Misplaced Pages

#872127

76-533: It occurs naturally as the mineral sylvite , which is named after salt's historical designations sal degistivum Sylvii and sal febrifugum Sylvii , and in combination with sodium chloride as sylvinite . The majority of the potassium chloride produced is used for making fertilizer , called potash , since the growth of many plants is limited by potassium availability. The term "potash" refers to various mined and manufactured salts that contain potassium in water-soluble form. Potassium chloride sold as fertilizer

152-517: A phyllosilicate , to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below: A mineral's hardness is a function of its structure. Hardness is not necessarily constant for all crystallographic directions; crystallographic weakness renders some directions softer than others. An example of this hardness variability exists in kyanite, which has a Mohs hardness of 5 1 ⁄ 2 parallel to [001] but 7 parallel to [100] . Potassium-40 Potassium-40 ( K )

228-585: 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

304-417: 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

380-416: 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 . The International Mineralogical Association (IMA)

456-473: A distinct mineral: 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. 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. Some authors require

532-463: A key to defining a substance as a mineral. A 2011 article defined icosahedrite , an aluminium-iron-copper alloy, as a mineral; named for its unique natural icosahedral symmetry , it is a quasicrystal . Unlike a true crystal, quasicrystals are ordered but not periodic. 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

608-605: A lilac flame . Potassium chloride is extracted from minerals sylvite , carnallite , and potash . It is also extracted from salt water and can be manufactured by crystallization from solution, flotation or electrostatic separation from suitable minerals. It is a by-product of the production of nitric acid from potassium nitrate and hydrochloric acid . Most potassium chloride is produced as agricultural and industrial-grade potash in Saskatchewan, Canada , Russia, and Belarus. Saskatchewan alone accounted for over 25% of

684-409: A mineral defines how much it can resist scratching or indentation. This physical property is controlled by the chemical composition and crystalline structure of a mineral. The most commonly used scale of measurement is the ordinal Mohs hardness scale, which measures resistance to scratching. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc,

760-432: A sedimentary mineral, and silicic acid ): Under low-grade metamorphic conditions, kaolinite reacts with quartz to form pyrophyllite (Al 2 Si 4 O 10 (OH) 2 ): As metamorphic grade increases, the pyrophyllite reacts to form kyanite and quartz: 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

836-406: 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. Twinning is the intergrowth of two or more crystals of a single mineral species. The geometry of

SECTION 10

#1732783468873

912-620: A trigonal structure containing K and Cl 3 is obtained; above 40 GPa this gives way to a phase isostructural with the intermetallic compound Cr 3 Si. Under ambient conditions, the crystal structure of potassium chloride is like that of NaCl. It adopts a face-centered cubic structure known as the B1 phase with a lattice constant of roughly 6.3 Å. Crystals cleave easily in three directions. Other polymorphic and hydrated phases are adopted at high pressures. Some other properties are As with other compounds containing potassium, KCl in powdered form gives

988-935: A variety of its SiO 2 polymorphs , such as tridymite and cristobalite at high temperatures, and coesite at high pressures. 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 . Crystal structure results from

1064-502: A variety of minerals because of the need to balance charges. 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

1140-402: A variety of polar solvents. Solutions of KCl are common standards, for example for calibration of the electrical conductivity of (ionic) solutions, since KCl solutions are stable, allowing for reproducible measurements. In aqueous solution , it is essentially fully ionized into solvated K and Cl ions. Although potassium is more electropositive than sodium , KCl can be reduced to

1216-595: A white mica, can be used for windows (sometimes referred to as isinglass), as a filler, or as an insulator. 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 2 ), an ore of tin; and colemanite , an ore of boron . 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

1292-509: Is a radioactive isotope of potassium which has a long half-life of 1.25 billion years. It makes up about 0.012% (120 ppm ) of the total amount of potassium found in nature. Potassium-40 undergoes three types of radioactive decay . In about 89.28% of events, it decays to calcium-40 ( Ca) with emission of a beta particle (β , an electron ) with a maximum energy of 1.31  MeV and an antineutrino . In about 10.72% of events, it decays to argon-40 ( Ar) by electron capture (EC), with

