1.
Metamorphic rock
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Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means change in form. The original rock is subjected to heat and pressure, causing profound physical and/or chemical change, the protolith may be a sedimentary, an igneous, or even an existing type of metamorphic rock. Metamorphic rocks make up a part of the Earths crust. They are classified by texture and by chemical and mineral assemblage and they may be formed simply by being deep beneath the Earths surface, subjected to high temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause horizontal pressure and they are also formed when rock is heated up by the intrusion of hot molten rock called magma from the Earths interior. The study of rocks provides information about the temperatures and pressures that occur at great depths within the Earths crust. Some examples of rocks are gneiss, slate, marble, schist. Metamorphic minerals are those that only at the high temperatures and pressures associated with the process of metamorphism. These minerals, known as index minerals, include sillimanite, kyanite, staurolite, andalusite, and some garnet. Other minerals, such as olivines, pyroxenes, amphiboles, micas, feldspars, and quartz, may be found in metamorphic rocks and these minerals formed during the crystallization of igneous rocks. They are stable at temperatures and pressures and may remain chemically unchanged during the metamorphic process. However, all minerals are only within certain limits. The change in the size of the rock during the process of metamorphism is called recrystallization. Both high temperatures and pressures contribute to recrystallization, high temperatures allow the atoms and ions in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact. The layering within metamorphic rocks is called foliation, and it occurs when a rock is being shortened along one axis during recrystallization. This causes the platy or elongated crystals of minerals, such as mica and chlorite and this results in a banded, or foliated rock, with the bands showing the colors of the minerals that formed them. Textures are separated into foliated and non-foliated categories, foliated rock is a product of differential stress that deforms the rock in one plane, sometimes creating a plane of cleavage. For example, slate is a metamorphic rock, originating from shale
2.
Rock (geology)
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Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a rock, is a combination of the minerals quartz, feldspar. The Earths outer solid layer, the lithosphere, is made of rock, rock has been used by mankind throughout history. The minerals and metals found in rocks have been essential to human civilization, three major groups of rocks are defined, igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is a component of geology. At a granular level, rocks are composed of grains of minerals, the aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed, many rocks contain silica, a compound of silicon and oxygen that forms 74. 3% of the Earths crust. This material forms crystals with other compounds in the rock, the proportion of silica in rocks and minerals is a major factor in determining their name and properties. Rocks are geologically classified according to such as mineral and chemical composition, permeability, the texture of the constituent particles. These physical properties are the end result of the processes that formed the rocks, over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock, igneous, sedimentary, and metamorphic, the three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks, hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. Igneous rock forms through the cooling and solidification of magma or lava and this magma can be derived from partial melts of pre-existing rocks in either a planets mantle or crust. Typically, the melting of rocks is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, igneous rocks are divided into two main categories, plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earths crust, a common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, the chemical abundance and the rate of cooling of magma typically forms a sequence known as Bowens reaction series. Most major igneous rocks are found along this scale, about 64. 7% of the Earths crust by volume consists of igneous rocks, making it the most plentiful category. Of these, 66% are basalts and gabbros, 16% are granite, only 0. 6% are syenites and 0. 3% peridotites and dunites
3.
Igneous rock
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Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava, the magma can be derived from partial melts of existing rocks in either a planets mantle or crust. Typically, the melting is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, Igneous and metamorphic rocks make up 90–95% of the top 16 km of the Earths crust by volume. Igneous rocks form about 15% of the Earths current land surface, most of the Earths oceanic crust is made of igneous rock. In terms of modes of occurrence, igneous rocks can be either intrusive or extrusive, the mineral grains in such rocks can generally be identified with the naked eye. Intrusive rocks can also be classified according to the shape and size of the intrusive body, typical intrusive formations are batholiths, stocks, laccoliths, sills and dikes. When the magma solidifies within the earths crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, the central cores of major mountain ranges consist of intrusive igneous rocks, usually granite. When exposed by erosion, these cores may occupy huge areas of the Earths surface, intrusive igneous rocks that form at depth within the crust are termed plutonic rocks and are usually coarse-grained. Intrusive igneous rocks that form near the surface are termed subvolcanic or hypabyssal rocks, hypabyssal rocks are less common than plutonic or volcanic rocks and often form dikes, sills, laccoliths, lopoliths, or phacoliths. Extrusive igneous rocks, also known as rocks, are formed at the crusts surface as a result of the partial melting of rocks within the mantle. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks and they are formed by the cooling of molten magma on the earths surface. The magma, which is brought to the surface through fissures or volcanic eruptions, hence such rocks are smooth, crystalline and fine-grained. Basalt is an extrusive igneous rock and forms lava flows, lava sheets. Some kinds of basalt solidify to form long polygonal columns, the Giants Causeway in Antrim, Northern Ireland is an example. The molten rock, with or without suspended crystals and gas bubbles, is called magma and it rises because it is less dense than the rock from which it was created. When magma reaches the surface from beneath water or air, it is called lava, eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black smokers and mid-ocean ridge basalt are examples of volcanic activity
4.
Sedimentary rock
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Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earths surface and within bodies of water. Sedimentation is the name for processes that cause mineral and/or organic particles to settle in place. The particles that form a rock by accumulating are called sediment. Sedimentation may also occur as minerals precipitate from solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earths crust is extensive, sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding, sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of rock strata is the main source for an understanding of the Earths history, including palaeogeography, paleoclimatology. The scientific discipline that studies the properties and origin of rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry, sedimentary rocks have also been found on Mars. Clastic sedimentary rocks are composed of rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, feldspar, rock fragments, clay minerals, and mica, any type of mineral may be present, clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions, gravel, sand, and mud and this tripartite subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature. The subdivision of these three categories is based on differences in clast shape, conglomerates and breccias), composition. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel, composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name. Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks, all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Clean sandstones with open space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes, six sandstone names are possible using the descriptors for grain composition and the amount of matrix. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles and these relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension
5.
Foliation (geology)
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Foliation in geology refers to repetitive layering in metamorphic rocks. Each layer may be as thin as a sheet of paper, the word comes from the Latin folium, meaning leaf, and refers to the sheet-like planar structure. It is caused by shearing forces, or differential pressure, the layers form parallel to the direction of the shear, or perpendicular to the direction of higher pressure. Nonfoliated metamorphic rocks are formed in the absence of significant differential pressure or sheer. Foliation is common in rocks affected by the regional metamorphic compression typical of areas of mountain belt formation, more technically, foliation is any penetrative planar fabric present in metamorphic rocks. Rocks exhibiting foliation include the sequence formed by the prograde metamorphism of mudrocks, slate, phyllite, schist. The slatey cleavage typical of slate is due to the orientation of microscopic phyllosilicate crystals. In gneiss the foliation is more typically represented by compositional banding due to segregation of mineral phases, foliated rock is also known as S-tectonite in sheared rock masses. Foliation is usually formed by the orientation of minerals within a rock. Usually this is a result of physical force, and its effect upon the growth of minerals. The planar fabric of a foliation typically forms at right angles to the principal strain direction. In sheared zones, however, planar fabric within a rock may not be perpendicular to the principal stress direction due to rotation, mass transport. Foliation may be formed by realignment of micas and clays via physical rotation of the minerals within the rock, often this foliation is associated with diagenetic metamorphism and low-grade burial metamorphism. Foliation may parallel original sedimentary bedding, but more often is oriented at angle to it. The growth of platy minerals, typically of the group, is usually a result of prograde metamorphic reactions during deformation. Often, retrograde metamorphism will not form a foliation because unroofing of a belt is not accompanied by significant compressive stress. Thermal metamorphism in the aureole of a granite is also unlikely to result in growth of mica in a foliation, alignment of tabular minerals in metamorphic rocks, igneous rocks and intrusive rocks may form a foliation. Typical examples of metamorphic rocks include porphyroblastic schists where large, oblate minerals form an alignment either due to growth or rotation in the groundmass, igneous rocks can become foliated by alignment of cumulate crystals during convection in large magma chambers, especially ultramafic intrusions, and typically plagioclase laths
6.
Plane (geometry)
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In mathematics, a plane is a flat, two-dimensional surface that extends infinitely far. A plane is the analogue of a point, a line. When working exclusively in two-dimensional Euclidean space, the article is used, so. Many fundamental tasks in mathematics, geometry, trigonometry, graph theory and graphing are performed in a space, or in other words. Euclid set forth the first great landmark of mathematical thought, a treatment of geometry. He selected a small core of undefined terms and postulates which he used to prove various geometrical statements. Although the plane in its sense is not directly given a definition anywhere in the Elements. In his work Euclid never makes use of numbers to measure length, angle, in this way the Euclidean plane is not quite the same as the Cartesian plane. This section is concerned with planes embedded in three dimensions, specifically, in R3. In a Euclidean space of any number of dimensions, a plane is determined by any of the following. A line and a point not on that line, a line is either parallel to a plane, intersects it at a single point, or is contained in the plane. Two distinct lines perpendicular to the plane must be parallel to each other. Two distinct planes perpendicular to the line must be parallel to each other. Specifically, let r0 be the vector of some point P0 =. The plane determined by the point P0 and the vector n consists of those points P, with position vector r, such that the vector drawn from P0 to P is perpendicular to n. Recalling that two vectors are perpendicular if and only if their dot product is zero, it follows that the plane can be described as the set of all points r such that n ⋅ =0. Expanded this becomes a + b + c =0, which is the form of the equation of a plane. This is just a linear equation a x + b y + c z + d =0 and this familiar equation for a plane is called the general form of the equation of the plane
7.
