title: Heidelberg

text: Among the most prominent museums of Heidelberg are for instance the Carl Bosch Museum which shows life and work of chemist and Nobel Prize-winner Carl Bosch. Then there is the Documentation and Culture Centre of German Sinti and Roma (Dokumentations- und Kulturzentrum Deutscher Sini und Roma) describing the Nazi genocide of the Sinti and Roma peoples. The German Packing Museum (Deutsches Verpackungsmuseum) gives an overview of the history of packing and wrapping goods, whereas the German Pharmacy Museum (Deutsches Apothekenmuseum) which is located in the castle illustrates the history of Pharmacy in Germany. The Kurpfälzisches Museum (Palatinate Museum) offers a great art collection and some Roman archeological artifacts from the region. In honour of Friedrich Ebert the President Friedrich Ebert Memorial, which commemorates the life of Germany's first democratic head of state, was established. Besides, there are guided tours in most of the historical monuments of Heidelberg, as well as organized tourist tours through the city available in several languages.


title: Heidelberg

text: Heidelberg was the centre of the epoch of "Romantik" (Romanticism) in Germany. The phase after Jena Romanticism is often called Heidelberg Romanticism (see also Berlin Romanticism). There was a famous circle of poets (the Heidelberg Romantics), such as Joseph von Eichendorff, Johann Joseph von Görres, Ludwig Achim von Arnim, and Clemens Brentano. A relic of Romanticism is the Philosophers' Walk (), a scenic walking path on the nearby Heiligenberg, overlooking Heidelberg.


title: Heidelberg

text: The "Romantik" epoch of German philosophy and literature, was described as a movement against classical and realistic theories of literature, a contrast to the rationality of the Age of Enlightenment. It elevated medievalism and elements of art and narrative perceived to be from the medieval period. It also emphasized folk art, nature and an epistemology based on nature, which included human activity conditioned by nature in the form of language, custom and usage.


title: Heidelberg

text: In 1901 Wilhelm Meyer-Förster wrote the play "Old Heidelberg" which was followed by a large number of film adaptations. It was the basis for Sigmund Romberg's 1924 operetta "The Student Prince" which was itself turned into a film of the same title.


title: Heidelberg

text: The 1925 song "I Lost My Heart in Heidelberg" composed by Fred Raymond was a major hit and inspired a stage musical and two films. It remains the theme song of Heidelberg.


title: Heidelberg

text: Heidelberg is one of the centres of Rugby union in Germany, along with Hanover. In 2008–09, four out of nine clubs in the Rugby-Bundesliga were from Heidelberg, these being RG Heidelberg, who play at the Fritz-Grunebaum-Sportpark, SC Neuenheim, Heidelberger RK and TSV Handschuhsheim. Heidelberger TV has a rugby department.


title: Heidelberg

text: Rugby League Deutschland has two teams based in Heidelberg, Heidelberg Sharks formed in 2005 and Rohrbach Hornets formed in 2007.


title: Heidelberg

text: The city is also home to the USC Heidelberg, which won 9 German Basketball Championships and remains the second most successful team in the history of German professional basketball. Today, the club plays in Germany's second division ProA. It is primarily known for its youth department which developed several members of Germany's senior national basketball team.


title: Heidelberg

text: They also hosted the 2019 WU24 Championships from July 13 to July 20. It was the fifth edition of this world championship and marked the third time Germany has hosted an ultimate frisbee tournament.


title: Mineral

text: In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.


title: Mineral

text: The geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite) or are organic compounds in the sense of chemistry (such as mellite). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite) that also occur in rocks.


title: Mineral

text: The concept of mineral is distinct from rock, which is any bulk solid geologic material that is relatively homogeneous at a large enough scale. A rock may consist of one type of mineral, or may be an aggregate of two or more different types of minerals, spacially segregated into distinct phases.


title: Mineral

text: Some natural solid substances without a definite crystalline structure, such as opal or obsidian, are more properly called mineraloids. If a chemical compound occurs naturally with different crystal structures, each structure is considered a different mineral species. Thus, for example, quartz and stishovite are two different minerals consisting of the same compound, silicon dioxide.


title: Mineral

text: The International Mineralogical Association (IMA) is the generally recognized standard body for the definition and nomenclature of mineral species. , the IMA recognizes 5,863 official mineral species.


title: Mineral

text: 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 conventional or 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; for example, the formula of mackinawite is given as , meaning , where "x" is a variable number between 0 and 9. Sometimes a mineral with variable composition is split into separate species, more or less arbitrarily, forming a mineral group; that is the case of the silicates , the olivine group.


title: Mineral

text: Besides the essential chemical composition and crystal structure, the description of a mineral species usually includes its common physical properties such as habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, specific gravity, magnetism, fluorescence, radioactivity, as well as its taste or smell and its reaction to acid.


title: Mineral

text: Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification. Silicate minerals comprise approximately 90% of the Earth's crust. Other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates.


title: Mineral

text: The International Mineralogical Association has established the following requirements for a substance to be considered a distinct mineral:


title: Mineral

text: The details of these rules are somewhat controversial. For instance, there have been several recent proposals to classify amorphous substances as minerals, but they have not been accepted by the IMA.


title: Mineral

text: The IMA is also reluctant to accept minerals that occur naturally only in the form of nanoparticles a few hundred atoms across, but has not defined a minimum crystal size.


title: Mineral

text: Some authors require the material to be a stable or metastable solid at room temperature (25 °C). However, the IMA only requires that the substance be stable enough for its structure and composition to be well-determined. For example, it has recently recognized meridianiite (a naturally occurring hydrate of magnesium sulfate) as a mineral, even though it is formed and stable only below 2 °C.


title: Mineral

text: , 5,863 mineral species are approved by the IMA. They are most commonly named after a person, followed by discovery location; names based on chemical composition or physical properties are the two other major groups of mineral name etymologies. Most names end in "-ite"; the exceptions are usually names that were well-established before the organization of mineralogy as a discipline, for example galena and diamond.


title: Mineral

text: A topic of contention among geologists and mineralogists has been the IMA's decision to exclude biogenic crystalline substances. For example, Lowenstam (1981) stated that "organisms are capable of forming a diverse array of minerals, some of which cannot be formed inorganically in the biosphere."


title: Mineral

text: Skinner (2005) views all solids as potential minerals and includes biominerals in the mineral kingdom, which are those that are created by the metabolic activities of organisms. Skinner expanded the previous definition of a mineral to classify "element or compound, amorphous or crystalline, formed through "biogeochemical " processes," as a mineral.


title: Mineral

text: Recent advances in high-resolution genetics and X-ray absorption spectroscopy are providing revelations on the biogeochemical relations between microorganisms and minerals that may shed new light on this question. For example, the IMA-commissioned "Working Group on Environmental Mineralogy and Geochemistry " deals with minerals in the hydrosphere, atmosphere, and biosphere. The group's scope includes mineral-forming microorganisms, which exist on nearly every rock, soil, and particle surface spanning the globe to depths of at least 1600 metres below the sea floor and 70 kilometres into the stratosphere (possibly entering the mesosphere).


title: Mineral

text: Biogeochemical cycles have contributed to the formation of minerals for billions of years. Microorganisms can precipitate metals from solution, contributing to the formation of ore deposits. They can also catalyze the dissolution of minerals.


title: Mineral

text: Prior to the International Mineralogical Association's listing, over 60 biominerals had been discovered, named, and published. These minerals (a sub-set tabulated in Lowenstam (1981)) are considered minerals proper according to Skinner's (2005) definition. These biominerals are not listed in the International Mineral Association official list of mineral names; however, many of these biomineral representatives are distributed amongst the 78 mineral classes listed in the Dana classification scheme.


title: Mineral

text: Skinner's (2005) definition of a mineral takes this matter into account by stating that a mineral can be crystalline or amorphous. Although biominerals are not the most common form of minerals, they help to define the limits of what constitutes a mineral proper. Nickel's (1995) formal definition explicitly mentioned crystallinity as a key to defining a substance as a mineral. A 2011 article defined icosahedrite, an aluminium-iron-copper alloy, as mineral; named for its unique natural icosahedral symmetry, it is a quasicrystal. Unlike a true crystal, quasicrystals are ordered but not periodic.


title: Mineral

text: A rock is an aggregate of one or more minerals or mineraloids. Some rocks, such as limestone or quartzite, are composed primarily of one mineral – calcite or aragonite in the case of limestone, and quartz in the latter case. Other rocks can be defined by relative abundances of key (essential) minerals; a granite is defined by proportions of quartz, alkali feldspar, and plagioclase feldspar. The other minerals in the rock are termed accessory minerals, and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal is a sedimentary rock composed primarily of organically derived carbon.


title: Mineral

text: In rocks, some mineral species and groups are much more abundant than others; these are termed the rock-forming minerals. The major examples of these are quartz, the feldspars, the micas, the amphiboles, the pyroxenes, the olivines, and calcite; except for the last one, all of these minerals are silicates. Overall, around 150 minerals are considered particularly important, whether in terms of their abundance or aesthetic value in terms of collecting.


title: Mineral

text: Commercially valuable minerals and rocks, other than gemstones, metal ores, or mineral fuels, are referred to as industrial minerals. For example, muscovite, a white mica, can be used for windows (sometimes referred to as isinglass), as a filler, or as an insulator.


title: Mineral

text: Ores are minerals that have a high concentration of a certain element, typically a metal. Examples are cinnabar (HgS), an ore of mercury; sphalerite (ZnS), an ore of zinc; cassiterite (SnO), an ore of tin; and colemanite, an ore of boron.


title: Mineral

text: Gems are minerals with an ornamental value, and are distinguished from non-gems by their beauty, durability, and usually, rarity. There are about 20 mineral species that qualify as gem minerals, which constitute about 35 of the most common gemstones. Gem minerals are often present in several varieties, and so one mineral can account for several different gemstones; for example, ruby and sapphire are both corundum, AlO.


title: Mineral

text: The first known use of the word "mineral" in the English language (Middle English) was the 15th century. The word came from , from , mine, ore.


