How Many Types of Rocks Are There

How Many Types of Rocks Are There?

Rocks are the coherent aggregate of either an aggregate of one mineral or more. There are three main types of rock on our planet Earth, which form mountains, plateaus, and other huge structures. The three main types of rocks are igneous, sedimentary, or metamorphic rock. Geologists study these rocks to know more about the planet Earth. The division of the rocks has been done keeping in mind various attributes such as chemical, mineralogical, and textural abilities. Here is a concise account of these rocks with their characteristics. But, first, let’s know about the formation of these rocks under the rock cycle.

The Rock Cycle

Before the types of rocks originated, There were various processes that took place, including the entire one called the rock cycle. The rock cycle refers to the cycling of the rocks through various parts to form the final one at last. The process of rock formation depends on various factors such as temperature, pressure, time, and changes in environmental conditions. 

In the course of rock formation, the main events that take place include erosion, i.e., the removal of surface materials like soil and debris. There are more processes within erosion that form the three different types of rocks as present on the earth’s surface. Here are the main process:-


This includes the process of physical and chemical breakdown of minerals and the deposition of residue from the place of removal to the site of deposition. 


It is the process of the formation of sedimentary rock by the compaction and the natural cementation of the grains with the crystals of water. 

In turn, the formation of the three types of rocks takes place. Here are the characteristics of these rocks. 

3 Main Types of Rocks

Sedimentary Rocks

  • Type of rock formed from particles of sand, shells, pebbles, etc. called sediments
  • Sediments accumulate in layers to form the rock
  • Soft and may break easily.
  • The only type of rock which contains fossils
  • Common classification: clastic sedimentary rock, conglomerates, and sandstones
  • Example: limestone, mica

Metamorphic Rocks

  • Type of rock formed under the earth’s surface through intense heat and pressure
  • Have ribbon-like structure and shiny crystals
  • Found minerals growing overtime on the surface
  • Split into two categories: foliated and a non-foliated metamorphic rock
  • Example: gneiss, slate, and marbles

Igneous Rocks

  • Type of rock formed when magma inside the earth cools and harden 
  • No crystals are formed, and rock looks shiny due to lava.
  • Have tiny holes as gas particles trapped in rock
  • Based on formation, classified into two forms: extrusive and intrusive igneous rocks
  • Common examples: basalt, dacite, and obsidian

These were some essential details about different types of rocks. If you need to know more about these, get online assignment help from our experts. Feel free to contact us anytime.