Difference Between Igneous, Sedimentary, and Metamorphic Rocks

Edited by Diffzy | Updated on: April 30, 2023


Difference Between Igneous, Sedimentary, and Metamorphic Rocks

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Magma (molten rocks) or lava (molten rocks that burst through the earth's surface) cools and solidifies to form igneous rocks. The majority of these rocks are crystalline. Granite, basalt, and pumice are examples of igneous rocks.

Sedimentary rocks are formed by the aggregation and deposition of other pre-existing rocks or microscopic animal remnants at the bottom of bodies of water. The structure of these rocks is fragmented. Sandstone, chalk, and coal are examples of sedimentary rocks.

Pre-existing rocks undergo chemical and solid-state changes as a result of heat and pressure, resulting in metamorphic rocks. These rocks are extremely hard and may have foliated appearances. Marble, quartzite, phyllite, and other metamorphic rocks are examples.

Igneous Rocks vs. Sedimentary Rocks vs. Metamorphic Rocks

The primary distinction between igneous, sedimentary, and metamorphic rocks is found in their origin, formation, texture, categorization, and other characteristics.

Difference Between Igneous Rocks, Sedimentary Rocks and Metamorphic Rocks in Tabular Form

Parameters of Comparison Igneous Rocks Sedimentary Rocks Metamorphic Rocks
Origin Igneous rocks are formed by the cooling of molten material (magma or lava). Sedimentary rocks are made up of pre-existing rock deposits, fossils, and small fragments of the animal remains. Metamorphic rocks are derived from other rocks.
Formation When molten material from volcanoes cools and solidifies, igneous rocks develop. Sedimentary rocks occur as sediments collect, deposit, and cement at the bottom of bodies of water. Metamorphic rocks are generated when heat and pressure cause chemical and physical changes in pre-existing rocks.
Structure Igneous rocks mainly have a crystal-like structure. Sedimentary rocks have a fragmented structure and contain bedding, which is an interior layering system. Metamorphic rocks are extremely hard and might seem layered or banded.
Texture The texture of igneous rocks is determined by how quickly they cooled. The texture ranges from gritty to glossy. Sedimentary rocks have different textures depending on their clasts, age, and depositional environment. Most of these are blurry. Because of the pressure, metamorphic rocks have a foliated texture. Some rocks may even appear to be banded and non-foliated.
Types Intrusive (formed from magma under the earth's surface) and extrusive (formed from magma above the earth's surface) igneous rocks are the two varieties (solidified from lava on the surface of the earth) Clastic sedimentary rocks (detrital), organic sedimentary rocks (biochemical), and chemically precipitated sedimentary rocks are the three kinds of sedimentary rocks. Foliated metamorphic rocks and non-foliated metamorphic rocks are the two primary types of metamorphic rocks.
Examples Granite, diorite, and pegmatite are examples of intrusive igneous rocks; basalt, tuff, pumice, scoria, and other extrusive igneous rocks are examples of extrusive igneous rocks. Limestone, iron ore, chalk, coal, sandstone, siltstone, shale, flint, etc. Slate, marble, quartzite, phyllite, gneiss, hornfels, etc.

What are Igneous Rocks?

When molten material cools and hardens into crystalline substance, igneous rocks develop. These rocks are referred to as 'primary' since they are formed from liquid (as opposed to sedimentary and metamorphic rocks, which are formed from pre-existing rocks). Igneous rocks are plentiful, accounting for 95 percent of the earth's top crust. In addition, there are about 700 different varieties of these rocks. Granite is a well-known igneous rock that is used to make the majority of kitchen worktops.

All igneous rocks have one thing in common: they were previously hot enough to melt. The following characteristics are all linked to this.

  • They are relatively robust rocks because their mineral grains became closely packed when the melt cooled.
  • They're made up largely of black, white, or gray primary minerals. Any additional colors they have are quite light.
  • Their textures resemble that of something cooked in the oven. Coarse-grained granite has a uniform texture that is similar to that of construction stones or kitchen countertops. Fine-grained lava can take on the appearance of black bread (with gas bubbles) or dark peanut brittle (including larger crystals).


