The Chemical Composition of Granite

Granite is a very common type of rock that has been, and is still used for a variety of purposes. Its strength makes it an excellent building material used in the past and in the present, and it isn’t very porous or affected by temperature. Granite is even incredibly resistant to weathering and chemical erosion (even acid rain). The color of granite can range from pink to gray and it keeps great consistency in its texture and coloring.

With so many useful properties, it’s no wonder that granite continues to be used for monuments, building stones, gravestones, flooring, kitchen counter-tops, and a variety of other applications. Granite is so strong and durable that the word itself has a second meaning that can be used as an adjective to describe something with similar physical properties. It’s definitely more than enough to make you wonder what exactly this incredible rock is made of. Interestingly enough, the chemical composition of granite can vary quite a bit, depending on where it is formed and the magma it was formed from.

How granite is formed

Being an igneous rock, granite is formed from the solidification and cooling of magma. It is also an intrusive rock which means that it does not form on the surface but actually underneath the surface. What elements are present in the magma will directly affect what minerals are formed when it cools. Crystallization will occur when the granite starts cooling, and many different minerals will form at varying rates. Over a very long period of time, the granite will cool and get pushed to the surface.

Chemical composition

The resulting granite will likely have been made primarily from quartz, different feldspars, and biotite, however, it can also have a variety of other minerals and oxides present. Quartz content can range from 10-60%, while the feldspar content typically ranges from 65-95%, and biotite content is around 10-15% in most granite.

The exact chemical composition will vary greatly but there is an average chemical composition for granite. This composition is as follows: 70.18% silicon dioxide (SiO2), 14.47% aluminum oxide (Al2O3), 4.11% potassium oxide (K2O), 3.48% sodium oxide (Na2O), 1.99% calcium oxide (CaO), 1.78% iron (II) oxide (FeO), 1.57% iron (III) oxide, 0.88% magnesium oxide (MgO), 0.84% water (H2O), 0.39% titanium dioxide (TiO2), 0.19% diphosphorus pentoxide (P2O5), and 0.12% manganese oxide (MnO).

The chemical composition as well as the formation of granite inside the Earth’s surface produces an incredible material that is valued for its looks and physical properties. It has even started replacing marble because of its more durable qualities and resistance to weather and acid rain. Though a very common rock, granite is far from ordinary.