document_title: Diamond

question_text: where do most of the worlds diamonds come from

question_tokens: where do most of the worlds diamonds come from

text: Diamond

text: History

text: The name diamond is derived from the ancient Greek αδάμας (adámas), "proper", "unalterable", "unbreakable", "untamed", from ἀ- (a-), "un-" + δαμάω (damáō), "I overpower", "I tame".[3] Diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could be found many centuries ago along the rivers Penner, Krishna and Godavari. Diamonds have been known in India for at least 3,000 years but most likely 6,000 years.[4]

text: Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history.[5][6] The popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns.[7]

text: In 1772, the French scientist Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen, and showed that the only product of the combustion was carbon dioxide, proving that diamond is composed of carbon.[8] Later in 1797, the English chemist Smithson Tennant repeated and expanded that experiment.[9] By demonstrating that burning diamond and graphite releases the same amount of gas, he established the chemical equivalence of these substances.[10]

text: The most familiar uses of diamonds today are as gemstones used for adornment, and as industrial abrasives for cutting hard materials. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds. In the 20th century, experts in gemology developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds: these are carat (its weight), cut (quality of the cut is graded according to proportions, symmetry and polish), color (how close to white or colorless; for fancy diamonds how intense is its hue), and clarity (how free is it from inclusions).[11] A large, flawless diamond is known as a paragon.

text: Geology

text: Diamonds are extremely rare, with concentrations of at most parts per billion in source rock.[12] Before the 20th century, most diamonds were found in alluvial deposits. Loose diamonds are also found along existing and ancient shorelines, where they tend to accumulate because of their size and density.[13]:149 Rarely, they have been found in glacial till (notably in Wisconsin and Indiana), but these deposits are not of commercial quality.[13]:19 These types of deposit were derived from localized igneous intrusions through weathering and transport by wind or water.[14]

text: Most diamonds come from the Earth's mantle, and most of this section discusses those diamonds. However, there are other sources. Some blocks of the crust, or terranes, have been buried deep enough as the crust thickened so they experienced ultra-high-pressure metamorphism. These have evenly distributed microdiamonds that show no sign of transport by magma. In addition, when meteorites strike the ground, the shock wave can produce high enough temperatures and pressures for microdiamonds and nanodiamonds to form.[14] Impact-type microdiamonds can be used as an indicator of ancient impact craters.[15] Popigai crater in Russia may have the world's largest diamond deposit, estimated at trillions of carats, and formed by an asteroid impact.[16]

text: A common misconception is that diamonds are formed from highly compressed coal. Coal is formed from buried prehistoric plants, and most diamonds that have been dated are far older than the first land plants. It is possible that diamonds can form from coal in subduction zones, but diamonds formed in this way are rare, and the carbon source is more likely carbonate rocks and organic carbon in sediments, rather than coal.[17][18]

text: Surface distribution

text: Diamonds are far from evenly distributed over the Earth. A rule of thumb known as Clifford's rule states that they are almost always found in kimberlites on the oldest part of cratons, the stable cores of continents with typical ages of 2.5 billion years or more.[14][19]:314 However, there are exceptions. The Argyle diamond mine in Australia, the largest producer of diamonds by weight in the world, is located in a mobile belt, also known as an orogenic belt,[20] a weaker zone surrounding the central craton that has undergone compressional tectonics. Instead of kimberlite, the host rock is lamproite. Lamproites with diamonds that are not economically viable are also found in the United States, India and Australia.[14] In addition, diamonds in the Wawa belt of the Superior province in Canada and microdiamonds in the island arc of Japan are found in a type of rock called lamprophyre.[14]

text: Kimberlites can be found in narrow (1–4 meters) dikes and sills, and in pipes with diameters that range from about 75 meters to 1.5 kilometers. Fresh rock is dark bluish green to greenish gray, but after exposure rapidly turns brown and crumbles.[21] It is hybrid rock with a chaotic mixture of small minerals and rock fragments (clasts) up to the size of watermelons. They are a mixture of xenocrysts and xenoliths (minerals and rocks carried up from the lower crust and mantle), pieces of surface rock, altered minerals such as serpentine, and new minerals that crystallized during the eruption. The texture varies with depth. The composition forms a continuum with carbonatites, but the latter have too much oxygen for carbon to exist in a pure form. Instead, it is locked up in the mineral calcite (CaCO3).[14]

