Granite is a common type of felsic intrusive igneous rock which is granular and phaneritic in texture. The word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a holocrystalline rock

The term 'granite' also applies to a group of intrusive igneous rocks with similar textures and slight variations on composition and origin. These rocks mainly consist of eldspar,quartz,mica, and amphibolemi. These form interlocking somewhat equigranular matrix of felddspar and quartz with scattered darkerbiotite mica and amphibole (often hornblende) peppering the lighter color minerals. 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 known as a granite porphyry. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy. By definition, granite is an igneous rock with at least 20% quartz and up to 65% alkali feldspar by volume. Granite differs from granodiorite in that at least 35% of the feldspar in granite is alkali feldspar as opposed to plagioclase; it is the potassium feldspar that gives many granites a distinctive pink color.

Granite is nearly always massive (lacking any internal structures), hard and tough, and therefore it has gained widespread use throughout humanity, and more recently as a construction stone. The average density of granite is between 2.65 and 2.75 g/cm3, its compressive strength usually lies above 200 MPa, and its viscosity near STP is 3–6 • 10 19 Pa·s. Melting temperature is 1215–1260 °C.

Granite has poor primary permeabilitybut strong secondary permeability.


Physical Properties of Granite

Physically, commercial granites are Hard, Compact rocks with fine to coarse grains of metamorphic or igneous origin.

Color Minor color tonal variations exist but within the tolerance limit.
Hardness 6.5 to 7 on Moh's Scale
Density 2.6 to 2.8 Kg/cm3
Compressive Strength 140 to 210 N/mm2
Modulus of Rupture 15 to 25 N/mm2
Water Absorption 0.1-0.6%
Average Wear Less then 1%
Porosity Quite low
Weather Impact Resistant
Chemical Properties of Granite

Chemically, they are igneous/metamorphic rocks composed of quartz, feldspar & ferromagnesian minerals like kriolite, chlorite, garnet, etc. A typical granite will have following chemical composition:

Silica (SiO2) 70-75%
Al2O3 10-15%
CaO+MgO Less then 0.5%
FeO + Fe2O3 2-4%
Alkalies 4-6%
TiO2 Less then 0.5%
Loss On Ignition (LOI) Less then 0.5%
Uses of Granite

Roadstone, building blocks, but has poor resistance to fire as it crumbles when exposed to intense heat.

Traditionally the main use of black granite is in tombstones and other monumental items, and to a lesser extent for various types of counters, especially in the financial world, decorative applications, elegant trimmings and luxury floorings.

Stones on bolo cord slides and pendants, paperweights, bookends, lazy susan turntables, etc.