A mineral is, broadly speaking, a solid chemical compound that occurs in pure form. A rock may consist of a single mineral, or may be an aggregate of two or more different minerals, spacially segregated into distinct phases. Compounds that occur only in living beings are excluded, but some minerals are biogenic and/or are organic compounds in the sense of chemistry. Moreover, living beings synthesize inorganic minerals that occur in rocks. In geology and mineralogy, the term "mineral" is reserved for mineral species: crystalline compounds with a well-defined chemical composition and a specific crystal structure. Minerals without a definite crystalline structure, such as opal or obsidian, are more properly called mineraloids. If a chemical compound may occur with different crystal structures, each structure is considered different mineral species. Thus, for example and stishovite are two different minerals consisting of the same compound, silicon dioxide; the International Mineralogical Association is the world's premier standard body for the definition and nomenclature of mineral species.
As of November 2018, the IMA recognizes 5,413 official mineral species. Out of more than 5,500 proposed or traditional ones; the chemical composition of a named mineral species may vary somewhat by the inclusion of small amounts of impurities. Specific varieties of a species sometimes have official names of their own. For example, amethyst is a purple variety of the mineral species quartz; some mineral species can have variable proportions of two or more chemical elements that occupy equivalent positions in the mineral's structure. Sometimes a mineral with variable composition is split into separate species, more or less arbitrarily, forming a mineral group. Besides the essential chemical composition and crystal structure, the description of a mineral species includes its common physical properties such as habit, lustre, colour, tenacity, fracture, specific gravity, fluorescence, radioactivity, as well as its taste or smell and its reaction to acid. Minerals are classified by key chemical constituents.
Silicate minerals comprise 90% of the Earth's crust. Other important mineral groups include the native elements, oxides, carbonates and phosphates. One definition of a mineral encompasses the following criteria: Formed by a natural process. Stable or metastable at room temperature. In the simplest sense, this means. Classical examples of exceptions to this rule include native mercury, which crystallizes at −39 °C, water ice, solid only below 0 °C. Modern advances have included extensive study of liquid crystals, which extensively involve mineralogy. Represented by a chemical formula. Minerals are chemical compounds, as such they can be described by fixed or a variable formula. Many mineral groups and species are composed of a solid solution. For example, the olivine group is described by the variable formula 2SiO4, a solid solution of two end-member species, magnesium-rich forsterite and iron-rich fayalite, which are described by a fixed chemical formula. Mineral species themselves could have a variable composition, such as the sulfide mackinawite, 9S8, a ferrous sulfide, but has a significant nickel impurity, reflected in its formula.
Ordered atomic arrangement. This means crystalline. An ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form and cleavage. There have been several recent proposals to classify amorphous substances as minerals; the formal definition of a mineral approved by the IMA in 1995: "A mineral is an element or chemical compound, crystalline and, formed as a result of geological processes." Abiogenic. Biogenic substances are explicitly excluded by the IMA: "Biogenic substances are chemical compounds produced by biological processes without a geological component and are not regarded as minerals. However, if geological processes were involved in the genesis of the compound the product can be accepted as a mineral."The first three general characteristics are less debated than the last two. Mineral classification schemes and their definitions are evolving to match recent advances in mineral science. Recent changes have included the addition of an organic class, in both the new Dana and the Strunz classification schemes.
The organic class includes a rare group of minerals with hydrocarbons. The IMA Commission on New Minerals and Mineral Names adopted in 2009 a hierarchical scheme for the naming and classification of mineral groups and group names and established seven commissions and four working groups to review and classify minerals into an official listing of their published names. According to these new r
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of small particules and subsequent cementation of mineral or organic particles on the floor of oceans or other bodies of water at the Earth's surface. Sedimentation is the collective name for processes; the particles that form a sedimentary rock are called sediment, may be composed of geological detritus or biological detritus. Before being deposited, the geological detritus was formed by weathering and erosion from the source area, transported to the place of deposition by water, ice, mass movement or glaciers, which are called agents of denudation. Biological detritus was formed by bodies and parts of dead aquatic organisms, as well as their fecal mass, suspended in water and piling up on the floor of water bodies. Sedimentation may occur as dissolved minerals precipitate from water solution; the sedimentary rock cover of the continents of the Earth's crust is extensive, but the total contribution of sedimentary rocks is estimated to be only 8% of the total volume of the crust.
