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.
Quartz
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Quartz is the second most abundant mineral in Earths continental crust, behind feldspar. There are many different varieties of quartz, several of which are semi-precious gemstones, since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. The word quartz is derived from the German word Quarz and its Middle High German ancestor twarc, the Ancient Greeks referred to quartz as κρύσταλλος derived from the Ancient Greek κρύος meaning icy cold, because some philosophers apparently believed the mineral to be a form of supercooled ice. Today, the rock crystal is sometimes used as an alternative name for the purest form of quartz. Quartz belongs to the crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end, well-formed crystals typically form in a bed that has unconstrained growth into a void, usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, a quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward. α-quartz crystallizes in the crystal system, space group P3121 and P3221 respectively. β-quartz belongs to the system, space group P6222 and P6422. These space groups are truly chiral, both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks. The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is an identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. The most important distinction between types of quartz is that of macrocrystalline and the microcrystalline or cryptocrystalline varieties, the cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a form of silica consisting of fine intergrowths of both quartz, and its monoclinic polymorph moganite. Other opaque gemstone varieties of quartz, or mixed rocks including quartz, often including contrasting bands or patterns of color, are agate, carnelian or sard, onyx, heliotrope, amethyst is a form of quartz that ranges from a bright to dark or dull purple color. The worlds largest deposits of amethysts can be found in Brazil, Mexico, Uruguay, Russia, France, Namibia, sometimes amethyst and citrine are found growing in the same crystal. It is then referred to as ametrine, an amethyst is formed when there is iron in the area where it was formed
3.
Muscovite
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Muscovite is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl22, or 236. It has a perfect basal cleavage yielding remarkably thin laminae which are often highly elastic. Sheets of muscovite 5 m ×3 m have been found in Nellore, Muscovite has a Mohs hardness of 2–2.25 parallel to the face,4 perpendicular to the and a specific gravity of 2. 76–3. It can be colorless or tinted through grays, browns, greens, yellows, or violet or red and it is anisotropic and has high birefringence. The green, chromium-rich variety is called fuchsite, mariposite is also a type of muscovite. In pegmatites, it is found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of fireproofing and insulating materials, the name muscovite comes from Muscovy-glass, a name given to the mineral in Elizabethan England due to its use in medieval Russia as a cheaper alternative to glass in windows. Media related to Muscovite at Wikimedia Commons
4.
Illite
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Illite is a non-expanding clay crystalline mineral. Illite is a secondary mineral precipitate phyllosilicate or layered alumino-silicate and its structure is a 2,1 clay of silica tetrahedron – alumina octahedron – silica tetrahedron layers. The space between individual clay crystals is occupied by poorly hydrated potassium cations which is responsible for the absence of swelling, structurally, illite is quite similar to muscovite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer potassium. The chemical formula is given as 24O10, but there is considerable ion substitution and it occurs as aggregates of small monoclinic grey to white crystals. Due to the size, positive identification usually requires x-ray diffraction or SEM-EDS analysis. Illite occurs as a product of muscovite and feldspar in weathering and hydrothermal environments. It is common in sediments, soils, and argillaceous sedimentary rocks as well as in low grade metamorphic rocks. The iron rich member of the group, glauconite, in sediments can be differentiated by x-ray analysis. The cation-exchange capacity of illite is smaller than that of smectite but higher than that of kaolinite, illite was first described for occurrences in the Maquoketa shale in Calhoun County, Illinois, US, in 1937. The name was derived from its location in Illinois. Illite is also called hydromica or hydromuscovite, brammallite is a sodium rich analogue. Avalite is a chromium bearing variety which has been described form Mt. Avala, Belgrade, the crystallinity of illite has been used as an indicator of metamorphic grade in clay-bearing rocks metamorphosed under conditions between diagenesis and low-grade metamorphism. With increasing temperature, illite is thought to undergo a transformation into muscovite,437 pp, see Chapter 3, Soil Mineralogy, p.32
5.
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
6.
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
7.
Hematite
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Hematite, also spelled as haematite, is the mineral form of iron oxide, one of several iron oxides. Hematite crystallizes in the lattice system, and it has the same crystal structure as ilmenite. Hematite and ilmenite form a solid solution at temperatures above 950 °C. Hematite is colored black to steel or silver-gray, brown to reddish brown and it is mined as the main ore of iron. Varieties include kidney ore, martite, iron rose and specularite, while the forms of hematite vary, they all have a rust-red streak. Hematite is harder than iron, but much more brittle. Maghemite is a hematite- and magnetite-related oxide mineral, huge deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that can have still standing water or mineral hot springs, the mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water. Hematite can also occur without water, however, usually as the result of volcanic activity, the name hematite is derived from the Greek word for blood αἷμα haima, due to the red coloration found in some varities of hematite. The color of hematite lends itself to use as a pigment, ochre is a clay that is colored by varying amounts of hematite, varying between 20% and 70%. Red ochre contains unhydrated hematite, whereas yellow ochre contains hydrated hematite, the principal use of ochre is for tinting with a permanent color. The red chalk writing of this mineral was one of the earliest in the history of humans, the powdery mineral was first used 164,000 years ago by the Pinnacle-Point man possibly for social purposes. Hematite residues are found in graves from 80,000 years ago. Near Rydno in Poland and Lovas in Hungary red chalk mines have been found that are from 5000 BC, rich deposits of hematite have been found on the island of Elba that have been mined since the time of the Etruscans. Adding to the surprise was a transition with a decrease in temperature at around 260 K to a phase with no net magnetic moment. The disappearance of the moment with a decrease in temperature at 260 K is caused by a change in the anisotropy which causes the moments to align along the c axis, in this configuration, spin canting does not reduce the energy. The magnetic properties of bulk hematite differ from their nanoscale counterparts, for example, the Morin transition temperature of hematite decreases with a decrease in the particle size. Two other end-members are referred to as protohematite and hydrohematite, enhanced magnetic coercivities for hematite have been achieved by dry-heating a 2-line ferrihydrite precursor prepared from solution
8.
Pyrite
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The mineral pyrite, or iron pyrite, also known as fools gold, is an iron sulfide with the chemical formula FeS2. This minerals metallic luster and pale brass-yellow hue give it a resemblance to gold. The color has led to the nicknames brass, brazzle. Pyrite is the most common of the sulfide minerals, the name pyrite is derived from the Greek πυρίτης, of fire or in fire, in turn from πύρ, fire. 1550, the term had become a term for all of the sulfide minerals. Pyrite is usually associated with other sulfides or oxides in quartz veins, sedimentary rock. Despite being nicknamed fools gold, pyrite is sometimes found in association with small quantities of gold, Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin–type gold deposits, arsenian pyrite contains up to 0.37 wt% gold, Pyrite has been used since classical times to manufacture copperas, that is, iron sulfate. Iron pyrite was heaped up and allowed to weather, the acidic runoff from the heap was then boiled with iron to produce iron sulfate. In the 15th century, such leaching began to replace the burning of sulfur as a source of sulfuric acid, by the 19th century, it had become the dominant method. Pyrite remains in use for the production of sulfur dioxide, for use in such applications as the paper industry. Thermal decomposition of pyrite into FeS and elemental sulfur starts at 540 °C, a newer commercial use for pyrite is as the cathode material in Energizer brand non-rechargeable lithium batteries. Pyrite is a material with a band gap of 0.95 eV. During the early years of the 20th century, pyrite was used as a detector in radio receivers. Pyrite detectors occupied a midway point between galena detectors and the more mechanically complicated perikon mineral pairs, Pyrite detectors can be as sensitive as a modern 1N34A germanium diode detector. Pyrite has been proposed as an abundant, inexpensive material in low-cost photovoltaic solar panels, synthetic iron sulfide was used with copper sulfide to create the photovoltaic material. Pyrite is used to make marcasite jewelry, marcasite jewelry, made from small faceted pieces of pyrite, often set in silver, was known since ancient times and was popular in the Victorian era. Marcasite jewelry does not actually contain the mineral marcasite, from the perspective of classical inorganic chemistry, which assigns formal oxidation states to each atom, pyrite is probably best described as Fe2+S22−
9.
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
10.
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
11.
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
12.
Clay
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Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to water content and become hard, brittle. Depending on the content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size, silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in size and other physical properties. The distinction between silt and clay varies by discipline, geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm, sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils Atterberg limits, ISO14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. These solvents, usually acidic, migrate through the rock after leaching through upper weathered layers. In addition to the process, some clay minerals are formed through hydrothermal activity. There are two types of deposits, primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation, secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are associated with very low energy depositional environments such as large lakes. Depending on the source, there are three or four main groups of clays, kaolinite, montmorillonite-smectite, illite, and chlorite. Chlorites are not always considered to be a clay, sometimes being classified as a group within the phyllosilicates. There are approximately 30 different types of clays in these categories. Varve is clay with visible annual layers, which are formed by deposition of those layers and are marked by differences in erosion. This type of deposit is common in glacial lakes
13.
Volcano
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A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earths volcanoes occur because its crust is broken into 17 major, therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. This type of volcanism falls under the umbrella of plate hypothesis volcanism, Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called hotspots, for example Hawaii, are postulated to arise from upwelling diapirs with magma from the boundary,3,000 km deep in the Earth. Volcanoes are usually not created where two plates slide past one another. Erupting volcanoes can pose hazards, not only in the immediate vicinity of the eruption. Historically, so-called volcanic winters have caused catastrophic famines, the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology, at the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Most divergent plate boundaries are at the bottom of the oceans, therefore, most volcanic activity is submarine, black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the temperature of the overlying mantle wedge. This magma tends to be very viscous due to its high content, so it often does not reach the surface. When it does reach the surface, a volcano is formed, typical examples of this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire. Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume and this theory is currently under criticism, however. The most common perception of a volcano is of a mountain, spewing lava and poisonous gases from a crater at its summit, however. The features of volcanoes are more complicated and their structure. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have features such as massive plateaus
14.
