Minas Gerais is a state in the north of Southeastern Brazil. It ranks as the second most populous, the third by gross domestic product, the fourth largest by area in the country; the state's capital and largest city, Belo Horizonte, is a major urban and finance center in Latin America, the sixth largest municipality in Brazil, after the cities of São Paulo, Rio de Janeiro, Salvador and Fortaleza, but its metropolitan area is the third largest in Brazil with just over 5,500,000 inhabitants, after those of São Paulo and Rio de Janeiro. Nine Brazilian presidents were born in the most of any state. With an area of 586,528 square kilometres —larger than Metropolitan France—it is the fourth most extensive state in Brazil; the main producer of coffee and milk in the country, Minas Gerais is known for its heritage of architecture and colonial art in historical cities such as São João del Rei, Ouro Preto, Diamantina and Mariana. In the south, the tourist points are the hydro mineral spas, such as Caxambu, Lambari, São Lourenço, Poços de Caldas, São Thomé das Letras, Monte Verde and the national parks of Caparaó and Canastra.
The landscape of the State is marked by mountains and large areas of fertile lands. In the Serra do Cipó, Sete Lagoas and Lagoa Santa, the caves and waterfalls are the attractions; some of Brazil's most famous caverns are located there. In recent years, the state has emerged as one of the largest economic forces of Brazil, exploring its great economic potential. Two interpretations are given for the origin of the name Minas Gerais, it comes from "Minas dos Matos Gerais", the former name of the colonial province. So a first and more common understanding affirms that the name means "General Mines", with the word Gerais serving as an adjective to the mines, which were themselves spread in several spots around a larger region. Another explanation is that this ignores the two large geographical spaces which conformed the state in its history: the region of the mines, the region of the Gerais; these corresponded to the areas of Sertão which were farther and hard to access from the mining spots. The confusion comes from the fact that the term "Gerais" is taken as an adjective to "Minas" in the first version, although according to this point of view it refers to the region called Gerais.
A further complication is that this is not a well-defined area on the map of the state, but rather a designation to these parts outside the mining spots, more related to the geography of Sertão, more isolated from the state's nucleus. Minas Gerais is in the north of the southeastern subdivision of Brazil, which contains the states of São Paulo, Rio de Janeiro and Espírito Santo, it borders on Bahia, Goiás, Mato Grosso do Sul, the states of São Paulo and Rio de Janeiro and the state of Espírito Santo. It shares a short boundary with the Distrito Federal. Minas Gerais is situated between 14°13'58" and 22°54'00" S latitude and between 39°51'32" and 51°02'35" W longitude, it is larger in area than Metropolitan Spain. Minas Gerais features some of the longest rivers in Brazil, most notably the São Francisco, the Paraná and to a lesser extent, the Rio Doce; the state holds many hydroelectric power plants, including Furnas. Some of the highest peaks in Brazil are in the mountain ranges in the southern part of the state, such as Serra da Mantiqueira and Serra do Cervo, that mark the border between Minas and its neighbors São Paulo and Rio de Janeiro.
The most notable one is the Pico da Bandeira, the third highest mountain in Brazil at 2890 m, standing on the border with Espírito Santo state. The state has huge reserves of iron and sizeable reserves of gold and gemstones, including emerald and aquamarine mines. Emeralds found in this location are comparable to the best Colombia-origin emeralds, are most a bluish-green color; each region of the state has a distinct character, geographically and to a certain extent culturally. The central and eastern area of the state is hilly and rocky, with little vegetation on the mountains. Around Lagoa Santa and Sete Lagoas a typical Karst topography with caves and lakes is found; some of the mountains are entirely iron ore, which led to extensive mining. Recent advances in environmental policy helped to put limits to mining. About 200 kilometres to the east of Belo Horizonte is the second Metropolitan Region of the state, Vale do Aço, which has iron and steel processing companies along the course of the Rio Doce and its tributaries.
