NATURAL GRANITE

   Granite (pronounced /rænt/) is a common and widely occurring type of intrusive, felsic, igneous rock. Granites usually have a medium to coarse grained texture. Occasionally some individual crystals (phenocrysts) are larger than the groundmass in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is sometimes known as a porphyry. Granites can be pink to grey in color, depending on their chemistry and mineralogy. By definition, granite has a color index (i.e. the percentage of the rock made up of dark minerals) of less than 25%. Outcrops of granite tend to form tors, and rounded massifs. Granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels.

Granite is nearly always massive (lacking internal structures), hard and tough, and therefore it has gained widespread use as a construction stone. The average density of granite is located between 2.65[1] and 2.75 g/cm3, it's compressive strength usually lies above 200 GPa and its viscosity at standard temperature and pressure is ~4.5 • 1019 Pas.[2]

The word comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a crystalline rock.

Granitoid is used as a descriptive field term for general, light colored, coarse-grained igneous rocks for which a more specific name requires petrographic examination.[3]