Igneous rock
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Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)
Natural columns of igneous rock separated from each other by columnar joints, in Madeira
Formation of igneous rock
Extrusive igneous rock is made from lava released by volcanoes
Granite
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Granite is a coarse-grained intrusive igneous rock composed mostly of quartz, alkali feldspar, mica and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slow
Igneous rock
…tectonics); in some special circumstances they host important mineral deposits (ores): for example, tungsten, tin, and uranium are commonly associated with granites and diorites, whereas ores of chromium and platinum are commonly associated with gabbros. Igneous rocks can be either intrusive (plutonic and hypabyssal…
Granite containing plagioclase feldspar, potassium feldspar, quartz, biotite, and/or amphibole
Granite with a moderate amount of plagioclase, alkali feldspar, and quartz
Granite with a composition of alkali feldspar and quartz
Granite in thin section, under cross-polarized light