Q:

What is the difference between basalt and granite?

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Quick Answer

Granite is an intrusive rock with few contaminants, while basalt is an extrusive rock with many contaminants. Granite is the principal component of the continental crust, while basalt is the principal component of the oceanic crust.

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Full Answer

Granite is an intrusive rock that is formed when magma cools inside the crust. This slow cooling gives time for crystals to grow, making it more coarsely grained than an extrusive rock. This coarse grain makes granite a favorite of rock climbers. Basalt, on the other hand, has a smooth texture from rapid cooling, usually by water.

Granite is a felsic rock, meaning that it has a high silicon content; it is mostly made out of quartz, mica and feldspar. Basalt, as a mafic rock, contains more calcium oxide, manganese oxide and iron compounds than granite. Its high iron content gives it magnetic properties, and it may show signs of rust when exposed to air. These impurities make it roughly 10 percent heavier than granite.

Because it cools quickly, basalt is often found in formations where granite is not. While granite often takes the form of monoliths or boulders, basalt is often found in roughly hexagonal columns. These columns are created from the shock of cooling, as cracks propagate through the material.

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Related Questions

  • Q:

    How is granite formed?

    A:

    Granite is an igneous rock that forms when a pocket of magma rises into the upper levels of the Earth's crust and slowly cools. Cooling slowly gives granite, which is composed mainly of feldspar and quartz, enough time to develop large crystals that make the stone very hard and strong. Some granite, known as gneiss, can form from sedimentary rock that has gone through a long metamorphosis.

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  • Q:

    How much does granite weigh?

    A:

    Granite weighs approximately 2.75 grams per cubic centimeter, which is 2,750 kilograms per cubic meter. It is composed of slightly less than three-fourths silicon dioxide and roughly one-seventh aluminum oxide. The rest consists of other oxides, such as potassium oxide.

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  • Q:

    What is the texture of granite?

    A:

    Granite has a coarse to very coarse grained texture. It is typically granular and can be porphyritic with well-shaped large crystals of feldspar. Its structure contains cavities wherein well-formed crystals project.

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  • Q:

    Is granite a metamorphic rock?

    A:

    Granite is an igneous rock, not a metamorphic rock. It is the most predominant type of igneous rock on the surface of the earth.

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