egyptian Museum in Cairo.
Many large Hindu temples in South India were made of granite. There is a large amount of granite in these structures. They are comparable to the Great Pyramid of Giza
Granites Use in the Present Age
Granite has been widely used as dimension stone and as floor tiles in monuments and public and commercial buildings. With increasing amounts of acid rain in some parts of the world, granite has begun to supplant marble as a material for monuments, as it is much more durable. Polished granite is also a popular choice for kitchen countertops due to its high durability and aesthetic qualities.
Engineers have traditionally used polished granite surfaces to establish a reference plane, as they are relatively impervious and inflexible. High aggregate content sandblasted concrete has a similar appearance to rough granite and is often used as a substitute when the use of real granite is not practical. Due to the particular rarity of granite, the best stones can cost as much as US$1,500.
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