Sedimentary rocks are only a thin veneer over a crust consisting of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata; the study of sedimentary rocks and rock strata provides information about the subsurface, useful for civil engineering, for example in the construction of roads, tunnels, canals or other structures. Sedimentary rocks are important sources of natural resources like coal, fossil fuels, drinking water or ores; the study of the sequence of sedimentary rock strata is the main source for an understanding of the Earth's history, including palaeogeography and the history of life. The scientific discipline that studies the properties and origin of sedimentary rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps with other disciplines in the Earth sciences, such as pedology, geomorphology and structural geology. Sedimentary rocks have been found on Mars. Sedimentary rocks can be subdivided into four groups based on the processes responsible for their formation: clastic sedimentary rocks, biochemical sedimentary rocks, chemical sedimentary rocks, a fourth category for "other" sedimentary rocks formed by impacts and other minor processes.
Clastic sedimentary rocks are composed of other rock fragments that were cemented by silicate minerals. Clastic rocks are composed of quartz, rock fragments, clay minerals, mica. Clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions: gravel and mud; the classification of clastic sedimentary rocks parallels this scheme. This tripartite subdivision is mirrored by the broad categories of rudites and lutites in older literature; the subdivision of these three broad categories is based on differences in clast shape, grain size or texture. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel. Sandstone classification schemes vary but most geologists have adopted the Dott scheme, which uses the relative abundance of quartz and lithic framework grains and the abundance of a muddy matrix between the larger grains.
Composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name. Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks. All other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Quartz sandstones have >90% quartz grains Feldspathic sandstones have <90% quartz grains and more feldspar grains than lithic grains Lithic sandstones have <90% quartz grains and more lithic grains than feldspar grainsAbundance of muddy matrix material between sand grains When sand-sized particles are deposited, the space between the grains either remains open or is filled with mud. "Clean" sandstones with open pore space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes. Six sandstone names are possible using the descriptors for grain composition and the amount of matrix. For example, a quartz arenite would be composed of quartz grains and have little or no clayey matrix between the grains, a lithic wacke would have abundant lithic grains and abundant muddy matrix, etc.
Although the Dott classification scheme is used by sedimentologists, common names like greywacke and quartz sandstone are still used by non-specialists and in popular literature. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles; these fine-grained particles are transported by turbulent flow in water or air, deposited as the flow calms and the particles settle out of suspension. Most authors presently
A stalactite is a type of formation that hangs from the ceiling of caves, hot springs, or manmade structures such as bridges and mines. Any material, soluble, can be deposited as a colloid, or is in suspension, or is capable of being melted, may form a stalactite. Stalactites may be composed of lava, mud, pitch, sand and amberat. A stalactite is not a speleothem, though speleothems are the most common form of stalactite because of the abundance of limestone caves; the corresponding formation on the floor of the cave is known as a stalagmite. The most common stalactites are speleothems, they form through deposition of calcium carbonate and other minerals, precipitated from mineralized water solutions. Limestone is the chief form of calcium carbonate rock, dissolved by water that contains carbon dioxide, forming a calcium bicarbonate solution in underground caverns; the chemical formula for this reaction is: CaCO3 + H2O + CO2 → Ca2This solution travels through the rock until it reaches an edge and if this is on the roof of a cave it will drip down.