1368-437: Is a gas that does not ordinarily combine with other elements. So, when a mineral forms – whether from molten rock , or from substances dissolved in water – it will be initially argon-free, even if there is some argon in the liquid. However, if the mineral contains any potassium, then decay of the K isotope present will create fresh argon-40 that will remain locked up in the mineral. Since the rate at which this conversion occurs

1444-429: 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 (Fe,Ni) 9 S 8 , meaning Fe x Ni 9- x S 8 , where x is a variable number between 0 and 9. Sometimes a mineral with variable composition

1520-707: Is a sedimentary rock composed primarily of organically derived carbon. 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. Commercially valuable minerals and rocks, other than gemstones, metal ores, or mineral fuels, are referred to as industrial minerals . For example, muscovite ,

1596-443: Is also an optical crystal with a wide transmission range from 210 nm to 20 μm. While cheap, KCl crystals are hygroscopic . This limits its application to protected environments or short-term uses such as prototyping. Exposed to free air, KCl optics will "rot". Whereas KCl components were formerly used for infrared optics , they have been entirely replaced by much tougher crystals such as zinc selenide . Potassium chloride

SECTION 20

#1732783468873

1672-457: Is another medicine on the WHO's List of Essential Medicines . Overdose causes hyperkalemia which can disrupt cell signaling to the extent that the heart will stop, reversibly in the case of some open heart surgeries . Potassium chloride can be used as a salt substitute for food , but due to its weak, bitter, unsalty flavor , it is often mixed with ordinary table salt (sodium chloride) to improve

1748-585: Is approximately 0.4 grams (0.014 oz) per liter of water. Potassium is vital in the human body , and potassium chloride by mouth is the standard means to treat low blood potassium , although it can also be given intravenously. It is on the World Health Organization's List of Essential Medicines . It is also an ingredient in Oral Rehydration Therapy (ORT)/solution (ORS) to reduce hypokalemia caused by diarrhoea. This

1824-420: Is commonly used in eyeglasses, glassware, televisions, and computer monitors. Because natural potassium contains a tiny amount of the isotope potassium-40 , potassium chloride is used as a beta radiation source to calibrate radiation monitoring equipment . It also emits a relatively low level of 511 keV gamma rays from positron annihilation, which can be used to calibrate medical scanners. Potassium chloride

1900-448: Is in octahedral coordination. Other examples are the aluminosilicates kyanite , andalusite , and sillimanite (polymorphs, since they share the formula Al 2 SiO 5 ), 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

1976-445: Is known as "muriate of potash"—it is the common name for potassium chloride ( KCl ) used in agriculture. The vast majority of potash fertilizer worldwide is sold as muriate of potash. The dominance of muriate of potash in the fertilizer market is due to its high potassium content (approximately 60% K 2 O equivalent) and relative affordability compared to other potassium sources like sulfate of potash ( potassium sulfate ). Potassium

2052-521: Is known, it is possible to determine the elapsed time since the mineral formed by measuring the ratio of K and Ar atoms contained in it. The argon found in Earth's atmosphere is 99.6% Ar; whereas the argon in the Sun – and presumably in the primordial material that condensed into the planets – is mostly Ar , with less than 15% of Ar. It follows that most of the terrestrial argon derives from potassium-40 that decayed into argon-40, which eventually escaped to

2128-445: Is one of the three primary macronutrients essential for plant growth, alongside nitrogen and phosphorus. Potassium plays a vital role in various plant physiological processes, including enzyme activation, photosynthesis, protein synthesis, and water regulation. For watering plants, a moderate concentration of potassium chloride (KCl) is used to avoid potential toxicity: 6 mM (millimolar) is generally effective and safe for most plants, that

2204-408: 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

2280-470: 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. Orthoclase feldspar (KAlSi 3 O 8 ) is a mineral commonly found in granite , a plutonic igneous rock . When exposed to weathering, it reacts to form kaolinite (Al 2 Si 2 O 5 (OH) 4 ,

2356-653: Is split into separate species, more or less arbitrarily, forming a mineral group ; that is the case of the silicates Ca x Mg y Fe 2- x - y SiO 4 , the olivine group . 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 . Minerals are classified by key chemical constituents;