Volcanic ash
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Volcanic ash consists of fragments of pulverized rock, minerals and volcanic glass, created during volcanic eruptions and measuring less than 2 mm in diameter. The term volcanic ash is often loosely used to refer to all explosive eruption products. Volcanic ash is formed during volcanic eruptions when dissolved gases in magma expand. The force of the escaping gas shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, once in the air, ash is transported by wind up to thousands of kilometers away. Volcanic ash is formed during volcanic eruptions, phreatomagmatic eruptions. Explosive eruptions occur when magma decompresses as it rises, allowing dissolved volatiles to exsolve into gas bubbles, as more bubbles nucleate a foam is produced, which decreases the density of the magma, accelerating it up the conduit. Fragmentation occurs when bubbles occupy ~70-80 vol% of the erupting mixture, when fragmentation occurs, violently expanding bubbles tear the magma apart into fragments which are ejected into the atmosphere where they solidify into ash particles. Fragmentation is an efficient process of ash formation and is capable of generating very fine ash even without the addition of water. Volcanic ash is produced during phreatomagmatic eruptions. During these eruptions fragmentation occurs when magma comes into contact with bodies of water groundwater, as the magma, which is significantly hotter than the boiling point of water, comes into contact with water an insulating vapor film forms. Eventually this vapor film will collapse leading to direct coupling of the cold water and this increases the heat transfer which leads to the rapid expansion of water and fragmentation of the magma into small particles which are subsequently ejected from the volcanic vent. Fragmentation causes an increase in area between magma and water creating a feedback mechanism, leading to further fragmentation and production of fine ash particles. Pyroclastic density currents can also produce ash particles and these are typically produced by lava dome collapse or collapse of the eruption column. Within pyroclastic density currents particle abrasion occurs as particles interact with each resulting in a reduction in grain size. In addition, ash can be produced during secondary fragmentation of pumice fragments and these processes produce large quantities of very fine grained ash which is removed from pyroclastic density currents in co-ignimbrite ash plumes. Physical and chemical characteristics of volcanic ash are primarily controlled by the style of volcanic eruption, another parameter controlling the amount of ash produced is the duration of the eruption, the longer the eruption is sustained, the more ash will be produced. The types of minerals present in volcanic ash are dependent on the chemistry of the magma from which it erupted, low energy eruptions of basalt produce a characteristically dark coloured ash containing ~45 - 55% silica that is generally rich in iron and magnesium
15.
Metamorphism
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Metamorphism is the change of minerals or geologic texture in pre-existing rocks, without the protolith melting into liquid magma. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids, the chemical components and crystal structures of the minerals making up the rock may change even though the rock remains a solid. Changes at or just beneath Earths surface due to weathering and/or diagenesis are not classified as metamorphism, Metamorphism typically occurs between diagenesis, and melting. Three types of metamorphism exist, contact, dynamic, and regional, Metamorphism produced with increasing pressure and temperature conditions is known as prograde metamorphism. Conversely, decreasing temperatures and pressure characterize retrograde metamorphism, Metamorphic rocks can change without melting. When pressure is applied, somewhat flattened grains that orient in the same direction have a stable configuration. The upper boundary of metamorphic conditions is related to the onset of melting processes in the rock, the maximum temperature for metamorphism is typically 700 –900 °C, depending on the pressure and on the composition of the rock. Migmatites are rocks formed at this limit, which contain pods. Since the 1980s it has recognized that rocks are rarely dry enough. Conditions producing widespread regionally metamorphosed rocks occur during an orogenic event, the collision of two continental plates or island arcs with continental plates produce the extreme compressional forces required for the metamorphic changes typical of regional metamorphism. These orogenic mountains are eroded, exposing the intensely deformed rocks typical of their cores. The conditions within the slab as it plunges toward the mantle in a subduction zone also produce regional metamorphic effects. The techniques of structural geology are used to unravel the collisional history, regional metamorphism can be described and classified into metamorphic facies or metamorphic zones of temperature/pressure conditions throughout the orogenic terrane. Contact metamorphism occurs typically around intrusive igneous rocks as a result of the increase caused by the intrusion of magma into cooler country rock. The area surrounding the intrusion where the contact metamorphism effects are present is called the metamorphic aureole, contact metamorphic rocks are usually known as hornfels. Rocks formed by contact metamorphism may not present signs of deformation and are often fine-grained. Contact metamorphism is greater adjacent to the intrusion and dissipates with distance from the contact, the size of the aureole depends on the heat of the intrusion, its size, and the temperature difference with the wall rocks. Dikes generally have small aureoles with minimal metamorphism whereas large ultramafic intrusions can have significantly thick, the metamorphic grade of an aureole is measured by the peak metamorphic mineral which forms in the aureole
16.
Slaty cleavage
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Cleavage, in structural geology and petrology, describes a type of planar rock feature that develops as a result of deformation and metamorphism. The degree of deformation and metamorphism along with rock type determines the kind of feature that develops. Generally these structures are formed in fine grained rocks composed of minerals affected by pressure solution, Cleavage is a type of rock foliation, a fabric element that describes the way planar features develop in a rock. Foliation is separated into two groups, primary and secondary, primary deals with igneous and sedimentary rocks while secondary deals with rocks that undergo metamorphism as a result of deformation. Cleavage is a type of secondary foliation associated with fine grained rocks, for coarser grained rocks, schistosity is used to describe secondary foliation. There is a variety of definitions for cleavage which may cause confusion, the terminology used in this article is based largely on Passchier and Trouw. They state that cleavage is a type of foliation in fine grained rocks characterized by planar fabric elements that form in a preferred orientation. Some authors chose to use cleavage when describing any form of secondary foliation, the presence of fabric elements such as preferred orientation of platy or elongate minerals, compositional layering, grain size variations, etc. determines what type of cleavage forms. Cleavage is categorized as continuous or spaced. Continuous or penetrative cleavage describes fine grained rocks consisting of platy minerals evenly distributed in a preferred orientation, the type of continuous cleavage that forms depends on the minerals present. Undeformed platy minerals such as micas and amphiboles align in a preferred orientation, continuous cleavage is scale dependent, so a rock with a continuous cleavage on a microscopic level could show signs of spaced cleavage when observed on a macroscopic level. Since the nature of cleavage is dependent on scale, slaty cleavage is defined as having 0.01 mm or less of space occurring between layers, slaty cleavage often occurs after diagenesis and is the first cleavage feature to form after deformation begins. The tectonic strain must be enough to allow a new strong foliation to form, spaced Cleavage occurs in rocks with minerals that are not evenly distributed and as a result the rock forms discontinuous layers or lenses of different types of minerals. Spaced cleavage contains two types of domains, cleavage domains and microlithons, Cleavage domains are planar boundaries subparallel to the trend of the domain, and microlithons are bounded by the cleavage domains. Spaced cleavages can be categorized based on whether the grains inside the microlithons are randomly oriented or contain microfolds from a previous foliation fabric, other descriptions for spaced cleavages include the spacing size, the shape and percentage of cleavage domains, and the transition between cleavage domains and microlithons. Crenulation cleavage contains microlithons that were warped by a previous foliation, folding occurs when there are multiple phases of deformation, the latter one causes symmetric or asymmetric microfolds that deform previous foliations. The type of crenulation cleavage pattern that depends on lithology and degree of deformation. Disjunctive cleavage describes a type of spaced cleavage where the microlithons are not deformed into microfolds, a common outdated term for disjunctive cleavage is fracture cleavage
17.
Fissility (geology)
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Fissility or fissibility refers to the property of rocks to split along planes of weakness into thin sheets. This is commonly observed in shales, which are sedimentary rocks, and in slates and phyllites, the fissility in these rocks is caused by the preferred alignment of platy phyllosilicate grains due to compaction, deformation or new mineral growth. A highly fissile rock splits easily along the cleavage
18.
Roof
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A roof is part of a building envelope. It is the covering on the uppermost part of a building or shelter which provides protection from animals and weather, notably rain or snow, the word also denotes the framing or structure which supports that covering. In most countries a roof protects primarily against rain, a verandah may be roofed with material that protects against sunlight but admits the other elements. The roof of a garden conservatory protects plants from cold, wind, and rain, a roof may also provide additional living space, for example a roof garden. Old English hrof roof, ceiling, top, summit, heaven, sky, also figuratively, highest point of something, there are no apparent connections outside the Germanic family. English alone has retained the word in a sense, for which the other languages use forms corresponding to OE. In many parts of the ceramic tiles have been the predominant roofing material for centuries. Other roofing materials include asphalt, coal tar pitch, EPDM rubber, Hypalon, polyurethane foam, PVC, slate, Teflon fabric, TPO, and wood shakes and shingles. The construction of a roof is determined by its method of support and how the space is bridged. The pitch is the angle at which the roof rises from its lowest to highest point, most US domestic architecture, except in very dry regions, has roofs that are sloped, or pitched. Although modern construction such as drainpipes may remove the need for pitch, roofs are pitched for reasons of tradition. So the pitch is dependent upon stylistic factors, and partially to do with practicalities. Some types of roofing, for example thatch, require a steep pitch in order to be waterproof, other types of roofing, for example pantiles, are unstable on a steeply pitched roof but provide excellent weather protection at a relatively low angle. In regions where there is rain, an almost flat roof with a slight run-off provides adequate protection against an occasional downpour. Drainpipes also remove the need for a sloping roof, a person that specializes in roof construction is called a roofer. The shape of roofs differs greatly from region to region, the main factors which influence the shape of roofs are the climate and the materials available for roof structure and the outer covering. The basic shapes of roofs are flat, mono-pitched, gabled, hipped, butterfly, there are many variations on these types. Roofs constructed of sections that are sloped are referred to as pitched roofs
19.
