Granite is a light-colored igneous rock with grains large enough to be visible with the unaided eye. It forms from the slow crystallization of magma below Earth’s surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles and other minerals. This mineral composition usually gives granite a red, pink, gray or white color with dark mineral grains visible throughout the rock. Granite is the best-known igneous rock The term granitic means granite-like and is applied to granite and a group of intrusive igneous rocks with similar textures and slight variations on composition and origin. A granite containing both muscovite and biotite micas is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. Igneous rocks are formed from the solidification of molten rock material. There are two basic types. Intrusive igneous rocks crystallize below Earth's surface and the slow cooling that occurs there allows large crystals to form. Examples of intrusive igneous rocks are diorite, gabbro, granite, pegmatite, and peridotite. Extrusive igneous rocks erupt onto the surface where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include andesite, basalt, obsidian, pumice, rhyolite, scoria, and tuff. Pictures and brief descriptions of some common igneous rock types are shown on this page. Diorite is a coarse-grained, intrusive igneous rock that contains a mixture of feldspar, pyroxene, hornblende and sometimes quartz. Students of granites classify them in three or four categories. I-type (igneous) granites appear to arise from the melting of preexisting igneous rocks, S-type (sedimentary) granites from melted sedimentary rocks (or their metamorphic equivalents in both cases). By Andrew Alden. Granite is the signature rock of the continents. More than that, granite is the signature rock of the planet Earth itself. The other rocky planets— Mercury, Venus and Mars—are covered with basalt, as is the ocean floor on Earth. Granite is a coarse-grained, light-colored igneous rock composed mainly of feldspars and quartz with minor amounts of mica and amphibole minerals. This simple definition enables students to easily identify the rock based upon a visual inspection. It forms from the slow crystallization of magma below Earth’s surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles and other minerals. This mineral composition usually gives granite a red, pink, gray or white color with dark mineral grains visible throughout the rock. In the commercial stone industry a granite is a rock with visible grains that is harder than a marble. Under this definition gabbro, basalt, pegmatite, schist, gneiss, syenite, monzonite, anorthosite, grannodiorite, diabase, diorite and many other rocks will be called granite. It forms from the slow crystallization of magma below Earth’s surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles and other minerals. This mineral composition usually gives granite a red, pink, gray or white color with dark mineral grains visible throughout the rock. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy. The word granite comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a holocrystalline rock. A granite containing both muscovite and biotite micas is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. Granite differs from granodiorite in that at least 35% of the feldspar in granite is alkali feldspar as opposed to plagioclase; it is the potassium feldspar that gives many granites a distinctive pink color. A granite containing both muscovite and biotite micas is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. Gabbro is a coarse-grained, dark colored, intrusive igneous rock that contains feldspar, pyroxene and sometimes olivine. The specimen shown above is about two inches (five centimeters) across. Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. These rocks include andesite, basalt, obsidian, pumice, rhyolite, scoria, and tuff. Pictures and brief descriptions of some common igneous rock types are shown on this page. Diorite is a coarse-grained, intrusive igneous rock that contains a mixture of feldspar, pyroxene, hornblende and sometimes quartz. Granite /ˈɡraenɨt/ ˈɡrænɨt is a common type of felsic intrusive igneous rock that is granular and phaneritic in. Texture granites can be predominantly, white, pink or gray in, color depending on their. mineralogy A granite containing both muscovite and biotite micas is called a binary or two-mica granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites.
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types of granite geology