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Igneous rock (igneous from Latin igneus 'fiery'), 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. The magma can be derived from partial melts of existing rocks in either a planet 's mantle or crust.
A QAPF diagram is a doubled-triangle plot diagram used to classify intrusive igneous rocks based on their mineralogy. The acronym QAPF stands for " Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid) ", which are the four mineral groups used for classification in a QAPF diagram. The percentages (ratios) of the Q, A, P and F groups are ...
Claystone – Clastic sedimentary rock composed primarily of clay-sized particles. Coal – Combustible sedimentary rock composed primarily of carbon. Conglomerate – Sedimentary rock composed of smaller rock fragments. Coquina – Sedimentary rock that is composed mostly of fragments of shells.
Feldspar. Feldspar (/ ˈfɛl (d) ˌspɑːr / FEL (D)-spar; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. [3] The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium ...
A granitic rock with a porphyritic texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids. Granites can be predominantly white, pink, or gray in color, depending on their ...
Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. The six main types of textures are phaneritic, aphanitic, porphyritic, glassy, pyroclastic, and pegmatitic. Aphanitic (a = not, phaner = visible) rocks, in contrast to phaneritic rocks, typically form from lava which ...
Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which the original rock was formed. This process is called metamorphism, meaning to "change in form". The result is a profound change in physical properties ...
The rock cycle is a basic concept in geology that describes transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous. Each rock type is altered when it is forced out of its equilibrium conditions. For example, an igneous rock such as basalt may break down and dissolve when exposed to the ...