North Wales
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North Wales is the northernmost unofficial region of Wales. Retail, transport and educational infrastructure are centred on Wrexham, Rhyl, Colwyn Bay, Llandudno and Bangor. It is bordered to the south by the counties of Ceredigion and Powys in Mid Wales, the southern boundary is arbitrary and its definition may depend on the use being made of the term. For example, the boundary of North Wales Police differs from the boundary of the North Wales area of the Natural Resources Wales, montgomeryshire is sometimes referred to as being in north Wales. The region is steeped in history and was for almost a millennium known as the Kingdom of Gwynedd, the mountainous stronghold of Snowdonia formed the nucleus of that realm and would become the last redoubt of independent Wales — only overcome in 1283. To this day it remains a stronghold of the Welsh language, the area is home to two of the three UNESCO World Heritage Sites in Wales. These are Pontcysyllte Aqueduct and canal and, collectively, the Edwardian castles and town walls of the region which comprise those at Caernarfon, Beaumaris, Conwy and Harlech. It also shares with Powys and Ceredigion the distinction of hosting the only UNESCO Biosphere reserve in Wales, namely, the area is mostly rural with many mountains and valleys. This, in combination with its coast, has ensured that tourism is the principal industry, farming, which was once the principal economic force in the area, is now much reduced in importance. The average income per capita of the population is the lowest in the UK. The eastern part of North Wales contains the most populous areas, with more than 300,000 people living in the areas around Wrexham, Wrexham is North Wales largest town, with a population of 63,084 in 2001. The total population of North Wales is 687,937, the majority of other settlements are along the coast, including some popular resort towns, such as Rhyl, Llandudno and Pwllheli. The A55 road links these towns to cities like Manchester, Liverpool and Birmingham, the highest mountain in Wales, Snowdon, is situated in north west Wales. North Wales has a diverse and complex geology with Precambrian schists along the Menai Strait. To the east, around Llangollen, to the north on Halkyn Mountain, added to all this are the complexities posed by Parys Mountain and the outcrops of unusual minerals such as Jasper and Mona Marble which make the area of special interest to geologists. North Wales has a regional identity. Colloquially, a person from North Wales is known as a North Walian, areas close to the border with Cheshire can have Scouse accents of English, and along the coast Manchester accents are common. Two daily newspapers are published in the region, a weekly Welsh-language newspaper, Y Cymro is published each week by the Cambrian News from its Porthmadog office alongside two localised Welsh titles, Y Cyfnod and Y Dydd
20.
Cyan
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It is evoked by light with a predominant wavelength of between 490–520 nm, between the wavelengths of blue and green. In the subtractive color system, or CMYK, which can be overlaid to produce all colors in paint and color printing, cyan is one of the colors, along with magenta, yellow. In the additive color system, or RGB color model, used to all the colors on a computer or television display, cyan is made by mixing equal amounts of green. Cyan is the complement of red, it can be made by the removal of red from white light, mixing red light and cyan light at the right intensity will make white light. The web color cyan is synonymous with aqua, other colors in the cyan color range are teal, turquoise, electric blue, aquamarine, and others described as blue-green. Its name is derived from the Ancient Greek κύανος, transliterated kyanos, meaning blue, dark blue enamel. It was formerly known as blue or cyan-blue, and its first recorded use as a color name in English was in 1879. Further origins of the name can be traced back to a dye produced from the cornflower. In most languages, cyan is not a color term. Reasons for why cyan is not linguistically acknowledged as a color term can be found in the frequent lack of distinction between blue and green in many languages. The web color cyan shown at right is a color in the RGB color model. In X11 colors, this color is called both cyan and aqua, in the HTML color list, this same color is called aqua. The web colors are more vivid than the used in the CMYK color system. To reproduce the web color cyan in inks, it is necessary to add some white ink to the printers cyan below, so when it is reproduced in printing, it is not a primary subtractive color. It is called aqua because it is a commonly associated with water. Cyan is also one of the inks used in four-color printing, along with magenta, yellow, and black. While both the secondary and the subtractive primary are called cyan, they can be substantially different from one another. Cyan printing ink can be saturated or less saturated than the RGB secondary cyan, depending on what RGB color space
21.
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
22.
Slate (writing)
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A slate is a thin piece of hard flat material, such as the rock also called slate, that is used as a medium for writing. The rock is “a metamorphic rock created by the recrystallization of the minerals in shale from clay to parallel-aligned, flat, the writing slate consisted of a piece of slate, typically either 4x6 inches or 7x10 inches, encased in a wooden frame. A precise date range for writing slates of this type has not been established, usually, a piece of cloth or slate sponge was used to clean it and this was sometimes attached with a string to the bottom of the writing slate. The writing slate was used by children in America in one-room schoolhouses to practice writing and arithmetic during classes or at home, the writing slate was sometimes used by industry workers to track goods and by sailors to calculate their geographical location at sea. Sometimes multiple pieces of slate were bound together into a “book”, the exact origins of the writing slate remain unclear. References to its use can be found in the century and evidence suggests that it was used in the sixteenth and seventeenth centuries. ”By the nineteenth century. At the dawn of the century, writing slates were the primary tool in the classroom for students. In the 1930s writing slates began to be replaced by modern methods. However, writing slates did not become obsolete and they are still made in the twenty-first century, though in small quantities. Slate itself had been in use as a material long before it was used for writing. The use of slate as a material can be traced back to at least the Roman era in Wales. The slate used in roofing had to be of high quality, as the material is prone to cracking. Slate used for writing slates also had to be of good quality because of the thinness required, mining slate of this quality is a straightforward process since slate splits into nearly perfectly flat surfaces. The difficult part of the process is sorting out the quality slate from slate with “cats” or flaws. Properly sorted slate can be made into any required size, roofing slate is still in use, primarily for the restoration of eighteenth and nineteenth century buildings, as it is fairly expensive. Chalkboard Slate #Electronic devices Davies, Peter, U. S Department of Commerce, National Bureau of Standards
23.
Tabula rasa
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Tabula rasa refers to the epistemological idea that individuals are born without built-in mental content and that therefore all knowledge comes from experience or perception. Proponents of tabula rasa generally disagree with the doctrine of Innatism which holds that the mind is born already in possession of certain knowledge. Tabula rasa is a Latin phrase often translated as blank slate in English and originates from the Roman tabula used for notes and this roughly equates to the English term blank slate which refers to the emptiness of a slate sheet previous to it being written on with chalk. Both may be refreshed repeatedly, by melting the wax or by erasing the chalk, in Western philosophy, the concept of tabula rasa can be traced back to the writings of Aristotle who writes in his treatise Περί Ψυχῆς of the unscribed tablet. What it thinks must be in it just as characters may be said to be on a writing-tablet on which as yet nothing stands written and this idea was further developed in Ancient Greek philosophy by the Stoic school. Stoic epistemology emphasizes that the mind starts blank, but acquires knowledge as the world is impressed upon it. The doxographer Aetius summarizes this view as When a man is born, in the eleventh century, the theory of tabula rasa was developed more clearly by the Persian philosopher Avicenna. He further argued that the intellect itself, in the thirteenth century, St. Thomas Aquinas brought the Aristotelian and Avicennian notions to the forefront of Christian thought. St. Bonaventure was one of the fiercest intellectual opponents of Aquinas, the writings of Avicenna, Ibn Tufail, and Aquinas on the tabula rasa theory stood unprogressed and untested for several centuries. Therefore, Prince, whilst you are young and your mind is as it were a clean slate, impress on it these things, the modern idea of the theory, however, is attributed mostly to John Lockes expression of the idea in Essay Concerning Human Understanding. The notion is central to Lockean empiricism, as understood by Locke, tabula rasa meant that the mind of the individual was born blank, and it also emphasized the freedom of individuals to author their own soul. Individuals are free to define the content of their character—but basic identity as a member of the species cannot be altered. This presumption of a free, self-authored mind combined with a human nature leads to the Lockean doctrine of natural rights. Lockes idea of tabula rasa is frequently compared with Thomas Hobbess viewpoint of human nature, since tabula rasa states that humans are born with a blank-slate, Rousseau uses this to suggest that humans must learn warfare. Tabula rasa also features in Sigmund Freuds psychoanalysis, freud depicted personality traits as being formed by family dynamics. Freuds theories imply that humans lack free will, but also that genetic influences on personality are minimal. In Freudian psychoanalysis, one is determined by ones upbringing. The tabula rasa concept became popular in social sciences during the twentieth century, by the 1970s, scientists such as John Money had come to see gender identity as socially constructed, rather than rooted in genetics
24.