When the solution comes into contact with air the chemical reaction that created it is reversed and particles of calcium carbonate are deposited. The reversed reaction is: Ca2 → CaCO3 + H2O + CO2An average growth rate is 0.13 mm a year. The quickest growing stalactites are those formed by a constant supply of slow dripping water rich in calcium carbonate and carbon dioxide, which can grow at 3 mm per year; the drip rate must be slow enough to allow the CO2 to degas from the solution into the cave atmosphere, resulting in deposition of CaCO3 on the stalactite. Too fast a drip rate and the solution, still carrying most of the CaCO3, falls to the cave floor where degassing occurs and CaCO3 is deposited as a stalagmite. All limestone stalactites begin with a single mineral-laden drop of water; when the drop falls, it deposits the thinnest ring of calcite. Each subsequent drop that forms and falls deposits another calcite ring; these rings form a narrow, hollow tube known as a "soda straw" stalactite.
Soda straws can grow quite long, but are fragile. If they become plugged by debris, water begins flowing over the outside, depositing more calcite and creating the more familiar cone-shaped stalactite; the same water drops that fall from the tip of a stalactite deposit more calcite on the floor below resulting in a rounded or cone-shaped stalagmite. Unlike stalactites, stalagmites never start out as hollow "soda straws". Given enough time, these formations can meet and fuse to create pillars of calcium carbonate known as a "column". Stalactite formation begins over a large area, with multiple paths for the mineral rich water to flow; as minerals are dissolved in one channel more than other competing channels, the dominant channel begins to draw more and more of the available water, which speeds its growth resulting in all other channels being choked off. This is one reason; the larger the formation, the greater the interformation distance. Another type of stalactite is formed in lava tubes; the mechanism of formation is the deposition of material on the ceilings of caves, however with lava stalactites formation happens quickly in only a matter of hours, days, or weeks, whereas limestone stalactites may take up to thousands of years.
A key difference with lava stalactites is that once the lava has ceased flowing, so too will the stalactites cease to grow. This means; the generic term lavacicle has been applied to lava stalactites and stalagmites indiscriminately and evolved from the word icicle. Like limestone stalactites, they can leave lava drips on the floor that turn into lava stalagmites and may fuse with the corresponding stalactite to form a column. Shark tooth stalactites, it may begin as a small driblet of lava from a semi-solid ceiling, but grows by accreting layers as successive flows of lava rise and fall in the lava tube and recoating the stalactite with more material. They can vary from a few millimeters to over a meter in length. Splash stalactites As lava flows through a tube, material will be splashed up on the ceiling and ooze back down, hardening into a stalactite; this type of formation results in a irregularly shaped stalactite, looking somewhat like stretched taffy. They may be of a different color than the original lava that formed the cave.
Tubular lava stalactites When the roof of a lava tube is cooling, a skin will form that traps semi-molten material inside. Trapped gases force lava to extrude out through small openings that result in hollow, tubular stalactites analogous to the soda straws formed as depositional speleothems in solution caves, The longest known is 2 meters in length; these are common in Hawaiian lava tubes and are associated with a drip stalagmite that forms below as material is carried through the tubular stalactite and piles up on the floor beneath. Sometimes the tubular form collapses near the distal end, most when the pressure of escaping gases decreased and still-molten portions of the stalactites deflated and cooled; these tubular stalactites will acquire a twisted, vermiform appearance as bits of lava crystallize and force the flow in different directions. These tubular lava helictites may be influenced by air
Carbonate rocks are a class of sedimentary rocks composed of carbonate minerals. The two major types are limestone, composed of calcite or aragonite and dolostone, composed of the mineral dolomite. Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases; when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. Karst topography and caves develop in carbonate rocks because of their solubility in dilute acidic groundwater. Cooling groundwater or mixing of different groundwaters will create conditions suitable for cave formation. Marble is the metamorphic carbonate rock. Rare igneous carbonate rocks exist as intrusive carbonatites and rarer volcanic carbonate lava.
