1.
Chrysotile
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Chrysotile or white asbestos is the most commonly encountered form of asbestos, accounting for approximately 95% of the asbestos in the United States and a similar proportion in other countries. It is a soft, fibrous silicate mineral in the subgroup of phyllosilicates, as such. Its idealized chemical formula is Mg34, the material has physical properties which make it desirable for inclusion in building materials, but poses serious health risks when dispersed into air and inhaled. Three polytypes of chrysotile are known and these are very difficult to distinguish in hand specimens, and polarized light microscopy must normally be used. Clinochrysotile is the most common of the three forms, found notably at Asbestos, Quebec, Canada and its two measurable refractive indices tend to be lower than those of the other two forms. Bulk chrysotile has a similar to a human fingernail and is easily crumbled to fibrous strands composed of smaller bundles of fibrils. Naturally-occurring fibre bundles range in length from several millimetres to more than ten centimetres, the diameter of the fibre bundles is 0. 1–1 µm, and the individual fibrils are even finer,0. 02–0.03 µm, each fibre bundle containing tens or hundreds of fibrils. Chrysotile fibres have considerable strength, and may be spun into thread. They are also resistant to heat and are excellent thermal, electrical, the idealized chemical formula of chrysotile is Mg34, although some of the magnesium ions may be replaced by iron or other cations. Substitution of the ions for fluoride, oxide or chloride is also known. A related, but much rarer, mineral is pecoraite, in all the magnesium cations of chrysotile are substituted by nickel cations. Chrysotile is resistant to strong bases, but the fibres are attacked by acids. It is thermally stable up to around 550 °C, at which temperature it starts to dehydrate, dehydration is complete at about 750 °C, with the final products being forsterite, silica and water. In other scientific publications, epidemiologists have published peer reviewed scientific papers establishing that chrysotile is the cause of pleural mesothelioma. Chrysotile has been recommended for inclusion in the Rotterdam Convention on Prior Informed Consent, if listed, exports of chrysotile would only be permitted to countries that explicitly consent to imports. Canada, a producer of the mineral, has been harshly criticized by the Canadian Medical Association for its opposition to including chrysotile in the Convention. According to EU Regulation 1907/2006 the marketing and use of chrysotile, in May 1998, Canada requested consultations before the WTO and the European Commission concerning Frances 1996 prohibition of the importation and sale of all forms of asbestos. Canada said that the French measures contravened provisions of the Agreements on Sanitary and Phytosanitary Measures and on Technical Barriers to Trade, the EC claimed that safer substitute materials existed to take the place of asbestos
2.
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
3.
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
4.
Chromite
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Chromite is an iron chromium oxide, FeCr2O4. It is a mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts as it forms a solution with magnesiochromite. It is by far the most industrially important mineral for the production of chromium, used as an alloying ingredient in stainless. Chromite is found as orthocumulate lenses of chromitite in peridotite from the Earths mantle and it also occurs in layered ultramafic intrusive rocks. In addition, it is found in rocks such as some serpentinites. Ore deposits of chromite form as early magmatic differentiates and it is commonly associated with olivine, magnetite, serpentine, and corundum. The vast Bushveld igneous complex of South Africa is a layered mafic to ultramafic igneous body with some layers consisting of 90% chromite making the rare rock type. The Stillwater igneous complex in Montana also contains significant chromite, the only ores of chromium are the minerals chromite and magnesiochromite. Most of the time, economic geology names chromite the whole chromite-magnesiochromite series, the two main products of chromite refining are ferrochromium and metallic chromium, for those products the ore smelter process differs considerably. Chromite is also used as a material, because it has a high heat stability. The chromium extracted from chromite is used in plating and alloying for production of corrosion resistant superalloys, nichrome. Chromium is used as a pigment for glass, glazes, and paint and it is also sometimes used as a gemstone. In 200214,600,000 metric tons of chromite were mined, the largest producers were South Africa, India, Kazakhstan, Zimbabwe, Finland, Iran, and Brazil with several other countries producing the rest of less than 10% of the world production. Afghanistan has significant deposits of high grade ore, which is mined illegally in Khost Province. In Pakistan, chromite is mined from the rocks in mainly the Muslimbagh killa Saifullah District. Most of the chromite is of metallurgical grade with Cr2O3 averaging 54%, recently, the biggest user of chromite ore has been China, importing large quantities from South Africa, Pakistan, and other countries. The concentrate is used to make ferrochrome, which is in used to make stainless steel
5.
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
6.
Dunite
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Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse-grained or phaneritic texture. The mineral assemblage is greater than 90% olivine, with amounts of other minerals such as pyroxene, chromite, magnetite. Dunite is the olivine-rich end-member of the group of mantle-derived rocks. Dunite and other rocks are considered the major constituents of the Earths mantle above a depth of about 400 kilometers. It is also found in alpine peridotite massifs that represent slivers of sub-continental mantle exposed during collisional orogeny, Dunite typically undergoes retrograde metamorphism in near-surface environments and is altered to serpentinite and soapstone. Dunite may also form by the accumulation of crystals on the floor of large basaltic or picritic magma chambers. These cumulate dunites typically occur in layers in layered intrusions, associated with cumulate layers of wehrlite, olivine pyroxenite, harzburgite. Small layered intrusions may be of any age, for example, the Triassic Palisades Sill in New York. The largest layered mafic intrusions are tens of kilometers in size and almost all are Proterozoic in age, e. g. the Stillwater igneous complex, the Muskox intrusion, and the Great Dyke. Cumulate dunite may also be found in complexes, associated with layers of wehrlite, pyroxenite. Dunite was named by the German geologist, Ferdinand von Hochstetter in 1859 after Dun Mountain near Nelson, Dun Mountain was given its name because of the dun colour of the underlying ultramafic rocks. This color results from surface weathering that oxidizes the iron in olivine in temperate climates, a massive exposure of dunite in the United States can be found as Twin Sisters Mountain, near Mount Baker in the northern Cascade Range of Washington. In southern British Columbia, Canada dunite rocks form the core of an ultramafic rock complex located near the community of Tulameen. The rocks are enriched in platinum group metals, chromite and magnetite. Dunite could be used to sequester CO2 and help mitigate climate change via accelerated chemical rock weathering. This would involve the mining of dunite rocks in quarries followed by crushing and grinding as to create fine ground rock that would react with the carbon dioxide. The resulting products are magnesite and silica which could be commercialized. Mg 2 SiO4 +2 CO2 ⟶2 MgCO3 + SiO2 Dunite Blatt, Harvey and Robert J. Tracy,1996, Petrology, 2nd ed. W. H. Freeman, ISBN 0-7167-2438-3
7.
