An example of this is the Greenbushes pegmatite in Western Australia, the largest lithium mineral resource on earth that provides 60 percent of the world’s lithium. 0. A pegmatite is an igneous rock, formed underground, with interlocking crystals usually larger than 2.5 cm in size. Multicoloured tourmaline crystal in the Himalaya pegmatite. : Formations including grayite were originally documented in Rhodesia (now Zimbabwe) in 1957 and subsequently around the globe. Pegmatites are extreme igneous rocks that form during the final stage of a magmas crystallization. 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. Nice blog , I am just heading out to the 2nd day of the international y respected Pegmatite workshop in Maine featuring lectures by pegmatite experts and field trips to many Maine Pegmatite Mines. 0. Phaneritic texture evenly coarse-grained texture with large and visible crystals, due to slow cooling. Sometimes diorites are foliated due to the roughly parallel arrangement of the minerals. The granite, which is intruded through the Eocene beds, is associated with a pegmatite containing tourmaline and cassiterite. The residual melt rich in silica, alumina, alkali elements, water and other volatile elements, and incompatible elements, such as rare metals can then migrate into the wall rocks to form pegmatite dykes, sills, or pipe-like bodies. In most cases, there is no particular genetic significance to the presence of rare mineralogy within a pegmatite, however it is possible to see some causative and genetic links between, say, tourmaline-bearing granite dikes and tourmaline-bearing pegmatites within the area of influence of a composite granite intrusion (Mount Isa Inlier, Queensland, Australia). They are extreme because they contain exceptionally large crystals and they sometimes contain minerals that are rarely found in other types of rocks. Information on Pegmatite in the Keweenaw and on Isle Royal is difficult to find especially in modern professional papers. Feldspar within pegmatite may display exaggerated and perfect twinning, exsolution lamellae, and when affected by hydrous crystallization, macroscale graphic texture is known, with feldspar and quartz intergrown. Internal evolution of pegmatitic texture and zonation. 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. Hence, pegmatite is often characterised by sampling the individual minerals which comprise the pegmatite, and comparisons are made according to mineral chemistry. Most pegmatites … This is how pegmatit… These are concentric zones which conform roughly to the shape of the pegmatite … As is well known, the Earth is about 4.6 billion years old. : Hutton suggested the huttonite contained in the beach sand and fluvio-glacial deposits originated from Otago schists or pegmatitic veins in the Southern Alps. With Examples. Normally, pegmatites are unzoned and largely uniform in both composition and texture. The word pegmatite derives from Homeric Greek, πήγνυμι, which means “to bind together”, in reference to the intertwined crystals of quartz and feldspar in the texture known as graphic granite. For example! B – Aphanitic (basalt). For example, London (1985, 1986) describes FI from petalite, eucryptite, spodumene, and coexisting quartz from the Tanco Pegmatite, Bernic Lake, Manitoba. URL: https://www.sciencedirect. High-Grade, with the Main Unit are not attributed to slow rate of but! 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