Rocks are mineral aggregates with a combination of properties of all the mineral traces. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe rock types. Additionally, different classification systems exist for each major type of rock. There are different Types of Rocks existing in nature.
Rocks which are found in nature rarely show such simple characteristics and usually exhibit some variation in the set of properties as the measurement scale changes.
Types of Rocks – Rocks are broadly classified into three broad categories as the following.
- Igneous Rocks
- Sedimentary Rocks
- Metamorphic Rocks
Igneous rock is one of the three main rock types. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.
This magma can be derived from partial melts of existing rocks in either a planet’s mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition.
Sedimentary rocks are formed by the deposition and subsequent cementation of that material within bodies of water and at the surface of the earth. The process that causes various organic materials and minerals to settle in a place is termed as sedimentation.
The particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, the sediment was formed by weathering and erosion from the source area and then transported to the place of deposition by water, wind, ice, mass movement or glaciers, which are called agents of denudation. Sedimentation may also occur as minerals precipitate from water solution or shells of aquatic creatures settle out of suspension.
Metamorphic rocks make up a large part of the Earth’s crust and are classified by texture and by chemical and mineral assemblage. They may be formed simply by being deep beneath the Earth’s surface, subjected to high temperatures and the great pressure of the rock layers above it.
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means “change in form”. The original rock is subjected to heat with temperatures greater than 150 to 200°C and pressure around 1500 bars, causing profound physical and/or chemical change.