Coal mining
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Coal mining is the process of extracting coal from the ground. Coal is valued for its content, and, since the 1880s, has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore, in the United Kingdom and South Africa a coal mine and its structures are a colliery, a coal mine a pit, the above-ground structures the pit head. In Australia, colliery generally refers to a coal mine. In the United States colliery has been used to describe a coal mine operation, Coal mining has had many developments over the recent years, from the early days of men tunnelling, digging and manually extracting the coal on carts, to large open cut and long wall mines. Mining at this scale requires the use of draglines, trucks, conveyors, hydraulic jacks, small-scale mining of surface deposits dates back thousands of years. For example, in Roman Britain, the Romans were exploiting most of the major coalfields by the late 2nd century AD. The Industrial Revolution, which began in Britain in the 18th century and later spread to continental Europe, international trade expanded rapidly when coal-fed steam engines were built for the railways and steamships. Until the late nineteenth century coal was mined using a pick and shovel. Coal-cutting machines were introduced in the 1880s, by 1912, surface mining was conducted with steam shovels designed for coal mining. The most economical method of extraction from coal seams depends on the depth and quality of the seams. Coal mining processes are differentiated by whether they operate on the surface or underground, many coals extracted from both surface and underground mines require washing in a coal preparation plant. Surface mining and deep underground mining are the two methods of mining. Coal that occurs at depths of 180 to 300 ft are usually deep mined, for example, some western U. S. coal that occur at depths in excess of 200 ft are mined by the open pit methods, due to thickness of the seam 60–90 feet. Coals occurring below 300 ft are usually deep mined, However, there are open pit mining operations working on coal seams up to 1000–1500 feet below ground level, for instance Tagebau Hambach in Germany. When coal seams are near the surface, it may be economical to extract the coal using open cut mining methods, open cast coal mining recovers a greater proportion of the coal deposit than underground methods, as more of the coal seams in the strata may be exploited. In this mining method, explosives are first used in order to break through the surface or overburden, the overburden is then removed by draglines or by shovel and truck. Once the coal seam is exposed, it is drilled, fractured, the coal is then loaded onto large trucks or conveyors for transport to either the coal preparation plant or directly to where it will be used
25.
Apatite
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Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca1062, apatite is a mineral that is often mistaken for other minerals. This tendency is reflected in the name, which is derived from the Greek word απατείν. Apatite is one of a few minerals produced and used by biological micro-environmental systems, apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the component of tooth enamel. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate, fluoridated water allows exchange in the teeth of fluoride ions for hydroxyl groups in apatite. Similarly, toothpaste typically contains a source of fluoride anions, too much fluoride results in dental fluorosis and/or skeletal fluorosis. Fission tracks in apatite are commonly used to determine the history of orogenic belts. /He dating of apatite is also established for use in determining thermal histories and other. Phosphorite is a sedimentary rock, that contains between 18% and 40% P2O5. The apatite in phosphorite is present as cryptocrystalline masses referred to as collophane, the primary use of apatite is in the manufacture of fertilizer – it is a source of phosphorus. It is occasionally used as a gemstone, green and blue varieties, in finely divided form, are pigments with excellent covering power. During digestion of apatite with sulfuric acid to phosphoric acid. This byproduct is an industrial source of hydrofluoric acid. Fluoro-chloro apatite forms the basis of the now obsolete Halophosphor fluorescent tube phosphor system and this system has been almost entirely replaced by the Tri-Phosphor system. In the United States, apatite-derived fertilizers are used to supplement the nutrition of many agricultural crops by providing a source of phosphate. Apatites are also a proposed host material for storage of nuclear waste, apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon-cut, chatoyant stones are known as cats-eye apatite, transparent green stones are known as asparagus stone, and blue stones have been called moroxite
26.
Graphite
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Graphite, archaically referred to as plumbago, is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Graphite is the most stable form of carbon under standard conditions, therefore, it is used in thermochemistry as the standard state for defining the heat of formation of carbon compounds. Highly ordered pyrolytic graphite or more correctly highly oriented pyrolytic graphite refers to graphite with a spread between the graphite sheets of less than 1°. The name graphite fiber is sometimes used to refer to carbon fibers or carbon fiber-reinforced polymer. Graphite occurs in rocks as a result of the reduction of sedimentary carbon compounds during metamorphism. It also occurs in rocks and in meteorites. Minerals associated with graphite include quartz, calcite, micas and tourmaline, in meteorites it occurs with troilite and silicate minerals. Small graphitic crystals in meteoritic iron are called cliftonite, Graphite is not mined in the United States, but U. S. production of synthetic graphite in 2010 was 134 kt valued at $1.07 billion. Graphite has a layered, planar structure, the individual layers are called graphene. In each layer, the atoms are arranged in a honeycomb lattice with separation of 0.142 nm. Atoms in the plane are bonded covalently, with three of the four potential bonding sites satisfied. The fourth electron is free to migrate in the plane, making graphite electrically conductive, however, it does not conduct in a direction at right angles to the plane. Bonding between layers is via weak van der Waals bonds, which allows layers of graphite to be easily separated, the two known forms of graphite, alpha and beta, have very similar physical properties, except for that the graphene layers stack slightly differently. The alpha graphite may be flat or buckled. The alpha form can be converted to the form through mechanical treatment. The acoustic and thermal properties of graphite are highly anisotropic, since phonons propagate quickly along the tightly-bound planes, graphites high thermal stability and electrical and thermal conductivity facilitate its widespread use as electrodes and refractories in high temperature material processing applications. However, in oxygen containing atmospheres graphite readily oxidizes to form CO2 at temperatures of 700 °C, Graphite is an electric conductor, consequently, useful in such applications as arc lamp electrodes. It can conduct electricity due to the vast electron delocalization within the carbon layers and these valence electrons are free to move, so are able to conduct electricity
27.
Kaolinite
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Kaolinite /ˈkeɪəlᵻˌnaɪt/ is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a silicate mineral, with one tetrahedral sheet of silica linked through oxygen atoms to one octahedral sheet of alumina octahedra. Rocks that are rich in kaolinite are known as kaolin /ˈkeɪəlᵻn/ or china clay, the name kaolin is derived from Gaoling, a Chinese village near Jingdezhen in southeastern Chinas Jiangxi Province. The name entered English in 1727 from the French version of the word, kaolin, kaolinite has a low shrink–swell capacity and a low cation-exchange capacity. It is a soft, earthy, usually white, mineral, in many parts of the world it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield white, yellow, or light orange colors, alternating layers are sometimes found, as at Providence Canyon State Park in Georgia, United States. Commercial grades of kaolin are supplied and transported as dry powder, kaolinite group clays undergo a series of phase transformations upon thermal treatment in air at atmospheric pressure. Below 100 °C, exposure to dry air will slowly remove liquid water from the kaolin, the end-state for this transformation is referred to as leather dry. Between 100 °C and about 550 °C, any remaining water is expelled from kaolinite. The end state for this transformation is referred to as bone dry, throughout this temperature range, the expulsion of water is reversible, if the kaolin is exposed to liquid water, it will be reabsorbed and disintegrate into its fine particulate form. Subsequent transformations are not reversible, and represent permanent chemical changes, endothermic dehydration of kaolinite begins at 550–600 °C producing disordered metakaolin, but continuous hydroxyl loss is observed up to 900 °C. Al2Si2O54 → Al2Si2O7 +2 H2O, further heating to 925–950 °C converts metakaolin to an aluminium-silicon spinel which is sometimes also referred to as a gamma-alumina type structure,2 Al2Si2O7 → Si3Al4O12 + SiO2. Upon calcination above 1050 °C, the spinel phase nucleates and transforms to platelet mullite, finally, at 1400 °C the needle form of mullite appears, offering substantial increases in structural strength and heat resistance. This is a structural but not chemical transformation, see stoneware for more information on this form. Kaolinite clay occurs in abundance in soils that have formed from the weathering of rocks in hot. Such climatically-related differences in mineral content are often used to infer changes in climates in the geological past. In the Institut National pour lEtude Agronomique au Congo Belge classification system, in the US the main kaolin deposits are found in central Georgia, on a stretch of the Atlantic Seaboard fall line between Augusta and Macon. The deposits were formed between the late Cretaceous and early Paleogene, about 100 million to 45 million years ago, in sediments derived from weathered igneous, Kaolin production in the US during 2011 was 5.5 million tonnes
28.
Magnetite
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Magnetite is a mineral and one of the main iron ores. With the chemical formula Fe3O4, it is one of the oxides of iron, Magnetite is ferrimagnetic, it is attracted to a magnet and can be magnetized to become a permanent magnet itself. It is the most magnetic of all the minerals on Earth. Naturally-magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, today it is mined as iron ore. Small grains of magnetite occur in almost all igneous and metamorphic rocks, Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak. The chemical IUPAC name is iron oxide and the chemical name is ferrous-ferric oxide. In addition to rocks, magnetite also occurs in sedimentary rocks, including banded iron formations and in lake. Magnetite nanoparticles are also thought to form in soils, where they probably oxidize rapidly to maghemite, Magnetite has an inverse spinel crystal structure. As a member of the group, it can form solid solutions with similarly structured minerals, including ulvospinel. Titanomagnetite, also known as titaniferous magnetite, is a solution between magnetite and ulvospinel that crystallizes in many mafic igneous rocks. Titanomagnetite may undergo oxyexsolution during cooling, resulting in ingrowths of magnetite and ilmenite, Magnetite has been important in understanding the conditions under which rocks form. Magnetite reacts with oxygen to produce hematite, and the pair forms a buffer that can control oxygen fugacity. Commonly, igneous rocks contain solid solutions of both titanomagnetite and hemoilmenite or titanohematite, Magnetite also is produced from peridotites and dunites by serpentinization. Lodestones were used as a form of magnetic compass. At low temperatures, magnetite undergoes a crystal structure phase transition from a structure to a cubic structure known as the Verwey transition. The Verwey transition occurs around 121 K and is dependent on size, domain state. An isotropic point also occurs near the Verwey transition around 130 K, the Curie temperature of magnetite is 858 K. Magnetite is sometimes found in large quantities in beach sand. Such black sands are found in places, such as Lung Kwu Tan of Hong Kong, California of the United States
29.