Dunham classification Folk classification Sinkhole
Stoichiometry is the calculation of reactants and products in chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the products, leading to the insight that the relations among quantities of reactants and products form a ratio of positive integers; this means that if the amounts of the separate reactants are known the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of the products can be empirically determined the amount of the other reactants can be calculated; this is illustrated in the image here, where the balanced equation is: CH4 + 2 O2 → CO2 + 2 H2O. Here, one molecule of methane reacts with two molecules of oxygen gas to yield one molecule of carbon dioxide and two molecules of water; this particular chemical equation is an example of complete combustion. Stoichiometry measures these quantitative relationships, is used to determine the amount of products and reactants that are produced or needed in a given reaction.
Describing the quantitative relationships among substances as they participate in chemical reactions is known as reaction stoichiometry. In the example above, reaction stoichiometry measures the relationship between the methane and oxygen as they react to form carbon dioxide and water; because of the well known relationship of moles to atomic weights, the ratios that are arrived at by stoichiometry can be used to determine quantities by weight in a reaction described by a balanced equation. This is called composition stoichiometry. Gas stoichiometry deals with reactions involving gases, where the gases are at a known temperature and volume and can be assumed to be ideal gases. For gases, the volume ratio is ideally the same by the ideal gas law, but the mass ratio of a single reaction has to be calculated from the molecular masses of the reactants and products. In practice, due to the existence of isotopes, molar masses are used instead when calculating the mass ratio; the term stoichiometry was first used by Jeremias Benjamin Richter in 1792 when the first volume of Richter's Stoichiometry or the Art of Measuring the Chemical Elements was published.
The term is derived from the Ancient Greek words στοιχεῖον stoicheion "element" and μέτρον metron "measure". In patristic Greek, the word Stoichiometria was used by Nicephorus to refer to the number of line counts of the canonical New Testament and some of the Apocrypha. A stoichiometric amount or stoichiometric ratio of a reagent is the optimum amount or ratio where, assuming that the reaction proceeds to completion: All of the reagent is consumed There is no deficiency of the reagent There is no excess of the reagent. Stoichiometry rests upon the basic laws that help to understand it better, i.e. law of conservation of mass, the law of definite proportions, the law of multiple proportions and the law of reciprocal proportions. In general, chemical reactions combine in definite ratios of chemicals. Since chemical reactions can neither create nor destroy matter, nor transmute one element into another, the amount of each element must be the same throughout the overall reaction. For example, the number of atoms of a given element X on the reactant side must equal the number of atoms of that element on the product side, whether or not all of those atoms are involved in a reaction.
Chemical reactions, as macroscopic unit operations, consist of a large number of elementary reactions, where a single molecule reacts with another molecule. As the reacting molecules consist of a definite set of atoms in an integer ratio, the ratio between reactants in a complete reaction is in integer ratio. A reaction may consume more than one molecule, the stoichiometric number counts this number, defined as positive for products and negative for reactants. Different elements have a different atomic mass, as collections of single atoms, molecules have a definite molar mass, measured with the unit mole. By definition, carbon-12 has a molar mass of 12 g/mol. Thus, to calculate the stoichiometry by mass, the number of molecules required for each reactant is expressed in moles and multiplied by the molar mass of each to give the mass of each reactant per mole of reaction; the mass ratios can be calculated by dividing each by the total in the whole reaction. Elements in their natural state are mixtures of isotopes of differing mass, thus atomic masses and thus molar masses are not integers.
