Granite

Granite is the most common intrusive rock in Earth’s continental crust, It is familiar as a mottled pink, white, gray, and black ornamental stone. It is coarse- to medium-grained. Its three main minerals are feldspar, quartz, and mica, which occur as silvery muscovite or dark biotite or both. Of these minerals, feldspar predominates, and quartz usually accounts for more than 10 percent. The alkali feldspars are often pink, resulting in the pink granite often used as a decorative stone. Granite crystallizes from silica-rich magmas that are miles deep in Earth’s crust. Many mineral deposits form near crystallizing granite bodies from the hydrothermal solutions that such bodies release.

Name origin: The name appeared for the first time in works of the English botanist, physician and philosopher Caesalpinus in the 16th century.

Group – plutonic.

Colour: Pink-grey.

Structure: Massive, confining.

Texture: phaneritic (medium to coarse grained). , holocrystalline, pan-hypidiomorphically grained, porphyric in places.

Alterations: The rock is unaltered, feldspars are rarely sericitized

Major minerals of Granite: Orthoclase, quartz, biotite, muscovite and plagioclase, which is twinned according to the albite law and oscillatory zoned. Chemical composition of the core corresponds to oligoclase and andesine (An30-38), whereas more acidic oligoclase and andesine occur in the margin.

Accessory minerals of Granite: Zircon and apatite, mainly as inclusions in biotite, titanite, orthite, magnetite, pyrite.

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