1.
Maurienne
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Maurienne is one of the provinces of Savoy, corresponding to the arrondissement of Saint-Jean-de-Maurienne in France. It is also the name of the capital of the province. The Maurienne valley is one of the transverse valleys of the Alps. The river which has shaped the valley since the last glaciation is the Arc, the valley begins at the village of Écot, at the foot of the Col de lIseran, and ends at the confluence of the Arc and the Isère in the commune of Aiton. The mountains on the side are the Dauphiné Alps and the Cottian Alps. On the northern side are the part of the Graian Alps known as the Vanoise, the capital, Saint-Jean-de-Maurienne, lies at the confluence of the Arc and the Arvan River. Part of the road and rail route between Lyon and Turin runs through the valley. Numerous ski resorts line the valley, from the villages like Albiez-Montrond to the purpose-built resorts, dating from the 1970s like Le Corbier. The Vanoise National Park and its surroundings are a major tourist attraction. Alpine ibex, grey wolves, lynx, royal eagles or vultures are among the rare species that live in the numerous valleys of Maurienne. The region has numerous traces of habitation since the Paleolithic. In 1032, Humbert the White-Handed received the Maurienne, his land, from Conrad II the Salian whom he had helped in his Italian campaigns against Aribert. The House of Savoy maintained their independence as counts and then dukes until Savoy was linked with the Kingdom of Sardinia, which included Piedmont in north-western Italy. In the Maurienne are a series of five forts, La Barrière de lEsseillon, the Maurienne was not incorporated into France until 1860, as part of the political agreement with Napoleon III that brought about the unification of Italy. Despite this, the Maurienne and the Tarantaise valleys are classified as French towns and lands of Art and it lies along the Italian border around 45 km near Mont Cenis. The principal town is Modane, an old town, at the mouth of the Fréjus Road Tunnel. Much of the Haute-Maurienne is included in the Vanoise National Park and this borders the Gran Paradiso National Park of Italy. The two parks are important areas for ibexes, chamois, and golden eagles, the lammergeier was recently reintroduced into the area and it appears that wolves have reached the region within the past five years
2.
Golden Gate National Recreation Area
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The Golden Gate National Recreation Area is a U. S. National Recreation Area protecting 80,002 acres of ecologically and historically significant landscapes surrounding the San Francisco Bay Area. Much of the park is land used by the United States Army. GGNRA is managed by the National Park Service and is one of the most visited units of the National Park system in the United States, with more than 15 million visitors a year. It is also one of the largest urban parks in the world, the park is not one continuous locale, but rather a collection of areas that stretch from southern San Mateo County to northern Marin County, and includes several areas of San Francisco. The park is as diverse as it is expansive, it contains famous tourist attractions such as Muir Woods National Monument, Alcatraz, the park was created thanks to the cooperative legislative efforts of cosponsors Congressman William S. Mailliard and Congressman Phillip Burton. In 1972, President Richard Nixon signed into law An Act to Establish the Golden Gate National Recreation Area, the bill allocated $120 million for land acquisition and development. The National Park Service first purchased Alcatraz and Fort Mason from the U. S. Army, the Nature Conservancy then transferred the land to the GGNRA. These properties formed the basis for the park. Throughout the next 30 years, the National Park service acquired land and historic sites from the U. S. Army, private landowners and corporations, incorporating them into the GGNRA. Many decommissioned Army bases and fortifications were incorporated into the park, including Fort Funston, four Nike missile sites, The Presidio, the latest acquisition by the National Park Service is Mori Point, a small parcel of land on the Pacifica coast. In 1988, UNESCO designated the GGNRA and 12 adjacent protected areas the Golden Gate Biosphere Reserve, the property, located south of Pacifica and surrounding the communities of Moss Beach and Montara, is home to many diverse plant and animal species. The bill passed in the Senate, but did not pass the House of Representatives, Fort Baker - former Army post located on the northern side of the Golden Gate Headlands Center for the Arts - an artist residency program set in renovated military buildings in the Marin Headlands. Nike Missile Site SF-88 - a decommissioned Army surface-to-air missile site located near Fort Barry, located at the southwestern corner of the Presidio Battery Chamberlin - one of the last remaining coastal defense disappearing guns on the U. S. Trails lead across the ridge and to Sharp Park beach, the site includes recently restored wetlands and a pond, protecting endangered San Francisco garter snake and red-legged frog habitat. Rancho Corral de Tierra - the GGNRAs newest park, Golden Gate National Recreation Area Scenery Video, a video showing the scenery observed from the GGNRA, including footage from Lands End
3.