Peridotite
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Peridotite is a dense, coarse-grained igneous rock consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica and it is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron. Peridotite is derived from the Earths mantle, either as solid blocks and fragments, the compositions of peridotites from these layered igneous complexes vary widely, reflecting the relative proportions of pyroxenes, chromite, plagioclase, and amphibole. Peridotite is the dominant rock of the part of the Earths mantle. The word peridotite comes from the gemstone peridot, which consists of pale green olivine, classic peridotite is bright green with some specks of black, although most hand samples tend to be darker green. Peridotitic outcrops typically range from bright yellow to dark green in color. While green and yellow are the most common colors, peridotitic rocks may exhibit a range of colors such as blue, brown. Dunite, more than 90% olivine, typically with Mg/Fe ratio of about 9,1, wehrlite, mostly composed of olivine plus clinopyroxene. Harzburgite, mostly composed of olivine plus orthopyroxene, and relatively low proportions of basaltic ingredients, lherzolite, most common form of peridotite, mostly composed of olivine, orthopyroxene, and clinopyroxene, and have relatively high proportions of basaltic ingredients. Partial fusion of lherzolite and extraction of the melt fraction can leave a residue of harzburgite. Magnesium-rich olivine forms a proportion of peridotite, and so magnesium content is high. Layered igneous complexes have more varied compositions, depending on the fractions of pyroxenes, chromite, plagioclase. Minor minerals and mineral groups in peridotite include plagioclase, spinel, garnet, amphibole, in peridotite, plagioclase is stable at relatively low pressures, aluminous spinel at higher pressures, and garnet at yet higher pressures. Peridotite is the dominant rock of the Earths mantle above a depth of about 400 km, below that depth, olivine is converted to the higher-pressure mineral wadsleyite. Oceanic plates consist of up to about 100 km of peridotite covered by a thin crust, the crust, commonly about 6 km thick, consists of basalt, gabbro, and minor sediments. The peridotite below the ocean crust, abyssal peridotite, is found on the walls of rifts in the sea floor. Oceanic plates are usually subducted back into the mantle in subduction zones, peridotites also occur as fragments carried up by magmas from the mantle. Among the rocks that commonly include peridotite xenoliths are basalt and kimberlite, certain volcanic rocks, sometimes called komatiites, are so rich in olivine and pyroxene that they also can be termed peridotite
8.
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
9.
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
10.
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
11.
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
12.
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
13.
Ultramafic rock
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Ultramafic are igneous and meta-igneous rocks with a very low silica content, generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals. The Earths mantle is composed of ultramafic rocks, ultrabasic is a more inclusive term that includes igneous rocks with low silica content that may not be extremely enriched in Fe and Mg, such as carbonatites and ultrapotassic igneous rocks. Intrusive ultramafic rocks are found in large, layered ultramafic intrusions where differentiated rock types often occur in layers. Such cumulate rock types do not represent the chemistry of the magma from which they crystallized, the ultramafic intrusives include the dunites, peridotites and pyroxenites. Other rare varieties include troctolite which has a percentage of calcic plagioclase. Gabbro and norite often occur in the portions of the layered ultramafic sequences. Hornblendite and, rarely phlogopite, are also found, subvolcanic ultramafic rocks and dykes persist longer, but are also rare. Many of the lavas being produced on Io may be ultramafic, mercury also appears to have ultramafic volcanic rock. Examples include komatiite and picritic basalt, komatiites can be host to ore deposits of nickel. Ultrapotassic, ultramafic rocks such as lamprophyre, lamproite and kimberlite are known to have reached the surface of the Earth. Although no modern eruptions have been observed, analogues are preserved, most of these rocks occur as dikes, diatremes, lopoliths or laccoliths, and very rarely, intrusions. Most kimberlite and lampproite occurrences occur as volcanic and subvolcanic diatremes and maars, vents of Proterozoic lamproite, and Cenozoic lamproite are known, as are vents of Devonian lamprophyre. Kimberlite pipes in Canada, Russia and South Africa have incompletely preserved tephra and these are generally diatreme events and as such are not lava flows although tephra and ash deposits are partially preserved. These represent low-volume volatile melts and attain their ultramafic chemistry via a different process to typical ultramafic rocks, metamorphism of ultramafic rocks in the presence of water and/or carbon dioxide results in two main classes of metamorphic ultramafic rock, talc carbonate and serpentinite. When such metamorphic fluids have less than 10% molar proportion of CO2, reactions favor serpentinisation, the majority of ultramafic rocks are exposed in orogenic belts, and predominate in Archaean and Proterozoic terranes. Ultramafic magmas in the Phanerozoic are rarer, and there are very few recognised true ultramafic lavas in the Phanerozoic, many surface exposures of ultramafic rocks occur in ophiolite complexes where deep mantle-derived rocks have been obducted onto continental crust along and above subduction zones. Serpentine soil is a rich, calcium, potassium and phosphorus poor soil that develops on the regolith derived from ultramafic rocks. Ultramafic rocks also contain elevated amounts of chromium and nickel which may be toxic to plants, as a result, a distinctive type of vegetation develops on these soils
14.
Mantle (geology)
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The mantle is a layer inside a terrestrial planet and some other rocky planetary bodies. For a mantle to form, the body must be large enough to have undergone the process of planetary differentiation by density. The mantle surrounds the planetary core, the mantle is surrounded by the crust. The terrestrial planets, the Moon, two of Jupiters moons and the asteroid Vesta each have a made of silicate rock. Interpretation of spacecraft data suggests that at least two moons of Jupiter, as well as Titan and Triton each have a mantle made of ice or other solid volatile substances. The interior of Earth, similar to the terrestrial planets, is divided into layers of different composition. The mantle is a layer between the crust and the outer core, Earths mantle is a silicate rocky shell with an average thickness of 2,886 kilometres. The mantle makes up about 84% of Earths volume and it is predominantly solid but in geological time it behaves as a very viscous fluid. The mantle encloses the hot core rich in iron and nickel, past episodes of melting and volcanism at the shallower levels of the mantle have produced a thin crust of crystallized melt products near the surface. A thin crust, the part of the lithosphere, surrounds the mantle and is about 5 to 75 km thick. In some places under the ocean the mantle is exposed on the surface of Earth. The mantle is divided into sections which are based upon results from seismology and these layers are the following, the upper mantle, the transition zone, the lower mantle, and anomalous core–mantle boundary with a variable thickness. The uppermost mantle plus overlying crust are relatively rigid and form the lithosphere, below the lithosphere the upper mantle becomes notably more plastic. In some regions below the lithosphere, the shear velocity is reduced. Inge Lehmann discovered a seismic discontinuity at about 220 km depth, although this discontinuity has been found in other studies, the transition zone is an area of great complexity, it physically separates the upper and lower mantle. Very little is known about the lower mantle apart from that it appears to be relatively seismically homogeneous, the D layer at the core–mantle boundary separates the mantle from the core. A principal source of the heat that drives plate tectonics is the decay of uranium, thorium. The mantle differs substantially from the crust in its properties as the direct consequence of the difference in composition
15.