Vale do Aço's largest cities are Coronel Fabriciano and Timóteo. Now that mining is restricted large areas of forest are being removed for timber, charcoal and to clear land for cattle ranching; the original forest cover of these inland hills is much fragmented. The city of Governador Valadares is in the limit of this region with the poorer North; the south of Minas Gerais is green, with coffee and milk production. This region is notably cooler than the rest of the state, some locations are subject to temperatures just below the freezing point during the winter; the region is famed for its mineral-water resorts, including the cities of Poços de Caldas, Lambari, São Lourenço and Caxambu. Many industries are located at Pouso Alegre; the southeast of the state, called Zona da Mata was the richest region unti
Feldspars are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are present in many types of metamorphic rock. Rock formed entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are found in many types of sedimentary rocks; the name feldspar derives from the German Feldspat, a compound of the words Feld, "field", Spat meaning "a rock that does not contain ore". The change from Spat to -spar was influenced by the English word spar, meaning a non-opaque mineral with good cleavage. Feldspathic refers to materials; the alternate spelling, has fallen out of use. This group of minerals consists of tectosilicates. Compositions of major elements in common feldspars can be expressed in terms of three endmembers: potassium feldspar endmember KAlSi3O8, albite endmember NaAlSi3O8, anorthite endmember CaAl2Si2O8. Solid solutions between K-feldspar and albite are called "alkali feldspar".
Solid solutions between albite and anorthite are called "plagioclase", or more properly "plagioclase feldspar". Only limited solid solution occurs between K-feldspar and anorthite, in the two other solid solutions, immiscibility occurs at temperatures common in the crust of the Earth. Albite is considered both alkali feldspar. Alkali feldspars are grouped into two types: those containing potassium in combination with sodium, aluminum, or silicon; the first of these include: orthoclase KAlSi3O8, sanidine AlSi3O8, microcline KAlSi3O8, anorthoclase AlSi3O8. Potassium and sodium feldspars are not miscible in the melt at low temperatures, therefore intermediate compositions of the alkali feldspars occur only in higher temperature environments. Sanidine is stable at the highest temperatures, microcline at the lowest. Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition; the perthitic textures in the alkali feldspars of many granites can be seen with the naked eye.
Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope. Barium feldspars are considered alkali feldspars. Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure; the barium feldspars are monoclinic and include the following: celsian BaAl2Si2O8, hyalophane 4O8. The plagioclase feldspars are triclinic; the plagioclase series follows: albite NaAlSi3O8, oligoclase AlSi2O8, andesine NaAlSi3O8—CaAl2Si2O8, labradorite AlSi2O8, bytownite AlSi2O8, anorthite CaAl2Si2O8. Intermediate compositions of plagioclase feldspar may exsolve to two feldspars of contrasting composition during cooling, but diffusion is much slower than in alkali feldspar, the resulting two-feldspar intergrowths are too fine-grained to be visible with optical microscopes; the immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to fine-grained exsolution lamellae.
The specific gravity in the plagioclase series increases from albite to anorthite. Chemical weathering of feldspars results in the formation of clay minerals such as illite and kaolinite. About 20 million tonnes of feldspar were produced in 2010 by three countries: Italy and China. Feldspar is a common raw material used in glassmaking, to some extent as a filler and extender in paint and rubber. In glassmaking, alumina from feldspar improves product hardness and resistance to chemical corrosion. In ceramics, the alkalis in feldspar act as a flux. Fluxes melt at an early stage in the firing process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and glass fiber. Ceramics and other uses, such as fillers, accounted for the remainder. In earth sciences and archaeology, feldspars are used for K-Ar dating, argon-argon dating, luminescence dating. In October 2012, the Mars Curiosity rover analyzed a rock that turned out to have a high feldspar content.