Tourmaline
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Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a stone and the gemstone comes in a wide variety of colors. The name comes from the Tamil and Sinhalese word Turmali or Thoramalli, brightly colored Sri Lankan gem tourmalines were brought to Europe in great quantities by the Dutch East India Company to satisfy a demand for curiosities and gems. At the time it was not realised that schorl and tourmaline were the same mineral, tourmaline was sometimes called the Ceylonese Magnet because it could attract and then repel hot ashes due to its pyroelectric properties. Tourmalines were used by chemists in the 19th century to light by shining rays onto a cut. It may account for 95% or more of all tourmaline in nature, the early history of the mineral schorl shows that the name schorl was in use prior to 1400 because a village known today as Zschorlau was then named Schorl. This village had a tin mine where, in addition to cassiterite. The first description of schorl with the name schürl and its occurrence was written by Johannes Mathesius in 1562 under the title Sarepta oder Bergpostill, up to about 1600, additional names used in the German language were Schurel, Schörle, and Schurl. Beginning in the 18th century, the name Schörl was mainly used in the German-speaking area, in English, the names shorl and shirl were used in the 18th century. In the 19th century the names common schorl, schörl, schorl, dravite, also called brown tourmaline, is the sodium magnesium rich tourmaline endmember. Uvite, in comparison, is a calcium magnesium tourmaline, dravite forms multiple series, with other tourmaline members, including schorl and elbaite. Today this tourmaline locality at Dravograd, is a part of the Republic of Slovenia, tschermak gave this tourmaline the name dravite, for the Drava river area, which is the district along the Drava River in Austria and Slovenia. Dravite varieties include the green chromium dravite and the vanadium dravite. A lithium-tourmaline elbaite was one of three pegmatitic minerals from Utö, Sweden, in which the new alkali element lithium was determined in 1818 by Johan August Arfwedson for the first time. Elba Island, Italy, was one of the first localities where colored, in 1850 Karl Friedrich August Rammelsberg described fluorine in tourmaline for the first time. In 1870 he proved that all varieties of tourmaline contain chemically bound water, in 1889 Scharitzer proposed the substitution of by F in red Li-tourmaline from Sušice, Czech Republic. In 1914 Vladimir Vernadsky proposed the name Elbait for lithium-, sodium-, most likely the type material for elbaite was found at Fonte del Prete, San Piero in Campo, Campo nellElba, Elba Island, Province of Livorno, Tuscany, Italy. In 1933 Winchell published a formula for elbaite, H8Na2Li3Al3B6Al12Si12O62
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Zircon
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Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y, Zircon forms in silicate melts with large proportions of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%, the crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green, colorless specimens that show gem quality are a popular substitute for diamond and are also known as Matura diamond. The name derives from the Persian zargun meaning gold-hued and this word is corrupted into jargoon, a term applied to light-colored zircons. The English word zircon is derived from Zirkon, which is the German adaptation of this word, yellow, orange and red zircon is also known as hyacinth, from the flower hyacinthus, whose name is of Ancient Greek origin. Zircon is ubiquitous in the crust of Earth and it occurs as a common accessory mineral in igneous rocks, in metamorphic rocks and as detrital grains in sedimentary rocks. Their average size in granite rocks is about 0. 1–0.3 mm, Zircon is also very resistant to heat and corrosion. Because of their uranium and thorium content, some zircons undergo metamictization, connected to internal radiation damage, these processes partially disrupt the crystal structure and partly explain the highly variable properties of zircon. As zircon becomes more and more modified by internal radiation damage, the density decreases, the structure is compromised. Zircon occurs in many colors, including brown, yellow, green, blue, gray. The color of zircons can sometimes be changed by heat treatment, common brown zircons can be transformed into colorless and blue zircons by heating to 800 to 1000 °C. In geological settings, the development of pink, red, and purple zircon occurs after hundreds of millions of years, color in this red or pink series is annealed in geological conditions above the temperature about 350 °C. Zircon is mainly consumed as an opacifier, and has known to be used in the decorative ceramics industry. Zircon is one of the key used by geologists for geochronology. Zircon is a part of the ZTR index to classify highly-weathered sediments, Zircon is a common accessory to trace mineral constituent of most granite and felsic igneous rocks. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a constituent of most sands
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Feldspar
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Feldspars are a group of rock-forming tectosilicate minerals that make up about 40% of the Earths continental crust. Feldspars crystallize from magma as veins in both intrusive and extrusive rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of plagioclase feldspar is known as anorthosite. Feldspars are also found in types of sedimentary rocks. The name feldspar derives from the German Feldspat, a compound of the words Feld, field, and Spat, the change from Spat to -spar was influenced by the English word spar, a synonym for mineral. Feldspathic refers to materials that contain feldspar, the alternate spelling, felspar, has largely fallen out of use. This group of minerals consists of tectosilicates, solid solutions between albite and anorthite are called plagioclase, or more properly plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two solid solutions, immiscibility occurs at temperatures common in the crust of the earth. Albite is considered both a plagioclase and alkali feldspar, the alkali feldspars are as follows, orthoclase —KAlSi3O8 sanidine —AlSi3O8 microcline —KAlSi3O8 anorthoclase —AlSi3O8 Sanidine is stable at the highest temperatures, and microcline at the lowest. Perthite is a texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye, microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope. Barium feldspars are also considered alkali feldspars, barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. The barium feldspars are monoclinic and include the following, celsian—BaAl2Si2O8 hyalophane—4O8 The plagioclase feldspars are triclinic, the immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae, chemical weathering of feldspars results in the formation of clay minerals. About 20 million tonnes of feldspar were produced in 2010, mostly by three countries, Italy, Turkey, and China, Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, in ceramics, the alkalis in feldspar act as a flux, lowering the melting temperature of a mixture. Fluxes melt at a stage in the firing process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers, ceramics and other uses, such as fillers, accounted for the remainder
32.
Slate industry in Wales
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The existence of a slate industry in Wales is attested since the Roman period, when slate was used to roof the fort at Segontium, now Caernarfon. Penrhyn and Dinorwig were the two largest slate quarries in the world, and the Oakeley mine at Blaenau Ffestiniog was the largest slate mine in the world. Slate is mainly used for roofing, but is produced as thicker slab for a variety of uses including flooring, worktops. Towards the close of the century, the landowners began to operate the quarries themselves, after the government abolished slate duty in 1831, rapid expansion was propelled by the building of narrow gauge railways to transport the slates to the ports. The slate industry dominated the economy of north-west Wales during the half of the 19th century. In 1898, a force of 17,000 men produced half a million tons of slate. Slate production continues on a reduced scale. The Slate industry in North Wales is on the tentative World Heritage Site list, the slate deposits of Wales belong to three geological series, Cambrian, Ordovician and Silurian. The Cambrian deposits run south-west from Conwy to near Criccieth, these deposits were quarried in the Penrhyn and Dinorwig quarries, there are smaller outcrops elsewhere, for example on Anglesey. The Ordovician deposits run south-west from Betws-y-Coed to Porthmadog, these were the deposits mined at Blaenau Ffestiniog. There is another band of Ordovician slate further south, running from Llangynnog to Aberdyfi, quarried mainly in the Corris area, with a few outcrops in south-west Wales, the Silurian deposits are mainly further east in the Dee valley and around Machynlleth. The virtues of slate as a building and roofing material have been recognized since the Roman period, the Roman fort at Segontium, Caernarfon, was originally roofed with tiles, but the later levels contain numerous slates, used for both roofing and flooring. The nearest deposits are about five miles away in the Cilgwyn area, during the mediaeval period, there was small-scale quarrying of slate in several areas. The Cilgwyn quarry in the Nantlle Valley dates from the 12th century, Aberllefenni Slate Quarry may have started operating as a slate mine as early as the 14th century. The earliest confirmed date of operating dates from the early 16th century when the local house Plas Aberllefenni was roofed in slates from this quarry, transport problems meant that the slate was usually used fairly close to the quarries. There was some transport by sea, a poem by the 15th century poet Gutor Glyn asks the Dean of Bangor to send him a shipload of slates from Aberogwen, near Bangor, to Rhuddlan to roof a house at Henllan, near Denbigh. The wreck of a ship carrying finished slates was discovered in the Menai Strait and is thought to date from the 16th century. By the second half of the 16th century, there was an export trade of slates to Ireland from ports such as Beaumaris
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Cleavage (geology)
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Cleavage, in structural geology and petrology, describes a type of planar rock feature that develops as a result of deformation and metamorphism. The degree of deformation and metamorphism along with rock type determines the kind of feature that develops. Generally these structures are formed in fine grained rocks composed of minerals affected by pressure solution, Cleavage is a type of rock foliation, a fabric element that describes the way planar features develop in a rock. Foliation is separated into two groups, primary and secondary, primary deals with igneous and sedimentary rocks while secondary deals with rocks that undergo metamorphism as a result of deformation. Cleavage is a type of secondary foliation associated with fine grained rocks, for coarser grained rocks, schistosity is used to describe secondary foliation. There is a variety of definitions for cleavage which may cause confusion, the terminology used in this article is based largely on Passchier and Trouw. They state that cleavage is a type of foliation in fine grained rocks characterized by planar fabric elements that form in a preferred orientation. Some authors chose to use cleavage when describing any form of secondary foliation, the presence of fabric elements such as preferred orientation of platy or elongate minerals, compositional layering, grain size variations, etc. determines what type of cleavage forms. Cleavage is categorized as continuous or spaced. Continuous or penetrative cleavage describes fine grained rocks consisting of platy minerals evenly distributed in a preferred orientation, the type of continuous cleavage that forms depends on the minerals present. Undeformed platy minerals such as micas and amphiboles align in a preferred orientation, continuous cleavage is scale dependent, so a rock with a continuous cleavage on a microscopic level could show signs of spaced cleavage when observed on a macroscopic level. Since the nature of cleavage is dependent on scale, slaty cleavage is defined as having 0.01 mm or less of space occurring between layers, slaty cleavage often occurs after diagenesis and is the first cleavage feature to form after deformation begins. The tectonic strain must be enough to allow a new strong foliation to form, spaced Cleavage occurs in rocks with minerals that are not evenly distributed and as a result the rock forms discontinuous layers or lenses of different types of minerals. Spaced cleavage contains two types of domains, cleavage domains and microlithons, Cleavage domains are planar boundaries subparallel to the trend of the domain, and microlithons are bounded by the cleavage domains. Spaced cleavages can be categorized based on whether the grains inside the microlithons are randomly oriented or contain microfolds from a previous foliation fabric, other descriptions for spaced cleavages include the spacing size, the shape and percentage of cleavage domains, and the transition between cleavage domains and microlithons. Crenulation cleavage contains microlithons that were warped by a previous foliation, folding occurs when there are multiple phases of deformation, the latter one causes symmetric or asymmetric microfolds that deform previous foliations. The type of crenulation cleavage pattern that depends on lithology and degree of deformation. Disjunctive cleavage describes a type of spaced cleavage where the microlithons are not deformed into microfolds, a common outdated term for disjunctive cleavage is fracture cleavage
34.