Seabed
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The seabed is the bottom of the ocean. Most of the oceans have a structure, created by common physical phenomena, mainly from tectonic movement. The mid-ocean ridge, as its name implies, is a rise through the middle of all the oceans. Typically a rift runs along the edge of this ridge, along tectonic plate edges there are typically oceanic trenches – deep valleys, created by the mantle circulation movement from the mid-ocean mountain ridge to the oceanic trench. Hotspot volcanic island ridges are created by volcanic activity, erupting periodically, in areas with volcanic activity and in the oceanic trenches there are hydrothermal vents – releasing high pressure and extremely hot water and chemicals into the typically freezing water around it. Deep ocean water is divided into layers or zones, each with features of salinity, pressure, temperature and marine life. Lying along the top of the plain is the abyssal zone. The hadal zone – which includes the oceanic trenches, lies between 6, 000–11,000 metres and is the deepest oceanic zone, the acronym mbsf meaning meters below the seafloor is a convention used for depths below the seafloor. Benthos is the community of organisms which live on, in, or near the seabed and this community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths. The benthic zone is the region on, in and immediately above the seabed, including the sediment surface. Benthos generally live in relationship with the substrate bottom. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, each area of the seabed has typical features such as common soil composition, typical topography, salinity of water layers above it, marine life, magnetic direction of rocks, and sedimentation. Seabed topography is flat where sedimentation is heavy and covers the tectonic features, marine life is abundant in the deep sea, especially around hydrothermal vents. Large deep sea communities of life have been discovered around black and white smokers—vents emitting chemicals toxic to humans. This marine life receives its energy both from the temperature difference and from chemosynthesis by bacteria. Brine pools are another seabed feature, usually connected to cold seeps, the seabed has been explored by submersibles such as Alvin and, to some extent, scuba divers with special equipment. The process that adds new material to the ocean floor is seafloor spreading. In recent years satellite images show a very clear mapping of the seabed, some childrens play songs include elements such as Theres a hole at the bottom of the sea, or A sailor went to sea
16.
Plate tectonics
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The theoretical model builds on the concept of continental drift developed during the first few decades of the 20th century. The geoscientific community accepted plate-tectonic theory after seafloor spreading was validated in the late 1950s, the lithosphere, which is the rigid outermost shell of a planet, is broken up into tectonic plates. The Earths lithosphere is composed of seven or eight major plates, where the plates meet, their relative motion determines the type of boundary, convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The relative movement of the plates typically ranges from zero to 100 mm annually, tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle, the material lost is balanced by the formation of new crust along divergent margins by seafloor spreading. In this way, the surface of the lithosphere remains the same. This prediction of plate tectonics is also referred to as the conveyor belt principle, earlier theories, since disproven, proposed gradual shrinking or gradual expansion of the globe. Tectonic plates are able to move because the Earths lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the ridge and drag, with downward suction. Another explanation lies in the different forces generated by forces of the Sun. The relative importance of each of these factors and their relationship to other is unclear. The outer layers of the Earth are divided into the lithosphere and asthenosphere and this is based on differences in mechanical properties and in the method for the transfer of heat. Mechanically, the lithosphere is cooler and more rigid, while the asthenosphere is hotter, in terms of heat transfer, the lithosphere loses heat by conduction, whereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient. The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, Plate motions range up to a typical 10–40 mm/year, to about 160 mm/year. The driving mechanism behind this movement is described below, tectonic lithosphere plates consist of lithospheric mantle overlain by either or both of two types of crustal material, oceanic crust and continental crust. Average oceanic lithosphere is typically 100 km thick, its thickness is a function of its age, as passes, it conductively cools
17.
Mafic
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Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, common mafic rocks include basalt, dolerite and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar, chemically, mafic rocks are on the other side of the rock spectrum from the felsic rocks. The term roughly corresponds to the basic rock class. Mafic lava, before cooling, has a low viscosity, in comparison to felsic lava, water and other volatiles can more easily and gradually escape from mafic lava. As a result, eruptions of volcanoes made of mafic lavas are less violent than felsic-lava eruptions. Most mafic-lava volcanoes are shield volcanoes, like those in Hawaii, QAPF diagram List of minerals List of rock types
18.
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
19.
Hydrolyzed
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Hydrolysis usually means the cleavage of chemical bonds by the addition of water. When a carbohydrate is broken into its component sugar molecules by hydrolysis, generally, hydrolysis or saccharification is a step in the degradation of a substance. Hydrolysis can be the reverse of a reaction in which two molecules join together into a larger one and eject a water molecule. Thus hydrolysis adds water to break down, whereas condensation builds up by removing water, usually hydrolysis is a chemical process in which a molecule of water is added to a substance. Sometimes this addition causes both substance and water molecule to split into two parts, in such reactions, one fragment of the target molecule gains a hydrogen ion. A common kind of hydrolysis occurs when a salt of an acid or weak base is dissolved in water. Water spontaneously ionizes into hydroxide anions and hydronium cations, the salt also dissociates into its constituent anions and cations. For example, sodium acetate dissociates in water into sodium and acetate ions, sodium ions react very little with the hydroxide ions whereas the acetate ions combine with hydronium ions to produce acetic acid. In this case the net result is an excess of hydroxide ions. For example, dissolving sulfuric acid in water is accompanied by hydrolysis to give hydronium and bisulfate, for a more technical discussion of what occurs during such a hydrolysis, see Brønsted–Lowry acid–base theory. Acid–base-catalysed hydrolyses are very common, one example is the hydrolysis of amides or esters and their hydrolysis occurs when the nucleophile attacks the carbon of the carbonyl group of the ester or amide. In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules such as water, in acids, the carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with carboxylic acid groups, perhaps the oldest commercially practiced example of ester hydrolysis is saponification. It is the hydrolysis of a triglyceride with a base such as sodium hydroxide. During the process, glycerol is formed, and the fatty acids react with the base and these salts are called soaps, commonly used in households. In addition, in living systems, most biochemical reactions take place during the catalysis of enzymes, the catalytic action of enzymes allows the hydrolysis of proteins, fats, oils, and carbohydrates. As an example, one may consider proteases and they catalyse the hydrolysis of interior peptide bonds in peptide chains, as opposed to exopeptidases. However, proteases do not catalyse the hydrolysis of all kinds of proteins and their action is stereo-selective, Only proteins with a certain tertiary structure are targeted as some kind of orienting force is needed to place the amide group in the proper position for catalysis
20.
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
21.
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
22.
Awaruite
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Awaruite is a naturally occurring alloy of nickel and iron with a composition from Ni2Fe to Ni3Fe. Awaruite occurs in river placer deposits derived from serpentinized peridotites and ophiolites and it also occurs as a rare component of meteorites. It was first described in 1885 for an occurrence along Gorge River, near Awarua Bay, South Island, New Zealand, its type locality
23.
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
24.
Exothermic process
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Its etymology stems from the Greek prefix έξω and the Greek word θερμικός. The term exothermic was first coined by Marcellin Berthelot, the opposite of an exothermic process is an endothermic process, one that absorbs energy in the form of heat. The concept is applied in the physical sciences to chemical reactions. Exothermic describe two types of reactions or systems found in nature, as follows. Simply stated, after a reaction, more energy has been released to the surroundings than was absorbed to initiate. On the other hand, in a reaction or system. Exothermic refers to a transformation in which a system releases energy to the surroundings, when the transformation occurs at constant pressure, one has for the enthalpy ∆H <0, and constant volume, one has for the internal energy ∆U <0. In an adiabatic system, a process results in an increase in temperature of the system. In exothermic chemical reactions, the heat that is released by the reaction takes the form of electromagnetic energy, the transition of electrons from one quantum energy level to another causes light to be released. This light is equivalent in energy to the energy of the energy for the chemical reaction. This light that is released can be absorbed by other molecules in solution to give rise to molecular vibrations or rotations, which gives rise to the classical understanding of heat. In contrast, when endothermic reactions occur, energy is absorbed to place an electron in an energy state. Net energy is absorbed by an endothermic reaction, in an exothermic reaction, the energy needed to start the reaction is less than the energy that is subsequently released, so there is a net release of energy. This is the understanding of exothermic and endothermic reactions. In a thermochemical reaction that is exothermic, the heat may be listed among the products of the reaction, because of historical accident, students encounter a source of possible confusion between the terminology of physics and biology. Http, //chemistry. about. com/b/a/184556. htm Observe exothermic reactions in a simple experiment
25.
