The types of Granite are Igneous Protolith Granite, Sedimentary Protolith Granite, Mantle Granite, Anorogenic Granite, Hybrid Granite, Granodiorite and Alkali Feldspar Granite whereas types of Pegmatite are Granite Pegmatite, Gabbro Pegmatite and Diorite Pegmatite. This is because of the difficulty in counting and sampling mineral grains in a rock which may have crystals from centimeters to meters across. The process of formation of rocks is different for various rocks. Similarly, crystal texture and form within pegmatitic rock may be taken to extreme size and perfection. Most pegmatites are composed of quartz, feldspar and mica, having a similar silicic composition as granite. When we have to compare Granite vs Pegmatite, the texture, color and appearance plays an important role in determining the type of rock. Width of view 50 cm. textures marks the point of aqueous vapour saturation of melt; by implication, all 'granite' was the crystalline product of H2O-undersaturated magma. Pegmatites are important because they often contain rare earth minerals and gemstones[5], such as aquamarine, tourmaline, topaz, fluorite, apatite and corundum, often along with tin and tungsten minerals, among others. Perthite feldspar within a pegmatite often shows gigantic perthitic texture visible to the naked eye. These rocks are composed of many distinct minerals. Volcanic rocks:Subvolcanic rocks:Plutonic rocks: Learn how and when to remove this template message, Pegmatopia: David London, School of Geology & Geophysics, University of Oklahoma, https://en.wikipedia.org/w/index.php?title=Pegmatite&oldid=972054130, Articles needing additional references from November 2009, All articles needing additional references, Creative Commons Attribution-ShareAlike License, pegmatite fluids are created by removal of, pegmatites tend to occur in the aureoles of granites in most cases, and are usually granitic in character, often closely matching the compositions of nearby granites. While difficult to be certain of derivation of pegmatite in the strictest sense, often pegmatites are referred to as "metamorphic", "granitic" or "metasomatic", based on the interpretations of the investigating geologist. The mineralogy of a pegmatite is in most cases dominated by some form of feldspar, often with mica and usually with quartz, being altogether "granitic" in character. [6] The primary source for caesium is pollucite, a mineral from a zoned pegmatite. You can also check out the list of all Igneous Rocks. Pegmatite rock is holocrystalline, intrusive igneous rock which is formed by partial melting and dewatering during the process of metamorphism. Crystal size is the most striking feature of pegmatites, with crystals usually over 5 cm in size. Pegmatite veins have a lenticular form; sometimes these are schlieren-type pegmatoid isolations invariably of small sizes (length of a few dozen meters, thickness of a few meters). Pegmatite veins are differentiated, and their larger part is occupied by zones of graphic and pegmatoid texture, which sometimes contain large cavities with crystals of feldspars, quartz, topaz, and several other minerals. Other uses in ancient Egypt are columns, door lintels, sills, moldings and wall and floor covering. Learn more about Granite vs Pegmatite in the next section. Rhyolite is available in grey, white, light black colors whereas, Pegmatite is available in black, brown, cream, green, grey, pink, red, rust, silver, white, yellow colors. Occasionally, enrichment in the unusual trace elements will result in crystallisation of equally unusual and rare minerals such as beryl, tourmaline, columbite, tantalite, zinnwaldite and so forth. A pegmatite is an igneous rock, formed underground, with interlocking crystals usually larger than 2.5 cm in size (1 in). Here is a sample of alkali feldspar granite pegmatite from Northern Norway which is composed of alkali feldspar (pink), quartz (gray) and biotite (black). Pegmatites associated with granitic domes within the Archaean Yilgarn Craton intruding ultramafic and mafic rocks contain red, orange and brown almandine garnet. The word pegmatite derives from Homeric Greek (pegnymi), which means to bind together, in reference to the intertwined crystals of quartz and feldspar in the texture known as graphic granite. Syenite pegmatites are quartz depleted and contain large feldspathoid crystals instead. The ancient Egyptians built the pyramids from granites and limestones. Bismuth, molybdenum and tin have been won from pegmatite, but this is not yet an important source of these metals. Magmatic; pegmatites tend to occur in the aureoles of granites in most cases, and are usually granitic in character, often closely matching the compositions of nearby granites. The specific heat capacity of Granite is 0.79 kJ/Kg K and that of Pegmatite is Not Available. Similarly, pegmatite is often found within the contact zone of granite, transitional with some greisens, as a late-stage magmatic-hydrothermal effect of syn-metamorphic granitic magmatism. The majority of the world's beryllium is sourced from non-gem quality beryl within pegmatite. Beyond that, pegmatite may include most minerals associated with granite and granite-associated hydrothermal systems, granite-associated mineralisation styles, for example greisens, and somewhat with skarn associated mineralisation. Most pegmatites are composed of quartz, feldspar and mica; in essence a "granite". In the Jahns-Burnham model, conditions of crystallisation close to equilibrium were thought to prevail; this contrasted with the previous interpretations wherein crystal-liquid equilibrium was generally not attained. Often, bulk samples of some 50–60 kg of rock must be crushed to obtain a meaningful and repeatable result. Granite plutons that enclose pegmatites of this formational type are composed of coarse- to medium-grained leucogranite rocks. Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths. It has colorless grains, and it is mottled in white, red, pink, grey or dark grains. There is often no meaningful way to distinguish pegmatites according to chemistry due to the difficulty of obtaining a representative sample, but often groups of pegmatites can be distinguished on contact textures, orientation, accessory minerals and timing. Characteristics of rocks include texture, appearance, color, fracture, streak, hardness etc. Media related to Pegmatite at Wikimedia Commons. Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths. You can check out Granite vs Pegmatite information and Granite vs Pegmatite characteristics in the upcoming sections. Due to some exceptional properties of Granite and Pegmatite, they have various applications in construction industry. The streak of Granite and Pegmatite is white. Granite Uses. Crystal size and mineral assemblages are usually oriented parallel to the wall rock or even concentric for pegmatite lenses.[4]. Rocks with similar texture to pegmatites are called pegmatitic. Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 millimeters or more. Such rocks are referred to as pegmatitic. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. Granite is an intrusive igneous rock which is very hard, crystalline and is visibly homogeneous in texture and forms by melting of continental rocks Pegmatite rock is holocrystalline, intrusive igneous rock which is formed by partial melting and dewatering during the … The mineral content of Granite includes Amphibole, Biotite, Feldspar, Hornblade, Micas, Muscovite or Illite, Plagioclase, Pyroxene, Quartz and mineral content of Pegmatite includes Apatite, Beryl, Feldspar, Fluorite, Garnet, Lepidolite, Quartz, Silica, Spodumene, Topaz. However, It is impossible to quantify the mineralogy.Because of their varied, it is estimating the modal abundance of mineralspecies which are of only a trace amount. Within the metamorphic belts, pegmatite tends to concentrate around granitic bodies within zones of low mean strain and within zones of extension, for example within the strain shadow of a large rigid granite body. Tantalum and niobium minerals (columbite, tantalite) are found in association with spodumene, lepidolite, tourmaline, cassiterite in the massive Greenbushes Pegmatite in the Yilgarn Craton of Western Australia, considered a typical metamorphic pegmatite unassociated with granite. The uses of Granite in construction industry include As dimension stone and that of Pegmatite include As dimension stone, Building houses or walls, Construction aggregate, For road aggregate, Landscaping. A pegmatite is an igneous rock, formed underground, with interlocking crystals usually larger than 2.5 cm in size (1 in).
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