What is Igneous Rocks ??

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Igneus Rock

Igneous rock is formed from the cooling of magma. Where the minerals are arranged interlocking.
Igneous rock is an absolute need to know by a geologist same as other types of rock (Sedimentary, Metamorphic).

Classification of Igneous rocks

Every human being awarded the mind and thoughts, which led to frequent disagreements.
In the world of geology, among geologists often find a difference in perception or opinion.
It is reasonable, considering what is learned by a geologist are the things that have been happening for millions of years ago.

There are many opinions regarding the classification of Igneous rocks.
However, that is often used as a benchmark by the authors in describing igneous rocks are as follows:

1. Based on the genesis / spot formation, classified into 2 groups, namely :

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a. Outside Igneous Rocks (Extrusive).

Ekxtrusive Igneous rock are Igneous Rocks that formed near the surface of the earth, or the earth's surface.
Extrusive igneous rock has a characteristic shape even finer crystals are common extrusive igneous rocks that do not have a crystal form (amorphous), such as Obsidian.
Igneous outside formed at relatively low temperatures,and the freezing process is very fast.
examples of this rock is andesite, ryolite, and basalt

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b. In Ingeous Rock (Intrusive)
Intrusive igneous rocks are igneous rocks that formed in the bowels of the earth.
Intrusive igneous rocks have characteristic coarse crystals (faneritik).
Usually a geologist would easily recognize this type of igneous rock, as a rough crystal appearance, making it easy to move on notice of such minerals, even without the help of a magnifying glass or microscope.
Extrusive igneous rock formed at relatively high temperatures,and the formation of crystals is very slow.
examples of this rock is Granite, Diorite, and Gabro

2. Based on the chemical elements, the Igneous rock is classified into 4 groups, namely:

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a. Ultramafic Igneous Rocks
Ultramafic igneous rocks are igneous rocks formed from ultramafic magma.
This type of igneous rock composed by ultramafic minerals such as olivine and plagioclase rich in calcium.
This rock sample is : dunit and peridotite.

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b. Alkaline Igneous Rocks
Alkaline igneous rocks are igneous rocks formed from alkaline magma.
This type of Igneous rock composed by alkaline minerals such as pyroxene, olivine and plagioclase.
The special feature of this Igneous rocks is a relatively dark color.
This rock sample is : gabbro and basalt

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c. Intermediate Igneous Rocks
Intermediate igneous rocks are igneous rocks formed from magma intermediates.
This type of igneous  rock composed by intermediates minerals such as amphiboles, biotite and plagioclase.
The special feature of this Igneous rocks is a medium color (gray).
This rock sample is : Diorite and andesite

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d. Acid Igneous Rocks
Acid igneous rocks are Igneous rocks formed from magma acid.
This type of Igneous rock composed by acidic minerals such as quartz, muscovite ortoklas and sodium-rich plagioclase.
The special feature of this Igneous rocks are relatively light color.
This rock sample is : Granite and ryolit.

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