Granite is a coarse- to medium-grained intrusive igneous rock, primarily composed of quartz and feldspar. It forms deep within the Earth's crust from the slow cooling of magma. Granite is the most abundant plutonic rock in the Earth's crust. Historically, granite was a significant building material, and it continues to be quarried for tombstones, highway curbing, and building facades. It can form in various geological structures, from dikes and sills to large batholiths. The specific types of feldspar present, along with quartz and minor minerals like biotite, muscovite, amphibole, or pyroxene, are used to classify granite. Granite can also be formed through metamorphic processes, known as granitization, where sediments are transformed in a solid or partially molten state.

What minerals are found in granite?

Granite is an intrusive igneous rock primarily composed of quartz and feldspar. The principal constituent is feldspar, with both plagioclase and alkali feldspar typically abundant. Essential minor minerals can include muscovite, biotite, amphibole, or pyroxene. Accessory minerals, which are present in smaller amounts and not essential for naming the rock, can also be found in granite. These accessory minerals form during the rock's solidification from magma. Examples of accessory minerals include zircon, corundum, fluorite, garnet, and tourmaline.

How does granite form in nature?

Granite is a coarse-grained intrusive igneous rock that forms from the slow cooling of magma deep within the Earth's crust. This magma is rich in quartz and feldspar. As the magma cools, these minerals crystallize and interlock, creating the characteristic granular texture of granite. Granite can form in large masses called batholiths or in smaller dikes and sills. While igneous processes are the primary way granite forms, it can also be created through granitization, a metamorphic process where sediments transform in a solid or partially molten state.

How is granite used by humans?

Granite is a hard, crystalline igneous rock primarily composed of quartz and feldspar. Historically, it was extensively quarried for use as paving blocks and building stone. Today, its production is largely driven by demand for highway curbing and as veneer for commercial buildings. Granite also remains a popular choice for tombstones due to its durability and aesthetic appeal.

How does granite differ from other types of rocks, like basalt or limestone?

Granite is an intrusive igneous rock, meaning it forms from slowly cooling magma deep within the Earth's crust. It is characterized by its coarse or medium grain size and is rich in quartz and feldspar. In contrast, basalt is an extrusive igneous rock, formed from lava that cools rapidly on the Earth's surface, resulting in a finer-grained texture. Limestone, however, is a sedimentary rock primarily composed of calcium carbonate, often formed from the accumulation of fossilized marine organisms. These fundamental differences in origin and composition distinguish granite from basalt and limestone.

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Images & Videos

Learn about the use of gamma-ray spectroscopy to identify the quarry that was the source of granite found in ancient Roman ruins

Glacial erratic perched on low pedestal of massive granite, Tulare county, Calif.

Whaleback outcroppings of Precambrian granite of the basement complex in the Matopo Hills, southwestern Zimbabwe.

Figure 42: Granitic rock consisting of reddish orange feldspar, nearly white quartz, and green epidote that appears to have been introduced into an original quartz-feldspar granite. This rock, sometimes called unakite, is used widely in jewelry.

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Quick Facts

Type: igneous rock
Major mineral components: plagioclase feldspar, alkali feldspar, quartz.
Minor mineral components: muscovite, biotite, amphibole, and pyroxene.
Density range: 2.50–2.81 grams per cubic cm.
Mean density: 2.64 grams per cubic cm.
Notes: Granite is the most common plutonic rock in Earth’s crust; this rock is used to create paving blocks, building stones, and tombstones.

Top Questions

What is granite?
Granite is a coarse- to medium-grained intrusive igneous rock, primarily composed of quartz and feldspar. It forms deep within the Earth's crust from the slow cooling of magma. Granite is the most abundant plutonic rock in the Earth's crust.

