Amazing World of Granite

Amazing World of Granite

Granite is an igneous rock with grains large enough to be seen with the naked eye. It is light-colored and forms from the slow crystallization of mama below the Earth’s surface. It is made up mainly of quartz and feldspar. There are also minor amounts of mica, amphiboles, and other minerals. Due to its mineral composition, granite may appear as red, pink, gray, or white with dark mineral grains visible throughout the rock. It is the most popular and best known rock as it is the most common igneous rock found at the Earth’s surface. It is found in many objects people use in their daily lives. Granite is everywhere, especially in a city. Everyone knows that granite is one of the most sought-after materials for bathroom remodels and kitchen countertops. But here are a few fun facts that you might not have known about the granite that’s in your kitchen or bath:

What is Granite and How is it Formed?

Granite is an igneous rock made up of primarily quartz, feldspar, micas, amphiboles, and a mixture of additional trace minerals. These minerals and their variation in abundance and alteration give granite the numerous colors and textures we see in granite countertops. Formally, granite is a plutonic rock that is composed of between 10 to 50% quartz (typically semi-transparent white) and 65 to 90% total feldspar (typically a pinkish or white hue).

Granite is an intrusive igneous rock, which means it was formed in place during the cooling of molten rock. Generally, the slower the molten rock cooled, the larger it’s mineral crystals with K-Feldspar megacrysts forming in special circumstances greater than 5cm. During formation of granite it is buried below kilometers of rock and sediment necessary to produce enough heat to melt rock.

Of course, the granite we see today is near surface, and thus at some point was uplifted, causing overlying sediment to be shed via erosion. This transition from high pressure and temperature to atmospheric temperature and pressure can cause the granite to slightly expand and crack. This, in addition to seasonal variations in temperature can leave you with a weakened and less desirable granite to use for countertops.

Mineralogy

Granite is classified according to the QAPF diagram for coarse grained plutonic rocks and is named according to the percentage of quartz, alkali feldspar (orthoclase, sanidine, or microcline) and plagioclase feldspar on the A-Q-P half of the diagram. True granite (according to modern petrologic convention) contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite. When a granitoid contains less than 10% orthoclase, it is called tonalite; pyroxene and amphibole are common in tonalite.

Formation

A granite containing both muscovite and biotite micas is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites.

Granite has a felsic composition and is more common in recent geologic time in contrast to Earth’s ultramafic ancient igneous history. Felsic rocks are less dense than mafic and ultramafic rocks, and thus they tend to escape subduction, whereas basaltic or gabbroic rocks tend to sink into the mantle beneath the granitic rocks of the continental cratons. Therefore, granitic rocks form the basement of all land continents.

Geochemical origins

Granitoids have crystallized from magmas that have compositions at or near a eutectic point (or a temperature minimum on a cotectic curve). Magmas will evolve to the eutectic because of igneous differentiation, or because they represent low degrees of partial melting. Fractional crystallisation serves to reduce a melt in iron, magnesium, titanium, calcium and sodium, and enrich the melt in potassium and silicon – alkali feldspar (rich in potassium) and quartz (SiO2), are two of the defining constituents of granite.

Granitization

This was supposed to occur across a migrating front. The production of granite by metamorphic heat is difficult, but is observed to occur in certain amphibolite and granulite terrains. In-situ granitisation or melting by metamorphism is difficult to recognise except where leucosome and melanosome textures are present in migmatites.

Interesting Granite Geology Fact-o-logy:

  • The word “granite” comes from the Latin word “Granum,” which means “a coarse grain.” Granite got its name because of the grain-like patterns formed by its densely packed crystals.
  • Granite is the oldest igneous rock in the world, believed to have been formed as long as 300 million years ago.
  • Granite is also what’s called a “plutonic” rock, meaning that it forms deep underground.
  • Granite is the main component that makes up the earth’s continental crust.
  • The white mineral grains that you see in granite are feldspar, which is the most abundant rock on the planet, comprising around 60% of the earth’s surface.
  • Granite has a density of around 162 pounds per cubic foot.
  • The commercial definition used by sellers and buyers usually call rocks with visible grains that are harder than marble as granite. They may call gabbro, basalt, pegmatite, gneiss, and many other rocks granite.
  • Granite’s fame comes from many world-famous natural exposures including Stone Mountain, Georgia; Yosemite Valley, California; Pike’s Peak, Colorado; and White Mountains, New Hampshire.
  • Granite is often defined as a “dimension stone” that can be cut into specific lengths, widths, and thicknesses.
  • Granite is tough enough to resist most abrasion, bear large weights, resist weathering, and can accept polish. It is a very desirable and useful stone.
  • Granite has been used for thousands of years, in outside and inside environments as building material, bridges, paving, monuments, granite slabs, tiles, countertops, and many other places. In addition, it may be used as crushed stone in road construction.
  • Granite’s cost is much higher than in price than other man-made materials for projects, but it is considered a prestige material, used to impress others because of its elegance, durability, and quality.