Styria
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Styria is a state or Bundesland, located in the southeast of Austria. In area it is the second largest of the nine Austrian federated states and it borders Slovenia and the Austrian states of Upper Austria, Lower Austria, Salzburg, Burgenland, and Carinthia. The capital city is Graz which had 276,526 inhabitants at the beginning of 2015, the March of Styria derived its name from the original seat of its ruling Otakar dynasty, Steyr, in todays Upper Austria. In German, the area is still called Steiermark while in English the Latin name Styria is used, the ancient link between Steyr and Styria is also apparent in their nearly identical coats of arms, a white Panther on a green background. The term Upper Styria used by an Austrian refers to the northern and northwestern parts of the federal-state, the term West Styria is used for the districts to the west of Graz, the districts east of Graz are referred to as East Styria. The western and eastern parts of the district Graz-Umgebung may or may not be considered parts of West and East Styria, the southern parts of the Duchy of Styria, which have formed part of Yugoslavia or Slovenia since 1918, were referred to as Lower Styria. During early Roman times, Styria was inhabited by Celtic tribes, after its conquest by the Romans, the eastern part of what is now Styria was part of Pannonia, while the western one was included in Noricum. During the Barbarian invasions, it was conquered or crossed by the Visigoths, the Huns, the Ostrogoths, the Rugii, the Lombards, the Franks, in 595 the latter were defeated by the Slavs, who thenceforth ruled it. In 1180 Styria separated from the Duchy of Carinthia and became a Grand Duchy of its own, after the hereditary subdivision of the latter, Styria formed the central part of Inner Austria. Styria developed culturally and economically under John, Archduke of Inner Austria between 1809 and 1859, as elsewhere in the developed world, there has been a shift away from the manufacturing sector towards the service sector in Styria. This has had consequences for the industrial regions of upper Styria which have suffered a steady decline in population in recent years. Styria is home to more than 150 clean technology companies, of one dozen are world technology leaders in their field. The revenue of Styrian cleantech companies totals €2.7 billion and this equals to 8 percent of the Gross Regional Product, and is one of the highest concentrations of leading clean technology companies in Europe. The companies have a growth rate of 22 percent per year—well above the worldwide cleantech market growth of 18 percent per year. The region created roughly 2,000 additional green jobs in 2008 alone, the state is divided into 13 districts, one of them a statutory city. Graz however is a stronghold of the left-wing Communist Party, the governor has usually been an ÖVP member. In these elections, the KPÖ also received votes after it had gained much popularity through its role in local politics in Graz during the preceding few years. The two right-wing populist parties, the Freedom Party of Austria and the Alliance for the Future of Austria, gebirgsdivision Robert Stolz, composer born in Graz Getty Kaspers, lead vocals of Dutch band Teach-In, who won the 1975 Eurovision Song Contest
4.
Tux Alps
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The Tux Alps or Tux Prealps are a sub-group of the Austrian Central Alps, which in turn form part of the Eastern Alps within Central Europe. They are located entirely within the Austrian federal state of Tyrol, the Tux Alps are one of three mountain ranges that form an Alpine backdrop to the city of Innsbruck. Their highest peak is the Lizumer Reckner,2,886 m and their name is derived from the village of Tux which is tucked away in a side valley of the Zillertal. The Alpine Club classification of the Eastern Alps calls this range the Tux Alps, the name Tux Prealps was declared in the 1984 edition of the AVE as outdated and not longer applicable. The reality is that the range can hardly be described as prealps in view of their sheer extent. The description only makes any sense when the range is seen in the context of the Zillertal Alps to the south, the Ziller valley borders the range in the east from the mouth of the Ziller on the Inn upstream as far as Mayrhofen. In the south the Tuxertal valley outlines the range from Mayrhofen to Hintertux, from there the boundary continues up to the saddle of the Tuxer Joch and through the Schmirntal valley to Sankt Jodok. To the west the Tux Alps are bounded by the Wipptal valley from Sankt Jodok downstream to Innsbruck, the Tuxer Joch saddle links the Tux Alps to the Zillertal Alps. The Tux Alps are a ski touring and hiking area. Its ski resorts are Glungezer, Lizum im Wattental, Hochfügen-Hochzillertal, Penken and Kellerjoch, the Patscherkofel mountain was a venue for the 1964 and 1976 Winter Olympics held in nearby Innsbruck. The largest part of the Tux Alps comprises low grade metamorphic rocks, next to this zone of Paleozoic rocks to the south there is a localised zone of various Mesozoic rocks, the so-called Tarntal Mesozoic. This complex zone belongs, like the quartz-phyllite zone, to the unit of the Lower Eastern Alps. Amongst the rocks of Tarntal Mesozoic may be found dolomite and limestones that are the basis of rock faces in the area of the Wattentaler Lizum. On the other hand, there are elements of the former ocean bed. The southern perimeter of the Tux Alps belongs to the tectonically deeper-lying Penninic Hohe Tauern window, here in the Tux Alps these are mainly rocks of the Penninic Glockner Nappe. The northeasternmost corner of the Tux Alps, from the area of Schwaz to Fügen im Zillertal, belongs to the Upper Eastern Alpine greywacke zone, silver and copper were once extensively mined in this zone in the area around Schwaz. The long-distance hiking trail known as the Munich to Venice Dream Path runs through the Tux Alps and this is not an official long-distance trail. Nevertheless, the route, which was first proposed in 1977, has achieved a profile than many of the other trails officially established and maintained by states or rambling clubs
5.
