Granite Wikipedia. Granite is a common type of felsicintrusiveigneous rock that is granular and phaneritic in texture. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy. The word granite comes from the Latingranum, a grain, in reference to the coarse grained structure of such a holocrystalline rock. Strictly speaking, granite is an igneous rock with between 2. The term granitic means granite like and is applied to granite and a group of intrusive igneous rocks with similar textures and slight variations in composition and origin. These rocks mainly consist of feldspar, quartz, mica, and amphiboleminerals, which form an interlocking, somewhat equigranularmatrix of feldspar and quartz with scattered darker biotite mica and amphibole often hornblende peppering the lighter color minerals. Occasionally some individual crystals phenocrysts are larger than the groundmass, in which case the texture is known as porphyritic. 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. The extrusive igneous rock equivalent of granite is rhyolite. Granite is nearly always massive lacking any internal structures, hard and tough, and therefore it has gained widespread use throughout human history as a construction stone. The average density of granite is between 2. MPa, and its viscosity near STP is 36 1. Pas. 4The melting temperature of dry granite at ambient pressure is 1. C 2. 21. 92. 30. F 5 it is strongly reduced in the presence of water, down to 6. Bathtub repair and refinishing, glazing and resurfacing services. Acrylic tub and wall liners, sinks, countertop repair and refinishing, with additional kitchen and. Corian, Quartz, Stainless Steel or Granite. Which worktop should I choose by www. One of the biggest dilemmas facing the modern kitchen consumer. Shop our selection of Vanity Tops in the Bath Department at The Home Depot. C at a few k. Bar pressure. Granite has poor primary permeability overall, but strong secondary permeability through cracks and fractures if present. Mineralogyedit. QAPF diagram for classification of plutonic rocks. Mineral assemblage of igneous rocks. Logitech Fc For Home Or Office Use Drivers. Granite is classified according to the QAPF diagram for coarse grained plutonic rocks and is named according to the percentage of quartz, alkali feldspar orthoclase, sanidine, or microcline and plagioclase feldspar on the A Q P half of the diagram. True granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite. When a granitoid contains less than 1. 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. 1 Click Youtube Er Chrome. Corian Sink Cracks' title='Corian Sink Cracks' />Chemical compositioneditA worldwide average of the chemical composition of granite, by weight percent, based on 2. OccurrenceeditGranite containing rock is widely distributed throughout the continental crust. Much of it was intruded during the Precambrian age it is the most abundant basement rock that underlies the relatively thin sedimentary veneer of the continents. Outcrops of granite tend to form tors and rounded massifs. Granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. Granite often occurs as relatively small, less than 1. Small dikes of granitic composition called aplites are often associated with the margins of granitic intrusions. In some locations, very coarse grained pegmatite masses occur with granite. Granite has a felsic composition and is more common in recent geologic time in contrast to Earths ultramafic ancient igneous history. Felsic rocks are less dense than mafic and ultramafic rocks, and thus they tend to escape subduction, whereas basaltic or gabbroic rocks tend to sink into the mantle beneath the granitic rocks of the continental cratons. Therefore, granitic rocks form the basement of all land continents. Geochemical originseditGranitoids have crystallized from magmas that have compositions at or near a eutectic point or a temperature minimum on a cotectic curve. Magmas will evolve to the eutectic because of igneous differentiation, or because they represent low degrees of partial melting. Fractional crystallisation serves to reduce a melt in iron, magnesium, titanium, calcium and sodium, and enrich the melt in potassium and silicon alkali feldspar rich in potassium and quartz Si. O2, are two of the defining constituents of granite. This process operates regardless of the origin of the parental magma to the granite, and regardless of its chemistry. However, the composition and origin of the magma that differentiates into granite leaves certain geochemical and mineral evidence as to what the granites parental rock was. The final mineralogy, texture and chemical composition of a granite is often distinctive as to its origin. For instance, a granite that is formed from melted sediments may have more alkali feldspar, whereas a granite derived from melted basalt may be richer in plagioclasefeldspar. It is on this basis that the modern alphabet classification schemes are based. Granite has a slow cooling process which forms larger crystals. Chappell White classification systemeditThe letter based Chappell White classification system was proposed initially to divide granites into I type granite or igneous protolith granite and S type or sedimentary protolith granite. Both of these types of granite are formed by the melting of high grade metamorphic rocks, either other granite or intrusivemafic rocks, or buried sediment, respectively. M type or mantle derived granite was later proposed to cover those granites that were clearly sourced from crystallized mafic magmas, generally sourced from the mantle. These are rare, because it is difficult to turn basalt into granite via fractional crystallisation. A type or anorogenic granites are formed above volcanic hot spot activity and have a peculiar mineralogy and geochemistry. These granites are formed by the melting of the lower crust under conditions that are usually extremely dry. A type granites occur in the Koettlitz Glacier Alkaline Province in the Royal Society Range, Antarctica. The rhyolites of the Yellowstone caldera are examples of volcanic equivalents of A type granite. H type or hybrid granites are formed following a mixing of two granitic magmas from different sources,1. M type and S type. GranitizationeditAn old, and largely discounted theory, granitization states that granite is formed in place by extreme metasomatism by fluids bringing in elements, e. This was supposed to occur across a migrating front. The production of granite by metamorphic heat is difficult, but is observed to occur in certain amphibolite and granulite terrains. In situ granitisation or melting by metamorphism is difficult to recognise except where leucosome and melanosome textures are present in migmatites. Once a metamorphic rock is melted it is no longer a metamorphic rock and is a magma, so these rocks are seen as a transitional between the two, but are not technically granite as they do not actually intrude into other rocks. In all cases, melting of solid rock requires high temperature, and also water or other volatiles which act as a catalyst by lowering the solidus temperature of the rock.