title: Mineral

text: The word "species" comes from the Latin "species", "a particular sort, kind, or type with distinct look, or appearance".


title: Mineral

text: The abundance and diversity of minerals is controlled directly by their chemistry, in turn dependent on elemental abundances in the Earth. The majority of minerals observed are derived from the Earth's crust. Eight elements account for most of the key components of minerals, due to their abundance in the crust. These eight elements, summing to over 98% of the crust by weight, are, in order of decreasing abundance: oxygen, silicon, aluminium, iron, magnesium, calcium, sodium and potassium. Oxygen and silicon are by far the two most important – oxygen composes 47% of the crust by weight, and silicon accounts for 28%.


title: Mineral

text: The minerals that form are those that are most stable at the temperature and pressure of formation, within the limits imposed by the bulk chemistry of the parent body. For example, in most igneous rocks, the aluminium and alkali metals (sodium and potassium) that are present are primarily found in combination with oxygen, silicon, and calcium as feldspar minerals. However, if the rock is unusually rich in alkali metals, there will not be enough aluminium to combine with all the sodium as feldspar, and the excess sodium will form sodic amphiboles such as riebeckite. If the aluminium abundance is unusually high, the excess aluminium will form muscovite or other aluminium-rich minerals. If silicon is deficient, part of the feldspar will be replaced by feldspathoid minerals. Precise predictions of which minerals will be present in a rock of a particular composition formed at a particular temperature and pressure requires complex thermodynamic calculations. However, approximate estimates may be made using relatively simple rules of thumb, such as the CIPW norm, which gives reasonable estimates for volcanic rock formed from dry magma.


title: Mineral

text: The chemical composition may vary between end member species of a solid solution series. For example, the plagioclase feldspars comprise a continuous series from sodium-rich end member albite (NaAlSiO) to calcium-rich anorthite (CaAlSiO) with four recognized intermediate varieties between them (given in order from sodium- to calcium-rich): oligoclase, andesine, labradorite, and bytownite. Other examples of series include the olivine series of magnesium-rich forsterite and iron-rich fayalite, and the wolframite series of manganese-rich hübnerite and iron-rich ferberite.


title: Mineral

text: Chemical substitution and coordination polyhedra explain this common feature of minerals. In nature, minerals are not pure substances, and are contaminated by whatever other elements are present in the given chemical system. As a result, it is possible for one element to be substituted for another. Chemical substitution will occur between ions of a similar size and charge; for example, K will not substitute for Si because of chemical and structural incompatibilities caused by a big difference in size and charge. A common example of chemical substitution is that of Si by Al, which are close in charge, size, and abundance in the crust. In the example of plagioclase, there are three cases of substitution. Feldspars are all framework silicates, which have a silicon-oxygen ratio of 2:1, and the space for other elements is given by the substitution of Si by Al to give a base unit of [AlSiO]; without the substitution, the formula would be charge-balanced as SiO, giving quartz. The significance of this structural property will be explained further by coordination polyhedra. The second substitution occurs between Na and Ca; however, the difference in charge has to accounted for by making a second substitution of Si by Al.


title: Mineral

text: Coordination polyhedra are geometric representations of how a cation is surrounded by an anion. In mineralogy, coordination polyhedra are usually considered in terms of oxygen, due its abundance in the crust. The base unit of silicate minerals is the silica tetrahedron – one Si surrounded by four O. An alternate way of describing the coordination of the silicate is by a number: in the case of the silica tetrahedron, the silicon is said to have a coordination number of 4. Various cations have a specific range of possible coordination numbers; for silicon, it is almost always 4, except for very high-pressure minerals where the compound is compressed such that silicon is in six-fold (octahedral) coordination with oxygen. Bigger cations have a bigger coordination numbers because of the increase in relative size as compared to oxygen (the last orbital subshell of heavier atoms is different too). Changes in coordination numbers leads to physical and mineralogical differences; for example, at high pressure, such as in the mantle, many minerals, especially silicates such as olivine and garnet, will change to a perovskite structure, where silicon is in octahedral coordination. Other examples are the aluminosilicates kyanite, andalusite, and sillimanite (polymorphs, since they share the formula AlSiO), which differ by the coordination number of the Al; these minerals transition from one another as a response to changes in pressure and temperature. In the case of silicate materials, the substitution of Si by Al allows for a variety of minerals because of the need to balance charges.


title: Mineral

text: Because the eight most common elements make up over 98% of the Earth's crust, the small quantities of the other elements that are typically present are substituted into the common rock-forming minerals. The distinctive minerals of most elements are quite rare, being found only where these elements have been concentrated by geological processes, such as hydrothermal circulation, to the point where they can no longer be accommodated in common minerals.


title: Mineral

text: Changes in temperature and pressure and composition alter the mineralogy of a rock sample. Changes in composition can be caused by processes such as weathering or metasomatism (hydrothermal alteration). Changes in temperature and pressure occur when the host rock undergoes tectonic or magmatic movement into differing physical regimes. Changes in thermodynamic conditions make it favourable for mineral assemblages to react with each other to produce new minerals; as such, it is possible for two rocks to have an identical or a very similar bulk rock chemistry without having a similar mineralogy. This process of mineralogical alteration is related to the rock cycle. An example of a series of mineral reactions is illustrated as follows.


title: Mineral

text: Orthoclase feldspar (KAlSiO) is a mineral commonly found in granite, a plutonic igneous rock. When exposed to weathering, it reacts to form kaolinite (AlSiO(OH), a sedimentary mineral, and silicic acid):


title: Mineral

text: Under low-grade metamorphic conditions, kaolinite reacts with quartz to form pyrophyllite (AlSiO(OH)):


title: Mineral

text: Alternatively, a mineral may change its crystal structure as a consequence of changes in temperature and pressure without reacting. For example, quartz will change into a variety of its SiO polymorphs, such as tridymite and cristobalite at high temperatures, and coesite at high pressures.


title: Mineral

text: Classifying minerals ranges from simple to difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex optical, chemical or X-ray diffraction analysis; these methods, however, can be costly and time-consuming. Physical properties applied for classification include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, cleavage and fracture, and specific gravity. Other less general tests include fluorescence, phosphorescence, magnetism, radioactivity, tenacity (response to mechanical induced changes of shape or form), piezoelectricity and reactivity to dilute acids.


title: Mineral

text: Crystal structure results from the orderly geometric spatial arrangement of atoms in the internal structure of a mineral. This crystal structure is based on regular internal atomic or ionic arrangement that is often expressed in the geometric form that the crystal takes. Even when the mineral grains are too small to see or are irregularly shaped, the underlying crystal structure is always periodic and can be determined by X-ray diffraction. Minerals are typically described by their symmetry content. Crystals are restricted to 32 point groups, which differ by their symmetry. These groups are classified in turn into more broad categories, the most encompassing of these being the six crystal families.


title: Mineral

text: These families can be described by the relative lengths of the three crystallographic axes, and the angles between them; these relationships correspond to the symmetry operations that define the narrower point groups. They are summarized below; a, b, and c represent the axes, and α, β, γ represent the angle opposite the respective crystallographic axis (e.g. α is the angle opposite the a-axis, viz. the angle between the b and c axes):


title: Mineral

text: The hexagonal crystal family is also split into two crystal "systems" – the trigonal, which has a three-fold axis of symmetry, and the hexagonal, which has a six-fold axis of symmetry.


title: Mineral

text: Chemistry and crystal structure together define a mineral. With a restriction to 32 point groups, minerals of different chemistry may have identical crystal structure. For example, halite (NaCl), galena (PbS), and periclase (MgO) all belong to the hexaoctahedral point group (isometric family), as they have a similar stoichiometry between their different constituent elements. In contrast, polymorphs are groupings of minerals that share a chemical formula but have a different structure. For example, pyrite and marcasite, both iron sulfides, have the formula FeS; however, the former is isometric while the latter is orthorhombic. This polymorphism extends to other sulfides with the generic AX formula; these two groups are collectively known as the pyrite and marcasite groups.


title: Mineral

text: Polymorphism can extend beyond pure symmetry content. The aluminosilicates are a group of three minerals – kyanite, andalusite, and sillimanite – which share the chemical formula AlSiO. Kyanite is triclinic, while andalusite and sillimanite are both orthorhombic and belong to the dipyramidal point group. These differences arise corresponding to how aluminium is coordinated within the crystal structure. In all minerals, one aluminium ion is always in six-fold coordination with oxygen. Silicon, as a general rule, is in four-fold coordination in all minerals; an exception is a case like stishovite (SiO, an ultra-high pressure quartz polymorph with rutile structure). In kyanite, the second aluminium is in six-fold coordination; its chemical formula can be expressed as AlAlSiO, to reflect its crystal structure. Andalusite has the second aluminium in five-fold coordination (AlAlSiO) and sillimanite has it in four-fold coordination (AlAlSiO).


title: Mineral

text: Differences in crystal structure and chemistry greatly influence other physical properties of the mineral. The carbon allotropes diamond and graphite have vastly different properties; diamond is the hardest natural substance, has an adamantine lustre, and belongs to the isometric crystal family, whereas graphite is very soft, has a greasy lustre, and crystallises in the hexagonal family. This difference is accounted for by differences in bonding. In diamond, the carbons are in sp hybrid orbitals, which means they form a framework where each carbon is covalently bonded to four neighbours in a tetrahedral fashion; on the other hand, graphite is composed of sheets of carbons in sp hybrid orbitals, where each carbon is bonded covalently to only three others. These sheets are held together by much weaker van der Waals forces, and this discrepancy translates to large macroscopic differences.