For instance, instead of an exact 14:3 proportion, 17.04 kg of ammonia consists of 14.01 kg of nitrogen and 3 × 1.01 kg of hydrogen, because natural nitrogen includes a small amount of nitrogen-15, natural hydrogen includes hydrogen-2. A stoichiometric reactant is a reactant, consumed in a reaction, as opposed to a catalytic reactant, not consumed in the overall reaction because it reacts in one step and is regenerated in another step. Stoichiometry is not only used to balance chemical equations but used in conversions, i.e. converting from grams to moles using molar mass as the conversion factor, or from grams to milliliters using density. For example, to find the amount of NaCl in 2.00 g, one would do the following: 2.00 g NaCl 58.44 g NaCl mol − 1 = 0.034 mol In the above example, when written out in fraction form, the units of grams form a multiplicative identity, equivalent to one, wit
Slovakia the Slovak Republic, is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the west, the Czech Republic to the northwest. Slovakia's territory spans about 49,000 square kilometres and is mountainous; the population is over 5.4 million and consists of Slovaks. The capital and largest city is Bratislava, the second largest city is Košice; the official language is Slovak. The Slavs arrived in the territory of present-day Slovakia in the 6th centuries. In the 7th century, they played a significant role in the creation of Samo's Empire and in the 9th century established the Principality of Nitra, conquered by the Principality of Moravia to establish Great Moravia. In the 10th century, after the dissolution of Great Moravia, the territory was integrated into the Principality of Hungary, which would become the Kingdom of Hungary in 1000. In 1241 and 1242, much of the territory was destroyed by the Mongols during their invasion of Central and Eastern Europe.
The area was recovered thanks to Béla IV of Hungary who settled Germans which became an important ethnic group in the area in what are today parts of central and eastern Slovakia. After World War I and the dissolution of the Austro-Hungarian Empire, the Czechoslovak National Council established Czechoslovakia. A separate Slovak Republic existed during World War II as a totalitarian, clero-fascist one-party client state of Nazi Germany. At the end of World War II, Czechoslovakia was re-established as an independent country. A coup in 1948 ushered in a totalitarian one-party state under the Communist regime during whose rule the country existed as a satellite of the Soviet Union. Attempts for liberalization of communism in Czechoslovakia culminated in the Prague Spring, crushed by the Warsaw Pact invasion of Czechoslovakia in August 1968. In 1989, the Velvet Revolution ended the Communist rule in Czechoslovakia peacefully. Slovakia became an independent state on 1 January 1993 after the peaceful dissolution of Czechoslovakia, sometimes known as the Velvet Divorce.
Slovakia is a developed country, with a high-income advanced economy and a high Human Development Index, a high standard of living and performs favourably in measurements of civil liberties, press freedom, internet freedom, democratic governance and peacefulness. The country maintains a combination of market economy with a comprehensive social security system. Citizens of Slovakia are provided with universal health care, free education and one of the longest paid parental leave in the OECD; the country joined the European Union on 1 May 2004 and joined the Eurozone on 1 January 2009. Slovakia is a member of the Schengen Area, NATO, the United Nations, the OECD, the WTO, CERN, the OSCE, the Council of Europe and the Visegrád Group. Although regional income inequality is high, 90% of citizens own their homes. In 2018, Slovak citizens had visa-free or visa-on-arrival access to 179 countries and territories, ranking the Slovak passport 10th in the world; as part of Eurozone, Slovak legal tender is the world's 2nd-most-traded currency.
Slovakia is the world's largest per-capita car producer with a total of 1,040,000 cars manufactured in the country in 2016 alone and the 7th largest car producer in the European Union. The car industry represents 43% of Slovakia's industrial output, a quarter of its exports; the first written mention of name Slovakia is in 1586. It derives from the Czech word Slováky; the native name Slovensko derives from an older name of Slovaks Sloven what may indicate its origin before the 15th century. The original meaning was geographic, since Slovakia was a part of the multiethnic Kingdom of Hungary and did not form a separate administrative unit in this period. Radiocarbon dating puts the oldest surviving archaeological artefacts from Slovakia – found near Nové Mesto nad Váhom – at 270,000 BCE, in the Early Paleolithic era; these ancient tools, made by the Clactonian technique, bear witness to the ancient habitation of Slovakia. Other stone tools from the Middle Paleolithic era come from the Prévôt cave in Bojnice and from other nearby sites.
