Rock types: igneous, sedimentary and metamorphic (with examples)

There are three types of rocks: igneous, sedimentary, and metamorphic. Rocks are a conglomerate of various types of minerals or other materials.

Rock types are determined by the processes involved in their formation. On the other hand, a rock can give rise to another type of rock, in what is known as the rock cycle.

rocks igneous	rocks sedimentary	rocks metamorphic
Definition	Rock resulting from the solidification of molten rock	Rock resulting from the compaction of sediments	Rock resulting from the transformation of other rocks
Processes involved in training	Fusion and solidification	Compaction and cementation	pressure and temperature
Guys	intrusive extrusive	clastic organic By chemical precipitation	foliate not foliated
examples	Slag, pumice, obsidian, basalt, porphyry, granite, andesite, gabbro, granite.	Sandstone, halite, coal, limestone, mudstone, travertine, gypsum.	Green schist, serpentinite, marble, gneiss, quartzite, epidosite.

Igneous rocks

Igneous rocks are rocks that form when molten material in the Earth's crust cools. He

magma is the molten material below the earth's surface and the wash It is the molten material that rises to the surface.

There are two types of igneous rocks:

• extrusive igneous rock: Also called volcanic rock, it is the rock that forms when lava hardens. Examples of extrusive stones are obsidian and rhyolite.
• intrusive igneous rock: Also called plutonic rock, when magma changes from fluid to solid under the earth. Examples of intrusive stones are basalt and granite.

The chemical composition varies between igneous rocks. Some igneous rocks are rich in light, light-colored minerals such as feldspar and silica. These rocks are called felsic (for happy: feldspar, and sic: silica). Other igneous rocks are rich in iron and magnesium compounds, which is why they are called mafic (ma for magnesium and F by ferrum, Latin for iron).

Granite, a felsic coarse-grained intrusive rock, has the same chemical and mineral composition as rhyolite, a fine-grained extrusive rock. Basalt is a mafic fine-grained extrusive rock, it has the same chemical composition as gabbro which is a coarse-grained mafic intrusive rock that cools at depth.

Examples of igneous rocks

Sedimentary rocks

Sedimentary rocks are rocks that form from fragments that have been cemented together. In general, sediments accumulate forming horizontal layers, which are compacted by the pressure of materials above the layers. Materials such as silica, calcium carbonate or iron oxides are used to cement or glue the fragments.

There are three main types of sedimentary rocks:

• clastic sedimentary rocks: clasts are fragments of pre-existing rocks, such as clay, sand, pebbles, boulders and cobblestones. Examples of these rocks are conglomerate, sandstone, siltstone, and shale.
• organic sedimentary rocks: They are produced by the remains of plants and animals that accumulate and compact. An example of this type of rock is coal.
• Sedimentary rocks by chemical precipitate: they are formed when the saturation of a material in a liquid medium occurs, forming a precipitate. Examples are dolomite, chalk, halite (common salt) and borates.

Examples of sedimentary rocks

Metamorphic rocks

Metamorphic rocks are rocks that derive from the transformation of other rocks without going through smelting. For example, granite metamorphoses into gneiss, limestone forms marble, and silica-rich sandstones fuse into quartzite.

Metamorphic rocks are characterized by being harder, more compact and resistant, and having a reoriented crystalline structure.

The metamorphism process commonly occurs in areas of high temperatures and pressure, such as in tectonic zones and at great depths.

There are two types of metamorphic rocks:

• foliate: presence of plates or waves of light and dark minerals, as in gneiss.
• not foliated: absence of plates, such as quartzite and marble.

Examples of metamorphic rocks

You may also be interested in seeing:

• Types of soils
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References

Petersen, J.F., Sack, D., Gabler, R.E. (2017) Physical Geography 11 ed. Cengage Learning. USES

Tarbuck, E.J., Lutgens, F.K. (2005) Earth Sciences- An Introduction to Physical Geology 8 ed. Pearson Prentice Hall.