Hydrothermal vent
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A hydrothermal vent is a fissure in a planets surface from which geothermally heated water issues. Hydrothermal vents are found near volcanically active places, areas where tectonic plates are moving apart, ocean basins. Hydrothermal vents exist because the earth is both active and has large amounts of water on its surface and within its crust. Common land types include hot springs, fumaroles and geysers, under the sea, hydrothermal vents may form features called black smokers. Chemosynthetic bacteria and archaea form the base of the chain, supporting diverse organisms, including giant tube worms, clams, limpets. Active hydrothermal vents are believed to exist on Jupiters moon Europa, and Saturns moon Enceladus, Hydrothermal vents in the deep ocean typically form along the mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two plates are diverging and new crust is being formed. The proportion of each varies from location to location, in contrast to the approximately 2 °C ambient water temperature at these depths, water emerges from these vents at temperatures ranging from 60 to as high as 464 °C. Due to the hydrostatic pressure at these depths, water may exist in either its liquid form or as a supercritical fluid at such temperatures. The critical point of water is 375 °C at a pressure of 218 atmospheres, however, introducing salinity into the fluid raises the critical point to higher temperatures and pressures. The critical point of seawater is 407 °C and 298.5 bars, accordingly, if a hydrothermal fluid with a salinity of 3.2 wt. % NaCl vents above 407 °C and 298.5 bars, furthermore, the salinity of vent fluids have been shown to vary widely due to phase separation in the crust. The critical point for lower salinity fluids is at lower temperature and pressure conditions than that for seawater, for example, a vent fluid with a 2.24 wt. % NaCl salinity has the point at 400 °C and 280.5 bars. Thus, water emerging from the hottest parts of some hydrothermal vents can be a supercritical fluid, examples of supercritical venting are found at several sites. Sister Peak vents low salinity phase-separated, vapor-type fluids, sustained venting was not found to be supercritical but a brief injection of 464 °C was well above supercritical conditions. A nearby site, Turtle Pits, was found to vent low salinity fluid at 407 °C, which is above the critical point of the fluid at that salinity. A vent site in the Cayman Trough named Beebe, which is the worlds deepest known hydrothermal site at ~5000 m below sea level, has shown sustained supercritical venting at 401 °C and 2.3 wt% NaCl
26.
Hydrogen
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Hydrogen is a chemical element with chemical symbol H and atomic number 1. With a standard weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form is the most abundant chemical substance in the Universe, non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium, has one proton, the universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays an important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a charge when it is known as a hydride. The hydrogen cation is written as though composed of a bare proton, Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing and ammonia production, mostly for the fertilizer market, Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. Hydrogen gas is flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion is −286 kJ/mol,2 H2 + O2 →2 H2O +572 kJ Hydrogen gas forms explosive mixtures with air in concentrations from 4–74%, the explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C, the detection of a burning hydrogen leak may require a flame detector, such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames, the destruction of the Hindenburg airship was a notorious example of hydrogen combustion and the cause is still debated. The visible orange flames in that incident were the result of a mixture of hydrogen to oxygen combined with carbon compounds from the airship skin. H2 reacts with every oxidizing element, the ground state energy level of the electron in a hydrogen atom is −13.6 eV, which is equivalent to an ultraviolet photon of roughly 91 nm wavelength. The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, however, the atomic electron and proton are held together by electromagnetic force, while planets and celestial objects are held by gravity. The most complicated treatments allow for the effects of special relativity
27.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
28.
Carbonate
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In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, a polyatomic ion with the formula of CO2−3. The name may mean an ester of carbonic acid, an organic compound containing the carbonate group C2. In geology and mineralogy, the term carbonate can refer both to carbonate minerals and carbonate rock, and both are dominated by the ion, CO2−3. Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock, sodium carbonate and potassium carbonate have been used since antiquity for cleaning and preservation, as well as for the manufacture of glass. Carbonates are widely used in industry, e. g. in iron smelting, as a raw material for Portland cement and lime manufacture, in the composition of ceramic glazes, the carbonate ion is the simplest oxocarbon anion. It consists of one carbon atom surrounded by three oxygen atoms, in a planar arrangement, with D3h molecular symmetry. It has a mass of 60.01 g/mol and carries a total formal charge of −2. It is the base of the hydrogen carbonate ion, HCO−3. The Lewis structure of the ion has two single bonds to negative oxygen atoms, and one short double bond to a neutral oxygen. This structure is incompatible with the symmetry of the ion. This process is called calcination, after calx, the Latin name of quicklime or calcium oxide, CaO, exceptions include lithium, sodium, potassium and ammonium carbonates, as well as many uranium carbonates. In aqueous solution, carbonate, bicarbonate, carbon dioxide, in strongly basic conditions, the carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent. In more acid conditions, aqueous carbon dioxide, CO2, is the main form, thus sodium carbonate is basic, sodium bicarbonate is weakly basic, while carbon dioxide itself is a weak acid. Carbonated water is formed by dissolving CO2 in water under pressure, in living systems an enzyme, carbonic anhydrase, speeds the interconversion of CO2 and carbonic acid. Although the carbonate salts of most metals are insoluble in water, in solution this equilibrium between carbonate, bicarbonate, carbon dioxide and carbonic acid changes consonant to changing temperature and pressure conditions. In the case of ions with insoluble carbonates, e. g. CaCO3. This is an explanation for the buildup of scale inside pipes caused by hard water, in organic chemistry a carbonate can also refer to a functional group within a larger molecule that contains a carbon atom bound to three oxygen atoms, one of which is double bonded. These compounds are known as organocarbonates or carbonate esters, and have the general formula ROCOOR′
29.