List of minerals – A list of minerals for which there are articles on Wikipedia List of countries by feldspar production This article incorporates public domain material from the United States Geological Survey document: "Feldspar and nepheline syenite". Bonewitz, Ronald Louis. Rock and Gem. New York: DK Publishing. ISBN 978-0-7566-3342-4. Media related to Feldspar at Wikimedia Commons
Phosphate minerals are those minerals that contain the tetrahedrally coordinated phosphate anion along with the substituting arsenate and vanadate. Chlorine and hydroxide anions that fit into the crystal structure; the phosphate class of minerals is a large and diverse group, only a few species are common. Phosphate rock is rock with high concentration of phosphate minerals, most of the apatite group, it is the major resource mined to produce phosphate fertilizers for the agriculture sector. Phosphate is used in animal feed supplements, food preservatives, anti-corrosion agents, fungicides, water treatment and metallurgy; the largest use of minerals mined for their phosphate content is the production of fertilizer. Phosphate minerals are used for control of rust and prevention of corrosion on ferrous materials applied with electrochemical conversion coatings. Phosphate minerals include: Triphylite LiPO4 Monazite PO4,rare earth metals Hinsdalite PbAl36 Pyromorphite Pb53Cl Vanadinite Pb53Cl Erythrite Co32·8H2O Amblygonite LiAlPO4F lazulite Al222 Wavellite Al323·5H2O Turquoise CuAl648·5H2O Autunite Ca22·10-12H2O Carnotite K222·3H2O Phosphophyllite Zn22•4H2O Struvite MgPO4·6H2O Xenotime-Y Y Apatite group Ca53 hydroxylapatite Ca53OH fluorapatite Ca53F chlorapatite Ca53Cl bromapatite Mitridatite group: Arseniosiderite-mitridatite series Arseniosiderite-robertsite series IMA-CNMNC proposes a new hierarchical scheme.
This list uses it to modify the classification of Nickel–Strunz. Abbreviations: "*" – discredited. "?" – questionable/doubtful. "REE" – Rare-earth element "PGE" – Platinum-group element 03. C Aluminofluorides, 06 Borates, 08 Vanadates, 09 Silicates: Neso: insular Soro: grouping Cyclo: ring Ino: chain Phyllo: sheet Tekto: three-dimensional framework Nickel–Strunz code scheme: NN. XY.##x NN: Nickel–Strunz mineral class number X: Nickel–Strunz mineral division letter Y: Nickel–Strunz mineral family letter ##x: Nickel–Strunz mineral/group number, x add-on letter 08. A Phosphates, etc. without additional anions, without H2O 08. AA With small cations: 05 Berlinite, 05 Rodolicoite. AB With medium-sized cations: 05 Farringtonite. AC With medium-sized and large cations: 10 IMA2008-054, 10 Alluaudite, 10 Hagendorfite, 10 Ferroalluaudite, 10 Maghagendorfite, 10 Varulite, 10 Ferrohagendorfite*. AD With only large cations: 05 Nahpoite, 10 Monetite, 15 Archerite, 15 Biphosphammite. 08. B Phosphates, etc. with Additional Anions, without H2O 08.
BA With small and medium-sized cations: 05 Vayrynenite. BB With only medium-sized cations,:RO4 £1:1: 05 Amblygonite, 05 Natromontebrasite?, 05 Montebrasite?, 05 Tavorite. BC With only medium-sized cations,:RO4 > 1:1 and < 2:1: 10 Plimerite, 10 Frondelite, 10 Rockbridgeite 08. BD With only medium-sized cations,:RO4 = 2:1: 05 Pseudomalachite, 05 Reichenbachite, 10 Gatehouseite, 25 Ludjibaite 08. BE With only medium-sized cations,:RO4 > 2:1: 05 Augelite, 10 Grattarolaite, 15 Cornetite, 30 Raadeite, 85 Waterhouseite 08. BF With medium-sized and large cations,:RO4 < 0.5:1: 05 Arrojadite, 05 Arrojadite-, 05 Arrojadite-, 05 Arrojadite-, 05 Arrojadite-, 05 Arrojadite-, 05 Arrojadite-, 05 Arrojadite-, 05 Fluorarrojadite-, 05 Fluorarrojadite-, 05 Fluorarrojadite-, 05 Ferri-arrojadite-, 05 Dickinsonite, 05 Dickinsonite-, 05 Dickinsonite-, 05 Dickinsonite-, 05 Dickinsonite-. BG With medium-sized and large cations,:RO4 = 0.5:1: 05 Bearthite, 05 Goedkenite, 05 Tsumebite. BH With medium-sized and large cations,:RO4 = 1:1: 05 Thadeuite.
In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how fast light propagates through the material. It is defined as n = c v, where c is the speed of light in vacuum and v is the phase velocity of light in the medium. For example, the refractive index of water is 1.333, meaning that light travels 1.333 times as fast in vacuum as in water. The refractive index determines how much the path of light is bent, or refracted, when entering a material; this is described by Snell's law of refraction, n1 sinθ1 = n2 sinθ2, where θ1 and θ2 are the angles of incidence and refraction of a ray crossing the interface between two media with refractive indices n1 and n2. The refractive indices determine the amount of light, reflected when reaching the interface, as well as the critical angle for total internal reflection and Brewster's angle; the refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is v = c/n, the wavelength in that medium is λ = λ0/n, where λ0 is the wavelength of that light in vacuum.
