In the field of geology the word stone is not used, in this way two other terms are used: rock or mineral. Rocks are formed after a geological process and are formed by one or more minerals. Minerals are composed of chemical elements. Igneous Rock
The rock masses that line the planet’s surface are formed by one or more minerals. Rocks are divided into three groups according to their origin: sedimentary, metamorphic and igneous.
Formation, Types and Texture
Igneous rocks constitute 90% of the earth’s crust and are formed by minerals that belong to the silicate group (this group is divided into ferromagnesian and non-ferromagnesian, which indicates that the rock contains iron or not). The word igneous is used in its description because this word means fire in Greek.
Igneous rocks are those that form after the magma cools down. Thus, magma from volcanic activity reaches the earth’s surface and finally solidifies. These rocks are subdivided into two different groups: plutonic and volcanic or extrusive. The former are formed from a slow cooling process of magma from the interior of the Earth’s crust (in this group, granite, diorite and peridotite stand out). Volcanics are formed from a rapid cooling process that occurs at the surface (among them are rhyolite, basalt and dacite).
When magma solidifies, large crystals are created. In this sense, the slower the cooling process, the greater the size of the igneous rock. If cooling is rapid, glass is formed instead of crystal.
Granite is the best known igneous rock
Granite was formed during the last 300 million years and is a direct consequence of the magma cooling process. This circumstance makes the granite present crystals of great size and that are observable with the naked eye. This rock can be found on the Earth’s surface due to erosion over the past 100 million years.
Large blocks are extracted from the mines, which are processed into smaller pieces. The crystals inside are evenly distributed.
Its final finish is carried out through a polishing process that removes the porosity of the original rock. This type of igneous rock has been and is highly valued as a building material, both for the interior and exterior of buildings. It is an elegant and attractive material and especially valued because it does not require special maintenance.