Sulfate
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The sulfate or sulphate ion is a polyatomic anion with the empirical formula SO2−4. Sulfate is the spelling recommended by IUPAC, but sulphate is used in British English, salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life, sulfates are salts of sulfuric acid and many are prepared from that acid. The sulfate anion consists of a sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. The symmetry is the same as that of methane, the sulfur atom is in the +6 oxidation state while the four oxygen atoms are each in the state. The sulfate ion carries a charge of −2 and it is the conjugate base of the bisulfate ion, HSO−4. Organic sulfate esters, such as sulfate, are covalent compounds. The tetrahedral molecular geometry of the ion is as predicted by VSEPR theory. Later, Linus Pauling used valence bond theory to propose that the most significant resonance canonicals had two pi bonds involving d orbitals and his reasoning was that the charge on sulfur was thus reduced, in accordance with his principle of electroneutrality. The S−O bond length of 149 pm is shorter than the bond lengths in sulfuric acid of 157 pm for S−OH, the double bonding was taken by Pauling to account for the shortness of the S−O bond. Paulings use of d orbitals provoked a debate on the importance of π bonding. The outcome was a consensus that d orbitals play a role. A widely accepted description involving pπ – dπ bonding was initially proposed by D. W. J. Cruickshank, in this model, fully occupied p orbitals on oxygen overlap with empty sulfur d orbitals. However, in description, despite there being some π character to the S−O bonds. For sulfuric acid, computational analysis confirms a positive charge on sulfur. Therefore, the representation with four single bonds is the optimal Lewis structure rather than the one with two double bonds, in this model, the structure obeys the octet rule and the charge distribution is in agreement with the electronegativity of the atoms. However, the representation of Pauling for sulfate and other main group compounds with oxygen is still a common way of representing the bonding in many textbooks. On the other hand, in the structure with an ionic bond, exceptions include calcium sulfate, strontium sulfate, lead sulfate, and barium sulfate, which are poorly soluble
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Chemotroph
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Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These molecules can be organic or inorganic, the chemotroph designation is in contrast to phototrophs, which utilize solar energy. Chemotrophs can be either autotrophic or heterotrophic, chemotrophs are commonly found in ocean floors where sunlight cannot reach them because they are not dependent on solar energy. Ocean floors often contain underwater volcanos that can provide heat to substitute sunlight for warmth, originally used with a different meaning, the term took its current definition after Lwoff and collaborators. Chemoautotrophs, in addition to deriving energy from chemical reactions, synthesize all necessary organic compounds from carbon dioxide, chemoautotrophs use inorganic energy sources, such as hydrogen sulfide, elemental sulfur, ferrous iron, and also molecular hydrogen, and ammonia. Most are bacteria or archaea that live in environments such as deep sea vents and are the primary producers in such ecosystems. Chemoautotrophs generally fall into groups, methanogens, halophiles, sulfur oxidizers and reducers, nitrifiers, anammox bacteria. An example of one of these prokaryotes would be Sulfolobus, chemolithotrophic growth can be dramatically fast, such as Thiomicrospira crunogena with a doubling time around one hour. Later, the term would also the chemoorganoautotrophy, that is. Chemoheterotrophs are unable to fix carbon to form their own organic compounds, in the deep oceans, iron-oxidizing bacteria derive their energy needs by oxidizing iron to iron. The extra electron obtained from this powers the cells, replacing or augmenting traditional phototrophism. In general, iron-oxidizing bacteria can exist only in areas with high iron concentrations, most of the ocean is devoid of iron, due to both the oxidative effect of dissolved oxygen in the water and the tendency of prokaryotes to take up the iron. Lava beds supply bacteria with iron straight from the Earths mantle, in addition, because oxygen is necessary for the reaction, these bacteria are much more common in the upper ocean, where oxygen is more abundant. What is still unknown is how exactly iron bacteria extract iron from rock and it is accepted that some mechanism exists that eats away at the rock, perhaps through specialized enzymes or compounds that bring more FeO to the surface. It has been debated about how much of the weathering of the rock is due to biotic components. Hydrothermal vents also release large quantities of dissolved iron into the deep ocean, in addition, the high thermal gradient around vent systems means a wide variety of bacteria can coexist, each with its own specialized temperature niche. Manganese-oxidizing bacteria also use of igneous lava rocks in much the same way. Manganese is much rarer than iron in oceanic crust, but is easier for bacteria to extract from igneous glass
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Microorganism
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A microorganism or microbe is a microscopic organism, which may be single-celled or multicellular. The study of microorganisms is called microbiology, a subject that began with the discovery of microorganisms in 1674 by Antonie van Leeuwenhoek, microorganisms are very diverse and include all bacteria, archaea and most protozoa. This group also contains some fungi, algae, and some such as rotifers. Many macroscopic animals and plants have microscopic juvenile stages, some microbiologists classify viruses and viroids as microorganisms, but others consider these as nonliving. In July 2016, scientists identified a set of 355 genes from the last universal ancestor of all life, including microorganisms. Microorganisms, under certain test conditions, have observed to thrive in the vacuum of outer space. Microorganisms likely far outweigh all other living things combined, the mass of prokaryote microorganisms including the bacteria and archaea may be as much as 0.8 trillion tons of carbon, out of the total biomass of between 1 and 4 trillion tons. Microorganisms appear to thrive in the Mariana Trench, the deepest spot in the Earths oceans, in August 2014, scientists confirmed the existence of microorganisms living 800 m below the ice of Antarctica. According to one researcher, You can find microbes everywhere — theyre extremely adaptable to conditions, microorganisms are crucial to nutrient recycling in ecosystems as they act as decomposers. As some microorganisms can fix nitrogen, they are a part of the nitrogen cycle. Microorganisms are also exploited in biotechnology, both in food and beverage preparation, and in modern technologies based on genetic engineering. A small proportion of microorganisms are pathogenic, causing disease and even death in plants, Robert Hooke coined the term cell after viewing plant cells under his microscope. Antonie Van Leeuwenhoek was one of the first people to observe microorganisms in 1673, later, in the 19th century, Louis Pasteur found that microorganisms caused food spoilage, debunking the theory of spontaneous generation. In 1876 Robert Koch discovered that microorganisms cause diseases, single-celled microorganisms were the first forms of life to develop on Earth, approximately 3–4 billion years ago. Further evolution was slow, and for about 3 billion years in the Precambrian eon, so, for most of the history of life on Earth, the only forms of life were microorganisms. Bacteria, algae and fungi have been identified in amber that is 220 million years old, microorganisms tend to have a relatively fast rate of evolution. Most microorganisms can reproduce rapidly, and bacteria are able to freely exchange genes through conjugation, transformation and transduction. This rapid evolution is important in medicine, as it has led to the development of multidrug resistant pathogenic bacteria, superbugs, the possible existence of microorganisms was discussed for many centuries before their discovery in the 17th century
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Olivine