title: Mineral

text: Twinning is the intergrowth of two or more crystals of a single mineral species. The geometry of the twinning is controlled by the mineral's symmetry. As a result, there are several types of twins, including contact twins, reticulated twins, geniculated twins, penetration twins, cyclic twins, and polysynthetic twins. Contact, or simple twins, consist of two crystals joined at a plane; this type of twinning is common in spinel. Reticulated twins, common in rutile, are interlocking crystals resembling netting. Geniculated twins have a bend in the middle that is caused by start of the twin. Penetration twins consist of two single crystals that have grown into each other; examples of this twinning include cross-shaped staurolite twins and Carlsbad twinning in orthoclase. Cyclic twins are caused by repeated twinning around a rotation axis. This type of twinning occurs around three, four, five, six, or eight-fold axes, and the corresponding patterns are called threelings, fourlings, fivelings, sixlings, and eightlings. Sixlings are common in aragonite. Polysynthetic twins are similar to cyclic twins through the presence of repetitive twinning; however, instead of occurring around a rotational axis, polysynthetic twinning occurs along parallel planes, usually on a microscopic scale.


title: Mineral

text: Crystal habit refers to the overall shape of crystal. Several terms are used to describe this property. Common habits include acicular, which describes needlelike crystals as in natrolite, bladed, dendritic (tree-pattern, common in native copper), equant, which is typical of garnet, prismatic (elongated in one direction), and tabular, which differs from bladed habit in that the former is platy whereas the latter has a defined elongation. Related to crystal form, the quality of crystal faces is diagnostic of some minerals, especially with a petrographic microscope. Euhedral crystals have a defined external shape, while anhedral crystals do not; those intermediate forms are termed subhedral.


title: Mineral

text: The hardness of a mineral defines how much it can resist scratching. This physical property is controlled by the chemical composition and crystalline structure of a mineral. A mineral's hardness is not necessarily constant for all sides, which is a function of its structure; crystallographic weakness renders some directions softer than others. An example of this property exists in kyanite, which has a Mohs hardness of 5 parallel to [001] but 7 parallel to [100].


title: Mineral

text: The most common scale of measurement is the ordinal Mohs hardness scale. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc, a phyllosilicate, to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below:


title: Mineral

text: Lustre indicates how light reflects from the mineral's surface, with regards to its quality and intensity. There are numerous qualitative terms used to describe this property, which are split into metallic and non-metallic categories. Metallic and sub-metallic minerals have high reflectivity like metal; examples of minerals with this lustre are galena and pyrite. Non-metallic lustres include: adamantine, such as in diamond; vitreous, which is a glassy lustre very common in silicate minerals; pearly, such as in talc and apophyllite; resinous, such as members of the garnet group; silky which is common in fibrous minerals such as asbestiform chrysotile.


title: Mineral

text: The diaphaneity of a mineral describes the ability of light to pass through it. Transparent minerals do not diminish the intensity of light passing through them. An example of a transparent mineral is muscovite (potassium mica); some varieties are sufficiently clear to have been used for windows. Translucent minerals allow some light to pass, but less than those that are transparent. Jadeite and nephrite (mineral forms of jade are examples of minerals with this property). Minerals that do not allow light to pass are called opaque.


title: Mineral

text: The diaphaneity of a mineral depends on the thickness of the sample. When a mineral is sufficiently thin (e.g., in a thin section for petrography), it may become transparent even if that property is not seen in a hand sample. In contrast, some minerals, such as hematite or pyrite, are opaque even in thin-section.


title: Mineral

text: Colour is the most obvious property of a mineral, but it is often non-diagnostic. It is caused by electromagnetic radiation interacting with electrons (except in the case of incandescence, which does not apply to minerals). Two broad classes of elements (idiochromatic and allochromatic) are defined with regards to their contribution to a mineral's colour: Idiochromatic elements are essential to a mineral's composition; their contribution to a mineral's colour is diagnostic. Examples of such minerals are malachite (green) and azurite (blue). In contrast, allochromatic elements in minerals are present in trace amounts as impurities. An example of such a mineral would be the ruby and sapphire varieties of the mineral corundum.


title: Mineral

text: The colours of pseudochromatic minerals are the result of interference of light waves. Examples include labradorite and bornite.


title: Mineral

text: In addition to simple body colour, minerals can have various other distinctive optical properties, such as play of colours, asterism, chatoyancy, iridescence, tarnish, and pleochroism. Several of these properties involve variability in colour. Play of colour, such as in opal, results in the sample reflecting different colours as it is turned, while pleochroism describes the change in colour as light passes through a mineral in a different orientation. Iridescence is a variety of the play of colours where light scatters off a coating on the surface of crystal, cleavage planes, or off layers having minor gradations in chemistry. In contrast, the play of colours in opal is caused by light refracting from ordered microscopic silica spheres within its physical structure. Chatoyancy ("cat's eye") is the wavy banding of colour that is observed as the sample is rotated; asterism, a variety of chatoyancy, gives the appearance of a star on the mineral grain. The latter property is particularly common in gem-quality corundum.


title: Mineral

text: The streak of a mineral refers to the colour of a mineral in powdered form, which may or may not be identical to its body colour. The most common way of testing this property is done with a streak plate, which is made out of porcelain and coloured either white or black. The streak of a mineral is independent of trace elements or any weathering surface. A common example of this property is illustrated with hematite, which is coloured black, silver, or red in hand sample, but has a cherry-red to reddish-brown streak. Streak is more often distinctive for metallic minerals, in contrast to non-metallic minerals whose body colour is created by allochromatic elements. Streak testing is constrained by the hardness of the mineral, as those harder than 7 powder the "streak plate" instead.


title: Mineral

text: By definition, minerals have a characteristic atomic arrangement. Weakness in this crystalline structure causes planes of weakness, and the breakage of a mineral along such planes is termed cleavage. The quality of cleavage can be described based on how cleanly and easily the mineral breaks; common descriptors, in order of decreasing quality, are "perfect", "good", "distinct", and "poor". In particularly transparent minerals, or in thin-section, cleavage can be seen as a series of parallel lines marking the planar surfaces when viewed from the side. Cleavage is not a universal property among minerals; for example, quartz, consisting of extensively interconnected silica tetrahedra, does not have a crystallographic weakness which would allow it to cleave. In contrast, micas, which have perfect basal cleavage, consist of sheets of silica tetrahedra which are very weakly held together.


title: Mineral

text: As cleavage is a function of crystallography, there are a variety of cleavage types. Cleavage occurs typically in either one, two, three, four, or six directions. Basal cleavage in one direction is a distinctive property of the micas. Two-directional cleavage is described as prismatic, and occurs in minerals such as the amphiboles and pyroxenes. Minerals such as galena or halite have cubic (or isometric) cleavage in three directions, at 90°; when three directions of cleavage are present, but not at 90°, such as in calcite or rhodochrosite, it is termed rhombohedral cleavage. Octahedral cleavage (four directions) is present in fluorite and diamond, and sphalerite has six-directional dodecahedral cleavage.


title: Mineral

text: Minerals with many cleavages might not break equally well in all of the directions; for example, calcite has good cleavage in three directions, but gypsum has perfect cleavage in one direction, and poor cleavage in two other directions. Angles between cleavage planes vary between minerals. For example, as the amphiboles are double-chain silicates and the pyroxenes are single-chain silicates, the angle between their cleavage planes is different. The pyroxenes cleave in two directions at approximately 90°, whereas the amphiboles distinctively cleave in two directions separated by approximately 120° and 60°. The cleavage angles can be measured with a contact goniometer, which is similar to a protractor.


title: Mineral

text: Parting, sometimes called "false cleavage", is similar in appearance to cleavage but is instead produced by structural defects in the mineral, as opposed to systematic weakness. Parting varies from crystal to crystal of a mineral, whereas all crystals of a given mineral will cleave if the atomic structure allows for that property. In general, parting is caused by some stress applied to a crystal. The sources of the stresses include deformation (e.g. an increase in pressure), exsolution, or twinning. Minerals that often display parting include the pyroxenes, hematite, magnetite, and corundum.


title: Mineral

text: When a mineral is broken in a direction that does not correspond to a plane of cleavage, it is termed to have been fractured. There are several types of uneven fracture. The classic example is conchoidal fracture, like that of quartz; rounded surfaces are created, which are marked by smooth curved lines. This type of fracture occurs only in very homogeneous minerals. Other types of fracture are fibrous, splintery, and hackly. The latter describes a break along a rough, jagged surface; an example of this property is found in native copper.


title: Mineral

text: Tenacity is related to both cleavage and fracture. Whereas fracture and cleavage describes the surfaces that are created when a mineral is broken, tenacity describes how resistant a mineral is to such breaking. Minerals can be described as brittle, ductile, malleable, sectile, flexible, or elastic.


title: Mineral

text: Specific gravity numerically describes the density of a mineral. The dimensions of density are mass divided by volume with units: kg/m or g/cm. Specific gravity is defined as the density of the mineral divided by the density of water at 4 °C and thus is a dimensionless quantity, identical in all unit systems. It can be measured as the quotient of the mass of the sample and difference between the weight of the sample in air and its corresponding weight in water. Among most minerals, this property is not diagnostic. Rock forming minerals – typically silicates or occasionally carbonates – have a specific gravity of 2.5–3.5.


title: Mineral

text: High specific gravity is a diagnostic property of a mineral. A variation in chemistry (and consequently, mineral class) correlates to a change in specific gravity. Among more common minerals, oxides and sulfides tend to have a higher specific gravity as they include elements with higher atomic mass. A generalization is that minerals with metallic or adamantine lustre tend to have higher specific gravities than those having a non-metallic to dull lustre. For example, hematite, FeO, has a specific gravity of 5.26 while galena, PbS, has a specific gravity of 7.2–7.6, which is a result of their high iron and lead content, respectively. A very high specific gravity is characteristic of native metals; for example, kamacite, an iron-nickel alloy common in iron meteorites has a specific gravity of 7.9, and gold has an observed specific gravity between 15 and 19.3.


title: Mineral

text: Other properties can be used to diagnose minerals. These are less general, and apply to specific minerals.


title: Mineral

text: Dropping dilute acid (often 10% HCl) onto a mineral aids in distinguishing carbonates from other mineral classes. The acid reacts with the carbonate ([CO]) group, which causes the affected area to effervesce, giving off carbon dioxide gas. This test can be further expanded to test the mineral in its original crystal form or powdered form. An example of this test is done when distinguishing calcite from dolomite, especially within the rocks (limestone and dolomite respectively). Calcite immediately effervesces in acid, whereas acid must be applied to powdered dolomite (often to a scratched surface in a rock), for it to effervesce. Zeolite minerals will not effervesce in acid; instead, they become frosted after 5–10 minutes, and if left in acid for a day, they dissolve or become a silica gel.