Igneous rocks (from the Latin word ignis, which means "fire") come in a variety of mineral compositions, but they all have one thing in common: they were produced by the cooling and crystallization of a melt. This material might have been lava erupted on the surface of the Earth, or magma (unruptured lava) at depths of a few kilometers, known as magma in deeper bodies.

Three basic kinds of igneous rocks result from these three diverse contexts. Extrusive rock is made of lava, intrusive rock is made of shallow magma, and plutonic rock is made of deep magma. The magma cools more slowly as it cools deeper, forming bigger mineral crystals.

Where They Form

Igneous rocks form at four main places on Earth:

  • Plates migrate apart along divergent boundaries, such as mid-ocean ridges, forming gaps that are filled by magma.
  • When a dense oceanic plate is subducted beneath another oceanic or continental plate, subduction zones form. The melting point of the upper mantle is powered by water from the descending oceanic crust, resulting in magma that rises to the surface and creates volcanoes.
  • Large land masses meet at continental-continental convergent borders, thickening and heating the crust to melting temperatures.
  • The crust slides over a thermal plume emerging from deep below the Earth, creating hot areas like Hawaii. Extrusive igneous rocks are formed by hot areas.

What are Sedimentary Rocks?

Weathering, transit, deposition, compaction, and cementation processes transform pre-existing rocks and bits of once-living organisms into sedimentary rocks. These rocks develop at the bottom of water bodies such as seas and rivers over millions of years. Clastic, organic, and chemically precipitated sedimentary rocks are the three types of sedimentary rocks. Clastic sedimentary rocks are those that form as a result of mechanical weathering on previously formed rocks. Organic sedimentary rocks are made up of the remnants of deceased plants and animals that have been collected and deposited through time. A chemical reaction between two minerals found in rocks can happen on occasion. When these minerals cool, they precipitate and form chemical sedimentary rocks.

In contrast to metamorphic and igneous rocks, which develop deep beneath the Earth, sedimentary rocks form on or near the surface. Erosion, weathering, dissolution, precipitation, and lithification are the geological processes that contribute to the formation of sedimentary rocks.

The actions of wind and rain, which gradually break down huge boulders into smaller ones, are included in erosion and weathering. Boulders and even mountains are eroded and weathered into sediments like sand and mud. Chemical weathering, or dissolution, is a kind of weathering. Water that is slightly acidic progressively wears away stone in this method. These three processes provide the foundation for the formation of new sedimentary rocks.

Precipitation and lithification are two processes that result in the formation of new rocks or minerals. The production of rocks and minerals from chemicals that precipitate from water is known as precipitation. For example, when a lake dries up over thousands of years, mineral deposits are left behind; this is what happened in Death Valley, California. Finally, lithification is the gradual compacting of clay, sand, and other sediments on the ocean's or other bodies of water's bottom into rocks due to the weight of overlying layers.

Sedimentary rocks are classified into two groups. The first is detrital rock, which is formed by the erosion and buildup of rock fragments, silt, and other components, which are collectively referred to as detritus or trash. Chemical rock, on the other hand, is formed by the dissolving and precipitation of minerals.

Organic or inorganic detritus can be found. Organic detrital rocks are formed when plant and animal components decompose in the earth, leaving biological material that is crushed and turned into rock. Coal is a sedimentary rock made up of compacted plants that have developed over millions of years. Inorganic detrital rocks, on the other hand, are made up of fragmented bits of other rocks rather than live organisms. Clastic sedimentary rocks are the name given to these rocks. Sandstone is one of the most well-known clastic sedimentary rocks. Sandstone is made up of compacted and lithified layers of sandy material.

Chemical sedimentary rocks may be found in a variety of environments, including the ocean, deserts, and caverns. For example, most limestone is formed at the ocean's bottom from calcium carbonate precipitation and the remnants of marine creatures with shells. If limestone is discovered on land, likely, that the region was once under water. Cave formations are sedimentary rocks as well, but they are formed uniquely. When water travels through bedrock and takes up calcium and carbonate ions, stalagmites and stalactites develop. When chemical-rich water enters a cave, it evaporates, leaving calcium carbonate on the cave's roof, making a stalactite, or on the cave's floor, generating a stalagmite.

