The pegmatites are named after the appropriate plutonic rock (ex: Granite pegmatite) or after the useful minerals (ex: mica pegmatite, feldspar pegmatite, gem stone pegmatite). Reported herein are the assay results for grab samples testing the Silverleaf Pegmatite, Greer Lake Quarry, and other locations on the Lithium One Project (Table 1). Pegmatites are the primary source of lithium either as spodumene, lithiophyllite or … Granite pegmatite typically contains feldspar, mica, and quartz. The number of crystal nuclei in pegmatites must be low and the ability of the necessary chemical components needed for crystal growth to migrate to the crystal surfaces must be enhanced to allow gigantic crystals to grow in pegmatites. Pegmatite is an exceptionally coarse-grained plutonic igneous rock. Large sheets of mica are often mined from pegmatite and used to make components electronic devices, circuit boards, optical filters, detector windows, and many other products. For instance, ThoughtCo uses cookies to provide you with a great user experience. Pegmatites are a variety of acid igneous rock with very large crystals, found in connection with the deep-seated, coarse-grained igneous rocks, especially the granites. 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. Basically, the presence of residual water has allowed the magma to cool slowly to permit coarse crystal growth. Pegmatites are extreme igneous rocks that form during the final stage of a magma’s crystallization. They are extreme because they contain exceptionally large crystals and they sometimes contain minerals that are rarely found in other types of rocks. Get to know more about Pegmatite rock and characteristics of Pegmatite rock in the next sections. As the water escapes, the ions deposit to form crystals. While the mineral chemistry is highly variable, the elemental composition often resembles that of granite. 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. Pegmatite form from the water separated from the melt so it will crystallise at the margins and in fractures of the country rock. Often, bulk samples of some 50–60 kg of rock must be crushed to obtain a meaningful and repeatable result. Pegmatite can also form in fractures that develop on the margins of the batholith. Thus, the possible growth mechanisms in a wide variety of known pegmatites may likely involve a combination of the following processes; Despite this hypothesis on likely chemical, thermal and compositional conditions required to promote pegmatite growth there are three main theories behind pegmatite formation; Metasomatism is currently not well favored as a mechanism for pegmatite formation and it is likely that metamorphism and magmatism are both contributors toward the conditions necessary for pegmatite genesis. Pegmatites are extreme igneous rocks that form during the final stage of a magmas crystallization. Rocks that display large, granular crystal structure are called "pegmatitic.". To be called a “pegmatite,” a rock should be composed almost entirely of crystals that are at least one centimeter in diameter. Most pegmatites are granites with or without exotic minerals but mafic pegmatites (gabbro, diorite) are known as well. One worth understanding. Pegmatite is an intrusive igneous rock made up of large interlocking crystals. Other elements that may be sourced from pegmatite include tantalum, niobium, bismuth, molybdenum, tin, tungsten, and the rare earths. Make sure to click to page 2 to see some amazing pegmatite photos! While pegmatite occurrences are not uncommon, those bearing gem-quality minerals in mineable quantities are exceedingly r… Most pegmatites are granites with or without exotic minerals but mafic pegmatites (gabbro, diorite) are known as well. Media related to Pegmatite at Wikimedia Commons. The product of pegmatite decomposition is euclase. The streak of Pegmatite is white. The term “pegmatite” refers to any extremely coarse-grained igneous rock, or to a body of such rock in which individual crystals exceed one centimeter (0.4 inches) in diameter. But when it comes to healing crystals, pegmatites play an important role. For example, "lithian pegmatite" contains lithium, while "boron pegmatite" contains boron or yields tourmaline. 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. Pegmatite is available in black, brown, cream, green, grey, pink, red, rust, silver, white, yellow colors. The alkali feldspar may be orthoclase or microcline and Albite (plagioclase). These mineral deposits which are known as pegmatite dikes or veins are frequently found around the borders of granite masses either within the igneous mass itself, or in the adjoining rocks. The contemporary definition of pegmatite was assigned by Austrian mineralogist Wilhelm Heidinger in 1845. Pegmatite is the host rock for numerous mineral deposits and can be the commercial sources of beryllium, bismuth, tin, titanium, tungsten, niobium, and many other elements. • Mapping and rock chip sampling have identified highly fractionated, tin and tantalum-bearing pegmatites at Cowans Cowarna exploration target. By using ThoughtCo, you accept our. pegmatites can exceed by several orders of magni- tude the amounts found in other rocks. Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths. Worldwide, notable pegmatite occurrences are within the major cratons, and within greenschist-facies metamorphic belts. Importance this four-foot-section of a magma ’ s crystallization metal lithium graduate levels make it even more and... The composition of pegmatites is so diverse, they may be also pegmatitic... Pegmatites play an important source of the difficulty in counting and sampling mineral grains a! 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