title: Mineral

text: Magnetism is a very conspicuous property of a few minerals. Among common minerals, magnetite exhibits this property strongly, and magnetism is also present, albeit not as strongly, in pyrrhotite and ilmenite. Some minerals exhibit electrical properties – for example, quartz is piezoelectric – but electrical properties are rarely used as diagnostic criteria for minerals because of incomplete data and natural variation.


title: Mineral

text: Minerals can also be tested for taste or smell. Halite, NaCl, is table salt; its potassium-bearing counterpart, sylvite, has a pronounced bitter taste. Sulfides have a characteristic smell, especially as samples are fractured, reacting, or powdered.


title: Mineral

text: Radioactivity is a rare property found in minerals containing radioactive elements. The radioactive elements could be a defining constituent, such as uranium in uraninite, autunite, and carnotite, or present as trace impurities, as in zircon. The decay of a radioactive element damages the mineral crystal structure rendering it locally amorphous (metamict state); the optical result, termed a "radioactive halo" or "pleochroic halo", is observable with various techniques, such as thin-section petrography.


title: Mineral

text: In 315 BCE, Theophrastus presented his classification of minerals in his treatise "On Stones". His classification was influenced by the ideas of his teachers Plato and Aristotle. Theophrastus classified minerals as stones, earths or metals.


title: Mineral

text: Georgius Agricola's classification of minerals in his book "De Natura Fossilium", published in 1546, divided minerals into three types of substance: simple (stones, earths, metals, and congealed juices), compound (intimately mixed) and composite (separable).


title: Mineral

text: An early classification of minerals was given by Carl Linnaeus in his seminal 1735 book "Systema Naturae". He divided the natural world into three kingdoms – plants, animals, and minerals – and classified each with the same hierarchy. In descending order, these were Phylum, Class, Order, Family, Tribe, Genus, and Species.


title: Mineral

text: However, while his system was justified by Charles Darwin's theory of species formation and has been largely adopted and expanded by biologists in the following centuries (who still use his Greek- and Latin-based binomial naming scheme), it had little success among mineralogists (although each distinct mineral is still formally referred to as a mineral "species").


title: Mineral

text: Minerals are classified by variety, species, series and group, in order of increasing generality. The basic level of definition is that of mineral species, each of which is distinguished from the others by unique chemical and physical properties. For example, quartz is defined by its formula, SiO, and a specific crystalline structure that distinguishes it from other minerals with the same chemical formula (termed polymorphs). When there exists a range of composition between two minerals species, a mineral series is defined. For example, the biotite series is represented by variable amounts of the endmembers phlogopite, siderophyllite, annite, and eastonite. In contrast, a mineral group is a grouping of mineral species with some common chemical properties that share a crystal structure. The pyroxene group has a common formula of XY(Si,Al)O, where X and Y are both cations, with X typically bigger than Y; the pyroxenes are single-chain silicates that crystallize in either the orthorhombic or monoclinic crystal systems. Finally, a mineral variety is a specific type of mineral species that differs by some physical characteristic, such as colour or crystal habit. An example is amethyst, which is a purple variety of quartz.


title: Mineral

text: Two common classifications, Dana and Strunz, are used for minerals; both rely on composition, specifically with regards to important chemical groups, and structure. James Dwight Dana, a leading geologist of his time, first published his "System of Mineralogy" in 1837; as of 1997, it is in its eighth edition. The Dana classification assigns a four-part number to a mineral species. Its class number is based on important compositional groups; the type gives the ratio of cations to anions in the mineral, and the last two numbers group minerals by structural similarity within a given type or class. The less commonly used Strunz classification, named for German mineralogist Karl Hugo Strunz, is based on the Dana system, but combines both chemical and structural criteria, the latter with regards to distribution of chemical bonds.


title: Mineral

text: As the composition of the Earth's crust is dominated by silicon and oxygen, silicates are by far the most important class of minerals in terms of rock formation and diversity. However, non-silicate minerals are of great economic importance, especially as ores. Non-silicate minerals are subdivided into several other classes by their dominant chemistry, which includes native elements, sulfides, halides, oxides and hydroxides, carbonates and nitrates, borates, sulfates, phosphates, and organic compounds. Most non-silicate mineral species are rare (constituting in total 8% of the Earth's crust), although some are relatively common, such as calcite, pyrite, magnetite, and hematite. There are two major structural styles observed in non-silicates: close-packing and silicate-like linked tetrahedra. Close-packed structures are a way to densely pack atoms while minimizing interstitial space. Hexagonal close-packing involves stacking layers where every other layer is the same ("ababab"), whereas cubic close-packing involves stacking groups of three layers ("abcabcabc"). Analogues to linked silica tetrahedra include (sulfate), (phosphate), (arsenate), and (vanadate) structures. The non-silicates have great economic importance, as they concentrate elements more than the silicate minerals do.


title: Mineral

text: The largest grouping of minerals by far are the silicates; most rocks are composed of greater than 95% silicate minerals, and over 90% of the Earth's crust is composed of these minerals. The two main constituents of silicates are silicon and oxygen, which are the two most abundant elements in the Earth's crust. Other common elements in silicate minerals correspond to other common elements in the Earth's crust, such as aluminium, magnesium, iron, calcium, sodium, and potassium. Some important rock-forming silicates include the feldspars, quartz, olivines, pyroxenes, amphiboles, garnets, and micas.


title: Mineral

text: The base unit of a silicate mineral is the [SiO] tetrahedron. In the vast majority of cases, silicon is in four-fold or tetrahedral coordination with oxygen. In very high-pressure situations, silicon will be in six-fold or octahedral coordination, such as in the perovskite structure or the quartz polymorph stishovite (SiO). In the latter case, the mineral no longer has a silicate structure, but that of rutile (TiO), and its associated group, which are simple oxides. These silica tetrahedra are then polymerized to some degree to create various structures, such as one-dimensional chains, two-dimensional sheets, and three-dimensional frameworks. The basic silicate mineral where no polymerization of the tetrahedra has occurred requires other elements to balance out the base 4- charge. In other silicate structures, different combinations of elements are required to balance out the resultant negative charge. It is common for the Si to be substituted by Al because of similarity in ionic radius and charge; in those cases, the [AlO] tetrahedra form the same structures as do the unsubstituted tetrahedra, but their charge-balancing requirements are different.


title: Mineral

text: The degree of polymerization can be described by both the structure formed and how many tetrahedral corners (or coordinating oxygens) are shared (for aluminium and silicon in tetrahedral sites):


title: Mineral

text: Tectosilicates, also known as framework silicates, have the highest degree of polymerization. With all corners of a tetrahedra shared, the silicon:oxygen ratio becomes 1:2. Examples are quartz, the feldspars, feldspathoids, and the zeolites. Framework silicates tend to be particularly chemically stable as a result of strong covalent bonds.


title: Mineral

text: Forming 12% of the Earth's crust, quartz (SiO) is the most abundant mineral species. It is characterized by its high chemical and physical resistivity. Quartz has several polymorphs, including tridymite and cristobalite at high temperatures, high-pressure coesite, and ultra-high pressure stishovite. The latter mineral can only be formed on Earth by meteorite impacts, and its structure has been compressed so much that it has changed from a silicate structure to that of rutile (TiO). The silica polymorph that is most stable at the Earth's surface is α-quartz. Its counterpart, β-quartz, is present only at high temperatures and pressures (changes to α-quartz below 573 °C at 1 bar). These two polymorphs differ by a "kinking" of bonds; this change in structure gives β-quartz greater symmetry than α-quartz, and they are thus also called high quartz (β) and low quartz (α).


title: Mineral

text: Feldspars are the most abundant group in the Earth's crust, at about 50%. In the feldspars, Al substitutes for Si, which creates a charge imbalance that must be accounted for by the addition of cations. The base structure becomes either [AlSiO] or [AlSiO] There are 22 mineral species of feldspars, subdivided into two major subgroups – alkali and plagioclase – and two less common groups – celsian and banalsite. The alkali feldspars are most commonly in a series between potassium-rich orthoclase and sodium-rich albite; in the case of plagioclase, the most common series ranges from albite to calcium-rich anorthite. Crystal twinning is common in feldspars, especially polysynthetic twins in plagioclase and Carlsbad twins in alkali feldspars. If the latter subgroup cools slowly from a melt, it forms exsolution lamellae because the two components – orthoclase and albite – are unstable in solid solution. Exsolution can be on a scale from microscopic to readily observable in hand-sample; perthitic texture forms when Na-rich feldspar exsolve in a K-rich host. The opposite texture (antiperthitic), where K-rich feldspar exsolves in a Na-rich host, is very rare.


title: Mineral

text: Feldspathoids are structurally similar to feldspar, but differ in that they form in Si-deficient conditions, which allows for further substitution by Al. As a result, feldspathoids are almost never found in association with quartz. A common example of a feldspathoid is nepheline ((Na, K)AlSiO); compared to alkali feldspar, nepheline has an AlO:SiO ratio of 1:2, as opposed to 1:6 in alkali feldspar. Zeolites often have distinctive crystal habits, occurring in needles, plates, or blocky masses. They form in the presence of water at low temperatures and pressures, and have channels and voids in their structure. Zeolites have several industrial applications, especially in waste water treatment.


title: Mineral

text: Phyllosilicates consist of sheets of polymerized tetrahedra. They are bound at three oxygen sites, which gives a characteristic silicon:oxygen ratio of 2:5. Important examples include the mica, chlorite, and the kaolinite-serpentine groups. In addition to the tetrahedra, phyllosilicates have a sheet of octahedra (elements in six-fold coordination by oxygen) that balance out the basic tetrahedra, which have a negative charge (e.g. [SiO]) These tetrahedra (T) and octahedra (O) sheets are stacked in a variety of combinations to create phyllosilicate layers. Within an octahedral sheet, there are three octahedral sites in a unit structure; however, not all of the sites may be occupied. In that case, the mineral is termed dioctahedral, whereas in other case it is termed trioctahedral. The layers are weakly bound by van der Waals forces, hydrogen bonds, or sparse ionic bonds, which causes a crystallographic weakness, in turn leading to a prominent basal cleavage among the phyllosilicates.