text: All three of the diamond-bearing rocks (kimberlite, lamproite and lamprophyre) lack certain minerals (melilite and kalsilite) that are incompatible with diamond formation. In kimberlite, olivine is large and conspicuous, while lamproite has Ti-phlogopite and lamprophyre has biotite and amphibole. They are all derived from magma types that erupt rapidly from small amounts of melt, are rich in volatiles and magnesium oxide, and are less oxidizing than more common mantle melts such as basalt. These characteristics allow the melts to carry diamonds to the surface before they dissolve.[14]

text: Exploration

text: Kimberlite pipes can be difficult to find. They weather quickly (within a few years after exposure) and tend to have lower topographic relief than surrounding rock. If they are visible in outcrops, the diamonds are never visible because they are so rare. In any case, kimberlites are often covered with vegetation, sediments, soils or lakes. In modern searches, geophysical methods such as aeromagnetic surveys, electrical resistivity and gravimetry, help identify promising regions to explore. This is aided by isotopic dating and modeling of the geological history. Then surveyors must go to the area and collect samples, looking for kimberlite fragments or indicator minerals. The latter have compositions that reflect the conditions where diamonds form, such as extreme melt depletion or high pressures in eclogites. However, indicator minerals can be misleading; a better approach is geothermobarometry, where the compositions of minerals are analyzed as if they were in equilibrium with mantle minerals.[14]

text: Finding kimberlites requires persistence, and only a small fraction contain diamonds that are commercially viable. The only major discoveries since about 1980 have been in Canada. Since existing mines have lifetimes of as little as 25 years, there could be a shortage of new diamonds in the future.[14]

text: Ages

text: Diamonds are dated by analyzing inclusions using the decay of radioactive isotopes. Depending on the elemental abundances, one can look at the decay of rubidium to strontium, samarium to neodymium, uranium to lead, argon-40 to argon-39, or rhenium to osmium. Those found in kimberlites have ages ranging from 1 to 3.5 billion years, and there can be multiple ages in the same kimberlite, indicating multiple episodes of diamond formation. The kimberlites themselves are much younger. Most of them have ages between tens of millions and 300 million years old, although there are some older exceptions (Argyle, Premier and Wawa). Thus, the kimberlites formed independently of the diamonds and served only to transport them to the surface.[12][14] Kimberlites are also much younger than the cratons they have erupted through. The reason for the lack of older kimberlites is unknown, but it suggests there was some change in mantle chemistry or tectonics. No kimberlite has erupted in human history.[14]

text: Origin in mantle

text: Most gem-quality diamonds come from depths of 150 to 250 kilometers in the lithosphere. Such depths occur below cratons in mantle keels, the thickest part of the lithosphere. These regions have high enough pressure and temperature to allow diamonds to form and they are not convecting, so diamonds can be stored for billions of years until a kimberlite eruption samples them.[14]

text: Host rocks in a mantle keel include harzburgite and lherzolite, two type of peridotite. The most dominant rock type in the upper mantle, peridotite is an igneous rock consisting mostly of the minerals olivine and pyroxene; it is low in silica and high in magnesium. However, diamonds in peridotite rarely survive the trip to the surface.[14] Another common source that does keep diamonds intact is eclogite, a metamorphic rock that typically forms from basalt as an oceanic plate plunges into the mantle at a subduction zone.[12]

text: A smaller fraction of diamonds (about 150 have been studied) come from depths of 330–660 kilometers, a region that includes the transition zone. They formed in eclogite but are distinguished from diamonds of shallower origin by inclusions of majorite (a form of garnet with excess silicon). A similar proportion of diamonds comes from the lower mantle at depths between 660 and 800 kilometers.[12]