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The mineral olivine is a magnesium iron silicate with the formula 2SiO4. Thus it is a type of nesosilicate or orthosilicate and it is a common mineral in the Earths subsurface but weathers quickly on the surface. The ratio of magnesium and iron varies between the two endmembers of the solid solution series, forsterite and fayalite, compositions of olivine are commonly expressed as molar percentages of forsterite and fayalite. Forsterite has a high melting temperature at atmospheric pressure, almost 1,900 °C. The melting temperature varies smoothly between the two endmembers, as do other properties, olivine incorporates only minor amounts of elements other than oxygen, silicon, magnesium and iron. Manganese and nickel commonly are the elements present in highest concentrations. Olivine gives its name to the group of minerals with a structure which includes tephroite, monticellite and kirschsteinite. It has a structure similar to magnetite but uses one quadravalent. Olivine gemstones are called peridot and chrysolite, olivine is named for its typically olive-green color, though it may alter to a reddish color from the oxidation of iron. Translucent olivine is sometimes used as a gemstone called peridot, some of the finest gem-quality olivine has been obtained from a body of mantle rocks on Zabargad island in the Red Sea. Olivine occurs in mafic and ultramafic igneous rocks and as a primary mineral in certain metamorphic rocks. Mg-rich olivine crystallizes from magma that is rich in magnesium and low in silica and that magma crystallizes to mafic rocks such as gabbro and basalt. Ultramafic rocks such as peridotite and dunite can be left after extraction of magmas. Olivine and high pressure structural variants constitute over 50% of the Earths upper mantle, the metamorphism of impure dolomite or other sedimentary rocks with high magnesium and low silica content also produces Mg-rich olivine, or forsterite. In contrast, Mg-rich olivine does not occur stably with silica minerals, Mg-rich olivine is stable to pressures equivalent to a depth of about 410 km within Earth. Mg-rich olivine has also discovered in meteorites, on the Moon and Mars, falling into infant stars. Such meteorites include chondrites, collections of debris from the early Solar System, the spectral signature of olivine has been seen in the dust disks around young stars. The tails of comets often have the signature of olivine
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Solid solution
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A solid solution is a solid-state solution of one or more solutes in a solvent. The solid solution needs to be distinguished from a mechanical mixtures of powdered solids like two salts, sugar and salt, etc, the mechanical mixtures have total or partial miscibility gap in solid state. Examples of solid solutions include crystallized salts from their liquid mixture, metal alloys, in the case of metal alloys intermetallic compounds occur frequently. The solute may incorporate into the solvent crystal lattice substitutionally, by replacing a solvent particle in the lattice, or interstitially, by fitting into the space between solvent particles. Both of these types of solid solution affect the properties of the material by distorting the crystal lattice, some mixtures will readily form solid solutions over a range of concentrations, while other mixtures will not form solid solutions at all. The propensity for any two substances to form a solution is a complicated matter involving the chemical, crystallographic. 1 displays an alloy of two metals which forms a solution at all relative concentrations of the two species. Solid solutions have important commercial and industrial applications, as such mixtures often have superior properties to pure materials, many metal alloys are solid solutions. Even small amounts of solute can affect the electrical and physical properties of the solvent, the binary phase diagram in Fig.2 shows the phases of a mixture of two substances in varying concentrations, A and B. The region labeled α is a solution, with B acting as the solute in a matrix of A. On the other end of the scale, the region labeled β is also a solid solution. The large solid region in between the α and β solid solutions, labeled α + β, is not a solid solution, at other proportions, the material will enter a mushy or pasty phase until it warms up to being completely melted. The mixture at the dip point of the diagram is called a eutectic alloy, lead-tin mixtures formulated at that point are useful when soldering electronic components, particularly if done manually, since the solid phase is quickly entered as the solder cools. In contrast, when lead-tin mixtures were used to solder seams in automobile bodies a pasty state enabled a shape to be formed with a paddle or tool. When a solid solution becomes unstable — due to a temperature, for example — exsolution occurs. This is mainly caused by difference in cation size, cations which have a large difference in radii are not likely to readily substitute. Take the alkali feldspar minerals for example, whose end members are albite, NaAlSi3O8 and microcline and this leads to exsolution where they will separate into two separate phases. In the case of the feldspar minerals, thin white albite layers will alternate between typically pink microcline
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Magnesium
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Magnesium is a chemical element with symbol Mg and atomic number 12. Magnesium is the ninth most abundant element in the universe and it is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus. When such stars explode as supernovas, much of the magnesium is expelled into the medium where it may recycle into new star systems. Magnesium is the eighth most abundant element in the Earths crust and the fourth most common element in the Earth, making up 13% of the planets mass and it is the third most abundant element dissolved in seawater, after sodium and chlorine. Magnesium occurs naturally only in combination with elements, where it invariably has a +2 oxidation state. The free element can be produced artificially, and is highly reactive, the free metal burns with a characteristic brilliant-white light. The metal is now obtained mainly by electrolysis of magnesium salts obtained from brine, Magnesium is less dense than aluminium, and the alloy is prized for its combination of lightness and strength. Magnesium is the eleventh most abundant element by mass in the body and is essential to all cells. Magnesium ions interact with polyphosphate compounds such as ATP, DNA, hundreds of enzymes require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids, elemental magnesium is a gray-white lightweight metal, two-thirds the density of aluminium. Magnesium has the lowest melting and the lowest boiling point 1,363 K of all the alkaline earth metals, Magnesium reacts with water at room temperature, though it reacts much more slowly than calcium, a similar group 2 metal. When submerged in water, hydrogen bubbles form slowly on the surface of the metal—though, if powdered, the reaction occurs faster with higher temperatures. Magnesiums reversible reaction with water can be harnessed to store energy, Magnesium also reacts exothermically with most acids such as hydrochloric acid, producing the metal chloride and hydrogen gas, similar to the HCl reaction with aluminium, zinc, and many other metals. Magnesium is highly flammable, especially when powdered or shaved into thin strips, flame temperatures of magnesium and magnesium alloys can reach 3,100 °C, although flame height above the burning metal is usually less than 300 mm. Once ignited, such fires are difficult to extinguish, with combustion continuing in nitrogen, carbon dioxide, Magnesium may also be used as an igniter for thermite, a mixture of aluminium and iron oxide powder that ignites only at a very high temperature. When burning in air, magnesium produces a light that includes strong ultraviolet wavelengths. Magnesium powder was used for illumination in the early days of photography. Later, magnesium filament was used in electrically ignited single-use photography flashbulbs, Magnesium powder is used in fireworks and marine flares where a brilliant white light is required
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Forsterite
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Forsterite is the magnesium-rich end-member of the olivine solid solution series. It is isomorphous with the iron-rich end-member, fayalite, forsterite crystallizes in the orthorhombic system with cell parameters a 4.75 Å, b 10.20 Å and c 5.98 Å. Forsterite is associated with igneous and metamorphic rocks and has also found in meteorites. In 2005 it was found in cometary dust returned by the Stardust probe. In 2011 it was observed as tiny crystals in the dusty clouds of gas around a forming star, two polymorphs of forsterite are known, wadsleyite and ringwoodite. Both are mainly known from meteorites, peridot is the gemstone variety of forsterite olivine. Forsterite reacts with quartz to form the orthopyroxene mineral enstatite in the following reaction, pure forsterite is composed of magnesium, oxygen and silicon. Other minerals such as monticellite, an uncommon mineral, share the olivine structure. Monticellite is found in contact metamorphosed dolomites, forsterite-rich olivine is the most abundant mineral in the mantle above a depth of about 400 km, pyroxenes are also important minerals in this upper part of the mantle. Due to its melting point, olivine crystals are the first minerals to precipitate from a magmatic melt in a cumulate process. Forsterite-rich olivine is a common product of mantle-derived magma. Olivine in mafic and ultramafic rocks typically is rich in the forsterite end-member, forsterite also occurs in dolomitic marble which results from the metamorphism of high magnesium limestones and dolostones. Nearly pure forsterite occurs in some metamorphosed serpentinites, fayalite-rich olivine is much less common. Nearly pure fayalite is a constituent in some granite-like rocks. Forsterite is mainly composed of the anion SiO44− and the cation Mg2+ in a molar ratio 1,2, silicon is the central atom in the SiO44− anion. Each oxygen atom is bonded to the silicon by a covalent bond. The four oxygen atoms have a negative charge because of the covalent bond with silicon. Therefore, oxygen atoms need to stay far from other in order to reduce the repulsive force between them