This implies that vacuum has a refractive index of 1, that the frequency of the wave is not affected by the refractive index. As a result, the energy of the photon, therefore the perceived color of the refracted light to a human eye which depends on photon energy, is not affected by the refraction or the refractive index of the medium. While the refractive index affects wavelength, it depends on photon frequency and energy so the resulting difference in the bending angle causes white light to split into its constituent colors; this is called dispersion. It can be observed in prisms and rainbows, chromatic aberration in lenses. Light propagation in absorbing materials can be described using a complex-valued refractive index; the imaginary part handles the attenuation, while the real part accounts for refraction. The concept of refractive index applies within the full electromagnetic spectrum, from X-rays to radio waves, it can be applied to wave phenomena such as sound. In this case the speed of sound is used instead of that of light, a reference medium other than vacuum must be chosen.
The refractive index n of an optical medium is defined as the ratio of the speed of light in vacuum, c = 299792458 m/s, the phase velocity v of light in the medium, n = c v. The phase velocity is the speed at which the crests or the phase of the wave moves, which may be different from the group velocity, the speed at which the pulse of light or the envelope of the wave moves; the definition above is sometimes referred to as the absolute refractive index or the absolute index of refraction to distinguish it from definitions where the speed of light in other reference media than vacuum is used. Air at a standardized pressure and temperature has been common as a reference medium. Thomas Young was the person who first used, invented, the name "index of refraction", in 1807. At the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers; the ratio had the disadvantage of different appearances. Newton, who called it the "proportion of the sines of incidence and refraction", wrote it as a ratio of two numbers, like "529 to 396".
Hauksbee, who called it the "ratio of refraction", wrote it as a ratio with a fixed numerator, like "10000 to 7451.9". Hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1. Young did not use a symbol for the index of refraction, in 1807. In the next years, others started using different symbols: n, m, µ; the symbol n prevailed. For visible light most transparent media have refractive indices between 1 and 2. A few examples are given in the adjacent table; these values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, as is conventionally done. Gases at atmospheric pressure have refractive indices close to 1 because of their low density. All solids and liquids have refractive indices above 1.3, with aerogel as the clear exception. Aerogel is a low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the other end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, but some high-refractive-index polymers can have values as high as 1.76.
For infrared light refractive indices can be higher. Germanium is transparent in the wavelength region from 2 to 14 µm and has a refractive index of about 4. A type of new materials, called topological insulator, was found holding higher refractive index of up to 6 in near to mid infrared frequency range. Moreover, topological insulator material are transparent; these excellent properties make them a type of significant materials for infrared optics. According to the theory of relativity, no information can travel faster than the speed of light in vacuum, but this does not mean that the refractive index cannot be lower than 1; the refractive index measures the phase velocity of light. The phase velocity is the speed at which the crests of the wave move and can be faster than the speed of light in vacuum, thereby give a refractive index below 1; this can occur close to resonance frequencies, for absorbing media, in plasmas, for X-rays. In the X-ray regime the refractive indices are
Triclinic crystal system
In crystallography, the triclinic crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. In addition, the angles between these vectors must all be different and may include 90°; the triclinic lattice is the least symmetric of the 14 three-dimensional Bravais lattices. It has the minimum symmetry all lattices have: points of inversion at each lattice point and at 7 more points for each lattice point: at the midpoints of the edges and the faces, at the center points, it is the only lattice type. The triclinic crystal system class names, Schönflies notation, Hermann-Mauguin notation, point groups, International Tables for Crystallography space group number, orbifold and space groups are listed in the table below. There are a total 2 space groups. With each only one space group is associated. Pinacoidal is known as triclinic normal. Pedial is triclinic hemihedral Mineral examples include plagioclase, rhodonite, turquoise and amblygonite, all in triclinic normal.
Crystal structure Hurlbut, Cornelius S..