Potassium chloride - Misplaced Pages Continue

2432-524: Is the angle opposite the a-axis, viz. the angle between the b and c axes): 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. 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

2508-422: Is the generally recognized standard body for the definition and nomenclature of mineral species. As of November 2024 , the IMA recognizes 6,100 official mineral species. The chemical composition of a named mineral species may vary somewhat due to the inclusion of small amounts of impurities. Specific varieties of a species sometimes have conventional or official names of their own. For example, amethyst

2584-405: 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

2660-456: 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. The hardness of

2736-471: Is used as a scotophor with designation P10 in dark-trace CRTs , e.g. in the Skiatron . The typical amounts of potassium chloride found in the diet appear to be generally safe. In larger quantities, however, potassium chloride is toxic. The LD 50 of orally ingested potassium chloride is approximately 2.5 g/kg, or 190 grams (6.7 oz) for a body mass of 75 kilograms (165 lb). In comparison,

2812-420: Is used in some de-icing products designed to be safer for pets and plants, though these are inferior in melting quality to calcium chloride . It is also used in various brands of bottled water . Potassium chloride was once used as a fire extinguishing agent , and in portable and wheeled fire extinguishers . Known as Super-K dry chemical, it was more effective than sodium bicarbonate -based dry chemicals and

2888-618: The CIPW norm , which gives reasonable estimates for volcanic rock formed from dry magma. 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 (NaAlSi 3 O 8 ) to calcium -rich anorthite (CaAl 2 Si 2 O 8 ) 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

2964-455: The LD 50 of sodium chloride (table salt) is 3.75 g/kg. Intravenously, the LD 50 of potassium chloride is far smaller, at about 57.2 mg/kg to 66.7 mg/kg; this is found by dividing the lethal concentration of positive potassium ions (about 30 to 35 mg/kg) by the proportion by mass of potassium ions in potassium chloride (about 0.52445 mg K/mg KCl). KCl is soluble in

3040-496: 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 ). Biogeochemical cycles have contributed to the formation of minerals for billions of years. Microorganisms can precipitate metals from solution , contributing to

3116-497: The taste , to form low sodium salt . The addition of 1 ppm of thaumatin considerably reduces this bitterness. Complaints of bitterness or a chemical or metallic taste are also reported with potassium chloride used in food. In the United States, potassium chloride is used as the final drug in the three-injection sequence of lethal injection as a form of capital punishment . It induces cardiac arrest , ultimately killing

Potassium chloride - Misplaced Pages Continue

3192-455: The 78 mineral classes listed in the Dana classification scheme. 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

3268-431: 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." 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

3344-455: 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 . A topic of contention among geologists and mineralogists has been

3420-556: The Latin species , "a particular sort, kind, or type with distinct look, or appearance". 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

3496-488: 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

3572-644: The atmosphere. The radioactive decay of K in the Earth's mantle ranks third, after Th and U , as the source of radiogenic heat . The core also likely contains radiogenic sources, although how much is uncertain. It has been proposed that significant core radioactivity (1–2 TW) may be caused by high levels of U, Th, and K. Potassium-40 is the largest source of natural radioactivity in animals including humans. A 70 kg human body contains about 140 g of potassium, hence about 140g × 0.0117% ≈ 16.4 mg of K; whose decay produces about 3850 to 4300 disintegrations per second ( becquerel ) continuously throughout

3648-449: 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

3724-424: 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

3800-415: 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

3876-417: 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%. The minerals that form are those that are most stable at the temperature and pressure of formation, within the limits imposed by

SECTION 50

#1732783468873

3952-434: The difference in charge has to accounted for by making a second substitution of Si by Al . 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

4028-414: 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 2 , an ultra-high pressure quartz polymorph with rutile structure). In kyanite,

4104-418: The emission of a neutrino and then a 1.460 MeV gamma ray . The radioactive decay of this particular isotope explains the large abundance of argon (nearly 1%) in the Earth's atmosphere , as well as prevalence of Ar over other isotopes . Very rarely (0.001% of events), it decays to Ar by emitting a positron (β ) and a neutrino. Potassium-40 is especially important in potassium–argon (K–Ar) dating. Argon

