Ijolite (Oka Carbonatite Complex, Early Cretaceous, 124-125 Ma; Oka Niobium Mine, Quebec, Canada) (1
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Ijolite (Oka Carbonatite Complex, Early Cretaceous, 124-125 Ma; Oka Niobium Mine, Quebec, Canada) (1
Ijolite is an igneous rock consisting essentially of nepheline and augite. Ijolite is a rare rock type of considerable importance from a mineralogical and petrological standpoint. The word is derived from the first syllable of the Finnish words such as ''Iivaara'', ''Iijoki'', common as geographical names in Finland, and the Ancient Greek ''Xiflos'', a stone. Ijolite occurs in various parts of the Kainuu region of eastern Finland and in the Kola Peninsula of northwest Russia on the shores of the White Sea. Ijolite was first defined and named by Finnish geologist Wilhelm Ramsay. The pyroxene is , yellow or green, and is surrounded by formless areas of nepheline. The accessory minerals are apatite, cancrinite, calcite, titanite and iivaarite, a dark-brown titaniferous variety of melanite-garnet. This rock is the plutonic and holo-crystalline analogue of the nephelinites -volcanic equivalent and nepheline-dolerites; it bears the same relation to them as the nepheline syenites h ...
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Ijolite (Oka Carbonatite Complex, Early Cretaceous, 124-125 Ma; Oka Niobium Mine, Quebec, Canada) (14822252052)
Ijolite is an igneous rock consisting essentially of nepheline and augite. Ijolite is a rare rock type of considerable importance from a mineralogy, mineralogical and petrology, petrological standpoint. The word is derived from the first syllable of the Finnish words such as ''Iivaara'', ''Iijoki'', common as geographical names in Finland, and the Ancient Greek ''Xiflos'', a stone. Ijolite occurs in various parts of the Kainuu region of eastern Finland and in the Kola Peninsula of northwest Russia on the shores of the White Sea. Ijolite was first defined and named by Finnish geologist Wilhelm Ramsay. The pyroxene is , yellow or green, and is surrounded by formless areas of nepheline. The accessory minerals are apatite, cancrinite, calcite, titanite and iivaarite, a dark-brown titaniferous variety of melanite-garnet. This rock is the plutonic and holo-crystalline analogue of the nephelinites -volcanic equivalent and nepheline-dolerites; it bears the same relation to them as the nep ...
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Cancrinite
Cancrinite is a complex carbonate and silicate of sodium, calcium and aluminium with the formula Na6 Ca2 O3)2.html" ;"title="carbon">C Coxygen">O3)2">[ Coxygen">O3)2">aluminum">Al6silicon.html" ;"title="luminum.html" ;"title="oxygen.html" ;"title="carbon.html" ;"title=" Coxygen">O3)2">aluminum">Al6silicon">Si6O24·2water.html" ;"title="carbon">Coxygen">O3)2">aluminum">Al6silicon">Si6O24·2water">H2O. It is classed as a member of the feldspathoid group of minerals; the alkali feldspars that are poor in silica. Yellow, orange, pink, white or even blue, it has a vitreous or pearly lustre (mineralogy), luster; a Mohs scale of mineral hardness, hardness of 5–6 and an uneven conchoidal fracture. It is unusual among the silicate minerals in that it will effervesce with hydrochloric acid due to the associated carbonate ions. Found originally in 1839 in the Ural Mountains, it is named after Georg von Cancrin, a Russia Russia (, , ), or the Russian Federation, is a transcontine ...
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Fort Benton, Montana
Fort Benton is a city in and the county seat of Chouteau County, Montana, United States. Established in 1846, Fort Benton is the oldest continuously occupied settlement in Montana. The city's waterfront area, the most important aspect of its 19th century growth, was designated the Fort Benton Historic District, a National Historic Landmark, in 1961. The population was 1,449 at the 2020 census. History Established in 1846 by Alexander Culbertson, who worked for Auguste Chouteau and Pierre Chouteau, Jr. of St. Louis, the original fort was the last fur trading post on the Upper Missouri River, Chouteau County Courthouse, 2009 the fort became an important economic center. For 30 years, the port attracted steamboats carrying goods, merchants, gold miners and settlers, coming from New Orleans, Memphis, St. Louis, Hannibal, Bismarck, Kansas City, etc. As the terminus for the 642-mile-long Mullan Road, completed by the United States Army in 1860, and at the head of navigation of ...
