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Igneous or magmatic rocks are generated within the earth, in the earth's mantle or crust. In general, they can be classified under two criteria: textural and mineralogical.
Through their texture one can determine the geological conditions under which these rocks formed. By knowing the texture, one can determine the size and arrangement of the minerals that make up the rock.
When magma stabilization occurs within the earth's crust so that cooling is slow, allowing the crystals to develop consecutively, the rocks originating from this process are called plutonic rocks.
The texture of this rock type is commonly equigranular phaneritic, meaning that the minerals that compose it have a good formation and a considerable size.
When magma extravasation occurs on the surface, transposed from liquid to gaseous in a short period of time, the originated rocks will be called volcanic or extrusive rocks, whose texture will be glassy, as a consequence of the short time that makes the crystallization of minerals impossible. .
If the onset of crystallization occurs within the magmatic chambers, the crystals will be driven by the magma to the surface, and with the high temperature variation between the chambers and the surface, the lava will solidify very quickly and form a texture called texture. porphyritic. A type of vesicular texture may also occur.
The vesicular texture arises when bubbles are released from the lava, which are then retained by the solidification of the lava itself.
Pegmatites are rocks that have been generated from a magma that has a large amount of gases and volatile elements. Magma under these conditions is in a very fluid form and will enable the formation of crystals whose size is quite large.
Rocks can be considered acidic, basic or neutral. This is directly related to the silicon content of the rock in its composition. We call these rocks acidic when the silicon content is higher than 65%, with the development of silicates and quartz crystals.
Neutral rocks are those whose silicon content ranges from 52 to 65%. And finally we have the basic rocks where the silicon content goes from 45 to 52%, with no formation of quartz.