Recrystallization (geology)
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The basic composition remains the same. This process can be illustrated by observing how snow recrystallizes to ice without melting, as opposed to metasomatism, which is a chemical change caused by metamorphism, recrystallization is a physical process. However, recrystallization can occur when a local migration of chemicals results in the change of the rock or mineral with no external addition of materials. Limestone is a rock that undergoes metamorphic recrystallization to form marble
8.
Mica
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The mica group of sheet silicate minerals includes several closely related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition, the nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms. The word mica is derived from the Latin word mica, meaning a crumb, and probably influenced by micare, to glitter. Chemically, micas can be given the general formula X2Y4–6Z8O204 in which X is K, Na, or Ca or less commonly Ba, Rb, or Cs, Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc. Z is chiefly Si or Al, but also may include Fe3+ or Ti, structurally, micas can be classed as dioctahedral and trioctahedral. If the X ion is K or Na, the mica is a common mica, whereas if the X ion is Ca, mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites, until the 19th century, large crystals of mica were quite rare and expensive as a result of the limited supply in Europe. However, their price dramatically dropped when large reserves were found and mined in Africa, the largest documented single crystal of mica was found in Lacey Mine, Ontario, Canada, it measured 10 ×4.3 ×4.3 m and weighed about 330 tonnes. Similar-sized crystals were found in Karelia, Russia. The British Geological Survey reported that as of 2005, Koderma district in Jharkhand state in India had the largest deposits of mica in the world. China was the top producer of mica with almost a third of the share, closely followed by the US, South Korea. Large deposits of mica were mined in New England from the 19th century to the 1970s. Large mines existed in Connecticut, New Hampshire, and Maine, scrap and flake mica is produced all over the world. In 2010, the producers were Russia, Finland, United States, South Korea, France. The total production was 350,000 t, although no data were available for China. Most sheet mica was produced in India and Russia, flake mica comes from several sources, the metamorphic rock called schist as a byproduct of processing feldspar and kaolin resources, from placer deposits, and from pegmatites. Sheet mica is considerably less abundant than flake and scrap mica, the most important sources of sheet mica are pegmatite deposits. Sheet mica prices vary with grade and can range from less than $1 per kilogram for low-quality mica to more than $2,000 per kilogram for the highest quality, the mica group represents 37 phyllosilicate minerals that have a layered or platy texture
9.
Chlorite group
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The chlorites are a group of phyllosilicate minerals. Chlorites can be described by the following four endmembers based on their chemistry via substitution of the four elements in the silicate lattice, Mg, Fe, Ni. Clinochlore, O108 Chamosite, O108 Nimite, O108 Pennantite, 64O108 In addition, zinc, lithium, the great range in composition results in considerable variation in physical, optical, and X-ray properties. Similarly, the range of chemical composition allows chlorite group minerals to exist over a range of temperature and pressure conditions. For this reason chlorite minerals are ubiquitous minerals within low and medium temperature metamorphic rocks, some rocks, hydrothermal rocks. The name chlorite is from the Greek chloros, meaning green, the typical general formula is, 34O102·36. This formula emphasizes the structure of the group, chlorites have a 2,1 sandwich structure, this is often referred to as a talc layer. Unlike other 2,1 clay minerals, a chlorites interlayer space is composed of 6 and this 6 unit is more commonly referred to as the brucite-like layer, due to its closer resemblance to the mineral brucite. Therefore, chlorites structure appears as follows, -t-o-t-brucite-t-o-t-brucite, thats why they are also called 2,1,1 minerals. An older classification divided the chlorites into two subgroups, the orthochlorites and leptochlorites, the terms are seldom used and the ortho prefix is somewhat misleading as the chlorite crystal system is monoclinic and not orthorhombic. Chlorite is commonly found in rocks as an alteration product of mafic minerals such as pyroxene, amphibole. Chlorite is a common mineral associated with ore deposits and commonly occurs with epidote, sericite, adularia. Chlorite is also a metamorphic mineral, usually indicative of low-grade metamorphism. It is the species of the zeolite facies and of lower greenschist facies. It occurs in the quartz, albite, sericite, chlorite, within ultramafic rocks, metamorphism can also produce predominantly clinochlore chlorite in association with talc. Chlorite occurs naturally in a variety of locations and forms, for example, chlorite is found naturally in certain parts of Wales in mineral schists. Chlorite is found in large boulders scattered on the surface on Ring Mountain in Marin County. Clinoclore, pennantite, and chamosite are the most common varieties, several other sub-varieties have been described
10.
Mineral
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A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids, the study of minerals is called mineralogy. There are over 5,300 known mineral species, over 5,070 of these have been approved by the International Mineralogical Association, the silicate minerals compose over 90% of the Earths crust. The diversity and abundance of species is controlled by the Earths chemistry. Silicon and oxygen constitute approximately 75% of the Earths crust, which translates directly into the predominance of silicate minerals, minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various properties, which are related to their chemical structure. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, more specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid. Minerals are classified by key chemical constituents, the two dominant systems are the Dana classification and the Strunz classification, the silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a unit of a 4− silica tetrahedron—that is, a silicon cation coordinated by four oxygen anions. These tetrahedra can be polymerized to give the subclasses, orthosilicates, disilicates, cyclosilicates, inosilicates, phyllosilicates, other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. The first criterion means that a mineral has to form by a natural process, stability at room temperature, in the simplest sense, is synonymous to the mineral being solid. More specifically, a compound has to be stable or metastable at 25 °C, modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula, many mineral groups and species are composed of a solid solution, pure substances are not usually found because of contamination or chemical substitution. Finally, the requirement of an ordered atomic arrangement is usually synonymous with crystallinity, however, crystals are also periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage. There have been recent proposals to amend the definition to consider biogenic or amorphous substances as minerals. The formal definition of an approved by the IMA in 1995, A mineral is an element or chemical compound that is normally crystalline. However, if geological processes were involved in the genesis of the compound, Mineral classification schemes and their definitions are evolving to match recent advances in mineral science
11.
Granite
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Granite is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Granites can be white, pink, or gray in color. The word granite comes from the Latin granum, a grain, in reference to the structure of such a holocrystalline rock. By definition, granite is a rock with at least 20% quartz. The term granitic means granite-like and is applied to granite and a group of igneous rocks with similar textures and slight variations in composition. Occasionally some individual crystals are larger than the groundmass, in case the texture is known as porphyritic. A granitic rock with a texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks, petrographic examination is required for identification of specific types of granitoids. The extrusive igneous rock equivalent of granite is rhyolite, Granite is nearly always massive, hard and tough, and therefore it has gained widespread use throughout human history, and more recently as a construction stone. The average density of granite is between 2.65 and 2.75 g/cm3, its compressive strength usually lies above 200 MPa, and its viscosity near STP is 3–6 •1019 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C, it is reduced in the presence of water. Granite has poor primary permeability, but strong secondary permeability, true granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite, when a granitoid contains less than 10% orthoclase, it is called tonalite, pyroxene and amphibole are common in tonalite. A granite containing both muscovite and biotite micas is called a binary or two-mica granite, two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. A worldwide average of the composition of granite, by weight percent, based on 2485 analyses. Much of it was intruded during the Precambrian age, it is the most abundant basement rock that underlies the relatively thin veneer of the continents. Outcrops of granite tend to form tors and rounded massifs, granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. Granite often occurs as small, less than 100 km² stock masses
12.
Diorite
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Diorite is an intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar, biotite, hornblende, and/or pyroxene. The chemical composition of diorite is intermediate, between that of gabbro and felsic granite. Diorite is usually grey to dark-grey in colour, but it can also be black or bluish-grey and it is distinguished from gabbro on the basis of the composition of the plagioclase species, the plagioclase in diorite is richer in sodium and poorer in calcium. Diorite may contain small amounts of quartz, microcline, and olivine, zircon, apatite, titanite, magnetite, ilmenite, and sulfides occur as accessory minerals. Minor amounts of muscovite may also be present, varieties deficient in hornblende and other dark minerals are called leucodiorite. When olivine and more iron-rich augite are present, the grades into ferrodiorite. The presence of significant quartz makes the rock type quartz-diorite or tonalite, and if orthoclase is present at greater than 10 percent, a dioritic rock containing feldspathoid mineral/s and no quartz is termed foid-bearing diorite or foid diorite according to content. Diorite has a phaneritic, often speckled, texture of coarse grain size and is occasionally porphyritic, orbicular diorite shows alternating concentric growth bands of plagioclase and amphibole surrounding a nucleus, within a diorite porphyry matrix. Diorites may be associated with granite or gabbro intrusions, into which they may subtly merge. Diorite results from the melting of a mafic rock above a subduction zone. It is commonly produced in volcanic arcs, and in mountain building, such as in the Andes Mountains. The extrusive volcanic equivalent rock type is andesite, diorite is an extremely hard rock, making it difficult to carve grand work with. It is so hard that ancient civilizations used diorite balls to work granite and its hardness, however, also allows it to be worked finely and take a high polish, and to provide a durable finished work. One comparatively frequent use of diorite was for inscription, as it is easier to carve in relief than in three-dimensional statuary, perhaps the most famous diorite work extant is the Code of Hammurabi, inscribed upon a 2.23 m pillar of black diorite. The original can be today in Paris Musée du Louvre. The use of diorite in art was most important among very early Middle Eastern civilizations such as Ancient Egypt, Babylonia, Assyria, and Sumer. It was so valued in early times that the first great Mesopotamian empire—the Empire of Sargon of Akkad—listed the taking of diorite as a purpose of military expeditions. Although one can find diorite art from later periods, it more popular as a structural stone and was frequently used as pavement due to its durability
13.