title: Mineral

text: The kaolinite-serpentine group consists of T-O stacks (the 1:1 clay minerals); their hardness ranges from 2 to 4, as the sheets are held by hydrogen bonds. The 2:1 clay minerals (pyrophyllite-talc) consist of T-O-T stacks, but they are softer (hardness from 1 to 2), as they are instead held together by van der Waals forces. These two groups of minerals are subgrouped by octahedral occupation; specifically, kaolinite and pyrophyllite are dioctahedral whereas serpentine and talc trioctahedral.


title: Mineral

text: Micas are also T-O-T-stacked phyllosilicates, but differ from the other T-O-T and T-O-stacked subclass members in that they incorporate aluminium into the tetrahedral sheets (clay minerals have Al in octahedral sites). Common examples of micas are muscovite, and the biotite series. Mica T-O-T layers are bonded together by metal ions, giving them a greater hardness than other phyllosilicate minerals, though they retain perfect basal cleavage. The chlorite group is related to mica group, but a brucite-like (Mg(OH)) layer between the T-O-T stacks.


title: Mineral

text: Because of their chemical structure, phyllosilicates typically have flexible, elastic, transparent layers that are electrical insulators and can be split into very thin flakes. Micas can be used in electronics as insulators, in construction, as optical filler, or even cosmetics. Chrysotile, a species of serpentine, is the most common mineral species in industrial asbestos, as it is less dangerous in terms of health than the amphibole asbestos.


title: Mineral

text: Inosilicates consist of tetrahedra repeatedly bonded in chains. These chains can be single, where a tetrahedron is bound to two others to form a continuous chain; alternatively, two chains can be merged to create double-chain silicates. Single-chain silicates have a silicon:oxygen ratio of 1:3 (e.g. [SiO]), whereas the double-chain variety has a ratio of 4:11, e.g. [SiO]. Inosilicates contain two important rock-forming mineral groups; single-chain silicates are most commonly pyroxenes, while double-chain silicates are often amphiboles. Higher-order chains exist (e.g. three-member, four-member, five-member chains, etc.) but they are rare.


title: Mineral

text: The pyroxene group consists of 21 mineral species. Pyroxenes have a general structure formula of XY(SiO), where X is an octahedral site, while Y can vary in coordination number from six to eight. Most varieties of pyroxene consist of permutations of Ca, Fe and Mg to balance the negative charge on the backbone. Pyroxenes are common in the Earth's crust (about 10%) and are a key constituent of mafic igneous rocks.


title: Mineral

text: Amphiboles have great variability in chemistry, described variously as a "mineralogical garbage can" or a "mineralogical shark swimming a sea of elements". The backbone of the amphiboles is the [SiO]; it is balanced by cations in three possible positions, although the third position is not always used, and one element can occupy both remaining ones. Finally, the amphiboles are usually hydrated, that is, they have a hydroxyl group ([OH]), although it can be replaced by a fluoride, a chloride, or an oxide ion. Because of the variable chemistry, there are over 80 species of amphibole, although variations, as in the pyroxenes, most commonly involve mixtures of Ca, Fe and Mg. Several amphibole mineral species can have an asbestiform crystal habit. These asbestos minerals form long, thin, flexible, and strong fibres, which are electrical insulators, chemically inert and heat-resistant; as such, they have several applications, especially in construction materials. However, asbestos are known carcinogens, and cause various other illnesses, such as asbestosis; amphibole asbestos (anthophyllite, tremolite, actinolite, grunerite, and riebeckite) are considered more dangerous than chrysotile serpentine asbestos.


title: Mineral

text: Cyclosilicates, or ring silicates, have a ratio of silicon to oxygen of 1:3. Six-member rings are most common, with a base structure of [SiO]; examples include the tourmaline group and beryl. Other ring structures exist, with 3, 4, 8, 9, 12 having been described. Cyclosilicates tend to be strong, with elongated, striated crystals.


title: Mineral

text: Tourmalines have a very complex chemistry that can be described by a general formula XYZ(BO)TOVW. The TO is the basic ring structure, where T is usually Si, but substitutable by Al or B. Tourmalines can be subgrouped by the occupancy of the X site, and from there further subdivided by the chemistry of the W site. The Y and Z sites can accommodate a variety of cations, especially various transition metals; this variability in structural transition metal content gives the tourmaline group greater variability in colour. Other cyclosilicates include beryl, AlBeSiO, whose varieties include the gemstones emerald (green) and aquamarine (bluish). Cordierite is structurally similar to beryl, and is a common metamorphic mineral.


title: Mineral

text: Sorosilicates, also termed disilicates, have tetrahedron-tetrahedron bonding at one oxygen, which results in a 2:7 ratio of silicon to oxygen. The resultant common structural element is the [SiO] group. The most common disilicates by far are members of the epidote group. Epidotes are found in variety of geologic settings, ranging from mid-ocean ridge to granites to metapelites. Epidotes are built around the structure [(SiO)(SiO)] structure; for example, the mineral "species" epidote has calcium, aluminium, and ferric iron to charge balance: CaAl(Fe, Al)(SiO)(SiO)O(OH). The presence of iron as Fe and Fe helps buffer oxygen fugacity, which in turn is a significant factor in petrogenesis.


title: Mineral

text: Other examples of sorosilicates include lawsonite, a metamorphic mineral forming in the blueschist facies (subduction zone setting with low temperature and high pressure), vesuvianite, which takes up a significant amount of calcium in its chemical structure.


title: Mineral

text: Orthosilicates consist of isolated tetrahedra that are charge-balanced by other cations. Also termed nesosilicates, this type of silicate has a silicon:oxygen ratio of 1:4 (e.g. SiO). Typical orthosilicates tend to form blocky equant crystals, and are fairly hard. Several rock-forming minerals are part of this subclass, such as the aluminosilicates, the olivine group, and the garnet group.


title: Mineral

text: The aluminosilicates –bkyanite, andalusite, and sillimanite, all AlSiO – are structurally composed of one [SiO] tetrahedron, and one Al in octahedral coordination. The remaining Al can be in six-fold coordination (kyanite), five-fold (andalusite) or four-fold (sillimanite); which mineral forms in a given environment is depend on pressure and temperature conditions. In the olivine structure, the main olivine series of (Mg, Fe)SiO consist of magnesium-rich forsterite and iron-rich fayalite. Both iron and magnesium are in octahedral by oxygen. Other mineral species having this structure exist, such as tephroite, MnSiO. The garnet group has a general formula of XY(SiO), where X is a large eight-fold coordinated cation, and Y is a smaller six-fold coordinated cation. There are six ideal endmembers of garnet, split into two group. The pyralspite garnets have Al in the Y position: pyrope (MgAl(SiO)), almandine (FeAl(SiO)), and spessartine (MnAl(SiO)). The ugrandite garnets have Ca in the X position: uvarovite (CaCr(SiO)), grossular (CaAl(SiO)) and andradite (CaFe(SiO)). While there are two subgroups of garnet, solid solutions exist between all six end-members.


title: Mineral

text: Other orthosilicates include zircon, staurolite, and topaz. Zircon (ZrSiO) is useful in geochronology as U can substitute for Zr; furthermore, because of its very resistant structure, it is difficult to reset it as a chronometer. Staurolite is a common metamorphic intermediate-grade index mineral. It has a particularly complicated crystal structure that was only fully described in 1986. Topaz (AlSiO(F, OH), often found in granitic pegmatites associated with tourmaline, is a common gemstone mineral.


title: Mineral

text: Native elements are those that are not chemically bonded to other elements. This mineral group includes native metals, semi-metals, and non-metals, and various alloys and solid solutions. The metals are held together by metallic bonding, which confers distinctive physical properties such as their shiny metallic lustre, ductility and malleability, and electrical conductivity. Native elements are subdivided into groups by their structure or chemical attributes.


title: Mineral

text: The gold group, with a cubic close-packed structure, includes metals such as gold, silver, and copper. The platinum group is similar in structure to the gold group. The iron-nickel group is characterized by several iron-nickel alloy species. Two examples are kamacite and taenite, which are found in iron meteorites; these species differ by the amount of Ni in the alloy; kamacite has less than 5–7% nickel and is a variety of native iron, whereas the nickel content of taenite ranges from 7–37%. Arsenic group minerals consist of semi-metals, which have only some metallic traits; for example, they lack the malleability of metals. Native carbon occurs in two allotropes, graphite and diamond; the latter forms at very high pressure in the mantle, which gives it a much stronger structure than graphite.


title: Mineral

text: The sulfide minerals are chemical compounds of one or more metals or semimetals with a chalcogen or pnictogen, of which sulfur is most common. Tellurium, arsenic, or selenium can substitute for the sulfur. Sulfides tend to be soft, brittle minerals with a high specific gravity. Many powdered sulfides, such as pyrite, have a sulfurous smell when powdered. Sulfides are susceptible to weathering, and many readily dissolve in water; these dissolved minerals can be later redeposited, which creates enriched secondary ore deposits. Sulfides are classified by the ratio of the metal or semimetal to the sulfur, such as M:S equal to 2:1, or 1:1. Many sulfide minerals are economically important as metal ores; examples include sphalerite (ZnS), an ore of zinc, galena (PbS), an ore of lead, cinnabar (HgS), an ore of mercury, and molybdenite (MoS, an ore of molybdenum. Pyrite (FeS), is the most commonly occurring sulfide, and can be found in most geological environments. It is not, however, an ore of iron, but can be instead oxidized to produce sulfuric acid. Related to the sulfides are the rare sulfosalts, in which a metallic element is bonded to sulfur and a semimetal such as antimony, arsenic, or bismuth. Like the sulfides, sulfosalts are typically soft, heavy, and brittle minerals.