More Granite Glory: 

  • Granite is one of the hardest substances in the world, second only to diamonds. In fact, granite is so tough and durable that the pedestal that the Statue of Liberty stands on is made from granite.

  • Granite has been used in construction since the Ancient Egyptians.

  • Granite was also the reason for the first commercial railroad in the United States—the “Granite Railway” of Quincy, MA.

  • Blue Hone granite, taken from the island of Ailsa Craig, near Scotland, is used in the manufacture of curling stones—those odd stone discs with handles used in the sport of curling.

The city of Aberdeen in Scotland is nicknamed the Granite City as most of the buildings here have been built from granite, which was extracted from the local quarries.

  • The highest granite mountain in the world is Kangchenjunga in the Himalayas. At 8,586 meters, Kangchenjunga is the third-highest mountain in the world, behind Everest (which is limestone) and K2 (which is gneiss).

  • Quarrying granite is difficult even in modern times. However, ancient Roman builders thought the trouble was worth getting to use the beautiful stone in many of their buildings. In fact, many Roman buildings, including the Pantheon in Rome, feature columns made out of granite. The Romans also used granite for public baths and even their streets because it is such a durable material.

  • The Hyderabadi cuisine has many popular dishes whose preparation methods are markedly different from those in other regions. Apart from Haleem which comes to mind first, another dish in this category is Patthar Ka Gosht, where a heated stone is used to cook pieces of boneless marinated meat. A favorite from the days of Nizam Asaf Jahi VI, this dish is still much sought-after by food lovers on any visit to the city. It is said that late in the 19th century, the Nizam Asaf Jahi VI used to frequently go hunting in the forests. On one such trip, his Bawarchis (Cooks) forgot to carry their skewers and shikanjas were required to prepare kebabs and innovated by cooking mutton on a flat granite stone heated by firewood from below. The Nizam developed a liking for the dish, and so this recipe was replicated repeatedly at the royal kitchens. More than a century later, the dish is still popular in many areas in the city.

Famous Monuments Made of Granite:

Here are some world famous statues and monuments that you might not realise are made of granite.

Avukana Buddha Statue (Sri Lanka)

Found just outside Kekirawa in Sri Lanka this amazing statue of Buddha is an impressive 40ft tall and carved in the likeness of the Buddha.

Brihadeeswarar Temple of Shiva (India)

Dedicated to one of the primary forms of God in Hinduism, Shiva, the Brihadeeswarar Temple (Thanjavur), in India is made from a single enormous piece of granite. Built in 1004AD, it was finished just five years later in 1009AD. Starting with a single block, esteemed engineer and architect Kunjara Mallan Raja Raja Pernunthachan used the same architectural principles found in ancient texts to design the temple. For example, using measures such as the Angula, a 1 3/8 inch found in the Vaastu Shastras book. The truly breathtaking temple sits on the banks of a river that is channelled around it to form a moat around the structure. Raised on a solid base at 5 metres above ground level, the many levels to the exterior have numerous decorations. Along with representations of Shiva, classic Hindu dances and a big Nanda (bull) weighing 20 tonnes are present. The Nandi is also made from a single piece of stone and is in itself a remarkable stone structure.

The Colossal Red Granite head of Amenhotep III (England)

Located in the British Museum in London, the ancient head of the King of Thebes is a gigantic red granite statue on display for visitors all year round. It was originally found in the temple of Mut at Karnak in Egypt. The statue only survives in two parts, the head and the arm. Both are on display in the British Museum. The statue is thought to have been one of many statues that King Amenhotep II had commissioned of himself but it is unknown if it was on display in the temple it was found in. This is because reigning Kings would often destroy the statues of their predecessors or remake them in their own image. This great, imposing head of the statue is made from red granite.

Mount Rushmore in South Dakota (USA)

The literal face(s) of granite construction is one of the world’s most famous landmarks, Mount Rushmore. Carved into the south side of a mountain, the monument depicts the faces of four US Presidents: George Washington, Thomas Jefferson, Abraham Lincoln and Theodore Roosevelt.Construction of the mammoth spectacle started in 1927 led by sculptor Gutzon Borglum. His original plan was to have the Presidents depicted from the waist up. Sadly, only the faces were completed due to insufficient funds. There are few granite structures in the world that have involved as much work as Mount Rushmore. It took 14 years to complete and involved the removal of 450,000 tons of rock to create the 18 metre high heads. In 1991, Mount Rushmore underwent a $40million restoration to mark its 50th anniversary. A truly mind blowing granite structure, the Presidents now look as impressive as they ever did.

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