Garnet
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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, the different species are pyrope, almandine, spessartine, grossular, uvarovite and andradite. The garnets make up two solid solution series, pyrope-almandine-spessartine and uvarovite-grossular-andradite, the word garnet comes from the 14th‑century Middle English word gernet, meaning dark red. It is derived from the Latin granatus, from granum, Garnet species are found in many colors including red, orange, yellow, green, purple, brown, blue, black, pink, and colorless, with reddish shades most common. Garnet species light transmission properties can range from the gemstone-quality transparent specimens to the varieties used for industrial purposes as abrasives. The minerals luster is categorized as vitreous or resinous, garnets are nesosilicates having the general formula X3Y23. The X site is occupied by divalent cations 2+ and the Y site by trivalent cations 3+ in an octahedral/tetrahedral framework with 4− occupying the tetrahedra. Garnets are most often found in the crystal habit, but are also commonly found in the trapezohedron habit. They crystallize in the system, having three axes that are all of equal length and perpendicular to each other. Garnets do not show cleavage, so when they fracture under stress, because the chemical composition of garnet varies, the atomic bonds in some species are stronger than in others. As a result, this group shows a range of hardness on the Mohs scale of about 6.5 to 7.5. The harder species like almandine are often used for abrasive purposes, for gem identification purposes, a pick-up response to a strong neodymium magnet separates garnet from all other natural transparent gemstones commonly used in the jewelry trade. Almandine, Fe3Al23 Pyrope, Mg3Al23 Spessartine, Mn3Al23 Almandine, sometimes incorrectly called almandite, is the modern gem known as carbuncle, the term carbuncle is derived from the Latin meaning live coal or burning charcoal. The name Almandine is a corruption of Alabanda, a region in Asia Minor where these stones were cut in ancient times, chemically, almandine is an iron-aluminium garnet with the formula Fe3Al23, the deep red transparent stones are often called precious garnet and are used as gemstones. Almandine occurs in metamorphic rocks like mica schists, associated with such as staurolite, kyanite, andalusite. Almandine has nicknames of Oriental garnet, almandine ruby, and carbuncle, Pyrope is red in color and chemically an aluminium silicate with the formula Mg3Al23, though the magnesium can be replaced in part by calcium and ferrous iron. The color of pyrope varies from red to black. A variety of pyrope from Macon County, North Carolina is a shade and has been called rhodolite
14.
Biotite
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Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K 3AlSi 3O102. Hausmann in 1847 in honor of the French physicist Jean-Baptiste Biot, iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called iron mica because it is more iron-rich than phlogopite and it is also sometimes called black mica as opposed to white mica – both form in some rocks, and in some instances side-by-side. Like other mica minerals, biotite has a perfect basal cleavage, and consists of flexible sheets, or lamellae. It has a crystal system, with tabular to prismatic crystals with an obvious pinacoid termination. It has four faces and two pinacoid faces to form a pseudohexagonal crystal. Although not easily seen because of the cleavage and sheets, fracture is uneven and it appears greenish to brown or black, and even yellow when weathered. It can be transparent to opaque, has a vitreous to pearly luster, when biotite is found in large chunks, they are called “books” because it resembles a book with pages of many sheets. The color of biotite is usually black and the mineral has a hardness of 2. 5-3 on the Mohs scale of mineral hardness, biotite dissolves in both acid and alkaline aqueous solutions, with the highest dissolution rates at low pH. However, biotite dissolution is highly anisotropic with crystal edge surfaces reacting 45 to 132 times faster than basal surfaces, under cross-polarized light biotite can generally be identified by the gnarled birds eye extinction. Biotite is found in a variety of igneous and metamorphic rocks. For instance, biotite occurs in the lava of Mount Vesuvius, biotite in granite tends to be poorer in magnesium than the biotite found in its volcanic equivalent, rhyolite. Biotite is an essential phenocryst in some varieties of lamprophyre, biotite is occasionally found in large cleavable crystals, especially in pegmatite veins, as in New England, Virginia and North Carolina. Other notable occurrences include Bancroft and Sudbury, Ontario and it is an essential constituent of many metamorphic schists, and it forms in suitable compositions over a wide range of pressure and temperature. It has been estimated that biotite comprises up to 7% of the continental crust. The largest documented single crystals of biotite were approximately 7 m2 sheets found in Iveland, biotite is used extensively to constrain ages of rocks, by either potassium-argon dating or argon-argon dating. Because argon escapes readily from the crystal structure at high temperatures. Biotite is also useful in assessing temperature histories of metamorphic rocks, because the partitioning of iron and magnesium between biotite and garnet is sensitive to temperature
15.
Albite
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Albite is a plagioclase feldspar mineral. It is the sodium endmember of the solid solution series. As such it represents a plagioclase with less than 10% anorthite content, the pure albite endmember has the formula NaAlSi3O8. Its color is pure white, hence its name from Latin albus. It is a constituent in felsic rocks. Albite crystallizes with triclinic pinacoidal forms and its specific gravity is about 2.62 and it has a Mohs hardness of 6 -6.5. Albite almost always exhibits crystal twinning often as minute parallel striations on the crystal face, Albite often occurs as fine parallel segregations alternating with pink microcline in perthite as a result of exolution on cooling. There are two variants of albite, which are referred to as low albite and high albite, the latter is known as analbite. Although both variants are triclinic, they differ in the volume of their cell, which is slightly larger for the high form. The high form can be produced from the low form by heating above c.750 °C, upon further heating to more than c.1050 °C the crystal symmetry changes from triclinic to monoclinic, this variant is also known as monalbite. It occurs in granitic and pegmatite masses, in hydrothermal vein deposits. It was first reported in 1815 for an occurrence in Finnbo, Falun, Dalarna and it is used as a gemstone. Mineral galleries This article incorporates text from a now in the public domain, Chisholm, Hugh
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Mafic
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Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, common mafic rocks include basalt, dolerite and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar, chemically, mafic rocks are on the other side of the rock spectrum from the felsic rocks. The term roughly corresponds to the basic rock class. Mafic lava, before cooling, has a low viscosity, in comparison to felsic lava, water and other volatiles can more easily and gradually escape from mafic lava. As a result, eruptions of volcanoes made of mafic lavas are less violent than felsic-lava eruptions. Most mafic-lava volcanoes are shield volcanoes, like those in Hawaii, QAPF diagram List of minerals List of rock types
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Magnesium
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Magnesium is a chemical element with symbol Mg and atomic number 12. Magnesium is the ninth most abundant element in the universe and it is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus. When such stars explode as supernovas, much of the magnesium is expelled into the medium where it may recycle into new star systems. Magnesium is the eighth most abundant element in the Earths crust and the fourth most common element in the Earth, making up 13% of the planets mass and it is the third most abundant element dissolved in seawater, after sodium and chlorine. Magnesium occurs naturally only in combination with elements, where it invariably has a +2 oxidation state. The free element can be produced artificially, and is highly reactive, the free metal burns with a characteristic brilliant-white light. The metal is now obtained mainly by electrolysis of magnesium salts obtained from brine, Magnesium is less dense than aluminium, and the alloy is prized for its combination of lightness and strength. Magnesium is the eleventh most abundant element by mass in the body and is essential to all cells. Magnesium ions interact with polyphosphate compounds such as ATP, DNA, hundreds of enzymes require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids, elemental magnesium is a gray-white lightweight metal, two-thirds the density of aluminium. Magnesium has the lowest melting and the lowest boiling point 1,363 K of all the alkaline earth metals, Magnesium reacts with water at room temperature, though it reacts much more slowly than calcium, a similar group 2 metal. When submerged in water, hydrogen bubbles form slowly on the surface of the metal—though, if powdered, the reaction occurs faster with higher temperatures. Magnesiums reversible reaction with water can be harnessed to store energy, Magnesium also reacts exothermically with most acids such as hydrochloric acid, producing the metal chloride and hydrogen gas, similar to the HCl reaction with aluminium, zinc, and many other metals. Magnesium is highly flammable, especially when powdered or shaved into thin strips, flame temperatures of magnesium and magnesium alloys can reach 3,100 °C, although flame height above the burning metal is usually less than 300 mm. Once ignited, such fires are difficult to extinguish, with combustion continuing in nitrogen, carbon dioxide, Magnesium may also be used as an igniter for thermite, a mixture of aluminium and iron oxide powder that ignites only at a very high temperature. When burning in air, magnesium produces a light that includes strong ultraviolet wavelengths. Magnesium powder was used for illumination in the early days of photography. Later, magnesium filament was used in electrically ignited single-use photography flashbulbs, Magnesium powder is used in fireworks and marine flares where a brilliant white light is required
18.
Iron
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Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is also the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, and transport in plasma. The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have also been studied extensively
19.