title: Mineral

text: Oxide minerals are divided into three categories: simple oxides, hydroxides, and multiple oxides. Simple oxides are characterized by O as the main anion and primarily ionic bonding. They can be further subdivided by the ratio of oxygen to the cations. The periclase group consists of minerals with a 1:1 ratio. Oxides with a 2:1 ratio include cuprite (CuO) and water ice. Corundum group minerals have a 2:3 ratio, and includes minerals such as corundum (AlO), and hematite (FeO). Rutile group minerals have a ratio of 1:2; the eponymous species, rutile (TiO) is the chief ore of titanium; other examples include cassiterite (SnO; ore of tin), and pyrolusite (MnO; ore of manganese). In hydroxides, the dominant anion is the hydroxyl ion, OH. Bauxites are the chief aluminium ore, and are a heterogeneous mixture of the hydroxide minerals diaspore, gibbsite, and bohmite; they form in areas with a very high rate of chemical weathering (mainly tropical conditions). Finally, multiple oxides are compounds of two metals with oxygen. A major group within this class are the spinels, with a general formula of XYO. Examples of species include spinel (MgAlO), chromite (FeCrO), and magnetite (FeO). The latter is readily distinguishable by its strong magnetism, which occurs as it has iron in two oxidation states (FeFeO), which makes it a multiple oxide instead of a single oxide.


title: Mineral

text: The halide minerals are compounds in which a halogen (fluorine, chlorine, iodine, or bromine) is the main anion. These minerals tend to be soft, weak, brittle, and water-soluble. Common examples of halides include halite (NaCl, table salt), sylvite (KCl), and fluorite (CaF). Halite and sylvite commonly form as evaporites, and can be dominant minerals in chemical sedimentary rocks. Cryolite, NaAlF, is a key mineral in the extraction of aluminium from bauxites; however, as the only significant occurrence at Ivittuut, Greenland, in a granitic pegmatite, was depleted, synthetic cryolite can be made from fluorite.


title: Mineral

text: The carbonate minerals are those in which the main anionic group is carbonate, [CO]. Carbonates tend to be brittle, many have rhombohedral cleavage, and all react with acid. Due to the last characteristic, field geologists often carry dilute hydrochloric acid to distinguish carbonates from non-carbonates. The reaction of acid with carbonates, most commonly found as the polymorph calcite and aragonite (CaCO), relates to the dissolution and precipitation of the mineral, which is a key in the formation of limestone caves, features within them such as stalactite and stalagmites, and karst landforms. Carbonates are most often formed as biogenic or chemical sediments in marine environments. The carbonate group is structurally a triangle, where a central C cation is surrounded by three O anions; different groups of minerals form from different arrangements of these triangles. The most common carbonate mineral is calcite, which is the primary constituent of sedimentary limestone and metamorphic marble. Calcite, CaCO, can have a significant percentage of magnesium substituting for calcium. Under high-Mg conditions, its polymorph aragonite will form instead; the marine geochemistry in this regard can be described as an aragonite or calcite sea, depending on which mineral preferentially forms. Dolomite is a double carbonate, with the formula CaMg(CO). Secondary dolomitization of limestone is common, in which calcite or aragonite are converted to dolomite; this reaction increases pore space (the unit cell volume of dolomite is 88% that of calcite), which can create a reservoir for oil and gas. These two mineral species are members of eponymous mineral groups: the calcite group includes carbonates with the general formula XCO, and the dolomite group constitutes minerals with the general formula XY(CO).


title: Mineral

text: The sulfate minerals all contain the sulfate anion, [SO]. They tend to be transparent to translucent, soft, and many are fragile. Sulfate minerals commonly form as evaporites, where they precipitate out of evaporating saline waters. Sulfates can also be found in hydrothermal vein systems associated with sulfides, or as oxidation products of sulfides. Sulfates can be subdivided into anhydrous and hydrous minerals. The most common hydrous sulfate by far is gypsum, CaSO⋅2HO. It forms as an evaporite, and is associated with other evaporites such as calcite and halite; if it incorporates sand grains as it crystallizes, gypsum can form desert roses. Gypsum has very low thermal conductivity and maintains a low temperature when heated as it loses that heat by dehydrating; as such, gypsum is used as an insulator in materials such as plaster and drywall. The anhydrous equivalent of gypsum is anhydrite; it can form directly from seawater in highly arid conditions. The barite group has the general formula XSO, where the X is a large 12-coordinated cation. Examples include barite (BaSO), celestine (SrSO), and anglesite (PbSO); anhydrite is not part of the barite group, as the smaller Ca is only in eight-fold coordination.


title: Mineral

text: The phosphate minerals are characterized by the tetrahedral [PO] unit, although the structure can be generalized, and phosphorus is replaced by antimony, arsenic, or vanadium. The most common phosphate is the apatite group; common species within this group are fluorapatite (Ca(PO)F), chlorapatite (Ca(PO)Cl) and hydroxylapatite (Ca(PO)(OH)). Minerals in this group are the main crystalline constituents of teeth and bones in vertebrates. The relatively abundant monazite group has a general structure of ATO, where T is phosphorus or arsenic, and A is often a rare-earth element (REE). Monazite is important in two ways: first, as a REE "sink", it can sufficiently concentrate these elements to become an ore; secondly, monazite group elements can incorporate relatively large amounts of uranium and thorium, which can be used in monazite geochronology to date the rock based on the decay of the U and Th to lead.


title: Mineral

text: The Strunz classification includes a class for . These rare compounds contain organic carbon, but can be formed by a geologic process. For example, whewellite, CaCO⋅HO is an oxalate that can be deposited in hydrothermal ore veins. While hydrated calcium oxalate can be found in coal seams and other sedimentary deposits involving organic matter, the hydrothermal occurrence is not considered to be related to biological activity.


title: Mineral

text: 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 very 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 rules, "mineral species can be grouped in a number of different ways, on the basis of chemistry, crystal structure, occurrence, association, genetic history, or resource, for example, depending on the purpose to be served by the classification."


title: Mineral

text: It has been suggested that biominerals could be important indicators of extraterrestrial life and thus could play an important role in the search for past or present life on Mars. Furthermore, organic components (biosignatures) that are often associated with biominerals are believed to play crucial roles in both pre-biotic and biotic reactions.


title: Mineral

text: In January 2014, NASA reported that studies by the "Curiosity" and "Opportunity" rovers on Mars would search for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic and/or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable. The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars became a primary NASA objective.


title: Marshmallow

text: Marshmallow (, ) is a type of confectionery that is typically made from sugar, water and gelatin whipped to a solid-but-soft consistency. It is used as a filling in baking or normally molded into shapes and coated with corn starch. The sugar confection is inspired by a historical medicinal confection made from "Althaea officinalis", the marsh-mallow plant.


title: Marshmallow

text: The word "marshmallow" comes from the mallow plant species ("Althaea officinalis"), a herb native to parts of Europe, North Africa, and Asia which grows in marshes and other damp areas. The plant's stem and leaves are fleshy, and its white flower has five petals. It is not known exactly when marshmallows were invented, but their history goes back as early as . Ancient Egyptians were said to be the first to make and use the root of the plant to soothe coughs and sore throats and to heal wounds. The first marshmallows were prepared by boiling pieces of root pulp with honey until thick. Once thickened, the mixture was strained, cooled, then used as intended.


title: Marshmallow

text: Whether used for candy or medicine, the manufacture of marshmallows was limited to a small scale. In the early- to mid-1800s, the marshmallow had made its way to France, where confectioners augmented the plant's traditional medicinal value with indulgent ingredients utilized by the Egyptians. Owners of small candy stores would whip the sap from the mallow root into a fluffy candy mold. This candy, called Pâte de Guimauve, was a spongy-soft dessert made from whipping dried marshmallow roots with sugar, water, and egg whites. It was sold in bar form as a lozenge. Drying and preparation of the marshmallow took one-to-two days before the final product was produced. In the late 1800s, candy makers started looking for a new process and discovered the starch mogul system, in which trays of modified corn starch had a mold firmly pushed down in them to create cavities within the starch. The cavities were then filled with the whipped marshmallow sap mixture and allowed to cool or harden. At the same time, candy makers began to replace the mallow root with gelatin which created a stable form of marshmallow.


title: Marshmallow

text: By the early 1900s, thanks to the starch mogul system, marshmallows were introduced to the United States and available for mass consumption. They were sold in tins as penny candy and were soon used in a variety of food recipes like banana fluff, lime mallow sponge, and tutti frutti. In 1956, Alex Doumak patented the extrusion process which involved running marshmallow ingredients through tubes. The tubes created a long rope of marshmallow mixture and were then set out to cool. The ingredients were then cut into equal pieces and packaged.


title: Marshmallow

text: Modern marshmallow manufacturing is highly automated and has been since the early 1950s when the extrusion process was first developed. Numerous improvements and advancements allow for the production of thousands of pounds of marshmallow a day. Today, the marshmallow typically consists of four ingredients: sugar, water, air, and a whipping agent.


title: Marshmallow

text: Marshmallows consist of four ingredients: sugar, water, air, and a whipping agent/aerator (usually a protein). The type of sugar and whipping agent varies depending on desired characteristics. Each ingredient plays a specific role in the final product.


title: Marshmallow

text: The marshmallow is a foam, consisting of an aqueous continuous phase and a gaseous dispersed phase (in other words, a liquid with gas bubbles spread throughout). In addition to being a foam, this also makes marshmallows an "aerated" confection because it is made up of 50% air. The goal of an aerated confection like a marshmallow is to incorporate gas into a sugar mixture, and stabilize the aerated product before the gas can escape. When the gas is introduced into the system, tiny air bubbles are created. This is what contributes to the unique textural properties and mouth-feel of this product.