Rock (geology)
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Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a rock, is a combination of the minerals quartz, feldspar. The Earths outer solid layer, the lithosphere, is made of rock, rock has been used by mankind throughout history. The minerals and metals found in rocks have been essential to human civilization, three major groups of rocks are defined, igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is a component of geology. At a granular level, rocks are composed of grains of minerals, the aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed, many rocks contain silica, a compound of silicon and oxygen that forms 74. 3% of the Earths crust. This material forms crystals with other compounds in the rock, the proportion of silica in rocks and minerals is a major factor in determining their name and properties. Rocks are geologically classified according to such as mineral and chemical composition, permeability, the texture of the constituent particles. These physical properties are the end result of the processes that formed the rocks, over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock, igneous, sedimentary, and metamorphic, the three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks, hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. Igneous rock forms through the cooling and solidification of magma or lava and this magma can be derived from partial melts of pre-existing rocks in either a planets mantle or crust. Typically, the melting of rocks is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, igneous rocks are divided into two main categories, plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earths crust, a common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, the chemical abundance and the rate of cooling of magma typically forms a sequence known as Bowens reaction series. Most major igneous rocks are found along this scale, about 64. 7% of the Earths crust by volume consists of igneous rocks, making it the most plentiful category. Of these, 66% are basalts and gabbros, 16% are granite, only 0. 6% are syenites and 0. 3% peridotites and dunites
6.
Serpentine subgroup
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The serpentine subgroup are greenish, brownish, or spotted minerals commonly found in serpentinite rocks. They are used as a source of magnesium and asbestos, the name is thought to come from the greenish color being that of a serpent. In mineralogy and gemology, serpentine may refer to any of 20 varieties belonging to the serpentine group, owing to admixture, these varieties are not always easy to individualize, and distinctions are not usually made. There are three important mineral polymorphs of serpentine, antigorite, chrysotile and lizardite, the serpentine group of minerals are polymorphous, meaning that they have the same chemical formulae, but the atoms are arranged into different structures, or crystal lattices. Chrysotile, which has a habit, is one polymorph of serpentine and is an important component of asbestos. Other polymorphs in the group may have a platy habit. Antigorite and lizardite are the polymorphs with platy habit, many types of serpentine have been used for jewellery and hardstone carving, sometimes under the name false jade or Teton jade. Their olive green colour and smooth or scaly appearance is the basis of the name from the Latin serpentinus, meaning serpent rock and they have their origins in metamorphic alterations of peridotite and pyroxene. Serpentines may also pseudomorphously replace other magnesium silicates, alterations may be incomplete, causing physical properties of serpentines to vary widely. Where they form a significant part of the surface, the soil is unusually high in clay. Antigorite is the polymorph of serpentine that most commonly forms during metamorphism of wet ultramafic rocks and is stable at the highest temperatures—to over 600 °C at depths of 60 km or so. In contrast, lizardite and chrysotile typically form near the Earths surface and break down at low temperatures. It has been suggested that chrysotile is never stable relative to either of the other two serpentine polymorphs, samples of the oceanic crust and uppermost mantle from ocean basins document that ultramafic rocks there commonly contain abundant serpentine. Antigorite contains water in its structure, about 13 percent by weight, the flora is generally very distinctive, with specialised, slow-growing species. Areas of serpentine-derived soil will show as strips of shrubland and open, scattered small trees within otherwise forested areas, most serpentines are opaque to translucent, light, soft, infusible and susceptible to acids. All are microcrystalline and massive in habit, never being found as single crystals, lustre may be vitreous, greasy or silky. Colours range from white to grey, yellow to green, and brown to black, many are intergrown with other minerals, such as calcite and dolomite. Occurrence is worldwide, New Caledonia, Canada, US, Afghanistan, Britain, Greece, China, Ural Mountains, France, Korea, Austria, India, Myanmar, New Zealand, Norway and Italy are notable localities
7.