Felsic
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In geology, felsic refers to igneous rocks that are relatively rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are richer in magnesium. It refers to those rocks rich in minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium. They are usually light in color and have specific gravities less than 3, the most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars, in terms of chemistry, felsic minerals and rocks are at the other end of the elemental spectrum from the mafic minerals and rocks. In modern usage, the acid rock, although sometimes used as a synonym, refers to a high-silica-content volcanic rock. The term was used broadly in older geologic literature. It is considered archaic now, as the acidic and basic rock were based on an incorrect idea, dating from the 19th century. The term felsic combines the words feldspar and silica, in order for a rock to be classified as felsic, it generally needs to contain more than 75% felsic minerals, namely quartz, orthoclase and plagioclase. Rocks with greater than 90% felsic minerals can also be called leucocratic, the chemical name of a felsic rock is given according to the TAS classification of Le Maitre. However, this applies to volcanic rocks. If the rock is analyzed and found to be felsic but is metamorphic and has no definite volcanic protolith, there are examples known of highly sheared granites which can be mistaken for rhyolites. For phaneritic felsic rocks, the QAPF diagram should be used, the rock texture thus determines the basic name of a felsic rock. QAPF diagram List of minerals List of rock types Le Maitre, igneous Rocks, A Classification and Glossary of Terms 2nd edition, Cambridge
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Silicate minerals
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Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of rock-forming minerals and they are classified based on the structure of their silicate groups, which contain different ratios of silicon and oxygen. Nesosilicates, or orthosilicates, have the orthosilicate ion, which constitute isolated 4− tetrahedra that are connected only by interstitial cations and these exist as 3-member 6− and 6-member 12− rings, where T stands for a tetrahedrally coordinated cation. Inosilicates, or chain silicates, have interlocking chains of silicate tetrahedra with either SiO3,1,3 ratio, for single chains or Si4O11,4,11 ratio, for double chains. Nickel–Strunz classification,09. D Pyroxene group Enstatite – orthoferrosilite series Enstatite – MgSiO3 Ferrosilite – FeSiO3 Pigeonite – Ca0.251, all phyllosilicate minerals are hydrated, with either water or hydroxyl groups attached. Serpentine subgroup Antigorite – Mg3Si2O54 Chrysotile – Mg3Si2O54 Lizardite – Mg3Si2O54 Clay minerals group Halloysite – Al2Si2O54 Kaolinite – Al2Si2O54 Illite – 24O10 Montmorillonite –0 and this group comprises nearly 75% of the crust of the Earth. Tectosilicates, with the exception of the group, are aluminosilicates. Nickel–Strunz classification,09. F and 09. G,04. A, an introduction to the rock-forming minerals. Wise, W. S. Zussman, J. Rock-forming minerals, P.982 pp. Hurlbut, Cornelius S. Danas Manual of Mineralogy. Mindat. org, Dana classification Webmineral, Danas New Silicate Classification Media related to Silicates at Wikimedia Commons
21.
Plasticity (physics)
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In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. In engineering, the transition from elastic behavior to plastic behavior is called yield, plastic deformation is observed in most materials, particularly metals, soils, rocks, concrete, foams, bone and skin. However, the mechanisms that cause plastic deformation can vary widely. At a crystalline scale, plasticity in metals is usually a consequence of dislocations, such defects are relatively rare in most crystalline materials, but are numerous in some and part of their crystal structure, in such cases, plastic crystallinity can result. In brittle materials such as rock, concrete and bone, plasticity is caused predominantly by slip at microcracks, for many ductile metals, tensile loading applied to a sample will cause it to behave in an elastic manner. Each increment of load is accompanied by an increment in extension. When the load is removed, the returns to its original size. However, once the load exceeds a threshold – the yield strength – the extension increases more rapidly than in the region, now when the load is removed. Elastic deformation, however, is an approximation and its quality depends on the time frame considered, if, as indicated in the graph opposite, the deformation includes elastic deformation, it is also often referred to as elasto-plastic deformation or elastic-plastic deformation. Perfect plasticity is a property of materials to undergo irreversible deformation without any increase in stresses or loads, plastic materials with hardening necessitate increasingly higher stresses to result in further plastic deformation. Generally, plastic deformation is dependent on the deformation speed. Such materials are said to deform visco-plastically, the plasticity of a material is directly proportional to the ductility and malleability of the material. Plasticity in a crystal of pure metal is primarily caused by two modes of deformation in the lattice, slip and twinning. Slip is a deformation which moves the atoms through many interatomic distances relative to their initial positions. Twinning is the plastic deformation takes place along two planes due to a set of forces applied to a given metal piece. Most metals show more plasticity when hot than when cold, lead shows sufficient plasticity at room temperature, while cast iron does not possess sufficient plasticity for any forging operation even when hot. This property is of importance in forming, shaping and extruding operations on metals, most metals are rendered plastic by heating and hence shaped hot
22.
Sandstone
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Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension. The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar. Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone
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Shale
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Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable, shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. Mudstones, on the hand, are similar in composition. Before the mid 19th century, the slate, shale. In the context of underground mining, shale was frequently referred to as slate well into the 20th century. Non-fissile rocks of similar composition but made of smaller than 0.06 mm are described as mudstones or claystone. Rocks with similar sizes but with less clay and therefore grittier are siltstones. Shale is the most common sedimentary rock, shales are typically composed of variable amounts of clay minerals and quartz grains and the typical color is gray. Addition of variable amounts of minor constituents alters the color of the rock, black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Black shale can also be referred to as black metal, red, brown and green colors are indicative of ferric oxide, iron hydroxide, or micaceous minerals. Clays are the constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite, clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid- to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and these released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor minerals found in shales and other mudrocks. Shales and mudrocks contain roughly 95 percent of the matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale, black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron and sulfur. Pyrite and amorphous iron sulfide along with carbon produce the black coloration, the process in the rock cycle which forms shale is called compaction. The fine particles that compose shale can remain suspended in long after the larger particles of sand have deposited. Shales are typically deposited in very slow moving water and are found in lakes and lagoonal deposits, in river deltas, on floodplains
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Quartzite
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Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure related to tectonic compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in shades of pink. Other colors, such as yellow, green, blue and orange, are due to other minerals, when sandstone is cemented to quartzite, the individual quartz grains recrystallize along with the former cementing material to form an interlocking mosaic of quartz crystals. Most or all of the texture and sedimentary structures of the sandstone are erased by the metamorphism. The grainy, sandpaper-like surface becomes glassy in appearance, minor amounts of former cementing materials, iron oxide, silica, carbonate and clay, often migrate during recrystallization and metamorphosis. This causes streaks and lenses to form within the quartzite, orthoquartzite is a very pure quartz sandstone composed of usually well-rounded quartz grains cemented by silica. Orthoquartzite is often 99% SiO2 with only minor amounts of iron oxide and trace resistant minerals such as zircon, rutile. Although few fossils are present, the original texture and sedimentary structures are preserved. The term is traditionally used for quartz-cemented quartz arenites. Quartzite is very resistant to weathering and often forms ridges. The nearly pure silica content of the rock provides little for soil, therefore, because of its hardness and angular shape, crushed quartzite is often used as railway ballast. Quartzite is a stone and may be used to cover walls, as roofing tiles, as flooring. Its use for countertops in kitchens is expanding rapidly and it is harder and more resistant to stains than granite. Crushed quartzite is used in road construction. High purity quartzite is used to produce ferrosilicon, industrial silica sand, during the Paleolithic quartzite was used, in addition to flint, quartz, and other lithic raw materials, for making stone tools. Quartzite is also found in the Morenci Copper Mine in Arizona, the town of Quartzsite in western Arizona derives its name from the quartzites in the nearby mountains in both Arizona and Southeastern California. A glassy vitreous quartzite has been described from the Belt Supergroup in the Coeur d’Alene district of northern Idaho, in the United Kingdom, a craggy ridge of quartzite called the Stiperstones runs parallel with the Pontesford-Linley fault,6 km north-west of the Long Mynd in south Shropshire
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Kyanite
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Kyanite is a typically blue silicate mineral, commonly found in aluminium-rich metamorphic pegmatites and/or sedimentary rock. Kyanite in metamorphic rocks generally indicates pressures higher than four kilobars, kyanite is also known as disthene, rhaeticite and cyanite. Kyanite is a member of the series, which also includes the polymorph andalusite. Kyanite is strongly anisotropic, in that its hardness varies depending on its crystallographic direction, in kyanite, this anisotropism can be considered an identifying characteristic. At temperatures above 1100 °C kyanite decomposes into mullite and vitreous silica via the reaction,3 → 3Al2O3·2SiO2 + SiO2. This transformation results in an expansion and its name comes from the same origin as that of the color cyan, being derived from the Ancient Greek word κύανος. This is generally rendered into English as kyanos or kuanos and means dark blue, kyanite is used primarily in refractory and ceramic products, including porcelain plumbing fixtures and dishware. It is also used in electronics, electrical insulators and abrasives, kyanite has been used as a semiprecious gemstone, which may display cats eye chatoyancy, though this use is limited by its anisotropism and perfect cleavage. Color varieties include recently discovered orange kyanite from Tanzania, the orange color is due to inclusion of small amounts of manganese in the structure. Kyanite is one of the minerals that are used to estimate the temperature, depth. Kyanites elongated, columnar crystals are usually a good first indication of the mineral, associated minerals are useful as well, especially the presence of the polymorphs of staurolite, which occur frequently with kyanite. However, the most useful characteristic in identifying kyanite is its anisotropism, kyanite occurs in gneiss, schist, pegmatite, and quartz veins resulting from high pressure regional metamorphism of principally pelitic rocks. It occurs as detrital grains in sedimentary rocks and it occurs associated with staurolite, andalusite, sillimanite, talc, hornblende, gedrite, mullite and corundum. Kyanite occurs in Manhattan schist, formed under extreme pressure as a result of the two landmasses that formed supercontinent Pangaea
26.