title: Marshmallow

text: In marshmallows, proteins are the main surface-active agents responsible for the formation, and stabilization of the dispersed air. Due to their structure, surface-active molecules gather at the surface area of a portion of (water-based) liquid. A portion of each protein molecule is hydrophilic, with a polar charge, and another portion is hydrophobic and non-polar. The non-polar section has little or no affinity for water, and so this section orients as far away from the water as possible. However, the polar section is attracted to the water and has little or no affinity for the air. Therefore, the molecule orients with the polar section in the water, with the non-polar section in the air. Two primary proteins that are commonly used as aerators in marshmallows are albumen (egg whites) and gelatin.


title: Marshmallow

text: Albumen is a mixture of proteins found in egg whites and is utilized for its capacity to create foams. In a commercialized setting, dried albumen is used as opposed to fresh egg whites. In addition to convenience, the advantages of using dried albumen are an increase in food safety and the reduction of water content in the marshmallow. Fresh egg whites carry a higher risk of "Salmonella," and are approximately 90 percent water. This is undesirable for the shelf life and firmness of the product. For artisan-type marshmallows, prepared by a candy maker, fresh egg whites are usually used. Albumen is rarely used on its own when incorporated into modern marshmallows, and instead is used in conjunction with gelatin.


title: Marshmallow

text: Gelatin is the aerator most often used in the production of marshmallows. It is made up of collagen, a structural protein derived from animal skin, connective tissue, and bones. Not only can it stabilize foams, like albumen, but when combined with water it forms a thermally-reversible gel. This means that gelatin can melt, then reset due to its sensitivity to temperature. The melting point of gelatin gel is around , which is just below normal body temperature (around ). This is what contributes to the "melt-in-your-mouth" sensation when a marshmallow is consumed—it actually starts to melt when it touches the tongue.


title: Marshmallow

text: During preparation, the temperature needs to be just above the melting point of the gelatin, so that as soon as it is formed it cools quickly, and the gelatin will set, retaining the desired shape. If the marshmallow rope mixture exiting the extruder during processing is too warm, the marshmallow starts to flow before the gelatin sets. Instead of a round marshmallow, it will take a more oval form. Excessive heat can also degrade, or break down, the gelatin itself. Therefore, when marshmallows are being produced at home or by artisan candy makers, the gelatin is added after the syrup has been heated and cooled down.


title: Marshmallow

text: In commercial operations, the gelatin is simply cooked with the sugar syrup, rather than being added later after the syrup has cooled. In this case, kinetics play an important role, with both time and temperature factoring in. If the gelatin was added at the beginning of a batch that was then cooked to 112–116 °C in 20–30 minutes, a significant amount of gelatin would break down. The marshmallow would have reduced springiness from that loss of gelatin. But since the time the syrup spends at elevated temperature in modern cookers is so short, there is little to no degradation of the gelatin.


title: Marshmallow

text: In terms of texture, and mouth-feel, gelatin makes marshmallows chewy by forming a tangled 3-D network of polymer chains. Once gelatin is dissolved in warm water (dubbed the "blooming stage"), it forms a dispersion, which results in a cross-linking of its helix-shaped chains. The linkages in the gelatin protein network trap air in the marshmallow mixture and immobilize the water molecules in the network. The result is the well-known spongy structure of marshmallows. This is why the omission of gelatin from a marshmallow recipe will result in marshmallow creme, since there is no gelatin network to trap the water and air bubbles.


title: Marshmallow

text: A traditional marshmallow might contain about 60% corn syrup, 30% sugar, and 1% to 2% gelatin. A combination of different sugars is used to control the solubility of the solution. The corn syrup/sugar ratio will influence the texture by slowing crystallization of the sucrose. The smooth texture of marshmallows relies on disordered, or amorphous, sugar molecules. In contrast, increasing the sugar ratio to about 60% to 65% will produce a grainy marshmallow. Temperature also plays an important role in producing smooth marshmallows by reducing the time window for ordered crystals to form. To ensure the sugars are disordered, the sugar syrup solution is heated to a high temperature and then cooled rapidly.


title: Marshmallow

text: Sugarcane and sugar beet are the two primary sources of sugar, consisting of sucrose molecules. Sucrose is a disaccharide that consists of one glucose and fructose molecule. This sugar provides sweetness and bulk to the marshmallow, while simultaneously setting the foam to a firm consistency as it cools. Sucrose, and sugars in general, impair the ability of a foam to form, but improve foam stability. Therefore, sucrose is used in conjunction with a protein like gelatin. The protein can adsorb, unfold, and form a stable network, while the sugar can increase the viscosity. Liquid drainage of the continuous phase must be minimized as well. Thick liquids drain more slowly than thin ones, and so increasing the viscosity of the continuous phase will reduce drainage. A high viscosity is essential if a stable foam is to be produced. Therefore, sucrose is a main component of marshmallow. But sucrose is seldom used on its own, because of its tendency to crystallize.


title: Marshmallow

text: Corn syrup, derived from maize, contains glucose, maltose, and other oligosaccharides. Corn syrup can be obtained from the partial hydrolysis of cornstarch. Corn syrup is important in the production of marshmallow because it prevents the crystallization of other sugars (like sucrose). It may also contribute body, reduce sweetness, and alter flavor release, depending on the Dextrose Equivalent (DE) of the glucose syrup used.


title: Marshmallow

text: The DE is the measure of the amount of reducing sugars present in a sugar product in relation to glucose. Lower-DE glucose syrups will provide a chewier texture, while higher-DE syrups will make the product more tender. In addition, depending on the type of DE used, can alter the sweetness, hygroscopicity, and browning of the marshmallow. Corn syrup is flavorless and cheap to produce which is why candy companies love using this product.


title: Marshmallow

text: Invert sugar is produced when sucrose breaks down due to the addition of water, also known as hydrolysis. This molecule exhibits all the characteristics of honey except the flavor because it is the primary sugar found in honey. This means that invert sugar has the ability to prevent crystallization, and produce a tender marshmallow. It is also an effective humectant, which allows it to trap water, and prevent the marshmallow from drying out. For some candies, this is not a good trait to have, but for marshmallows, it is an advantage since it has a high moisture content.


title: Marshmallow

text: While not widely used for traditional or commercial recipes, fruit syrups have been proposed as an alternative sugar for marshmallows.


title: Marshmallow

text: Unless a variation of the standard marshmallow is being made, vanilla is always used as the flavoring. The vanilla can either be added in extract form, or by infusing the vanilla beans in the sugar syrup during cooking. This is the best technique to get an even distribution of flavor throughout the marshmallow.


title: Marshmallow

text: Acids, such as cream of tartar or lemon juice, may also be used to increase foam stability. Addition of acid decreases the pH. This reduces the charge on the protein molecules, and brings them closer to their isoelectric point. This results in a stronger, more stable inter-facial film. When added to egg whites, acid prevents excessive aggregation at the interface. However, acid delays foam formation. It may therefore be added toward the end of the whipping process after a stable foam has been created.


title: Marshmallow

text: Gelatin is cooked with sugar and syrup. After the gelatin-containing syrup is cooked, it is allowed to cool slightly before air is incorporated. Whipping is generally accomplished in a rotor-stator type device. Compressed air is injected into the warm syrup, held at a temperature just above the melting point of gelatin. In a marshmallow aerator, pins on a rotating cylinder (rotor) intermesh with stationary pins on the wall (stator) provide the shear forces necessary to break the large injected air bubbles into numerous tiny bubbles that provide the smooth, fine-grained texture of the marshmallow. A continuous stream of light, fluffy marshmallow exits the aerator en route to the forming step.


title: Marshmallow

text: The marshmallow confection is typically formed in one of three ways. First, it can be extruded in the desired shape and cut into pieces, as done for Jet-Puffed marshmallows. Second, it can be deposited onto a belt, as done for Peeps. Third, it can be deposited into a starch-based mold in a mogul to make various shapes.


title: Marshmallow

text: The home process for making marshmallow differs from commercial processes. A mixture of corn syrup and sugar is boiled to about . In a separate step, gelatin is hydrated with enough warm water to make a thick solution. Once the sugar syrup has cooled to about , the gelatin solution is blended in along with desired flavoring, and whipped in a mixer to reach the final density. The marshmallow is then scooped out of the bowl, slabbed on a table, and cut into pieces.


title: Marshmallow

text: A popular camping or backyard tradition in the United Kingdom, North America, New Zealand and Australia is the roasting or toasting of marshmallows over a campfire or other open flame. A marshmallow is placed on the end of a stick or skewer and held carefully over the fire. This creates a caramelized outer skin with a liquid, molten layer underneath. Major flavor compounds and color polymers associated with sugar browning are created during the caramelization process.


title: Marshmallow

text: S'mores are a traditional campfire treat in the United States, made by placing a toasted marshmallow on a slab of chocolate, which is placed between two graham crackers. These can then be squeezed together, causing the chocolate to begin melting.


title: Marshmallow

text: The traditional marshmallow recipe uses powdered marshmallow root, but most commercially manufactured marshmallows instead use gelatin in their manufacture. Vegans and vegetarians avoid gelatin, but there are versions which use a substitute non-animal gelling agent such as agar. In addition, marshmallows are generally not considered to be kosher or halal unless either their gelatin is derived from kosher or halal animals or they are vegan.


title: Marshmallow

text: Marshmallow creme and other less firm marshmallow products generally contain little or no gelatin, which mainly serves to allow the familiar marshmallow confection to retain its shape. They generally use egg whites instead. Non-gelatin, egg-containing versions of this product may be consumed by ovo vegetarians. Several brands of vegetarian and vegan marshmallows and marshmallow fluff exist.


title: Japanese people

text: The are an East Asian ethnic group native to the Japanese archipelago. Japanese people constitute 97.9% of the population of the country of Japan. Worldwide, approximately 129 million people are of Japanese descent; of these, approximately 122.5 million are residents of Japan. People of Japanese ancestry who live outside Japan are referred to as , the Japanese diaspora. Depending on the context, the term may be limited or not to mainland Japanese people, specifically the Yamato (as opposed to Ryukyuan and Ainu people). Japanese people are one of the largest ethnic groups in the world. In recent decades, there has also been an increase in the number of multiracial people with both Japanese and non-Japanese roots, including half Japanese people.