Thuringia
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The Free State of Thuringia is a federal state in central Germany. It has an area of 16,171 square kilometres and 2.29 million inhabitants, making it the sixth smallest by area, most of Thuringia is within the watershed of the Saale, a left tributary of the Elbe. Thuringia has been known as the heart of Germany from the late 19th century. It is home to the Rennsteig, Germanys most well-known hiking trail, half of Germanys 136 Winter Olympic gold medals have been won by Thuringian athletes. Johann Sebastian Bach spent the first part of his life and important further stages of his career in Thuringia, goethe and Schiller lived in Weimar and both worked at the University of Jena, which today hosts Thuringias most important science centre. Other Universities in this state are the Ilmenau University of Technology, the University of Erfurt. The name Thuringia or Thüringen derives from the Germanic tribe Thuringii, an older theory claims that they were successors of the Hermunduri, but later research rejected the idea. Other historians argue that the Thuringians were allies of the Huns, came to central Europe together with them, publius Flavius Vegetius Renatus first mentioned the Thuringii around 400, during that period, the Thuringii were famous for their excellent horses. The Thuringian Realm existed until after 531, the Landgraviate of Thuringia was the largest state in the region, after the Treaty of Leipzig, Thuringia had its own dynasty again, the Ernestine Wettins. Their various lands formed the Free State of Thuringia, founded in 1920, the Prussian territories around Erfurt, Mühlhausen and Nordhausen joined Thuringia in 1945. The coat of arms of Thuringia shows the lion of the Ludowingian Landgraves of 12th-century origin, the eight stars around it represent the eight former states which formed Thuringia. The flag of Thuringia is a bicolor, derived from the white. The coat of arms and flag of Hesse are quite similar to the Thuringian ones, symbols of Thuringia in popular culture are the Bratwurst and the Forest, because a large amount of the territory is forested. Named after the Thuringii tribe who occupied it around AD300, Thuringia became a landgraviate in 1130 AD. Most of the remaining Thuringia came under the rule of the Wettin dynasty of the nearby Margraviate of Meissen, in Mühlhausen and elsewhere, the Anabaptists found many adherents. Thomas Müntzer, a leader of some groups of this sect, was active in this city. Some reordering of the Thuringian states occurred during the German Mediatisation from 1795 to 1814, in 1920, after World War I, these small states merged into one state, called Thuringia, only Saxe-Coburg voted to join Bavaria instead. Weimar became the new capital of Thuringia, the coat of arms of this new state was simpler than those of its predecessors
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Frankfurt
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The city is at the centre of the larger Frankfurt Rhine-Main Metropolitan Region, which has a population of 5.8 million and is Germanys second-largest metropolitan region after Rhine-Ruhr. Since the enlargement of the European Union in 2013, the centre of the EU is about 40 km to the east of Frankfurts CBD. Frankfurt is culturally and ethnically diverse, with half of the population. A quarter of the population are foreign nationals, including many expatriates, Frankfurt is an alpha world city and a global hub for commerce, culture, education, tourism and traffic. Its the site of many global and European headquarters, Frankfurt Airport is among the worlds busiest. Automotive, technology and research, services, consulting, media, Frankfurts DE-CIX is the worlds largest internet exchange point. Messe Frankfurt is one of the worlds largest trade fairs, major fairs include the Frankfurt Motor Show, the worlds largest motor show, the Music Fair, and the Frankfurt Book Fair, the worlds largest book fair. Frankfurt is home to educational institutions, including the Goethe University, the UAS, the FUMPA. Its renowned cultural venues include the concert hall Alte Oper, Europes largest English Theatre and many museums, Frankfurts skyline is shaped by some of Europes tallest skyscrapers. In sports, the city is known as the home of the top football club Eintracht Frankfurt, the basketball club Frankfurt Skyliners, the Frankfurt Marathon. Its the seat of German sport unions for Olympics, football, Frankfurt is the largest financial centre in continental Europe. It is home to the European Central Bank, Deutsche Bundesbank, Frankfurt Stock Exchange, the Frankfurt Stock Exchange is one of the worlds largest stock exchanges by market capitalization and accounts for more than 90 percent of the turnover in the German market. Frankfurt is considered a city as listed by the GaWC groups 2012 inventory. Among global cities it was ranked 10th by the Global Power City Index 2011, among financial centres it was ranked 8th by the International Financial Centers Development Index 2013 and 9th by the Global Financial Centres Index 2013. Its central location within Germany and Europe makes Frankfurt a major air, rail, Frankfurt Airport is one of the worlds busiest international airports by passenger traffic and the main hub for Germanys flag carrier Lufthansa. Frankfurter Kreuz, the Autobahn interchange close to the airport, is the most heavily used interchange in the EU, in 2011 human-resource-consulting firm Mercer ranked Frankfurt as seventh in its annual Quality of Living survey of cities around the world. According to The Economist cost-of-living survey, Frankfurt is Germanys most expensive city, Frankfurt has many high-rise buildings in the city centre, forming the Frankfurt skyline. It is one of the few cities in the European Union to have such a skyline and because of it Germans sometimes refer to Frankfurt as Mainhattan, the other well known and obvious nickname is Bankfurt
36.
Roof shingle
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Roof shingles are a roof covering consisting of individual overlapping elements. These elements are flat, rectangular shapes laid in courses from the bottom edge of the roof up. Shingles are made of materials such as wood, slate, flagstone, fibre cement, metal, plastic. Ceramic roof tiles, which dominate in Europe and some parts of Asia, are still usually called tiles. Roof shingles are a common roofing material in the United States. Shingle is a corruption of German schindle meaning a roofing slate, shingles historically were called tiles and shingle was a term applied to wood shingles, as is still mostly the case outside the US. Shingles are laid in courses usually with each shingle offset from its neighbors, the first course is the starter course and the last being a ridge course or ridge slates for a slate roof. The ridge is often being covered with a cap, board, piece. Roof shingles are almost always visible and so are an important aspect of a buildings aesthetics in patterns, textures. Roof shingles, like other building materials on vernacular buildings, are typically of a locally available. All shingle roofs are installed from the bottom upward beginning with a starter course, many shingle installations benefit from being placed on top of an underlayment material such as asphalt felt paper to prevent leaks even from wind driven rain and snow and ice dams in cold climates. At the ridge the shingles on one side of the roof extend past the ridge or there is a ridge cap consisting of boards, copper. An asphalt shingle roof has asphalt shingles as the ridge cap. Due to increased fire hazard, wood shingles and organic-based asphalt shingles have become less common than fiberglass-based asphalt shingles, no shingles are water-tight so the minimum recommended roof pitch is 4,12 without additional underlayment materials. Roof shingles of Fitzroya came to be used as money and called Real de Alerce, in the United States, fiberglass-based asphalt shingles are by far the most common roofing material used for residential roofing applications. In Europe they are called bitumen roof shingles or tile strips and they are easy to install, relatively affordable, last 20 to 50 years and are recyclable in some areas. Asphalt shingles come in a number of styles and colors. Over time in the hot sun, these oils soften and when rain falls the oils are washed out of the shingles
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Roof tiles
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Roof tiles are designed mainly to keep out rain, and are traditionally made from locally available materials such as terracotta or slate. Modern materials such as concrete and plastic are used and some clay tiles have a waterproof glaze. Roof tiles are hung from the framework of a roof by fixing them with nails, the tiles are usually hung in parallel rows, with each row overlapping the row below it to exclude rainwater and to cover the nails that hold the row below. There are also roof tiles for special positions, particularly where the planes of the several pitches meet and they include ridge, hip and valley tiles. These can either be bedded and pointed in cement mortar or mechanically fixed, similarly to roof tiling, tiling has been used to provide a protective weather envelope to the sides of timber frame buildings. These are hung on laths nailed to wall timbers, with specially molded to cover corners. Often these tiles are shaped at the end to give a decorative effect. Another form of this is the so-called mathematical tile, which was hung on laths, nailed and this form of tiling gives an imitation of brickwork and was developed to give the appearance of brick, but avoided the brick taxes of the 18th century. Slate roof tiles were traditional in some areas near sources of supply and it is no longer a cheap material, however, and is now less common. A large number of shapes of tiles have evolved. These include, Flat tiles – the simplest type, which are laid in overlapping rows. An example of this is the clay-made beaver-tail tile, common in Southern Germany, Flat roof tiles are usually made of clay but also may be made of stone, wood, plastic, concrete, or solar cells. Imbrex and tegula – an ancient Roman pattern of curved and flat tiles that make rain channels on a roof, Roman tiles – flat in the middle, with a concave curve at one end at a convex curve at the other, to allow interlocking. Pantiles – with an S-shaped profile, allowing adjacent tiles to interlock and these result in a ridged pattern resembling a ploughed field. An example of this is the double Roman tile, dating from the late 19th century in England, mission or barrel tiles – semi-cylindrical tiles laid in alternating columns of convex and concave tiles. Originally they were made by forming clay around a curved surface, today barrel tiles are mass-produced from clay, metal, concrete or plastic. Interlocking roof tiles – similar to pantiles with side and top locking to improve protection from water, antefixes – vertical blocks which terminate the covering tiles of a tiled roof. Fired roof tiles are found as early as the 3rd millennium BC in the Early Helladic House of the tiles in Lerna, debris found at the site contained thousands of terracotta tiles having fallen from the roof
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Slater
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A slater, or slate mason, is a tradesman who covers buildings with slate. The various tools of the trade are all drop-forged. It consists of a claw for drawing nails, an edge for cutting slate. The ripper or Rip is also forged from crucible-cast steel and is 24 inches long and it consists of a blade and a hook, and is used for removing broken slate. The hook can be used to cut and remove slating nails, the vertical bar of the T is pointed to allow it to be driven into a rafter or other woodworking surface. The horizontal bar of the T is used to support slates whilst working on them with other tools, the long bar of the stake can also be used as a straight edge for marking. The zax is a tool for cutting, trimming. It consists of a heavy rectangular knife blade with a point, of square cross section. The tool is mounted to an offset handle to protect the users hand from sharp slate chips. Practical Guide to the Repair and Maintenance of Houses, — further information about slaters tools
39.