South Dakota is a U. S. state in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux Native American tribes, who compose a large portion of the population and dominated the territory. South Dakota is the seventeenth largest by area, but the fifth smallest by population and the 5th least densely populated of the 50 United States; as the southern part of the former Dakota Territory, South Dakota became a state on November 2, 1889 with North Dakota. Pierre is the state capital and Sioux Falls, with a population of about 187,200, is South Dakota's largest city. South Dakota is bordered by the states of North Dakota, Iowa, Nebraska and Montana; the state is bisected by the Missouri River, dividing South Dakota into two geographically and distinct halves, known to residents as "East River" and "West River". Eastern South Dakota is home to most of the state's population, the area's fertile soil is used to grow a variety of crops. West of the Missouri, ranching is the predominant agricultural activity, the economy is more dependent on tourism and defense spending.
Most of the Native American reservations are in West River. The Black Hills, a group of low pine-covered mountains sacred to the Sioux, are in the southwest part of the state. Mount Rushmore, a major tourist destination, is there. South Dakota has a temperate continental climate, with four distinct seasons and precipitation ranging from moderate in the east to semi-arid in the west; the state's ecology features species typical of a North American grassland biome. Humans have inhabited the area for several millennia, with the Sioux becoming dominant by the early 19th century. In the late 19th century, European-American settlement intensified after a gold rush in the Black Hills and the construction of railroads from the east. Encroaching miners and settlers triggered a number of Indian wars, ending with the Wounded Knee Massacre in 1890. Key events in the 20th century included the Dust Bowl and Great Depression, increased federal spending during the 1940s and 1950s for agriculture and defense, an industrialization of agriculture that has reduced family farming.
While several Democratic senators have represented South Dakota for multiple terms at the federal level, the state government is controlled by the Republican Party, whose nominees have carried South Dakota in each of the last 13 presidential elections. Dominated by an agricultural economy and a rural lifestyle, South Dakota has sought to diversify its economy in areas to attract and retain residents. South Dakota's history and rural character still influence the state's culture. South Dakota is in the north-central United States, is considered a part of the Midwest by the U. S. Census Bureau; the culture and geography of western South Dakota have more in common with the West than the Midwest. South Dakota has a total area of 77,116 square miles, making the state the 17th largest in the Union. Black Elk Peak named Harney Peak, with an elevation of 7,242 ft, is the state's highest point, while the shoreline of Big Stone Lake is the lowest, with an elevation of 966 ft. South Dakota is bordered to the north by North Dakota.
The geographical center of the U. S. is 17 miles west of Castle Rock in Butte County. The North American continental pole of inaccessibility is between Allen and Kyle, 1,024 mi from the nearest coastline; the Missouri River is the longest river in the state. Other major South Dakota rivers include the Cheyenne, Big Sioux, White Rivers. Eastern South Dakota has many natural lakes created by periods of glaciation. Additionally, dams on the Missouri River create four large reservoirs: Lake Oahe, Lake Sharpe, Lake Francis Case, Lewis and Clark Lake. South Dakota can be divided into three regions: eastern South Dakota, western South Dakota, the Black Hills; the Missouri River serves as a boundary in terms of geographic and political differences between eastern and western South Dakota. The geography of the Black Hills, long considered sacred by Native Americans, differs from its surroundings to such an extent it can be considered separate from the rest of western South Dakota. At times the Black Hills are combined with the rest of western South Dakota, people refer to the resulting two regions divided by the Missouri River as West River and East River.
Eastern South Dakota features higher precipitation and lower topography than the western part of the state. Smaller geographic regions of this area include the Coteau des Prairies, the Dissected Till Plains, the James River Valley; the Coteau des Prairies is a plateau bordered on the east by the Minnesota River Valley and on the west by the James River Basin. Further west, the James River Basin is low, flat eroded land, following the flow of the James River through South Dakota from north to south; the Dissected Till Plains, an area of rolling hills and fertile soil that covers much of Iowa and Nebraska, extends into the southeastern corner of South Dakota. Layers deposited during the Pleistocene epoch, starting around two million years ago, cover most of eastern South Dakota; these are the youngest rock and sediment layers in the state, the product of several successive periods of glaciation which deposited a large amount of rocks and soil, known as till, over the area. The Great Plains cover most of the western two-thirds of South Dakota.
West of the Missouri Rive