Historically, granite was a significant building material, and it continues to be quarried for tombstones, highway curbing, and building facades. It can form in various geological structures, from dikes and sills to large batholiths. The specific types of feldspar present, along with quartz and minor minerals like biotite, muscovite, amphibole, or pyroxene, are used to classify granite. Granite can also be formed through metamorphic processes, known as granitization, where sediments are transformed in a solid or partially molten state.
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What minerals are found in granite?
Granite is an intrusive igneous rock primarily composed of quartz and feldspar. The principal constituent is feldspar, with both plagioclase and alkali feldspar typically abundant. Essential minor minerals can include muscovite, biotite, amphibole, or pyroxene. Accessory minerals, which are present in smaller amounts and not essential for naming the rock, can also be found in granite. These accessory minerals form during the rock's solidification from magma. Examples of accessory minerals include zircon, corundum, fluorite, garnet, and tourmaline.
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How does granite form in nature?
Granite is a coarse-grained intrusive igneous rock that forms from the slow cooling of magma deep within the Earth's crust. This magma is rich in quartz and feldspar. As the magma cools, these minerals crystallize and interlock, creating the characteristic granular texture of granite. Granite can form in large masses called batholiths or in smaller dikes and sills. While igneous processes are the primary way granite forms, it can also be created through granitization, a metamorphic process where sediments transform in a solid or partially molten state.
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How is granite used by humans?
Granite is a hard, crystalline igneous rock primarily composed of quartz and feldspar. Historically, it was extensively quarried for use as paving blocks and building stone. Today, its production is largely driven by demand for highway curbing and as veneer for commercial buildings. Granite also remains a popular choice for tombstones due to its durability and aesthetic appeal.
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How does granite differ from other types of rocks, like basalt or limestone?
Granite is an intrusive igneous rock, meaning it forms from slowly cooling magma deep within the Earth's crust. It is characterized by its coarse or medium grain size and is rich in quartz and feldspar.

In contrast, basalt is an extrusive igneous rock, formed from lava that cools rapidly on the Earth's surface, resulting in a finer-grained texture. Limestone, however, is a sedimentary rock primarily composed of calcium carbonate, often formed from the accumulation of fossilized marine organisms. These fundamental differences in origin and composition distinguish granite from basalt and limestone.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

granite, coarse- or medium-grained intrusive igneous rock that is rich in quartz and feldspar; it is the most common plutonic rock of the Earth’s crust, forming by the cooling of magma (silicate melt) at depth.

Because of its use as paving block and as a building stone, the quarrying of granite was, at one time, a major industrial activity. Except for tombstones, however, for which there is a continuing demand, the present production of granite is geared to the fluctuating market for curbing in highway construction and veneer used in the facing of large industrial and commercial buildings.

Granite may occur in dikes or sills (tabular bodies injected in fissures and inserted between other rocks), but more characteristically it forms irregular masses of extremely variable size, ranging from less than eight kilometres (five miles) in maximum dimension to larger masses (batholiths) that are often hundreds or thousands of square kilometres in area.

Basalt sample returned by Apollo 15, from near a long sinous lunar valley called Hadley Rille. Measured at 3.3 years old.

Britannica Quiz

(Bed) Rocks and (Flint) Stones

The principal constituent of granite is feldspar. Both plagioclase feldspar and alkali feldspar are usually abundant in it, and their relative abundance has provided the basis for granite classifications. In most granite, the ratio of the dominant to the subdominant feldspar is less than two. This includes most granites from the eastern, central, and southwestern United States, southwestern England, the Fennoscandian (Baltic Shield) area, western and central France, Spain, and many other areas. Granites in which plagioclase greatly exceeds alkali feldspar are common in large regions of the western United States and are thought to be characteristic of the great series of batholiths stretching from Alaska and British Columbia southward through Idaho and California into Mexico. Granites with a great excess of alkali feldspar over plagioclase are known from New England; they occur in smaller bodies at numerous sites in British Paleogene and Neogene rocks and in the Oslo region of Norway, but their most extensive development is in northern Nigeria.

Rocks containing less than 20 percent quartz are almost never named granite, and rocks containing more than 20 percent (by volume) of dark, or ferromagnesian, minerals are also seldom called granite. The minor essential minerals of granite may include muscovite, biotite, amphibole, or pyroxene. Biotite may occur in granite of any type and is usually present, though sometimes in very small amounts. The sodic-amphiboles and pyroxenes (riebeckite, arfvedsonite, aegirine) are characteristic of the alkali granites. If neither feldspar is in great excess, neither amphibole nor pyroxene is likely to be an essential constituent; the other minerals will then ordinarily be either biotite or muscovite, or both.

There are two major source regions for producing molten granite: igneous and sedimentary protoliths (source rocks). These result in I-type granitoids, derived from igneous protoliths and containing moderate amounts of Al₂O₃ and high amounts of Na₂O, and S-type granitoids, derived from sedimentary protoliths and containing high amounts of Al₂O₃ and relatively low amounts of Na₂O. Amphibole and pyroxene are more common in I-type granitoids, while S-type granitoids may have garnet, cordierite, and sillimanite. Both types of granitoids may also contain biotite and muscovite.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by John P. Rafferty.

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