title: Japanese people

text: Archaeological evidence indicates that Stone Age people lived in the Japanese archipelago during the Paleolithic period between 39,000 and 21,000 years ago. Japan was then connected to mainland Asia by at least one land bridge, and nomadic hunter-gatherers crossed to Japan. Flint tools and bony implements of this era have been excavated in Japan.


title: Japanese people

text: In the 18th century, Arai Hakuseki suggested that the ancient stone tools in Japan were left behind by the Shukushin. Later, Philipp Franz von Siebold argued that the Ainu people were indigenous to northern Japan. Iha Fuyū suggested that Japanese and Ryukyuan people have the same ethnic origin, based on his 1906 research on the Ryukyuan languages. In the Taishō period, Torii Ryūzō claimed that Yamato people used Yayoi pottery and Ainu used Jōmon pottery.


title: Japanese people

text: After World War II, Kotondo Hasebe and Hisashi Suzuki claimed that the origin of Japanese people was not newcomers in the Yayoi period (300 BCE – 300 CE) but the people in the Jōmon period. However, Kazuro Hanihara announced a new racial admixture theory in 1984 and a "dual structure model" in 1991. According to Hanihara, modern Japanese lineages began with Jōmon people, who moved into the Japanese archipelago during Paleolithic times, followed by a second wave of immigration, from East Asia to Japan during the Yayoi period (300 BC). Following a population expansion in Neolithic times, these newcomers then found their way to the Japanese archipelago sometime during the Yayoi period. As a result, replacement of the hunter gatherers was common in the island regions of Kyūshū, Shikoku, and southern Honshū, but did not prevail in the outlying islands of Okinawa and Hokkaidō, and the Ryukyuan and Ainu people show mixed characteristics. Mark J. Hudson claims that the main ethnic image of Japanese people was biologically and linguistically formed from 400 BCE to 1,200 CE. Currently, the most well-regarded theory is that present-day Japanese people formed from both the Yayoi rice-agriculturalists and the various Jōmon period ethnicities. However, some recent studies have argued that the Jōmon people had more ethnic diversity than originally suggested or that the people of Japan bear significant genetic signatures from three ancient populations rather than just two.


title: Japanese people

text: Some of the world's oldest known pottery pieces were developed by the Jōmon people in the Upper Paleolithic period, dating back as far as 16,000 years. The name "Jōmon" (縄文 "Jōmon") means "cord-impressed pattern", and comes from the characteristic markings found on the pottery. The Jōmon people were mostly hunter-gatherers, but also practicized early agriculture, such as Azuki bean cultivation. At least one middle to late Jōmon site (, ca. 1200–1000 BC) had also a primitive rice-growing agriculture. They relied primarily on fish and nuts for protein. The ethnic roots of the Jōmon period population were heterogeneous and can be traced back to ancient Northeast Asia, the Tibetan plateau, ancient Taiwan, and Siberia.


title: Japanese people

text: Beginning around 300 BC, the Yayoi people from the Korean Peninsula entered the Japanese islands and displaced or intermingled with the Jōmon. The Yayoi brought wet-rice farming and advanced bronze and iron technology to Japan. The more productive paddy field systems allowed the communities to support larger populations and spread over time, in turn becoming the basis for more advanced institutions and heralding the new civilization of the succeeding Kofun period.


title: Japanese people

text: The estimated population of Japan in the late Jōmon period was about eight hundred thousand, compared to about three million by the Nara period. Taking the growth rates of hunting and agricultural societies into account, it is calculated that about one and half million immigrants moved to Japan in the period. According to Ann Kumar, the Yayoi created the "Japanese-hierarchical society".


title: Japanese people

text: During the Japanese colonial period of 1895 to 1945, the phrase "Japanese people" was used to refer not only to residents of the Japanese archipelago, but also to people from colonies who held Japanese citizenship, such as Taiwanese people and Korean people. The official term used to refer to ethnic Japanese during this period was . Such linguistic distinctions facilitated forced assimilation of colonized ethnic identities into a single Imperial Japanese identity.


title: Japanese people

text: After the end of World War II, many Nivkh people and Orok people from southern Sakhalin, who held Japanese citizenship in the Karafuto Prefecture, were forced to repatriate to Hokkaidō by the Soviet Union as a part of the Japanese people. On the other hand, many Sakhalin Koreans who had held Japanese citizenship until the end of the war were left stateless by the Soviet occupation.


title: Japanese people

text: The Japanese language is a Japonic language that is related to the Ryukyuan languages and was treated as a language isolate in the past. The earliest attested form of the language, Old Japanese, dates to the 8th century. Japanese phonology is characterized by a relatively small number of vowel phonemes, frequent gemination and a distinctive pitch accent system. The modern Japanese language has a tripartite writing system using hiragana, katakana and kanji. The language includes native Japanese words and a large number of words derived from the Chinese language. In Japan the adult literacy rate in the Japanese language exceeds 99%. Dozens of Japanese dialects are spoken in regions of Japan. For now, Japanese is classified as a member of the Japonic languages or as a language isolate with no known living relatives if Ryukyuan is counted as dialects.


title: Japanese people

text: Japanese religion has traditionally been syncretic in nature, combining elements of Buddhism and Shinto (Shinbutsu-shūgō). Shinto, a polytheistic religion with no book of religious canon, is Japan's native religion. Shinto was one of the traditional grounds for the right to the throne of the Japanese imperial family and was codified as the state religion in 1868 (State Shinto), but was abolished by the American occupation in 1945. Mahayana Buddhism came to Japan in the sixth century and evolved into many different sects. Today, the largest form of Buddhism among Japanese people is the Jōdo Shinshū sect founded by Shinran.


title: Japanese people

text: A large majority of Japanese people profess to believe in both Shinto and Buddhism. Japanese people's religion functions mostly as a foundation for mythology, traditions and neighborhood activities, rather than as the single source of moral guidelines for one's life.


title: Japanese people

text: According to the annual statistical research on religion in 2018 by the Agency for Culture Affairs, Government of Japan, about two million or slightly 1.5% of Japan's population are Christians. A larger proportion of members of the Japanese diaspora practice Christianity; about 60% of Japanese Brazilians and 90% of Japanese Mexicans are Roman Catholics, while about 37% of Japanese Americans are Christians (33% Protestant and 4% Catholic).


title: Japanese people

text: Certain genres of writing originated in and are often associated with Japanese society. These include the haiku, tanka, and I Novel, although modern writers generally avoid these writing styles. Historically, many works have sought to capture or codify traditional Japanese cultural values and aesthetics. Some of the most famous of these include Murasaki Shikibu's "The Tale of Genji" (1021), about Heian court culture; Miyamoto Musashi's "The Book of Five Rings" (1645), concerning military strategy; Matsuo Bashō's "Oku no Hosomichi" (1691), a travelogue; and Jun'ichirō Tanizaki's essay "In Praise of Shadows" (1933), which contrasts Eastern and Western cultures.


title: Japanese people

text: Following the opening of Japan to the West in 1854, some works of this style were written in English by natives of Japan; they include "" by Nitobe Inazō (1900), concerning "samurai" ethics, and "The Book of Tea" by Okakura Kakuzō (1906), which deals with the philosophical implications of the Japanese tea ceremony. Western observers have often attempted to evaluate Japanese society as well, to varying degrees of success; one of the most well-known and controversial works resulting from this is Ruth Benedict's "The Chrysanthemum and the Sword" (1946).


title: Japanese people

text: Twentieth-century Japanese writers recorded changes in Japanese society through their works. Some of the most notable authors included Natsume Sōseki, Jun'ichirō Tanizaki, Osamu Dazai, Fumiko Enchi, Akiko Yosano, Yukio Mishima, and Ryōtarō Shiba. Popular contemporary authors such as Ryū Murakami, Haruki Murakami, and Banana Yoshimoto have been translated into many languages and enjoy international followings, and Yasunari Kawabata and Kenzaburō Ōe were awarded the Nobel Prize in Literature.


title: Japanese people

text: Decorative arts in Japan date back to prehistoric times. Jōmon pottery includes examples with elaborate ornamentation. In the Yayoi period, artisans produced mirrors, spears, and ceremonial bells known as "dōtaku." Later burial mounds, or "kofun," preserve characteristic clay figures known as "haniwa," as well as wall paintings.


title: Japanese people

text: Beginning in the Nara period, painting, calligraphy, and sculpture flourished under strong Confucian and Buddhist influences from China. Among the architectural achievements of this period are the Hōryū-ji and the Yakushi-ji, two Buddhist temples in Nara Prefecture. After the cessation of official relations with the Tang dynasty in the ninth century, Japanese art and architecture gradually became less influenced by China. Extravagant art and clothing were commissioned by nobles to decorate their court, and although the aristocracy was quite limited in size and power, many of these pieces are still extant. After the Tōdai-ji was attacked and burned during the Genpei War, a special office of restoration was founded, and the Tōdai-ji became an important artistic center. The leading masters of the time were Unkei and Kaikei.


title: Japanese people

text: Painting advanced in the Muromachi period in the form of ink wash painting under the influence of Zen Buddhism as practiced by such masters as Sesshū Tōyō. Zen Buddhist tenets were also elaborated into the tea ceremony during the Sengoku period. During the Edo period, the polychrome painting screens of the Kanō school were made influential thanks to their powerful patrons (including the Tokugawas). Popular artists created "ukiyo-e", woodblock prints for sale to commoners in the flourishing cities. Pottery such as Imari ware was highly valued as far away as Europe.


title: Japanese people

text: In theater, Noh is a traditional, spare dramatic form that developed in tandem with kyōgen farce. In stark contrast to the restrained refinement of noh, kabuki, an "explosion of color", use every possible stage trick for dramatic effect. Plays include sensational events such as suicides, and many such works were performed in both kabuki and bunraku puppet theaters.


title: Japanese people

text: Since the Meiji Restoration, Japan has absorbed elements of Western culture and has given them a "Japanese" feel or modification into it. It's modern decorative, practical, and performing arts works span a spectrum ranging from the traditions of Japan to purely Western modes. Products of popular culture, including J-pop, J-rock, manga and anime have found audiences and fans around the world.