Types of Rocks: Igneous, Sedimentary, and Metamorphic

Study Notes

Rocks are naturally occurring aggregates of geological material, called minerals.
There are three major types of rocks: igneous, sedimentary, and metamorphic rocks.

Formed from the cooling and solidification of molten rock (magma).
Magma cools and solidifies beneath the Earth's crust or on the surface as lava.
Igneous rocks can be classified into two types:
- Intrusive igneous rocks: solidify within the Earth's crust, characterized by large, visible crystal formations.
- Extrusive igneous rocks: formed by the cooling and solidification of lava on the Earth's surface, characterized by small, invisible crystal structures.
Examples of igneous rocks include:
- Granite (intrusive): a common rock with large crystal structures, used in construction and decorative materials.
- Diorite (intrusive): a coarse-grained rock used in construction and road building.
- Basalt (extrusive): a common rock rich in iron and magnesium, used in construction and statue making.

Formed from the lithification of sediments, which are particles formed by the weathering of rocks or dead organic matter.
Sediments can be transported, deposited, and accumulated, eventually becoming lithified (turned into rock).
Sedimentary rocks can be classified into three types:
- Clastic sedimentary rocks: formed from the lithification of clasts, which are produced by the weathering of other rocks.
- Organic sedimentary rocks: formed from the lithification of sediments from organic materials, such as bones, shells, and teeth.
- Chemical sedimentary rocks: formed when water evaporates and produces sediments of dissolved matter.
Examples of sedimentary rocks include:
- Siltstone (clastic): a classical example of a clastic sedimentary rock.
- Sandstone (clastic): formed from the lithification of silt particles, used in construction and decorative materials.
- Limestone (organic): formed from the depositing, accumulation, and lithification of calcium-rich organic matter.
- Sea salt (chemical): formed when large amounts of sea water evaporate and leave behind the dissolved salts.

Formed through the metamorphosis of sedimentary or igneous rocks due to environmental factors like heat, pressure, or chemical environments.
Metamorphic rocks can be classified into two types:
- Foliated metamorphic rocks: characterized by the presence of parallel bands of minerals running through the rock.
- Unfoliated metamorphic rocks: formed when pressure is milder across the rock during metamorphosis, without distinct bands of minerals.
Examples of metamorphic rocks include:
- Marble (unfoliated): a metamorphic rock used in making monuments and sculptures.
- Slate (foliated): a fine-grained rock formed from mudstone or shale, used in roof tiles and flooring.
- Phyllite (foliated): a metamorphic rock formed when shale is subjected to low levels of heat and pressure, used in decorative rock formations.

Describes how geological material, such as rocks and minerals, are cycled over time.
Considers the relation between igneous, sedimentary, and metamorphic rocks and how transformations occur between each type.
The rock cycle involves the continuous transformation of rocks into different types over time, recycling the same geological material.