4180-517: 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 [AlSi 3 O 8 ] ; without the substitution, the formula would be charge-balanced as SiO 2 , giving quartz. The significance of this structural property will be explained further by coordination polyhedra. The second substitution occurs between Na and Ca ; however,

4256-425: The feed. As an added benefit, it is known to increase milk production. It is sometimes used in solution as a completion fluid in petroleum and natural gas operations, as well as being an alternative to sodium chloride in household water softener units. Glass manufacturers use granular potash as a flux , lowering the temperature at which a mixture melts. Because potash imparts excellent clarity to glass, it

4332-778: The formation of ore deposits. They can also catalyze the dissolution of minerals. 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

4408-410: The generic AX 2 formula; these two groups are collectively known as the pyrite and marcasite groups. Polymorphism can extend beyond pure symmetry content. The aluminosilicates are a group of three minerals – kyanite , andalusite , and sillimanite  – which share the chemical formula Al 2 SiO 5 . Kyanite is triclinic, while andalusite and sillimanite are both orthorhombic and belong to

4484-451: 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 2 ; however, the former is isometric while the latter is orthorhombic. This polymorphism extends to other sulfides with

4560-414: The inmate. As a chemical feedstock , the salt is used for the manufacture of potassium hydroxide and potassium metal. It is also used in medicine, lethal injections , scientific applications, food processing , soaps , and as a sodium-free substitute for table salt for people concerned about the health effects of sodium. It is used as a supplement in animal feed to boost the potassium level in

4636-461: 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. As of November 2024 , 6,100 mineral species are approved by

SECTION 60

#1732783468873

4712-532: The metal by reaction with metallic sodium at 850 °C because the more volatile potassium can be removed by distillation (see Le Chatelier's principle ): This method is the main method for producing metallic potassium. Electrolysis (used for sodium) fails because of the high solubility of potassium in molten KCl. Potassium chlorides with formulas other than KCl have been predicted to become stable under pressures of 20 GPa or more. Among these, two phases of KCl 3 were synthesized and characterized. At 20-40 GPa,

4788-494: 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 , Al 2 O 3 . The first known use of the word "mineral" in the English language ( Middle English ) was the 15th century. The word came from Medieval Latin : minerale , from minera , mine, ore. The word "species" comes from

4864-428: The most encompassing of these being the six crystal families. 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

4940-402: The olivine series of magnesium-rich forsterite and iron-rich fayalite, and the wolframite series of manganese -rich hübnerite and iron-rich ferberite . 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

5016-622: 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,

5092-563: The point where they can no longer be accommodated in common minerals. 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

5168-510: The presence of chlorine gas, also a very exothermic reaction: Mineral In geology and mineralogy , a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form. The geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite ) or organic compounds in

5244-447: The presence of repetitive twinning; however, instead of occurring around a rotational axis, polysynthetic twinning occurs along parallel planes, usually on a microscopic scale. 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

5320-568: The previous definition of a mineral to classify "element or compound, amorphous or crystalline, formed through biogeochemical processes," as a mineral. 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

5396-485: The second aluminium is in six-fold coordination; its chemical formula can be expressed as Al Al SiO 5 , to reflect its crystal structure. Andalusite has the second aluminium in five-fold coordination (Al Al SiO 5 ) and sillimanite has it in four-fold coordination (Al Al SiO 5 ). 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

5472-505: The sense of chemistry (such as mellite ). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite ) that also occur in rocks. 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 . Some natural solid substances without

5548-439: 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

5624-472: 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 . The International Mineralogical Association has established the following requirements for a substance to be considered

5700-427: The world's potash production in 2017. Potassium chloride is inexpensively available and is rarely prepared intentionally in the laboratory. It can be generated by treating potassium hydroxide (or other potassium bases) with hydrochloric acid : This conversion is an acid-base neutralization reaction . The resulting salt can then be purified by recrystallization. Another method would be to allow potassium to burn in

5776-402: Was compatible with protein foam . This agent fell out of favor with the introduction of potassium bicarbonate ( Purple-K ) dry chemical in the late 1960s, which was much less corrosive , as well as more effective. It is rated for B and C fires. Along with sodium chloride and lithium chloride , potassium chloride is used as a flux for the gas welding of aluminium . Potassium chloride

#872127