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Fayalite
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Fayalite, also called iron chrysolite, is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the group, fayalite crystallizes in the orthorhombic system with cell parameters a 4.82 Å, b 10.48 Å and c Å6.09. Fayalite forms solid solution series with the magnesium olivine endmember forsterite and its main occurrence is in ultramafic volcanic and plutonic rocks and less commonly in felsic plutonic rocks and rarely in granite pegmatite. It also occurs in lithophysae in obsidian and it also occurs in medium-grade thermally metamorphosed iron-rich sediments and in impure carbonate rocks. Fayalite is stable with quartz at low pressures, whereas more magnesian olivine is not, iron stabilizes the olivine + quartz pair. The pressure and compositional dependence of the reaction can be used to calculate constraints on pressures at which assemblages of olivine + quartz formed, fayalite can also react with oxygen to produce magnetite + quartz, the three minerals together make up the FMQ oxygen buffer. The reaction is used to control the fugacity of oxygen in laboratory experiments and it can also be used to calculate the fugacity of oxygen recorded by mineral assemblages in metamorphic and igneous processes. 6–7 GPa, i. e. at substantially lower pressure than the phase transitions of forsterite, the name fayalite is derived from Faial Island in the Azores where it was first described in 1840. Forsterite, the magnesium-rich end-member of the olivine solid-solution series, mineral redox buffer Deer, W. A. Howie, R. A. and Zussman, J. An introduction to the rock-forming minerals
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Portlandite
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Portlandite is a rare oxide mineral. It is the naturally occurring form of hydroxide and the calcium analogue of brucite. Portlandite occurs in a variety of environments, at the type location in Northern Ireland it occurs as an alteration of calc–silicate rocks by contact metamorphism of larnite–spurrite. It occurs as fumarole deposits in the Vesuvius area, in Jebel Awq, Oman it occurs as precipitates from an alkaline spring emanating from ultramafic bedrock. It also occurs in the mining area of Kuruman, Cape Province, South Africa in the Kalahari Desert where it occurs as large crystals. It occurs in association with afwillite, calcite, larnite, spurrite, halite, brownmillerite, hydrocalumite, mayenite and ettringite and it was first described in 1933 for an occurrence at Scawt Hill, Larne, County Antrim, Northern Ireland. It was named portlandite because the calcium hydroxide is a common hydrolysis product of Portland cement
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Cement
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A cement is a binder, a substance used in construction that sets, hardens and adheres to other materials, binding them together. Cement is seldom used solely, but is used to bind sand, Cement is used with fine aggregate to produce mortar for masonry, or with sand and gravel aggregates to produce concrete. Non-hydraulic cement will not set in wet conditions or underwater, rather, it sets as it dries and it is resistant to attack by chemicals after setting. Hydraulic cements set and become adhesive due to a reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble and so are quite durable in water and this allows setting in wet condition or underwater and further protects the hardened material from chemical attack. The chemical process for hydraulic cement found by ancient Romans used volcanic ash with added lime, the word cement can be traced back to the Roman term opus caementicium, used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick supplements that were added to the burnt lime, to obtain a hydraulic binder, were referred to as cementum, cimentum, cäment. In modern times, organic polymers are used as cements in concrete. Non-hydraulic cement, such as slaked lime, hardens by carbonation in the presence of carbon dioxide which is present in the air. The carbonation reaction requires the dry cement to be exposed to air and this whole process is called the lime cycle. Conversely, hydraulic cement hardens by hydration when water is added, Hydraulic cements are made of a mixture of silicates and oxides, the four main components being, Belite, Alite, Tricalcium aluminate, Brownmillerite. The chemistry of the above listed reactions is not completely clear and is still the object of research, Cement, chemically speaking, is a product that includes lime as the primary curing ingredient, but is far from the first material used for cementation. The Babylonians and Assyrians used bitumen to bind together burnt brick or alabaster slabs, in Egypt stone blocks were cemented together with a mortar made of sand and roughly burnt gypsum, which often contained calcium carbonate. Lime was used on Crete and by the ancient Greeks, there is evidence that the Minoans of Crete used crushed potshards as an artificial pozzolan for hydraulic cement. A kind of powder which from natural causes produces astonishing results and it is found in the neighborhood of Baiae and in the country belonging to the towns round about Mt. Vesuvius. This substance when mixed with lime and rubble not only lends strength to buildings of other kinds, the Greeks used volcanic tuff from the island of Thera as their pozzolan and the Romans used crushed volcanic ash with lime. This mixture was able to set under water increasing its resistance, the material was called pozzolana from the town of Pozzuoli, west of Naples where volcanic ash was extracted. In the absence of ash, the Romans used powdered brick or pottery as a substitute
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Belite
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Belite is an industrial mineral important in Portland cement manufacture. Its main constituent is dicalcium silicate, Ca2SiO4, sometimes formulated as 2 CaO · SiO2, the name was given by Törneborn in 1897 to a crystal identified in microscopic investigation of Portland cement. Belite is a name in use in the cement industry. It occurs naturally as the mineral larnite, the name being derived from Larne, Northern Ireland, the belite found in Portland cement differs in composition from pure dicalcium silicate. It is a solution and contains minor amounts of other oxides besides CaO. A typical composition, Based on this, the formula can be expressed as Ca1. 94Mg0. 02Na0. 01K0. 03Fe0. 02Al0. 07Si0. 90P0. 01O3.93. In practice, the composition varies with the composition of the clinker. Substitution of calcium ions or orthosilicate ions requires that electric charges be kept in balance, for instance, a limited number of orthosilicate ions can be replaced with sulfate ions, provided that for each sulfate ion, two aluminate ions are also substituted. Dicalcium silicate is stable, and is prepared from reactive CaO. The low temperature form is γ-belite, or lime olivine and this form does not hydrate, and is avoided in cement manufacture. As the temperature rises, it passes through several polymorphic states, the other silicate, alite contributes early strength, due to its higher reactivity. The hydrate phase, is referred to as the C-S-H phase and it grows as a mass of interlocking needles that provide the strength of the hydrated cement system. Relatively high belite reactivity is desirable in Portland cement manufacture, and this is achieved by rapid cooling, forming crystals that are small, distorted and highly defective. Defects provide sites for initial water attack, failure to cool the clinker rapidly leads to inversion of belite to the γ-form. This is observed macroscopically as dusting, the clinker nodules fall to a fine dust, the minerals in Portland cement clinker may be observed and quantified by petrographic microscopy. Clinker nodules are cut and ground to a flat, polished surface, the exposed minerals are made visible and identifiable by etching the surface. The surface can then be observed in reflected light by optical microscopy, in the example, a clinker nodule has been polished and etched with hydrogen fluoride vapour. The alite shows as brown, the belite as blue, electron microscopy can also be used, in which case the minerals may be identified by microprobe analysis