Matrix (geology)
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The matrix or groundmass of rock is the finer-grained mass of material wherein larger grains, crystals or clasts are embedded. The matrix of an igneous rock consists of finer-grained, often microscopic and this porphyritic texture is indicative of multi-stage cooling of magma. For example, porphyritic andesite will have large phenocrysts of plagioclase in a fine-grained matrix, also in South Africa, diamonds are often mined from a matrix of weathered clay-like rock called yellow ground. The matrix of sedimentary rocks is finer-grained sedimentary material, such as clay or silt and it also used to describe the rock material in which a fossil is embedded. All sediments are at first in an incoherent condition, and in this state they may remain for an indefinite period. Millions of years have elapsed since some of the early Tertiary strata gathered on the floor, yet they are quite friable. The pressure of newer sediments on underlying masses is one cause of this change. More efficiency is generally ascribed to the action of percolating water, the redeposited cementing material is most commonly calcareous or siliceous. Limestones, which were originally a loose accumulation of shells, corals, the change of aragonite to calcite and of calcite to dolomite, by forming new crystalline masses in the interior of the rock, usually also accelerates consolidations. Silica is less soluble in ordinary waters, but even this ingredient of rocks is dissolved and redeposited with great frequency. Others contain fine scales of kaolin or of mica, argillaceous materials may be compacted by mere pressure, like graphite and other scaly minerals
27.
Augen
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Augen are large, lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. In cross section they have the shape of an eye, feldspar, quartz, and garnet are common minerals which form augen. Augen form in rocks which have undergone metamorphism and shearing, the core of the augen is a porphyroblast or porphyroclast of a hard, resilient mineral such as garnet. The augen grows by crystallisation of a mantle of new mineral around the porphyroblast, the mantle is formed contiguous with the foliation which is imparted upon the rock, and forms a blanket which tapers off from either side of the porphyroblast within the strain shadows. During shearing, the poprhyroblast may rotate, to form a characteristic texture of asymmetric shearing. In this case, the position of the tails is unequal across the foliation and this derives a form of shear direction information. A metamorphic rock which is clotted with augen is often called an augen gneiss, a long wall of this augen gneiss can be felt at the Mineral and Lapidary Museum of Western North Carolina. Foliation Gneiss Rock microstructure Schist Shear
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German language
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German is a West Germanic language that is mainly spoken in Central Europe. It is the most widely spoken and official language in Germany, Austria, Switzerland, South Tyrol, the German-speaking Community of Belgium and it is also one of the three official languages of Luxembourg. Major languages which are most similar to German include other members of the West Germanic language branch, such as Afrikaans, Dutch, English, Luxembourgish and it is the second most widely spoken Germanic language, after English. One of the languages of the world, German is the first language of about 95 million people worldwide. The German speaking countries are ranked fifth in terms of publication of new books. German derives most of its vocabulary from the Germanic branch of the Indo-European language family, a portion of German words are derived from Latin and Greek, and fewer are borrowed from French and English. With slightly different standardized variants, German is a pluricentric language, like English, German is also notable for its broad spectrum of dialects, with many unique varieties existing in Europe and also other parts of the world. The history of the German language begins with the High German consonant shift during the migration period, when Martin Luther translated the Bible, he based his translation primarily on the standard bureaucratic language used in Saxony, also known as Meißner Deutsch. Copies of Luthers Bible featured a long list of glosses for each region that translated words which were unknown in the region into the regional dialect. Roman Catholics initially rejected Luthers translation, and tried to create their own Catholic standard of the German language – the difference in relation to Protestant German was minimal. It was not until the middle of the 18th century that a widely accepted standard was created, until about 1800, standard German was mainly a written language, in urban northern Germany, the local Low German dialects were spoken. Standard German, which was different, was often learned as a foreign language with uncertain pronunciation. Northern German pronunciation was considered the standard in prescriptive pronunciation guides though, however, German was the language of commerce and government in the Habsburg Empire, which encompassed a large area of Central and Eastern Europe. Until the mid-19th century, it was essentially the language of townspeople throughout most of the Empire and its use indicated that the speaker was a merchant or someone from an urban area, regardless of nationality. Some cities, such as Prague and Budapest, were gradually Germanized in the years after their incorporation into the Habsburg domain, others, such as Pozsony, were originally settled during the Habsburg period, and were primarily German at that time. Prague, Budapest and Bratislava as well as cities like Zagreb, the most comprehensive guide to the vocabulary of the German language is found within the Deutsches Wörterbuch. This dictionary was created by the Brothers Grimm and is composed of 16 parts which were issued between 1852 and 1860, in 1872, grammatical and orthographic rules first appeared in the Duden Handbook. In 1901, the 2nd Orthographical Conference ended with a standardization of the German language in its written form
29.
Porphyroclast
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A porphyroclast is a clast or mineral fragment in a metamorphic rock, surrounded by a groundmass of finer grained crystals. Porphyroclasts are fragments of the rock before dynamic recrystallisation or cataclasis produced the groundmass. This means they are older than the groundmass and they were stronger pieces of the original rock, that could not as easily deform and were therefore not or hardly affected by recrystallisation. They may have been phenocrysts or porphyroblasts in the original rock, porphyroclasts are often confused with porphyroblasts. The latter are large crystals in a finer matrix, but they grew during, or after deformation took place. The timing of porphyroblast growth can be determined by examining the microstructure preserved within them as poikiloblasts, in strongly deformed rocks porphyroclasts are often rotated by the shear stress in the rock. Their shape can be used to determine the direction of the shear, where porphyroclasts have rims made of finer grained crystals, they are referred to as porphyroclast systems. The geometries of porphyroclast systems can be used to determine the sense of shear within a shear zone
30.
Microcline
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Microcline is an important igneous rock-forming tectosilicate mineral. It is an alkali feldspar. Microcline typically contains minor amounts of sodium and it is common in granite and pegmatites. Microcline forms during cooling of orthoclase, it is more stable at lower temperatures than orthoclase. Sanidine is a polymorph of alkali feldspar stable at yet higher temperature and it is a fully ordered triclinic modification of potassium feldspar and is dimorphous with orthoclase. Perthite is either microcline or orthoclase with thin lamellae of exsolved albite, Amazon stone, or amazonite, is a green variety of microcline. It is not found anywhere in the Amazon Basin, however, the Spanish explorers who named it apparently confused it with another green mineral from that region. The largest documented single crystals of microcline were found in Devils Hole Beryl Mine, Colorado, US and this could be one of the largest crystals of any material found so far. Microcline is commonly used for the manufacturing of porcelain, list of minerals Alkali feldspars U
31.
North Carolina
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North Carolina is a state in the southeastern region of the United States. The state borders South Carolina and Georgia to the south, Tennessee to the west, Virginia to the north, North Carolina is the 28th most extensive and the 9th most populous of the U. S. states. The state is divided into 100 counties, the most populous municipality is Charlotte, which is the second largest banking center in the United States after New York City. The state has a range of elevations, from sea level on the coast to 6,684 feet at Mount Mitchell. The climate of the plains is strongly influenced by the Atlantic Ocean. Most of the falls in the humid subtropical climate zone. More than 300 miles from the coast, the western, mountainous part of the state has a highland climate. North Carolina is bordered by South Carolina on the south, Georgia on the southwest, Tennessee on the west, Virginia on the north, the United States Census Bureau places North Carolina in the South Atlantic division of the southern region. So many ships have been lost off Cape Hatteras that the area is known as the Graveyard of the Atlantic, the most famous of these is the Queen Annes Revenge, which went aground in Beaufort Inlet in 1718. The coastal plain transitions to the Piedmont region along the Atlantic Seaboard fall line, the Piedmont region of central North Carolina is the states most populous region, containing the six largest cities in the state by population. It consists of rolling countryside frequently broken by hills or low mountain ridges. The Piedmont ranges from about 300 feet in elevation in the east to about 1,500 feet in the west, the western section of the state is part of the Appalachian Mountain range. Among the subranges of the Appalachians located in the state are the Great Smoky Mountains, Blue Ridge Mountains, the Black Mountains are the highest in the eastern United States, and culminate in Mount Mitchell at 6,684 feet, the highest point east of the Mississippi River. North Carolina has 17 major river basins, the five basins west of the Blue Ridge Mountains flow to the Gulf of Mexico, while the remainder flow to the Atlantic Ocean. Of the 17 basins,11 originate within the state of North Carolina, but only four are contained entirely within the states border – the Cape Fear, the Neuse, the White Oak, and the Tar-Pamlico basin. Elevation above sea level is most responsible for temperature change across the state, the climate is also influenced by the Atlantic Ocean and the Gulf Stream, especially in the coastal plain. These influences tend to cause warmer winter temperatures along the coast, the coastal plain averages around 1 inch of snow or ice annually, and in many years, there may be no snow or ice at all. North Carolina experiences severe weather in summer and winter, with summer bringing threat of hurricanes, tropical storms, heavy rain