Cornwall
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Cornwall is a ceremonial county and unitary authority area of England within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, Cornwall has a population of 551,700 and covers an area of 3,563 km2. Cornwall forms the westernmost part of the south-west peninsula of the island of Great Britain, and this area was first inhabited in the Palaeolithic and Mesolithic periods. It continued to be occupied by Neolithic and then Bronze Age peoples, there is little evidence that Roman rule was effective west of Exeter and few Roman remains have been found. In the mid-19th century, however, the tin and copper mines entered a period of decline, subsequently, china clay extraction became more important and metal mining had virtually ended by the 1990s. Traditionally, fishing and agriculture were the important sectors of the economy. Railways led to a growth of tourism in the 20th century, however, the area is noted for its wild moorland landscapes, its long and varied coastline, its attractive villages, its many place-names derived from the Cornish language, and its very mild climate. Extensive stretches of Cornwalls coastline, and Bodmin Moor, are protected as an Area of Outstanding Natural Beauty, Cornwall is the homeland of the Cornish people and is recognised as one of the Celtic nations, retaining a distinct cultural identity that reflects its history. Some people question the present constitutional status of Cornwall, and a nationalist movement seeks greater autonomy within the United Kingdom in the form of a devolved legislative Cornish Assembly. On 24 April 2014 it was announced that Cornish people will be granted minority status under the European Framework Convention for the Protection of National Minorities. The modern English name Cornwall derives from the concatenation of two ancient demonyms from different linguistic traditions, Corn- records the native Brythonic tribe, the Cornovii. The Celtic word kernou is cognate with the English word horn. -wall derives from the Old English exonym walh, the Ravenna Cosmography first mentions a city named Purocoronavis in the locality. This is thought to be a rendering of Duro-cornov-ium, meaning fort of the Cornovii. The exact location of Durocornovium is disputed, with Tintagel and Carn Brea suggested as possible sites, in later times, Cornwall was known to the Anglo-Saxons as West Wales to distinguish it from North Wales. The name appears in the Anglo-Saxon Chronicle in 891 as On Corn walum, in the Domesday Book it was referred to as Cornualia and in c.1198 as Cornwal. Other names for the county include a latinisation of the name as Cornubia, the present human history of Cornwall begins with the reoccupation of Britain after the last Ice Age. The area now known as Cornwall was first inhabited in the Palaeolithic and Mesolithic periods and it continued to be occupied by Neolithic and then Bronze Age people. The Common Brittonic spoken at the time developed into several distinct tongues
40.
Efflorescence
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In chemistry, efflorescence is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, the water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt. In what has been described as primary efflorescence, the water is the invader, some people describe a reverse process, where the salt is originally present externally and is then carried inside in solution, as secondary efflorescence. However, others would give this latter phenomenon another name entirely, efflorescences can occur in natural and built environments. On porous construction materials it may present a cosmetic outer problem only, a 5 molar concentration aqueous droplet of NaCl will spontaneously crystallize at 45% relative humidity to form an NaCl cube by the mechanism of homogeneous nucleation. The original water is released to the gas phase, gypsum is a hydrate solid that, in a sufficiently dry environment, will give up its water to the gas phase and form anhydrite. Copper sulfate is a crystalline solid that when exposed to air. Sodium carbonate deca hydrate will lose water when exposed to air, senior Lecturer Keith Hardy at Nottingham Trent University said. Primary efflorescence is named such, as it occurs during the initial cure of a cementitious product. As the water evaporates, it leaves the salt behind, which forms a white, fluffy deposit, the resulting white deposits are referred to as efflorescence in this instance. In this context efflorescence is sometimes referred to as saltpetering, since primary efflorescence brings out salts that are not ordinarily part of the cement stone, it is not a structural, but, rather, an aesthetic concern. For controlling primary efflorescence, formulations containing liquid fatty acid mixtures have been commonly used, secondary efflorescence is named such as it does not occur as a result of the forming of the cement stone or its accompanying hydration products. Rather, it is due to the external influence of concrete poisons. A very common example of where secondary efflorescence occurs is steel-reinforced concrete bridges as well as parking garages, saline solutions are formed due to the presence of road salt in the winter. This saline solution is absorbed into the concrete, where it can begin to dissolve cement stone, virtual stalactites can be formed in some cases as a result of dissolved cement stone, hanging off cracks in concrete structures. Where this process has taken hold, the integrity of a concrete element is at risk. This is a common infrastructure and building maintenance concern. Secondary efflorescence is akin to osteoporosis of the concrete, for controlling secondary efflorescence, admixtures containing aqueous-based calcium stearate dispersion are often added at a later stage of the batching process with the mix water
41.
Blaenau Ffestiniog
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Blaenau Ffestiniog is a historic mining town in Wales. It is in the county of Merionethshire, although currently administered as part of the unitary authority of Gwynedd. After reaching 12,000 at the peak of the slate industry, Blaenau Ffestiniog at one time was the second largest town in North Wales, behind Wrexham. Today, the town relies heavily on tourists, who come to see the attractions within and around the town such as the Ffestiniog Railway. Before the slate industry developed, the now known as Blaenau Ffestiniog was a farming region, with scattered farms working the uplands below the cliffs of Dolgaregddu. A few of these historic farmhouses survive at Cwm Bowydd, Gelli, Pen y Bryn, much of the land was owned by large estates. The town of Blaenau Ffestiniog was created to support workers in the slate mines. In its heyday it was the largest town in Merioneth, in the 1760s men from the long established Cilgwyn quarry near Nantlle started quarrying in Ceunant y Diphwys to the north east of the present town. This valley had for a number of years been known for its slate beds and had worked on a very small scale. The exact location of this quarry has been obliterated by subsequent mining activity. Led by Methusalem Jones, eight Cilgwyn men formed a partnership, in 1800, William Turner and William Casson, quarry managers from the Lake District, bought out the lease and significantly expanded production. In 1819, quarrying began on the slopes of Allt-fawr near Rhiwbryfdir Farm and this was on land owned by the Oakeley family from Tan y Bwlch. Within a decade, three separate slate quarries were operating on Allt-fawr and these eventually amalgamated to form Oakeley Quarry which would become the largest underground mine in the world. Quarrying expanded rapidly in the first half of the 19th century, significant quarries opened at Llechwedd, Maenofferen and Votty & Bowydd, while Turner and Cassons Diphwys Casson flourished. To the south east another cluster of quarries worked the slopes of Manod Mawr, the workforce for these quarries was initially taken from nearby towns and villages such as Ffestiniog and Maentwrog. Before the arrival of railways in the district, travel to the quarries was difficult and these typically grew up around existing farms and along the roads between them. An early settlement was at Rhiwbryfdir, serving the Oakeley and Llechwedd quarries, as early as 1801, new roads were being built specifically to serve the quarries. By 1851, there were 3,460 people living in the new town of Blaenau Ffestiniog, during the 1860s and 1870s the slate industry went through a large boom
42.