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Silicic acid
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Silicic acid /sɪˈlɪsɪk ˌæsɪd/ is a chemical compound. Silicic acid is the name for a family of chemical compounds containing the element silicon attached to oxide. This family of compounds have the formula n. In general, silicic acid reactions are difficult to control, partial dehydration to metasilicic acid, for example, is challenging because the reaction typically progresses all the way to silicon dioxide and water. Like other silanols, silicic acid is a weak acid and it can be deprotonated in solution, the conjugate base silicate is known. Silicic acid was discovered by Jöns Jacob Berzelius between 1810 and 1836 when studying silicon generated by his experiments, however, he failed to recognise it as distinct from silicon dioxide. Naturally occurring silicic acid is produced by a process called hydration involving water, and quartz. The reaction producing silicic acid from quartz can be written as, if the products are left in air dry products are formed. Silicic acid can be produced by the acidification of sodium silicate in aqueous solution, the main problem in using silicic acids in chemical synthesis is that silicic acids readily lose water to form randomly polymeric silica gel, a form of silicon dioxide. Dissolved silica is a used in the field of oceanography to describe the form of water-soluble silica as silicon hydroxide which can be measured by standard analyses. However, the dissolved silica excludes silicate occurring as silicate minerals, which is a class of minerals forming rings, sheets, chains. Likewise, the dissolved silica is different from the term silicone. There exist three different species of DSi in natural waters, SiO222− SiO3− Si4 DSi is created near the oceans surface and it is carried into the abyssopelagic zone by falling water in the poles. Uncontrolled build-up of silicic acid in the ocean is naturally checked – although human influence can upset this natural regulation and it is primarily removed by conversion to silicon dioxide and water. In the oceans, silicon exists primarily as orthosilicic acid, and these algae polymerise the silicic acid to so-called biogenic silica, used to construct their cell walls. In the uppermost water column the surface ocean is undersaturated with respect to DSi, DSi is regenerated with increasing water depth, and DSi values increase along the conveyor belt from the Atlantic over the Indian into the Pacific Ocean. Study has shown that physiological concentration of orthosilicic acid stimulates collagen type 1 synthesis, choline-stabilized orthosilicic acid is a bioavailable nutritional supplement. Bioinorganic Chemistry of Aluminium and Silicon research group website
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Ion
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An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
42.
Diffusion
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Diffusion is the net movement of molecules or atoms from a region of high concentration to a region of low concentration. This is also referred to as the movement of a substance down a concentration gradient, a gradient is the change in the value of a quantity with the change in another variable. The word diffusion derives from the Latin word, diffundere, which means to spread out, a distinguishing feature of diffusion is that it results in mixing or mass transport, without requiring bulk motion. Thus, diffusion should not be confused with convection, or advection, an example of a situation in which bulk flow and diffusion can be differentiated is the mechanism by which oxygen enters the body during external respiration. The lungs are located in the cavity, which expands as the first step in external respiration. This expansion leads to an increase in volume of the alveoli in the lungs and this creates a pressure gradient between the air outside the body and the alveoli. The air moves down the gradient through the airways of the lungs and into the alveoli until the pressure of the air. The air arriving in the alveoli has a concentration of oxygen than the “stale” air in the alveoli. The increase in oxygen concentration creates a concentration gradient for oxygen between the air in the alveoli and the blood in the capillaries that surround the alveoli, oxygen then moves by diffusion, down the concentration gradient, into the blood. The other consequence of the air arriving in alveoli is that the concentration of carbon dioxide in the alveoli decreases and this creates a concentration gradient for carbon dioxide to diffuse from the blood into the alveoli. The pumping action of the heart then transports the blood around the body, as the left ventricle of the heart contracts, the volume decreases, which increases the pressure in the ventricle. This creates a gradient between the heart and the capillaries, and blood moves through blood vessels by bulk flow. The concept of diffusion is widely used in, physics, chemistry, biology, sociology, economics, however, in each case, the object that is undergoing diffusion is “spreading out” from a point or location at which there is a higher concentration of that object. In the phenomenological approach, diffusion is the movement of a substance from a region of high concentration to a region of low concentration without bulk motion, according to Ficks laws, the diffusion flux is proportional to the negative gradient of concentrations. It goes from regions of higher concentration to regions of lower concentration, some time later, various generalizations of Ficks laws were developed in the frame of thermodynamics and non-equilibrium thermodynamics. From the atomistic point of view, diffusion is considered as a result of the walk of the diffusing particles. In molecular diffusion, the molecules are self-propelled by thermal energy. Random walk of small particles in suspension in a fluid was discovered in 1827 by Robert Brown, the theory of the Brownian motion and the atomistic backgrounds of diffusion were developed by Albert Einstein
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Pyroxene
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The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes are silicon-aluminum oxides with Ca, Na, Fe, Mg, Zn, Mn, Li substituting for Si, although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes. They share a structure consisting of single chains of silica tetrahedra. The name pyroxene is derived from the Ancient Greek words for fire, however, they are simply early-forming minerals that crystallized before the lava erupted. The upper mantle of Earth is composed mainly of olivine and pyroxene, a piece of the mantle is shown at right and is dominated by olivine, typical for common peridotite. Pyroxene and feldspar are the minerals in basalt and gabbro. Pyroxene minerals are named according to the chemical species occupying the X site, the Y site, cations in Y site are closely bound to 6 oxygens in octahedral coordination. Cations in the X site can be coordinated with 6 to 8 oxygen atoms, twenty mineral names are recognised by the International Mineralogical Associations Commission on New Minerals and Mineral Names and 105 previously used names have been discarded. A typical pyroxene has mostly silicon in the site and predominately ions with a charge of +2 in both the X and Y sites, giving the approximate formula XYT2O6. The names of the common calcium – iron – magnesium pyroxenes are defined in the pyroxene quadrilateral shown in Figure 2, the enstatite-ferrosilite series contain up to 5 mol. % calcium and exists in three polymorphs, orthorhombic orthoenstatite and protoenstatite and monoclinic clinoenstatite. Increasing the calcium content prevents the formation of the orthorhombic phases, there is not complete solid solution in calcium content and Mg-Fe-Ca pyroxenes with calcium contents between about 15 and 25 mol. % are not stable with respect to a pair of exolved crystals. This leads to a miscibility gap between pigeonite and augite compositions, there is an arbitrary separation between augite and the diopside-hedenbergite solid solution. The divide is taken at >45 mol. % Ca, as the calcium ion cannot occupy the Y site, pyroxenes with more than 50 mol. % calcium are not possible. A related mineral wollastonite has the formula of the hypothetical calcium end member, magnesium, calcium and iron are by no means the only cations that can occupy the X and Y sites in the pyroxene structure. A second important series of minerals are the sodium-rich pyroxenes. The inclusion of sodium, which has a charge of +1, in jadeite and aegirine this is added by the inclusion of a +3 cation on the Y site. Table 1 shows the range of other cations that can be accommodated in the pyroxene structure. For example, Na and Al give the jadeite composition, coupled substitution of a 1+ ion on the X site and a mixture of equal numbers of 2+ and 4+ ions on the Y site
. PMID 15326313. Retrieved 2011-11-06.