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South Carolina
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South Carolina /ˌsaʊθ kærəˈlaɪnə/ is a state in the southeastern region of the United States. The state is bordered to the north by North Carolina, to the south and west by Georgia across the Savannah River, South Carolina became the eighth state to ratify the U. S. Constitution, doing so on May 23,1788. South Carolina became the first state to vote to secede from the Union on December 20,1860, after the American Civil War, it was readmitted into the United States on June 25,1868. South Carolina is the 40th most extensive and the 23rd most populous U. S. state and its GDP as of 2013 was $183.6 billion, with an annual growth rate of 3. 13%. The capital and largest city is Columbia with a 2013 population of 133,358, South Carolina is named in honor of King Charles I of England, under whose reign the English colony was first formed, with Carolus being Latin for Charles. There is evidence of activity in the area about 12000 years ago. Along the Savannah River were the Apalachee, Yuchi, and the Yamasee, further west were the Cherokee, and along the Catawba River, the Catawba. These tribes were village-dwellers, relying on agriculture as their food source. The Cherokee lived in wattle and daub houses made with wood and clay, about a dozen separate small tribes summered on the coast harvesting oysters and fish, and cultivating corn, peas and beans. Travelling inland as much as 50 miles mostly by canoe, they wintered on the plain, hunting deer and gathering nuts. The names of these survive in place names like Edisto Island, Kiawah Island. The Spanish were the first Europeans in the area, in 1521, founding San Miguel de Gualdape, established with 500 settlers, it was abandoned within a year by 150 survivors. In 1562 French settlers established a settlement at what is now the Charlesfort-Santa Elena archaeological site on Parris Island, three years later the Spanish built a fort on the same site, but withdrew following hostilities with the English navy. In 1629, King Charles I of England established the Province of Carolina an area covering what is now South and North Carolina, Georgia, in the 1670s, English planters from the Barbados established themselves near what is now Charleston. Settlers built rice plantations in the South Carolina Lowcountry, east of the Atlantic Seaboard fall line, settlers came from all over Europe. Plantation labor was done by African slaves who formed the majority of the population by 1720, another cash crop was the Indigo plant, a plant source of blue dye, developed by Eliza Lucas. Meanwhile, in Upstate South Carolina, west of the Fall Line, was settled by farmers and traders. Colonists overthrew the rule, seeing more direct representation
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Amphibolite
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Amphibolite is a metamorphic rock that contains amphibole, especially the species hornblende and actinolite, as well as plagioclase. A holocrystalline plutonic igneous rock composed primarily of hornblende amphibole is called a hornblendite, rocks with >90% amphiboles which have a feldspar groundmass may be a lamprophyre. Amphibolite is a grouping of rocks composed mainly of amphibole and plagioclase feldspars and it is typically dark-colored and heavy, with a weakly foliated or schistose structure. The small flakes of black and white in the rock often give it a salt-and-pepper appearance, amphibolites need not be derived from metamorphosed mafic rocks. Because metamorphism creates minerals based entirely upon the chemistry of the protolith, certain dirty marls, deposits containing dolomite and siderite also readily yield amphibolites especially where there has been a certain amount of contact metamorphism by adjacent granitic masses. Metamorphosed basalts create ortho-amphibolites and other chemically appropriate lithologies create para-amphibolites, tremolite, while it is a metamorphic amphibole, is derived most usually from highly metamorphosed ultramafic rocks, and thus tremolite-talc schists are not generally considered as amphibolites. If the amphibolite appears to transgress apparent protolith bedding surfaces it is an ortho-amphibolite, picking a sill and thin metamorphosed lava flows may be more troublesome. Thereafter, whole rock geochemistry will suitably identify ortho- from para-amphibolites, the word metabasalt was thus coined, largely to avoid the confusion between ortho-amphibolites and para-amphibolites. While not a metamorphic rock name, as it infers an origin. Amphibolites define a set of temperature and pressure conditions known as the amphibolite facies. However, caution must be applied here before embarking on metamorphic mapping based on amphibolites alone. Firstly, for an amphibolite to be classed as a metamorphic amphibolite, it must be certain that the amphibole in the rock is a prograde metamorphic product, for instance, actinolite amphibole is a common product of retrograde metamorphism of basalts at greenschist facies conditions. Actinolite schists are often the result of alteration or metasomatism. Secondly, the microstructure and crystal size of the rock must be appropriate, amphibolite facies conditions are experienced at temperatures in excess of 500 °C and pressures less than 1.2 GPa, well within the ductile deformation field. Gneissic texture may occur nearby, if not then mylonite zones, foliations and ductile behaviour, while it is not impossible to have remnant protolith mineralogy, this is rare. More common is to find phenocrysts of pyroxene, olivine, plagioclase and even magmatic amphibole such as pargasite rhombohedra, original magmatic textures, especially crude magmatic layering in layered intrusions, is often preserved. Amphibolite facies is a result of continuing burial and thermal heating after greenschist facies is exceeded, in dry rocks, however, additional heat may result in granulite facies conditions. The texture is distinctive, the pyroxene altered to fuzzy, radially arranged actinolite pseudomorphically after pyroxene, the archaic term epidiorite is sometimes used to refer to a metamorphosed ortho-amphibolite with a protolith of diorite, gabbro or other mafic intrusive rock
34.
Diabase
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Diabase or dolerite or microgabbro is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine grained to aphanitic chilled margins which may contain tachylite. Diabase normally has a fine, but visible texture of euhedral lath-shaped plagioclase crystals set in a matrix of clinopyroxene, typically augite, with minor olivine, magnetite. Accessory and alteration minerals include hornblende, biotite, apatite, pyrrhotite, chalcopyrite, serpentine, chlorite, the texture is termed diabasic and is typical of diabases. This diabasic texture is also termed interstitial, the feldspar is high in anorthite, the calcium endmember of the plagioclase anorthite-albite solid solution series, most commonly labradorite. Diabase is usually found in relatively shallow intrusive bodies such as dikes. Diabase dikes occur in regions of crustal extension and often occur in swarms of hundreds of individual dikes or sills radiating from a single volcanic center. The Palisades Sill which makes up the New Jersey Palisades on the Hudson River, parts of the Deccan Traps of India, formed at the end of the Cretaceous also includes dolerite. It is also abundant in parts of Curaçao, an island off the coast of Venezuela. West of the Norseman–Wiluna Belt is the Yalgoo–Singleton Belt, where complex dolerite dike swarms obscure the volcaniclastic sediments, large dolerite sills such as the Golden Mile Dolerite can exhibit course grained texture, and show a large diversity in petrography and geochemistry across the width of the sill. The vast areas of mafic volcanism/plutonism associated with the Jurassic breakup of Gondwanaland in the Southern Hemisphere include many large diabase/dolerite sills and dike swarms. These include the Karoo dolerites of South Africa, the Ferrar Dolerites of Antarctica, in Tasmania dolerite dominates much of the landscape, particularly alpine areas. Ring dikes are large, near vertical dikes showing above ground as circular outcrops up to 30 km in diameter, thicker dikes are made up of plutonic rocks, rather than hypabyssal and are centred on deep intrusions. Diabase is crushed and used as an aggregate for road beds, buildings, railroad beds. Diabase can also be cut for use as as ornamental stone for countertops, facing stone on buildings, a form of dolerite, known as bluestone, is one of the materials used as in the construction of Stonehenge. In Tasmania, being one of the most common rocks found, it has used as a building stone, for landscaping. List of rock types Collection of dikes in the Fish River Canyon, Namibia
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Migmatite
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Migmatite is a rock that is a mixture of metamorphic rock and igneous rock. They can also be known as diatexite, Migmatites form under extreme temperature conditions during prograde metamorphism, where partial melting occurs in pre-existing rocks. Migmatites are not crystallized from a molten material, and are not generally the result of solid-state reactions. Commonly, migmatites occur within extremely deformed rocks that represent the base of eroded mountain chains, if present, the mesosome, intermediate in color between a leucosome and melanosome, is mostly a more or less unmodified remnant of the original parent rock. The light-colored material has the appearance of having been mobilized or molten, a leucosome is the lightest-colored part of migmatite. The melanosome is the part, and occurs between two leucosomes or, if remnants of the more or less unmodified parent rock are still present. When present, the mesosome is intermediate in color between leucosome and melanosome, migmatite textures are the product of thermal softening of the metamorphic rocks. Schlieren textures are a common example of granite formation in migmatites. Ptygmatic folds are formed by highly plastic ductile deformation of the gneissic banding, ptygmatic folds can occur restricted to compositional zones of the migmatite, for instance in fine-grained shale protoliths versus in coarse granoblastic sandy protolith. When a rock undergoes partial melting some minerals will melt, while others remain solid, the neosome is composed of lightly-colored areas and dark areas. The leucosome lies in the center of the layers and is composed of quartz. The melanosome is composed of cordierite, hornblende and biotite and forms the wall zones of the neosome, for migmatised argillaceous rocks, the partial or fractional melting would first produce a volatile and incompatible-element enriched rich partial melt of granitic composition. Such granites derived from sedimentary rock protoliths would be termed S-type granite, are typically potassic, sometimes containing leucite, volcanic equivalents would be rhyolite and rhyodacite. Volcanic equivalents would be dacite, trachyte and trachydacite and it is difficult to melt mafic metamorphic rocks except in the lower mantle, so it is rare to see migmatitic textures in such rocks. However, eclogite and granulite are roughly equivalent mafic rocks, the Finnish petrologist Jakob Sederholm first used the term in 1907 for rocks within the Scandinavian craton in southern Finland. The term was derived from the Greek word μιγμα, migma meaning a mixture, the Canadian Mineralogist Special Publication 9. Mineralogical Association of Canada, Quebec, NRC Research Press, Ottawa, ISBN 978-0-660-19787-6 Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks,6. Migmatites and related rocks R. V. Dietrich - Migmatites North Cascades National Park, Orthogneisses and Migmatites Cooma Complex, SE Australia