Bethesda, Gwynedd
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Bethesda is a town on the River Ogwen and the A5 road on the edge of Snowdonia, in Gwynedd, north-west Wales, colloquially called Pesda by the locals. It all started in 1823 when the Bethesda Chapel was built, the chapel was rebuilt in 1840 and has now been converted into flats and is known as Arafa Don. The town grew around the slate and stone quarrying industries, the largest of the quarries is the Penrhyn Quarry. At its peak, the town was exporting its purple slate all over the world, the town was the site of a three-year strike led by the North Wales Quarrymens Union from 1900. This led to the creation of the village of Tregarth, built by the quarry owners. Most of the town is to the east and north east of the A5 road and this was due to the A5 marking the border between Lord Penrhyns land, and the freehold land. This can still be seen in the layout of the current high street, in 1884 a branch of the London and North Western Railways network from Bangor was opened. The line closed to passengers in 1951 and to freight in 1963 and these days the trackbed of the Penrhyn Quarry Railway towards Porth Penrhyn is taken over by the Lôn Las Ogwen cycle path. In its heyday, the population of Bethesda peaked at 10,000, it is currently around 4,327 people, there are also the villages of Rachub and Tregarth nearby. Current opportunities for employment in the town are limited, there are a few manufacturing businesses, most businesses are in the service sector. For employment with higher earning potential, residents tend to commute to towns along the North Wales coast, Bangor is the most popular destination, but some will commute daily as far as Cheshire. Because of the lack of degree-based employment opportunities, many people move out of the area to places such as Cardiff. Ysgol Dyffryn Ogwen is a comprehensive school, with 374 pupils. Zip World Velocity in Penryn Quarry is the longest zipline in Europe, at just over 1600 metres long, the architecture and layout of the town is largely utilitarian. Most of the buildings are constructed of stone slate roofs. Some are constructed wholly of slate blocks, although such buildings tend to suffer from damp and structural slippage because the very flat, the town has 40 Grade II listed buildings, including three pubs, in addition to the substantial and imposing Grade I listed Calvinistic Methodist Jerusalem Chapel. The upper parts of Carneddi, Cilfodan and Tan y Foel owe more to stone quarrying on the hills rather than slate quarrying that supported the lower end of the town. At the eastern limits, the town is bounded by the land of the Carneddau mountains which form some of the more remote landscapes of Snowdonia
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Wales
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Wales is a country that is part of the United Kingdom and the island of Great Britain. It is bordered by England to the east, the Irish Sea to the north and west, and it had a population in 2011 of 3,063,456 and has a total area of 20,779 km2. Wales has over 1,680 miles of coastline and is mountainous, with its higher peaks in the north and central areas, including Snowdon. The country lies within the temperate zone and has a changeable. Welsh national identity emerged among the Celtic Britons after the Roman withdrawal from Britain in the 5th century, Llywelyn ap Gruffudds death in 1282 marked the completion of Edward I of Englands conquest of Wales, though Owain Glyndŵr briefly restored independence to Wales in the early 15th century. The whole of Wales was annexed by England and incorporated within the English legal system under the Laws in Wales Acts 1535–1542, distinctive Welsh politics developed in the 19th century. Welsh Liberalism, exemplified in the early 20th century by Lloyd George, was displaced by the growth of socialism, Welsh national feeling grew over the century, Plaid Cymru was formed in 1925 and the Welsh Language Society in 1962. Established under the Government of Wales Act 1998, the National Assembly for Wales holds responsibility for a range of devolved policy matters, two-thirds of the population live in south Wales, mainly in and around Cardiff, Swansea and Newport, and in the nearby valleys. Now that the countrys traditional extractive and heavy industries have gone or are in decline, Wales economy depends on the sector, light and service industries. Wales 2010 gross value added was £45.5 billion, over 560,000 Welsh language speakers live in Wales, and the language is spoken by a majority of the population in parts of the north and west. From the late 19th century onwards, Wales acquired its popular image as the land of song, Rugby union is seen as a symbol of Welsh identity and an expression of national consciousness. The Old English-speaking Anglo-Saxons came to use the term Wælisc when referring to the Celtic Britons in particular, the modern names for some Continental European lands and peoples have a similar etymology. The modern Welsh name for themselves is Cymry, and Cymru is the Welsh name for Wales and these words are descended from the Brythonic word combrogi, meaning fellow-countrymen. The use of the word Cymry as a self-designation derives from the location in the post-Roman Era of the Welsh people in modern Wales as well as in northern England and southern Scotland. It emphasised that the Welsh in modern Wales and in the Hen Ogledd were one people, in particular, the term was not applied to the Cornish or the Breton peoples, who are of similar heritage, culture, and language to the Welsh. The word came into use as a self-description probably before the 7th century and it is attested in a praise poem to Cadwallon ap Cadfan c. 633. Thereafter Cymry prevailed as a reference to the Welsh, until c.1560 the word was spelt Kymry or Cymry, regardless of whether it referred to the people or their homeland. The Latinised forms of names, Cambrian, Cambric and Cambria, survive as lesser-used alternative names for Wales, Welsh
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Damp proofing
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Damp proofing in construction is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Damp problems are among the most frequent problems encountered in homes, generally damp proofing keeps moisture out of a building where vapor barriers keep interior moisture from getting into walls. Moisture resistance is not necessarily absolute, it is defined by a specific test method, limits. Damp proofing is accomplished several ways including, A damp-proof course is a barrier through the structure by capillary action such as through a known as rising damp. Rising damp is the effect of rising from the ground into property. The damp proof course may be horizontal or vertical, a DPC layer is usually laid below all masonry walls, regardless if the wall is a load bearing wall or a partition wall. A damp-proof membrane is a material applied to prevent moisture transmission. A common example is polyethylene sheeting laid under a slab to prevent the concrete from gaining moisture through capillary action. A DPM may be used for the DPC, integral damp proofing in concrete involves adding materials to the concrete mix to make the concrete itself impermeable. Cavity wall construction, such as construction, is where the interior walls are separated from the exterior walls by a cavity. Pressure grouting cracks and joints in masonry materials, materials widely used for damp proofing include, Flexible materials like butyl rubber, hot bitumen, plastic sheets, bituminous felts, sheets of lead, copper, etc. Semi-rigid materials like mastic asphalt Rigid materials like bricks, stones, slates, cement mortar or cement concrete painted with bitumen. It can often be seen as a line in the mortar near ground level. To create a barrier, pieces of DPC or DPM may be sealed together. In addition, the DPC may be sealed to the DPM around the edges of the ground floor. In a masonry cavity wall, there is usually a DPC in both the outer and inner wall, in the outer wall it is normally 150 millimetres to 200 millimetres above ground level. This allows rain to form puddles and splash up off the ground, the wall below the DPC may become saturated in rainy weather. The DPC in the wall is usually below floor level, or, with a solid concrete floor
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Shim (spacer)
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A shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, shims may also be used as spacers to fill gaps between parts subject to wear. Many materials make suitable shim stock, or base material, depending on the context, wood, stone, plastic, metal, or even paper. High quality shim stock can be commercially, for example as laminated shims. Laminated shim stock is stacked foil that can be peeled off one layer at a time to adjust the thickness of the shim, in automobiles, shims are commonly used to adjust the clearance or space between two parts. For example, shims are inserted into or under bucket tappets to control valve clearances, clearance is adjusted by changing the thickness of the shim. In Assembly and Weld Fixtures precision metal shims are used two parts so that the final production parts are created within the product drawings specified tolerances. In carpentry, small pieces of wood may be used to align gaps between larger timbers, in luthiery, shims made of various materials are often used to adjust neck alignment and can be used beneath a nut or saddle to raise the height of either. In masonry, small stones may be used to align or fill gaps between larger bricks or slabs, special CPU shims are used to protect the central processing unit when installing a heat sink. This is accomplished by manual shimming of individual shims, or automatic shimming procedure, to the Point, A Brief History of the Shim
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Insulator (electricity)
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An electrical insulator is a material whose internal electric charges do not flow freely, very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily, the property that distinguishes an insulator is its resistivity, insulators have higher resistivity than semiconductors or conductors. A perfect insulator does not exist, because even insulators contain small numbers of mobile charges which can carry current, in addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the voltage of an insulator. Some materials such as glass, paper and Teflon, which have high resistivity, are good electrical insulators. Examples include rubber-like polymers and most plastics which can be thermoset or thermoplastic in nature, insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation, the term insulator is also used more specifically to refer to insulating supports used to attach electric power distribution or transmission lines to utility poles and transmission towers. They support the weight of the suspended wires without allowing the current to flow through the tower to ground, electrical insulation is the absence of electrical conduction. Electronic band theory says that a charge flows if states are available into which electrons can be excited and this allows electrons to gain energy and thereby move through a conductor such as a metal. If no such states are available, the material is an insulator, most insulators have a large band gap. This occurs because the valence band containing the highest energy electrons is full, there is always some voltage that gives electrons enough energy to be excited into this band. Once this voltage is exceeded the material ceases being an insulator, however, it is usually accompanied by physical or chemical changes that permanently degrade the materials insulating properties. Materials that lack electron conduction are insulators if they lack other mobile charges as well, for example, if a liquid or gas contains ions, then the ions can be made to flow as an electric current, and the material is a conductor. Electrolytes and plasmas contain ions and act as conductors whether or not electron flow is involved, when subjected to a high enough voltage, insulators suffer from the phenomenon of electrical breakdown. These freed electrons and ions are in turn accelerated and strike other atoms, creating more charge carriers, rapidly the insulator becomes filled with mobile charge carriers, and its resistance drops to a low level. In a solid, the voltage is proportional to the band gap energy. The air in a region around a conductor can break down and ionise without a catastrophic increase in current. Even a vacuum can suffer a sort of breakdown, but in case the breakdown or vacuum arc involves charges ejected from the surface of metal electrodes rather than produced by the vacuum itself