The most important discovery from that era is a Neanderthal cranium, discovered near Gánovce, a village in northern Slovakia. Archaeologists have found prehistoric human skeletons in the region, as well as numerous objects and vestiges of the Gravettian culture, principally in the river valleys of Nitra, Ipeľ, Váh and as far as the city of Žilina, near the foot of the Vihorlat and Tribeč mountains, as well as in the Myjava Mountains; the most well-known finds include the oldest female statue made of mammoth-bone, the famous Venus of Moravany. The statue was found in the 1940s in Moravany nad Váhom near Piešťany. Numerous necklaces made of shells from Cypraca thermophile gastropods of the Tertiary period have come from the sites of Zákovská, Podkovice and Radošina; these findings provide the most ancient evidence of commercial exchanges carried out between the Mediterranean and central Europe. The Bronze Age in the geographical territory of modern-day Slovakia went through three stages of development, stretching from 2000 to 800 BCE.
Major cultural and political development can be attributed to the significant growth in production of copper in central Slovakia and northwe
Flowstones are composed of sheetlike deposits of calcite or other carbonate minerals, formed where water flows down the walls or along the floors of a cave. They are found in "solution caves", in limestone, where they are the most common speleothem. However, they may form in any type of cave. Flowstones are formed via the degassing of vadose percolation waters. Flowstone may form on manmade structures as a result of calcium hydroxide being leached from concrete, lime or mortar; these secondary deposits created outside the cave environment, which mimic the shapes and forms of speleothems, are classified as "calthemites" and are associated with concrete degradation. Flowing films of water that move along floors or down positive-sloping walls build up layers of calcium carbonate, gypsum, or other cave minerals; these minerals are dissolved in the water and are deposited when the water loses its dissolved carbon dioxide through the mechanism of agitation, meaning it can no longer hold the minerals in solution.
The flowstone forms when thin layers of these deposits build on each other, sometimes developing more rounded shapes as the deposit gets thicker. There are two common forms of flowstones and travertine. Tufa is formed via the precipitation of calcium carbonate, is spongy or porous in nature. Travertine is a calcium carbonate deposit formed in creeks or rivers; the deposits may grade into thin sheets called "draperies" or "curtains" where they descend from overhanging portions of the wall. Some draperies are translucent, some have brown and beige layers that look much like bacon. Though flowstones are among the largest of speleothems, they can still be damaged by a single touch; the oil from human fingers causes the flowing water to avoid the area, which dries out. Flowstones are good identifiers of periods of past droughts, since they need some form of water to develop. Flowstone derived from concrete, lime or mortar, can form on manmade structures, much more than in the natural cave environment due to the different chemistry involved.
On concrete structures, these secondary deposits are the result of concrete degradation, when calcium ions have been leached from the concrete in solution and redeposited on the structure's surface to form flowstone and stalagmites. Carbon dioxide is absorbed into the hyperalkaline leachate solution; this facilitates the chemical reactions which deposits calcium carbonate on vertical or sloping surfaces, in the form of flowstone. Concrete derived secondary deposits are classified as "calthemites"; these calcium carbonate deposits mimic the shapes of speleothems, created in caves. E.g. stalagmites, flowstone etc. It is most that calthemite flowstone is precipitated from leachate solution as calcite, "in preference to the other, less stable polymorphs and vaterite." Other trace elements such as iron from rusting reinforcing or copper oxide from pipework may be transported by the leachate and deposited at the same time as the CaCO3. This may cause the calthemites to take on colours of the leached oxides.
Cave onyx is any of various kinds of flowstone considered desirable for ornamental architectural purposes. "Cave onyx" was a common term in certain areas of the United States—particularly the Tennessee-Alabama-Georgia area and the Ozarks—during the 19th and early 20th centuries, being applied to calcite speleothems that were banded in a way suggestive of true onyx. There are a number of US caves called "Onyx Cave" because of the presence in them of such deposits; the Virtual Cave: Flowstone