Andesite is an intermediate rock that falls between mafic and felsic classification.
It forms outside of volcanoes from intermediate magmas.
The color and chemical composition of Andesite is intermediate between felsic and mafic rocks.
This article will help readers to understand more about Andesite’s composition, which falls between that of the mafic and Felsic.
Is Andesite Felsic or Mafic? (EXPLAINED)
Andesite Facts
Andesite is an exclusive igneous rock that has a light to dark grey color.
Andesite has a mineral composition which is intermediate between granite and basalt.
The rock is majorly formed after the eruption of volcanic magma and crystallization.
Andesite was named from the Andes Mountains.
Andesite is considered an average igneous rock.
Chemical Composition of Andesite
The chemical composition of Andesite is considered intermediate.
Andesite contains about 60 percent of silica.
The rock does not contain higher amounts of silica like rhyolite.
Andesite is composed of dark minerals like pyroxene and olivine.
The rock also contains light-colored minerals such as plagioclase feldspar and silica, which is about 60 percent.
Andesite constitutes about 63 percent of SIO2 content, and 5 percent of sodium oxide and potassium oxide content.
Physical characteristics of Andesite
The color of Andesite is light or dark grey.
The color of the rock is considered to be immediate. It is not as dark as basalt.
Andesite is a fine-grained rock with relatively large crystals.
The rock has a fine-grained texture as it cools quickly when coming out of a volcano vent and there is no time for crystal grains to form larger grains.
Andesite has a salt and pepper appearance due to a mixture of compositions of felsic and mafic minerals and rocks.
Andesite is mostly confused with basalt as they have similar colors.
Uses of Andesite
Andesite is utilized as a construction material.
It is used to fill materials during construction.
The rock is used in the making of tiles due to their resistance to slipping.
Andesite is also utilized in monuments and landscape design and construction.
Introduction To Mafic Rocks
Mafic rocks contain about 50 percent of silica and higher quantities of lighter elements such as iron, calcium and magnesium.
Most mafic rocks are dark in color, and basalt is a good example of mafic rock.
The main contents of Mafic rocks includes plagioclase and pyroxene even though they cannot be seen with the naked eye.
Mafic contains smaller quantities of olivine.
Mafic rocks tend to be black in color due to the presence of magnesium and iron.
For a rock to be classified as a mafic rock, it should contain higher elements like calcium, iron, magnesium, or calcium.
On the other hand, felsic rocks have a higher content of silica, potassium, sodium, as well as aluminum.
Felsic rocks have lower quantities of iron, calcium, and magnesium.
Dacite and rhyolite are common examples of felsic rocks.
Felsic magmas are more viscous as they contain higher amounts of silica.
For a rock or mineral to be felsic, it has to contain lighter components like silicon, aluminum, sodium, and potassium.
Why Andesite is Mafic (or Felsic)
It is important to understand that Andesite is an intermediate rock.
Hence, it is classified between mafic and felsic.
Just like mafic rocks and minerals, Andesite contains plagioclase which has sodium content.
The composition of Andesite is intermediate between rhyolite and basalt.
Andesite is a mixture of mafic minerals and felsic minerals; hence, it can only be classified as an intermediate rock.
Andesite, just like felsic minerals, has a higher silicon content that ranges between 57 and 63 percent.
The content of silicon in Andesite is higher than that found in basalt.
Andesite is an intermediate rock with a medium composition of silica content like felsic and mafic rocks.
Andesite is also classified as intermediate rocks due to its grey color, and is composed of the same quantities of minerals that are light and dark in color.
Wrap Up
Andesite is an intermediate rock that falls between mafic and felsic classification.
The rock is composed of the components of both mafic and felsic rocks.
Just like felsic minerals, Andesite has a higher silicon content which ranges between 57 and 63 percent.
The main contents of Mafic rocks are plagioclase and pyroxene, even though they cannot be seen with the naked eye.
Just like mafic rocks, Andesite contains plagioclase which has sodium content.
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