Granite Stone

What is Granite

Granite is a hard igneous rock having a coarse-grained surface, chiefly composed of four minerals including  quartz, alkali feldspar, plagioclase feldspar, and hornblende .The word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a polycrystalline rock. The term 'granite' also applies to a group of intrusive igneous rocks with similar textures and slight variations on composition and origin. . It is visibly homogeneous in texture. This unique and elegant natural stone is one of the oldest, hardest, and strongest stones available. A truly beautiful natural stone with hundreds of colors and patterns to choose from. The minerals provide the different colors to the granite that it possesses. It ranges in color from pink and red to light or dark gray or a mix of these. It is generally uniform in color and has high compressive strength and abrasion resistance.
The geological definition of granite is "any plutonic rock in which the mineral quartz makes up 10 to 50 per cent of the felsic components, and the ratio of alkali to total feldspar is between 65 and 95 per cent."Granite being an igneous rock, is formed from the process of magma cooling. This magma, which cools far below the earth's surface at a slow and steady rate, results in the expansion of the aforementioned minerals to a level that they can be conveniently seen with naked eyes. An important thing about granite is that it is not a homogeneous rock, thus its chemical properties vary according to its location.
Some granites change relatively little with changes in temperature. Which also makes granite a good choice for high precision applications that require little change due to temperature.
Flexural strength, or the ability to resist bending force. Makes granite a good material for load bearing applications.Granite is also resistant to many acids and other caustic chemicals. So it is often used as a liner in commercial vats and such. This also makes granite good for applications that are below grade in contact with soil and water.

Granite Uses

Granite common finishes include polished, honed, or thermal. Polished granite tiles are suitable for kitchen and bath walls, floors, or countertops. While granite holds its polish longer than marble and is not bothered by mild acids, such as orange juice or vinegar, over time the traffic on a kitchen floor will dull the finish. Use of doormats and frequent sweeping to remove abrasives from the floor will help prolong the finish. Re polishing the granite tends to be expensive due to the hardness of the material. Waxing and special coatings may help protect the polished finish, but frequent stripping and reapplication can, by itself, cause excessive wear. Another option for floors are honed or thermal finished granite tiles, which are more commonly used outdoors. These are less slippery when wet than polished granite. However, a sealer is required with this type of finish to prevent staining during grouting and to protect from oil or grease stains. These finishes are easy to apply and do not need stripping for touch-up reapplication.
Due to highly dense grain, it is impervious to stain. Polished granite slabs and granite tiles have achieved a special status as building stones globally. Granite is also used for wall cladding, roofing, flooring, and a variety of other interior and exterior applications. Granite is the hardest building stone, and granite slabs and granite tiles occupy a prominent place among dimensional stones. Due to its hardness, resistance to weathering, capability to take mirror polish, fascinating colors and textural patterns, granite slabs and granite tiles are extremely popular. The principal characteristics of granite also include high load bearing capacity, crushing strength, abrasive strength, amenability to cutting and shaping without secondary flaws, ability to yield thin and large slabs and - above all - durability. 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.

Physical Properties of Granite

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


6 to 7 on Moh's Scale


2.6 to 2.8 Kg/cm3

Compressive Strength

140 to 210 N/mm2

Modulus of Rupture

15 to 25 N/mm2

Water Absorption


Average Wear

Less then 1%


Quite low

Weather Impact



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)





Less then 0.5%

FeO + Fe2O3





Less then 0.5%

Loss On Ignition (LOI)

Less then 0.5%

Weather effects on Granite


Effects of Wind

Since granite is impervious to water, it does not expand and contract due to soaking up water. Instead, it expands and contracts once cracks open up on its surface, allowing water to seep in. One way in which these cracks are formed is through wind. Wind is formed due to thermal fluctuations in the atmosphere. Cold and hot winds weather granite by bombarding it with small grains of dust and dirt. It can also cause boulders to become unstable and fall, which can also create cracks. Once cracks are formed, the action of wind can further expand the cracks through the weathering process.

Effects of Rain

When rain falls, it collects in the cracks that opened up on the surface of granite. Rain water can be slightly acidic or basic, both of which can cause small reactions on the surface of the granite, which can break it down. When rain falls into cracks and crevices during the winter, it can become trapped and freeze. When rain freezes in the cracks, it expands the crack with it. Over time, this process can lead to cracks in the granite becoming larger and larger, breaking it down even further.

Effects of Heat

Large fluctuations in temperature can effect the weathering of granite. In desert environments, granite is subjected to large fluctuations between the heat of the day and the cold of the night. The heat of the day causes the rock to swell. With every 10-degree Celsius increase in temperature, there is a 2.5 times increase in the rate of a chemical reaction. When heat is coupled with water, like during a summer storm, the two factors can combine to create a stronger weathering process.

Effects of Cold

The cold causes granite to compress, or shrink, just as the heat causes it to expand. However, freezing temperatures also cause water to freeze and expand. During times of the year when rain is followed by a freeze, water trapped in cracks in the granite expand as the rock itself contracts. This causes the crack to expand and become weaker. When the weather warms, the water is heated as it melts, causing further chemical reactions to occur. The cycle of hot and cold, coupled with other meteorological factors such as rain and wind, is a part of the how granite is broken down into smaller pieces, eventually forming the rich soil in which plants thrive.