What are Metamorphic Rocks?

When pre-existing rocks are exposed to changes in heat and pressure, they undergo physical and chemical changes, resulting in metamorphic rocks. To produce new rocks, the rocks are exposed to temperatures of 150 degrees Celsius and pressures of about 1500 bars. There are two types of metamorphic rocks: foliated and non-foliated rocks. Foliated rocks have a structure of thin layers, but non-foliated rocks do not. The majority of the earth's crust is made up of metamorphic rocks. It's a rock that's plentiful. Interestingly, the Taj Mahal is one large metamorphic rock since it is entirely built of marble.

Types of Metamorphic Rocks

The metamorphic rocks are classified into two kinds based on their textures:

  1. Foliated metamorphic rocks

Foliation is a term used in geology to describe a layering process that occurs repeatedly. Foliated metamorphic rocks are metamorphic rocks with layers as thin as sheets of paper or as thick as a meter. When pressure and tension are in one direction in the Earth's interior, these rocks develop. New minerals form as a result of foliation, and the minerals in the parent rock reconfigure. Because the bands on the foliated rocks display the colors of the minerals that created them, they are also known as banded rocks. The pressure or tension must be differentiable but only in one direction for the production of foliated rocks.

  1. Non-foliated metamorphic rocks

When the temperature is high but the pressure is low, non-foliated metamorphic rocks develop. Minerals have crystallized and are closely packed in these rocks.

Types of Metamorphism

Metamorphism is of the following types:

  1. Contact Metamorphism: Contact metamorphism is a change caused by the intrusion of hot magma into colder surrounding rocks.
  2. Regional Metamorphism: Regional metamorphism is a shift caused by large-scale tectonic movements of Earth's lithospheric plates affecting the pressure-temperature conditions of the rocks.
  3. Dynamic Metamorphism: Dynamic Mechanical deformation and long-term temperature fluctuations are the primary causes of metamorphism, also known as cataclasis.
  4. Hydrothermal Metamorphism: It happens as a result of the broad interaction between rocks and high-temperature fluids. As a result of the differences in the composition of the rocks and fluids, chemical reactions occur. These high-temperature fluids are thought to come from magma and circulate through the crusts nearby.
  5. Burial Metamorphism: Rocks are exposed to constant lithostatic pressure stress in burial metamorphism, although they do not foliate. Deep-buried sedimentary rocks are the most prevalent place to find them. Zeolite, a category of low-density silicate minerals, is most commonly formed during burial metamorphism.

Main Differences Between Igneous Rocks, Sedimentary Rocks and Metamorphic Rocks in Points

  • Igneous rocks are created by the solidification of molten material. Sedimentary and metamorphic rocks, on the other hand, are formed from pre-existing rocks.
  • Igneous rocks have a crystalline structure, whereas sedimentary rocks are fragmented and stratified, and metamorphic rocks can be foliated or non-foliated.
  • Igneous rocks make up 95% of the earth's top crust, with other rocks and minerals accounting for the remaining 5%.
  • Igneous rocks, which are found in the earth's crust or mantle, and sedimentary rocks, which are found at the bottom of water bodies, are found closer to the earth's surface than metamorphic rocks.
  • Kitchen countertops are made of granite, the most well-known igneous rock. Rock salt is a sedimentary rock that is used to manufacture salt all over the world. In the construction of houses and structures, marble and other metamorphic rocks are used.


The genesis, texture, and structure of igneous, sedimentary, and metamorphic rocks may all be distinguished readily. The three sorts of rocks may be the same mineral or sediment cycling through the rock cycle. An igneous rock, for example, may undergo weathering and cementation to become sedimentary rock. When exposed to variations in heat and pressure, this rock can transform into a metamorphic rock.


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"Difference Between Igneous, Sedimentary, and Metamorphic Rocks." Diffzy.com, 2024. Thu. 11 Apr. 2024. <https://www.diffzy.com/article/difference-between-igneous-sedimentary-and-metamorphic-rocks-501>.

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