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QAPF diagram for classification of plutonic rocks. 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.
Grain size in igneous rocks results from cooling time so porphyritic rocks are created when the magma has two distinct phases of cooling. [18] Igneous rocks are classified on the basis of texture and composition. Texture refers to the size, shape, and arrangement of the mineral grains or crystals of which the rock is composed. [citation needed]
British Geological Survey rock classification scheme; Igneous rock classification Archived 2005-08-29 at the Wayback Machine; Rock Types Article by Encyclopædia Britannica; Classification of common rocks and soils; Metamorphic Rock Classification; Volcanic rocks; Earth Science Education Unit virtual rock kit
The TAS classification should be applied only to rocks for which the mineral mode analysis cannot be determined. Otherwise, a scheme based on mineralogy, such as the QAPF diagram, or one of the other diagrams available for igneous rocks may be suitable. Before classifying rocks using the TAS diagram, the chemical analyses must be recalculated ...
Igneous rocks are formed directly from magma, which is a mixture of molten rock, dissolved gases, and solid crystals. Sedimentary rock is formed from mineral or organic particles that collect at the Earth's surface and become lithified. Metamorphic rock forms by recrystallization of existing solid rock under conditions of great heat or pressure ...
Phaneritic (phaner = visible) textures are typical of intrusive igneous rocks, these rocks crystallized slowly below Earth's surface. As magma cools slowly the minerals have time to grow and form large crystals. The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye.
He also created classification schemes for igneous rocks which accounted for their mineralogy, texture, and composition, and showed that igneous rocks of different mineralogies could be formed from the same chemical composition, with different conditions of crystallization. [1] He named "esterellite" to the blue porphyry of Estérel in 1896. [5 ...
Rhyolite is an extrusive igneous rock, formed from magma rich in silica that is extruded from a volcanic vent to cool quickly on the surface rather than slowly in the subsurface. It is generally light in color due to its low content of mafic minerals, and it is typically very fine-grained ( aphanitic ) or glassy .