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Kosterhavet National Park
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Kosterhavet National Park is the first national marine park in Sweden, inaugurated on September 2009. It is part of the Skagerrak sea and is located in Strömstad and Tanum municipalities in Bohuslän, Västra Götaland County and it consists of the sea and shores around the Koster Islands, excluding everything else on the islands. In the north, it borders the Norwegian marine park of Ytre Hvaler, the environment in the park is unique to Swedish waters. Over 6,000 marine species have been identified, about 200 of them can not to be elsewhere in Sweden. The Kosterfjord is 200 m deep with low temperature –5 to 7 °C –. Brachiopod, sponge and coral larvae are brought in by currents from the Atlantic, rare seabirds, such as Arctic terns and skuas, along with a large population of harbor seals have their habitat here. Plaice, cod and sea trout breed in the shallow waters closer to the shore. Professional fishing is allowed although special regulations apply, the waters of the park is significant for the fishing of northern prawn and Norwegian lobster. Fishing is not subject to protection, and are instead regulated by fishery laws. Media related to Kosterhavet at Wikimedia Commons Kosterhavets webbplats Swedens National Parks, Kosterhavet National Park from the Swedish Environmental Protection Agency
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Koster Islands
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The Koster Islands situated 10 km west of Strömstad, Sweden, comprises an archipelago surrounding the two largest islands, South Koster and North Koster. South Koster has an area of 8 km² and North Koster an area of 4 km², the landscape, dominated by smooth bedrock, bears witness to volcanic activity and subsequent wear due to the Ice Age. The rocky coastline is broken by many sandy beaches the largest being Kilesand on South Kosters east side overlooking the 200 meter deep Koster Fjord, South and North Koster are communities with a permanent population of around 340. There is a school, sports hall, shops, church, both farming and fishing are important, and already during the 1600s Koster exported lobster to Holland. There are several small harbors, popular with sailors from both near and far, rooms can be rented from the Ekenäs Hotel or from private homes or cabins. There is also a campsite on North Koster, an electrically driven ferry operates constantly between the two islands, a distance of 58 meters. As one moves inland, farmland, woods and rich vegetation becomes apparent, South Koster has a network of roads and paths, which can be explored by bicycle or in small golf-buggies, both of which can be rented. On North Koster it is possible to rent small boats. Restrictions regarding the right of access, Allemansrätten, forbid open fires, the Koster Islands have a marine west coast climate that has a narrower range of temperatures than inland and areas on the east coast on similar parallels. Still yet, sleet was recorded on Nordkoster as late as June 12,1981, Koster is a well-established and popular tourist destination, attracting as many as 90000 tourists each year, renowned for being one of Swedens sunniest places offering bathing opportunities. During the summer there are a variety of events and activities, such as a festival, mackerel race. Several pubs and restaurants offer a menu, often based on seafood from local fisherman, such as shrimp, oyster, crayfish, crab. Connections to the mainland are good with 16 ferry departures daily from Strömstad, private cars can be parked at the car park just outside the center of Strömstad from where buses run free of charge to the square where the harbor lies. Kosterbladet 2010 Koster, Islands in the Skagerrak Map of Koster Islands
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Outer Hebrides
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The Outer Hebrides, also known as the Western Isles, Innse Gall or the Long Isle or Long Island, is an island chain off the west coast of mainland Scotland. The islands are geographically coextensive with Comhairle nan Eilean Siar, one of the 32 unitary council areas of Scotland. They form part of the Hebrides, separated from the Scottish mainland and from the Inner Hebrides by the waters of the Minch, the Little Minch, Scottish Gaelic is the predominant spoken language, although in a few areas English speakers form a majority. Most of the islands have a formed from ancient metamorphic rocks. The 15 inhabited islands have a population of 27,100. From Barra Head to the Butt of Lewis is roughly 210 kilometres, There are various important prehistoric structures, many of which pre-date the first written references to the islands by Roman and Greek authors. The Western Isles became part of the Norse kingdom of the Suðreyjar, control of the islands was then held by clan chiefs, principal of whom were the MacLeods, MacDonalds, Mackenzies and MacNeils. The Highland Clearances of the 19th century had an effect on many communities. Much of the land is now under control and commercial activity is based on tourism, crofting, fishing. Sea transport is crucial and a variety of services operate between the islands and to mainland Scotland. Modern navigation systems now minimise the dangers but in the past the stormy seas have claimed many ships, religion, music and sport are important aspects of local culture, and there are numerous designated conservation areas to protect the natural environment. The islands form an archipelago whose major islands are Lewis and Harris, North Uist, Benbecula, South Uist, and Barra. Lewis and Harris has an area of 217,898 hectares and is the largest island in Scotland and it incorporates Lewis in the north and Harris in the south, both of which are frequently referred to as individual islands, although they are connected by land. The island does not have a name in either English or Gaelic. The largest islands are deeply indented by arms of the sea such as Loch Ròg, Loch Seaforth, There are also more than 7,500 freshwater lochs in the Outer Hebrides, about 24% of the total for the whole of Scotland. North and South Uist and Lewis in particular have landscapes with a percentage of fresh water. Harris has fewer large bodies of water but has innumerable small lochans, Loch Langavat on Lewis is 11 kilometres long, and has several large islands in its midst, including Eilean Mòr. Although Loch Suaineabhal has only 25% of Loch Langavats surface area, of Loch Sgadabhagh on North Uist it has been said that there is probably no other loch in Britain which approaches Loch Scadavay in irregularity and complexity of outline
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Lewisian complex
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The Lewisian complex or Lewisian gneiss is a suite of Precambrian metamorphic rocks that outcrop in the northwestern part of Scotland, forming part of the Hebridean Terrane. These rocks are of Archaean and Paleoproterozoic age, ranging from 3. 0–1.7 Ga and they form the basement on which the Torridonian and Moine Supergroup sediments were deposited. The Lewisian consists mainly of granitic gneisses with an amount of supracrustal rocks. Rocks of the Lewisian complex were caught up in the Caledonian orogeny, the main outcrops of the Lewisian complex are on the islands of the Outer Hebrides, including Lewis, from which the complex takes its name. Lewisian like granitic gneisses of Paleoproterozoic age of the Rhinns complex are exposed on Islay and Colonsay in the part of the Inner Hebrides. Similar rocks also outcrop on Inishtrahull off the north coast of Donegal, the first comprehensive account of the Lewisian complex was published in 1907 as part of the Geological Survey memoir on the structure of the Northwest Highlands. Subsequent fieldwork, metamorphic studies and radiometric dating has refined their chronology, the oldest part of the Lewisian complex is a group of gneisses of Archaean age that formed in the interval 3. 0–2.7 Ga. These gneisses are found throughout the outcrop of the Lewisian complex in the mainland, the dominant lithology of the Scourie complex is banded grey gneisses, typically granodioritic, tonalitic or trondhjemitic in composition. The protolith for the Scourian gneisses are thought to be granitic, the main metamorphic event in the Central Region was the 2.5 Ga granulite facies Badcallian event. The Northern Region lacks evidence of granulite facies and in the Southern Region an earlier 2.73 Ga event is recognised locally and this tectonic and metamorphic event postdates the main granulite facies metamorphic event in the Scourian complex but mostly predates intrusion of the Scourie dykes. This event deforms a suite of post-Badcallian pegmatites dated at 2. 49-2.48 Ga and predates most of the Scourie dykes, the deformation was accompanied by retrograde metamorphism down to amphibolite facies, similar to the later Laxfordian event. Distinguishing between these two events has proved difficult, major Inverian shear zones have been identified in the Central and Southern Regions, including the Canisp Shear Zone. This basic dyke swarm cuts the banding of the Scourie complex gneisses and therefore postdates the main igneous, tectonic and metamorphic events that created them.4 Ga. Some dykes, which appear to have intruded into cooler Scourian crust give ages of about 2.0 Ga. Some of the main dyke suite show evidence of intrusion into hot country rock, most of the dykes are quartz-dolerites in terms of chemistry, with less common olivine gabbro, norite and bronzite picrite. Supracrustal rocks of the Loch Maree Group form two large areas of outcrop near Loch Maree and Gairloch in the Southern Region, the group consists of metasediments with intercalated amphibolites, interpreted to be metavolcanics with some basic sills. They were probably deposited at about 2.0 Ga, as they contain detrital zircons that give a mixture of Archaean, the Laxfordian was originally recognised from the presence of deformation and metamorphism of the Scourie dykes. The Laxfordian can be divided into an event before 1
40.
