Q:

How are granite and rhyolite different?

A:

Quick Answer

Rhyolite differs from granite in that it is formed via volcanism, has a greater abundance of potassium versus sodium, does not contain much if any muscovite and tends to cool much more quickly, resulting in glassy or microcrystalline structures. Otherwise, granite and rhyolite have very similar chemical compositions, and some rhyolite is difficult to distinguish from granite. Other types of rhyolite, such as obsidian or pumice, are easy to distinguish.

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Full Answer

Rhyolite is very diverse in its appearance despite its typical chemical composition due to the varied circumstances of solidification. Granite, on the other hand, while varied in color and coarseness of grain, is much more uniform and identifiable. Unlike rhyolite, which solidifies within or outside volcanoes, granite solidifies from magma deep beneath the earth. Its slow solidification allows it to form large, granular mineral crystals. Rhyolite usually cools quickly, creating only small crystals or even uncrystallized glasses. Glasses are amorphous solids, with constituent molecules frozen in a relatively random configuration. Perlite is a form of glassy rhyolite similar to obsidian, but with a much higher water content. Pumice is yet another form of rhyolite volcanic glass. Rhyolite cools extremely rapidly, releasing all contained gases, thus creating a porous, froth-like glass.

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Related Questions

  • Q:

    What color is granite?

    A:

    According to Climbing Magazine, the color of a granite depends on the feldspar present. Plagioclase feldspars are generally a milky white and alkali feldspars have a variety of colors, including pale yellow, emerald green and brick red.

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  • Q:

    What is granite made of?

    A:

    Granite is a large-grained igneous rock usually comprised of minerals like feldspar, quartz, mica and amphibole. It varies in color and appearance based on the mineral composition of the rock layers near where it is located. Granite, an igneous rock, is formed by magma cooling beneath the surface.

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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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