Mineral
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A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids, the study of minerals is called mineralogy. There are over 5,300 known mineral species, over 5,070 of these have been approved by the International Mineralogical Association, the silicate minerals compose over 90% of the Earths crust. The diversity and abundance of species is controlled by the Earths chemistry. Silicon and oxygen constitute approximately 75% of the Earths crust, which translates directly into the predominance of silicate minerals, minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various properties, which are related to their chemical structure. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, more specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid. Minerals are classified by key chemical constituents, the two dominant systems are the Dana classification and the Strunz classification, the silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a unit of a 4− silica tetrahedron—that is, a silicon cation coordinated by four oxygen anions. These tetrahedra can be polymerized to give the subclasses, orthosilicates, disilicates, cyclosilicates, inosilicates, phyllosilicates, other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. The first criterion means that a mineral has to form by a natural process, stability at room temperature, in the simplest sense, is synonymous to the mineral being solid. More specifically, a compound has to be stable or metastable at 25 °C, modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula, many mineral groups and species are composed of a solid solution, pure substances are not usually found because of contamination or chemical substitution. Finally, the requirement of an ordered atomic arrangement is usually synonymous with crystallinity, however, crystals are also periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage. There have been recent proposals to amend the definition to consider biogenic or amorphous substances as minerals. The formal definition of an approved by the IMA in 1995, A mineral is an element or chemical compound that is normally crystalline. However, if geological processes were involved in the genesis of the compound, Mineral classification schemes and their definitions are evolving to match recent advances in mineral science
8.
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
9.
Redox
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Redox is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a process and a complementary oxidation process, two key concepts involved with electron transfer processes. Redox reactions include all chemical reactions in which atoms have their oxidation state changed, in general, the chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in terms, Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom. Reduction is the gain of electrons or a decrease in state by a molecule, atom. As an example, during the combustion of wood, oxygen from the air is reduced, the reaction can occur relatively slowly, as in the case of rust, or more quickly, as in the case of fire. Redox is a portmanteau of reduction and oxidation, the word oxidation originally implied reaction with oxygen to form an oxide, since dioxygen was historically the first recognized oxidizing agent. Later, the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions, ultimately, the meaning was generalized to include all processes involving loss of electrons. The word reduction originally referred to the loss in weight upon heating a metallic ore such as an oxide to extract the metal. In other words, ore was reduced to metal, antoine Lavoisier showed that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the atom gains electrons in this process. The meaning of reduction then became generalized to all processes involving gain of electrons. Even though reduction seems counter-intuitive when speaking of the gain of electrons, it help to think of reduction as the loss of oxygen. Since electrons are charged, it is also helpful to think of this as reduction in electrical charge. The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes respectively when they occur at electrodes and these words are analogous to protonation and deprotonation, but they have not been widely adopted by chemists. The term hydrogenation could be used instead of reduction, since hydrogen is the agent in a large number of reactions. But, unlike oxidation, which has been generalized beyond its root element, the word redox was first used in 1928. The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another, the oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction
10.
Brucite
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Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg2. It is an alteration product of periclase in marble, a low-temperature hydrothermal vein mineral in metamorphosed limestones and chlorite schists. Brucite is often found in association with serpentine, calcite, aragonite, dolomite, magnesite, hydromagnesite, artinite, talc and it adopts a layered CdI2-like structure with hydrogen-bonds between the layers. Brucite was first described in 1824 and named for the discoverer, American mineralogist, a fibrous variety of brucite is called nemalite. It occurs in fibers or laths, usually elongated along, a notable location in the U. S. is Woods Chrome Mine, Cedar Hill Quarry, Lancaster County, Pennsylvania. Yellow and white brucite with a botryoidal habit has been found in Kharan District, brucite also occurs in the Bela Ophiolite of Khuzdar District, Pakistan. Synthetic brucite is mainly consumed as a precursor to magnesia, a useful refractory insulator and it finds some use as a flame retardant because it thermally decomposes to release water in a similar way to aluminium hydroxide and mixtures of huntite and hydromagnesite. It also constitutes a significant source of magnesium for industry, when cement or concrete are exposed to Mg2+. The neoformation of brucite, a material, induces mechanical stress in the hardened cement paste and is responsible for the formation of cracks. This kind of failure occurs upon prolonged contact between sea water or brines and concrete, the use of dolomite as aggregate in concrete can also cause the magnesian attack and should be avoided. List of minerals List of minerals named after people Portlandite, Ca2 Lee, Hyomin, Robert D. Cody, Anita M. Cody, effects of various deicing chemicals on pavement concrete deterioration. Archived from the original on March 20,2009, Lee, Hyomin, Robert D. Cody, Anita M. Cody, Paul G. Spry. Observations on brucite formation and the role of brucite in Iowa highway concrete deterioration, the protective layer and decalcification of C-S-H in the mechanism of chloride corrosion of cement paste. Biricik, Hasan, Fevziye Aköz, Fikret Türker, Ilhan Berktay, resistance to magnesium sulfate and sodium sulfate attack of mortars containing wheat straw ash
11.
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
12.
Iron
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Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is also the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, and transport in plasma. The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have also been studied extensively
. PMID 15326313. Retrieved 2011-11-06.