Moine Thrust Belt
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The Moine Thrust Belt is a linear geological feature in the Scottish Highlands which runs from Loch Eriboll on the north coast 190 kilometres south-west to the Sleat peninsula on the Isle of Skye. Mountains within the belt display complicated layers and the width of the zone varies up to 10 kilometres, often, summits of hard rock cap softer sedimentary rock layers visible on lower slopes. Ben More Assynt, in the centre of the belt, is an example that rises from a glen of limestone caves up through sandstone terraces to a quartzite summit cap. The discovery of the Moine Thrust in 1907 was a milestone in the history of geology as it was one of the first thrust belts discovered, the formation has since been re-interpreted many times. The thrust belt defines the boundary between the Hebridean Terrane to its northwest and the Northern Highlands Terrane to its southeast, the thrust carried metamorphic material over 200 km across Scotland entirely masking the geology of the previous terrane. However, small windows, such as the Assynt window and the Glen Achall imbricated thrust system, knockan Crag Inchnadamph Geology of Scotland Rob Butler. Goodenough, Kathryn, Geological Foundations, in Kempe, Nick, Wrightham, Mark, Hostile Habitats, Scottish Mountaineering Trust, ISBN090752193 2]
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Coll
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Coll is an island located west of Mull in the Inner Hebrides of Scotland. Coll is known for its beaches, which rise to form large sand dunes, for its corncrakes. It is in the area of Argyll and Bute. Coll is about 13 miles long by 3 miles wide and has a population of around 195, Colls sandy beaches rise to form large sand dunes. Arinagour, is the settlement on the island located at the head of Loch Eatharna. Other inhabited locations include, Acha, a settlement located 5 kilometres south-west of Arinagour. Arileod, located on the west coast,7 kilometres south-west of Arinagour, arnabost, located 3 kilometres miles north-west of Arinagour. It is the junction for travel between Sorisdale, Clabhach and Arinagour, ballyhaugh, located on the northern part of Hough Bay,5 kilometres west of Arinagour. Bousd, located 7 kilometres north-east of Arinagour, Clabhach, located on the north-west coast,5 kilometres north-west of Arinagour. Crossapol, located on the south-west coast, totronald, located on the west coast 7 kilometres southwest of Arinagour. Uig, located 1 kilometre north-east of the head of Loch Breachacha, Coll is sometimes derived from Gaelic coll, hazel. However, this does not match the early recorded forms of the name, the name of Coll is given as Colosus in the Life of St Columba by Adamnán, the seventh century abbot of Iona. As /s/ between vowels had been lost in Celtic before Adamnáns time, Watson suggests that Colosus may represent a pre-Celtic name. Richard Coates has proposed that the name may be related to Greek kolossós and may have referred to a standing stone located on the island, like those still seen on North Uist. In Icelandic, the word means a rounded protrusion, such as a rounded mountaintop. Coll was home to a branch of the Clan Maclean for 500 years, in 1583 the Macleans of Duart invaded their cousins on Coll with the intention of taking the island for themselves. The Macleans of Coll retained their fief and Castle of Breacachadh until 1848 when Alexander Maclean of Coll emigrated to Natal. Coll, like other Hebridean islands, has several crannógs located in some of its lochs, one such crannog is Dun Anlaimh, which is thought to date to at least the later Middle Ages
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Tiree
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Tiree is the most westerly island in the Inner Hebrides of Scotland. The low-lying island, southwest of Coll, has an area of 7,834 hectares, the land is highly fertile, and crofting, alongside tourism, and fishing are the main sources of employment for the islanders. Tiree, along with Colonsay, enjoys a high number of total hours of sunshine during the late spring. Tiree is a popular windsurfing venue and is a location for an offshore wind farm. Tiree is sometimes referred to as Hawaii of the north Tiree is known for the 1st-century-AD Dùn Mòr broch, for the prehistoric carved Ringing Stone, Adomnan of Iona, recorded several stories relating to St Columba and the island of Tiree. Columba gave the warning to Baithéne mac Brénaind who replied that both he and the whale were in Gods hands, and Columba told him to go. And Baithene set off for Tiree, and when the whale appeared, he raised his hands, in another story, Adomnan claimed there to be a monstery on the island of Tiree that was called Artchain. Adomnan wrote that an ordination to the priesthood of a man named Áed Dub had taken place. In another story, Columba instructed a monk to go the monastery on Tiree. In another story, Columba banished some demons from Iona who then went to the island of Tiree to afflict the monks there instead. Adomnan also records there being more than one monastery on Tiree in that period. Writing in 1549, Donald Munro, High Dean of the Isles wrote of Thiridh that it was, all inhabite and manurit with twa paroche kirkis in it, ane fresh water loch with an auld castell. Na cuntrie may be mair fertile of corn and very gude for wild fowls and for fishe, in 1770, half of the island was held by fourteen farmers who had drained land for hay and pasture. Instead of exporting cattle, they began to export salt beef in barrels to get better prices. The rest of the island was let to 45 groups of tenants on co-operative joint farms, field strips were allocated by annual ballot. Sowing and harvesting dates were decided communally and it is reported that in 1774, Tiresians were well-clothed and well-fed, having an abundance of corn and cattle. Its name derives from Tìr Iodh, land of the corn, from the days of the 6th century Celtic missionary, Tiree provided the monastic community on the island of Iona, south-east of the island, with grain. A number of early monasteries once existed on Tiree itself, and several sites have stone cross-slabs from this period, e. g. St Patricks Chapel, Ceann a Mhara and Soroby
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Marble
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Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Geologists use the marble to refer to metamorphosed limestone, however. Marble is commonly used for sculpture and as a building material and this stem is also the basis for the English word marmoreal, meaning marble-like. In Hungarian it is called márvány, Marble is a rock resulting from metamorphism of sedimentary carbonate rocks, most commonly limestone or dolomite rock. Metamorphism causes variable recrystallization of the carbonate mineral grains. The resulting marble rock is composed of an interlocking mosaic of carbonate crystals. Primary sedimentary textures and structures of the carbonate rock have typically been modified or destroyed. Pure white marble is the result of metamorphism of a very pure limestone or dolomite protolith, green coloration is often due to serpentine resulting from originally magnesium-rich limestone or dolostone with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure, examples of historically notable marble varieties and locations, White marble has been prized for its use in sculptures since classical times. This preference has to do with its softness, which made it easier to carve, relative isotropy and homogeneity, construction marble is a stone which is composed of calcite, dolomite or serpentine which is capable of taking a polish. More generally in construction, specifically the dimension stone trade, the marble is used for any crystalline calcitic rock useful as building stone. For example, Tennessee marble is really a dense granular fossiliferous gray to pink to maroon Ordovician limestone that geologists call the Holston Formation. Ashgabat, the city of Turkmenistan, was recorded in the 2013 Guinness Book of Records as having the worlds highest concentration of white marble buildings. According to the United States Geological Survey, U. S. domestic marble production in 2006 was 46,400 tons valued at about $18.1 million, compared to 72,300 tons valued at $18.9 million in 2005. Crushed marble production in 2006 was 11.8 million tons valued at $116 million, of which 6.5 million tons was finely ground calcium carbonate and the rest was construction aggregate. For comparison,2005 crushed marble production was 7.76 million tons valued at $58.7 million, of which 4.8 million tons was finely ground calcium carbonate, U. S. dimension marble demand is about 1.3 million tons. The DSAN World Demand for Marble Index has shown a growth of 12% annually for the 2000–2006 period, the largest dimension marble application is tile. In 1998, marble production was dominated by 4 countries that accounted for almost half of production of marble
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Schist
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Schist is a medium-grade metamorphic rock with medium to large, flat, sheet-like grains in a preferred orientation. It is defined by having more than 50% platy and elongated minerals, often finely interleaved with quartz and these lamellar minerals include micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a form called quartz schist is produced. Schist forms at a temperature and has larger grains than phyllite. Geological foliation with medium to large grained flakes in a preferred orientation is called schistosity. The names of various schists are derived from their mineral constituents, for example, schists rich in mica are called mica schists and include biotite or muscovite. Most schists are mica schists, but graphite and chlorite schists are also common, Schists are also named for their prominent or perhaps unusual mineral constituents, as in the case of garnet schist, tourmaline schist, and glaucophane schist. The individual mineral grains in schist, drawn out into flaky scales by heat and pressure, Schist is characteristically foliated, meaning that the individual mineral grains split off easily into flakes or slabs. Most schists are derived from clays and muds that have passed through a series of processes involving the production of shales, slates and phyllites as intermediate steps. Certain schists are derived from fine-grained igneous rocks such as basalts, before the mid-18th century, the terms slate, shale and schist were not sharply differentiated by those involved with mining. In the context of underground mining, shale was frequently referred to as slate well into the 20th century. During metamorphism, rocks which were originally sedimentary, igneous or metamorphic are converted into schists, if the composition of the rocks was originally similar, they may be very difficult to distinguish from one another if the metamorphism has been great. A quartz-porphyry, for example, and a fine grained feldspathic sandstone, usually, however, it is possible to distinguish between sedimentary and igneous schists and gneisses. If, for example, the district occupied by these rocks has traces of bedding, clastic structure, or unconformability. In other cases intrusive junctions, chilled edges, contact alteration or porphyritic structure may prove that in its original condition a metamorphic gneiss was an igneous rock. Such rocks as limestones, dolomites, quartzites and aluminous shales have very definite chemical characteristics which distinguish them even when completely recrystallized, the schists are classified principally according to the minerals they consist of and on their chemical composition. For example, many metamorphic limestones, marbles, and calc-schists, with crystalline dolomites, contain silicate minerals such as mica, tremolite, diopside, scapolite, quartz and they are derived from calcareous sediments of different degrees of purity. Another group is rich in quartz, with amounts of white and black mica, garnet, feldspar, zoisite
45.
Dike (geology)
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A dike or dyke, in geological usage, is a sheet of rock that formed in a fracture in a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin, magmatic dikes form when magma intrudes into a crack then crystallizes as a sheet intrusion, either cutting across layers of rock or through an unlayered mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack, an intrusive dike is an igneous body with a very high aspect ratio, which means that its thickness is usually much smaller than the other two dimensions. Thickness can vary from sub-centimeter scale to many meters, and the dimensions can extend over many kilometres. A dike is an intrusion into an opening cross-cutting fissure, shouldering aside other pre-existing layers or bodies of rock, near-horizontal, or conformable intrusions, along bedding planes between strata are called intrusive sills. Sometimes dikes appear in swarms, consisting of several to hundreds of dikes emplaced more or less contemporaneously during a single intrusive event, the worlds largest dike swarm is the Mackenzie dike swarm in the Northwest Territories, Canada. Dikes often form as either radial or concentric swarms around plutonic intrusives, the latter are known as ring dikes. Pegmatite dikes comprise extremely coarse crystalline granitic rocks - often associated with granite intrusions or metamorphic segregations. Aplite dikes are fine-grained or sugary-textured intrusives of granitic composition, in contrast to magmatic dikes, a sill is a magmatic sheet intrusion that forms within and parallel to the bedding of layered rock. Sedimentary dikes or clastic dikes are vertical bodies of rock that cut off other rock layers. Driven by the pressure the sediment breaks through overlying layers. When a soil is under permafrost conditions the water is totally frozen. When cracks are formed in rocks, they may fill up with sediments that fall in from above. The result is a body of sediment that cuts through horizontal layers. Batholith Ring dike Fissure vent Laccolith Runamo, formerly interpreted as a runic inscription
"Gneiss". Encyclopædia Britannica (11th ed.). 1911.
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