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Leucite
Leucite is a rock-forming mineral of the feldspathoid group, silica-undersaturated and composed of potassium and aluminium tectosilicate KAlSi2O6. Crystals have the form of cubic icositetrahedra but, as first observed by Sir David Brewster in 1821, they are not optically isotropic, and are therefore pseudo-cubic. Goniometric measurements made by Gerhard vom Rath in 1873 led him to refer the crystals to the tetragonal system. Optical investigations have since proved the crystals to be still more complex in character, and to consist of several orthorhombic or monoclinic individuals, which are optically biaxial and repeatedly twinned, giving rise to twin-lamellae and to striations on the faces. When the crystals are raised to a temperature of about 500 Â°C they become optically isotropic and the twin-lamellae and striations disappear, although they reappear when the crystals are cooled again. This pseudo-cubic character of leucite is very similar to that of the mineral boracit ...
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Phonolite
Phonolite is an uncommon extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous rock trachyte that contains nepheline or leucite rather than quartz. Its intrusive equivalent is nepheline syenite. Phonolite is typically fine grained and compact. The name ''phonolite'' comes from the Ancient Greek meaning "sounding stone" due to the metallic sound it produces if an unfractured plate is hit; hence, the English name ''clinkstone'' is given as a synonym. Formation Unusually, phonolite forms from magma with a relatively low silica content, generated by low degrees of partial melting (less than 10%) of highly aluminous rocks of the lower crust such as tonalite, monzonite and metamorphic rocks. Melting of such rocks to a very low degree promotes the liberation of aluminium, potassium, sodium and calcium by melting of f ...
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Nepheline Syenite
Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known. Phonolite is the fine-grained extrusive equivalent. Petrology Nepheline syenites are silica-undersaturated and some are peralkaline (terms discussed in igneous rock). Nepheline is a feldspathoid, a solid-solution mineral, that does not coexist with quartz; rather, nepheline would react with quartz to produce alkali feldspar. They are distinguished from ordinary basic syenites not only by the presence of nepheline but also by the occurrence of many other minerals rich in alkalis and in rare earths and other incompatible elements. Alkali feldspar dominates, commonly represented by orthoclase and the exsolved lamellar albite, form perthite. In some rocks the potash feldspar, in others the soda feldspar predominates. Fresh clear m ...
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Nephelinite
Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite). If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite is dark in color and may resemble basalt in hand specimen. However, basalt consists mostly of clinopyroxene (augite) and calcic plagioclase. Basalt, alkali basalt, basanite, tephritic nephelinite, and nephelinite differ partly in the relative proportions of plagioclase and nepheline. Alkali basalt may contain minor nepheline and does contain nepheline in its CIPW normative mineralogy. A critical ratio in the classification of these rocks is the ratio nepheline/(nepheline plus plagioclase). Basanite has a value of this ratio between 0.1 and 0.6 and also contains more than 10% olivine. Tephritic nephelinite has a value between 0.6 and 0.9. Nephelinite has a value greater than 0.9. Le Maitre (2002) defines and discusses these and other criteria in the classification of i ...
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Plutonic
Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March 27, 2017.Igneous intrusive rocks, accessdate: March 27, 2017.Britannica.comintrusive rock , geology , Britannica.com accessdate: March 27, 2017. Intrusion is one of the two ways igneous rock can form. The other is extrusion, such as a volcanic eruption or similar event. An intrusion is any body of intrusive igneous rock, formed from magma that cools and solidifies within the crust of the planet. In contrast, an ''extrusion'' consists of extrusive rock, formed above the surface of the crust. Some geologists use the term plutonic rock synonymously with intrusive rock, but other geologists subdivide intrusive rock, by crystal size, into coarse-grained plutonic rock (typically formed deeper in the Earth's crust in batholiths or stocks) and ...
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Garnet
Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different species are pyrope, almandine, spessartine, grossular (varieties of which are hessonite or cinnamon-stone and tsavorite), uvarovite and andradite. The garnets make up two solid solution series: pyrope-almandine-spessartine (pyralspite), with the composition range ; and uvarovite-grossular-andradite (ugrandite), with the composition range . Etymology The word ''garnet'' comes from the 14th-century Middle English word ''gernet'', meaning 'dark red'. It is borrowed from Old French ''grenate'' from Latin ''granatus,'' from ''granum'' ('grain, seed'). This is possibly a reference to ''mela granatum'' or even ''pomum granatum'' ('pomegranate', ''Punica granatum''), a plant whose fruits contain abundant and vivid red seed covers ( arils), whic ...
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Melanite
Andradite is a mineral species of the garnet group. It is a nesosilicate, with formula Ca3Fe2Si3O12. Andradite includes three varieties: * ''Melanite'': Black in color, referred to as "titanian andradite".Melanite
Mindat.org * : Vivid green in color, one of the most valuable and rare stones in the world. * ''Topazolite'': Yellow-green in color and sometimes of high enough quality to be cut into a faceted , it is rarer than demantoid. It was first describe ...
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