Diferencia entre afanítico y fanerítico (con tabla)

There are various types of rocks found in this world, and many of them are similar to each other but have slight differences as well. The igneous textures have the rock textures which occur in igneous rocks. There are six main types of rocks textures in Igneous textures. Aphanite and Phanerite are two of the types of these six forms of igneous rocks.

Aphanitic vs Phaneritic

The main difference between Aphanitic and Phaneritic is that the aphanitic rocks are very finely grained and their crystals cannot be seen with the naked eye. While on the other hand, the Phaneritic rocks are large in size and can be easily seen from the naked eye.

The aphanitic rocks are formed when the lava or magma is cooled down. the magma is called down very rapidly which causes the formation of these rocks. These crystal rocks crystallize on earth or near earth surfaces. These are so finely grained that they cannot be seen by the naked eye and so needs a magnification instrument to be seen.

The phaneritic rocks are formed when the magma is cooled down gradually. The magma is cooled down gradually under the earth and that forms large crystals phaneritic rocks. These rocks are visible to the naked eye, as they are large in size. The phaneritic rocks are intrusive igneous rocks.

Comparison Table Between Aphanitic And Phaneritic

Parámetros de comparaciónAphaniticPhaneritic
Coarse of GrainsThe aphanitic rocks are very finely grained.The phaneritic rocks are rock size grains, they are not finely grained.
Size of crystalsThe size of these crystal grains is ½ mm.The size of these crystal grains is ½ mm to centimeters.
EjemplosBasalt, Andesite, and Rhyolite.Gabbro, Diorite and Granite.
EnfriamientoThese rocks are formed when the magma is cooled down very rapidly.These rocks are formed when the magma is cooled down gradually.
NaturalezaThe cooling of magma is on or near the surface. That is, they are extrusive igneous rock.The cooling of magma is under the earth’s surface. That means they are intrusive igneous rocks.

What is Aphanitic?

Aphanitic is an adjective used for Aphanite, which is a form of igneous rock. It is one of the six forms of igneous rock. These certain forms of igneous rocks are very finely grained. They are so finely grained that their components are not visible to the human eye. The crystals are too small so they can’t be seen without magnification. A magnifying glass or magnifying instrument is used to see them. Their crystals are generally less than 1/2 mm in size. 

The geological texture specific to aphanitic rocks is due to the rapid cooling of these rocks in volcanic environments. They are formed when lava from volcanic eruptions crystallizes rapidly on or near Earth’s surface. These extrusive rocks make contact with the atmosphere and cool very quickly, and therefore the minerals do not get the time to form large crystals. The magma solidifies as there is a very rapid loss of heat and dissolved gases which eventually forms the Aphanite.

A few examples of aphanitic igneous rock are basalt, andesite, and rhyolite. An aphanitic igneous texture is seen in crystalline rocks with mineral grains that cannot be distinguished from one another without magnification. It indicates the rate of cooling of magma.

What is Phaneritic?

Phaneritic, is another form of Igneous rock. These rocks are different from Aphanitic rocks. These rocks are not finely grained. These rocks are big enough to be seen by the naked eye. They have rock grain size that is, the size of the matrix grains in these rocks are quite large. These rocks can be seen by the eye. No magnifying instrument is needed to see and note a phaneritic rock.

The word Phaner means visible. These rocks crystallize slowly, as the magma cools down gradually. And so the rocks get the time to form large crystal rocks.

The geological texture of phaneritic rocks forms because of the gradual cooling of magma. It does not result from rapid cooling. The magma cools down slowly under the ground in the plutonic environment. The crystals are large and are formed underground. The texture of these rocks is quite similar to that of metamorphic rocks.

The rock is made of large crystals, generally 1/2 mm to several centimeters in size. The first crystals formed have regular shapes while the later formed crystals have irregular shapes. This is because the first rocks have the space to fill by liquid while the later ones don’t find much space.

Main Differences Between Aphanitic And Phaneritic

  1. The aphanitic rocks are very finely grained while the Phaneritic rocks are not so finely grained.
  2. The aphanitic crystals are not visible to the naked eye while the phaneritic are visible to the naked eye.
  3. The aphanitic rocks are so smaller in size up to 1/2 mm while the size of phaneritic rocks is 1/2 mm to several centimeters in size.
  4. The aphanitic rocks are formed due to the rapid cooling of magma near the earth’s surface while the phaneritic rocks are formed by gradual cooling of magma under the surface.
  5. The aphanitic rocks are extrusive igneous rocks while the phaneritic rocks are intrusive igneous rocks.

Conclusión

The two rocks look the same however, there are differences between them at the atomic level or molecular level. The aphanitic rocks are not visible to the naked eye as they are so finely grained. They form when the magma of a volcanic eruption is cooled very rapidly on the surface of the earth or near the surface of the earth.

The phaneritic rocks are also a form of igneous rocks that are visible to the naked eye. They are not finely grained and so they are visible and don’t need a magnifying instrument. These rocks are larger in size than aphanitic as they are formed by the gradual cooling of magma under the surface of the earth. These are intrusive igneous rocks, they are formed underground.

Referencias

  1. https://academic.oup.com/petrology/article-abstract/3/2/238/1429008
  2. https://www.tandfonline.com/doi/abs/10.5408/0022-1368-35.3.150
  3. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.382.6868&rep=rep1&type=pdf#page=5

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