How are minerals classified?
Minerals are classified according to their chemical composition and crystalline structure, depending on the predominant anion or anionic group. The most common classification includes several groups:
1. Silicates: Contain silicon and oxygen, and are the most abundant in the earth’s crust. Some examples include quartz and feldspar.
2. Carbonates: Formed from calcium carbonate and other metals, such as calcite and dolomite.
3. Oxides: Composed of oxygen and other elements, such as aluminium oxide (bauxite) and iron oxide (hematite).
4. Sulphides: Contain sulphur and metals, such as pyrite and galena.
5. Phosphates: Formed by metal phosphates, such as apatite.
6. Halides: Minerals containing halogens, such as rock salt (halite).
Factors involved in their formation:
– Geological conditions: Temperature, pressure and geological environment are critical. For example, minerals can form from magma or hydrothermal solutions.
– Time: The duration of geological processes can affect the type and amount of minerals that form.
– Chemical composition: The availability of certain elements in the environment determines which minerals can form.
– Biological activity: Some minerals, such as phosphates, can form through biological processes, although most are inorganic.
These factors can interact in a number of ways, producing the variety of minerals found in nature.
What role do geological cycles (such as the water cycle and the rock cycle) play?
The rock cycle is the fundamental process by which igneous, sedimentary and metamorphic rocks are transformed from one form to another in a constant cycle driven by the Earth’s geological processes.
1. Internal processes
Igneous or magmatic rocks
The development of the rock cycle begins when volcanoes expel magma out of the Earth.
This contains a series of molten minerals which, when cooled, generate crystalline structures and together form igneous rocks.
On the other hand, igneous rocks can also form below the surface of the ground in cases where magma fails to escape. In this case, the magma cools slowly, the rock forms and, together with the movements of the earth’s layers, rises to the surface.
Therefore, igneous rocks can form in two ways, either on the surface or inside the earth’s crust.
Then, depending on where the igneous rocks are located and after the effects of erosion, water and wind, these rocks are eroded and fragmented into fine rocky sediments. These rocks include volcanic and plutonic rocks
Metamorphic rocks
Metamorphic rocks are derived from the transformation of other rocks. When these rocks are left between the various layers of the earth, a change in their structures occurs due to high pressure and high temperatures.
2. External or exogenous processes
Sedimentary rocks
Sedimentary rocks are formed by the agglomeration of rocky sediments. They lie on the ground surface and are affected by erosion and movement. Once deposited, different types of rocks are formed. Sedimentary rocks include dendritic rocks, chemical rocks and organic rocks.