text: Diamond is thermodynamically stable at high pressures and temperatures, with the phase transition from graphite occurring at greater temperatures as the pressure increases. Thus, underneath continents it becomes stable at temperatures of 950 degrees Celsius and pressures of 4.5 gigapascals, corresponding to depths of 150 kilometers or greater. In subduction zones, which are colder, it becomes stable at temperatures of 800 degrees C and pressures of 3.5 gigapascals. At depths greater than 240 km, iron-nickel metal phases are present and carbon is likely to be either dissolved in them or in the form of carbides. Thus, the deeper origin of some diamonds may reflect unusual growth environments.[12][14]

text: Carbon sources

text: The amount of carbon in the mantle is not well constrained, but its concentration is estimated at 0.5 to 1 parts per thousand.[14] It has two stable isotopes, 12C and 13C, in a ratio of approximately 99:1 by mass. This ratio has a wide range in meteorites, which implies that it was probably also broad in the early Earth. It can also be altered by surface processes like photosynthesis. The fraction is generally compared to a standard sample using a ratio δ13C expressed in parts per thousand. Common rocks from the mantle such as basalts, carbonatites and kimberlites have ratios between -8 and -2. On the surface, organic sediments have an average of -25 while carbonates have an average of 0.[12]

text: Populations of diamonds from different sources have distributions of δ13C that vary markedly. Peridotitic diamonds are mostly within the typical mantle range; eclogitic diamonds have values from -40 to +3, although the peak of the distribution is in the mantle range. This variability implies that they are not formed from carbon that is primordial (having resided in the mantle since the Earth formed). Instead, they are the result of tectonic processes, although (given the ages of diamonds) not necessarily the same tectonic processes that act in the present.[14]

text: Formation and growth

text: Diamonds in the mantle form through a metasomatic process where a C-O-H-N-S fluid or melt dissolves minerals in a rock and replaces them with new minerals. (The vague term C-O-H-N-S is commonly used because the exact composition is not known.) Diamonds form from this fluid either by reduction of oxidized carbon (e.g., CO2 or CO3) or oxidation of a reduced phase such as methane.[12]

text: Using probes such as polarized light, photoluminescence and cathodoluminescence, a series of growth zones can be identified in diamonds. The characteristic pattern in diamonds from the lithosphere involves a nearly concentric series of zones with very thin oscillations in luminescence and alternating episodes where the carbon is resorbed by the fluid and then grown again. Diamonds from below the lithosphere have a more irregular, almost polycrystalline texture, reflecting the higher temperatures and pressures as well as the transport of the diamonds by convection.[14]

text: Transport to the surface

text: Geological evidence supports a model in which kimberlite magma rose at 4–20 meters per second, creating an upward path by hydraulic fracturing of the rock. As the pressure decreases, a vapor phase exsolves from the magma, and this helps to keep the magma fluid. At the surface, the initial eruption explodes out through fissures at high speeds (over 200 meters per second). Then, at lower pressures, the rock is eroded, forming a pipe and producing fragmented rock (breccia). As the eruption wanes, there is pyroclastic phase and then metamorphism and hydration produces serpentinites.[14]

text: In space

text: Although diamonds on Earth are rare, they are very common in space. In meteorites, about 3 percent of the carbon is in the form of nanodiamonds, having diameters of a few nanometers. Sufficiently small diamonds can form in the cold of space because their lower surface energy makes them more stable than graphite. The isotopic signatures of some nanodiamonds indicate they were formed outside the Solar System in stars.[22]

text: High pressure experiments predict that large quantities of diamonds condense from methane into a "diamond rain" on the ice giant planets Uranus and Neptune.[23][24][25] Some extrasolar planets may be almost entirely composed of diamond.[26]

text: Diamonds may exist in carbon-rich stars, particularly white dwarfs. One theory for the origin of carbonado, the toughest form of diamond, is that it originated in a white dwarf or supernova.[27][28] Diamonds formed in stars may have been the first minerals.[29]

text: Material properties

text: A diamond is a transparent crystal of tetrahedrally bonded carbon atoms in a covalent network lattice (sp3) that crystallizes into the diamond lattice which is a variation of the face-centered cubic structure. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness and thermal conductivity (900–7003232000000000000♠2320 W·m−1·K−1),[30] as well as wide bandgap and high optical dispersion.[31] Above 7003197315000000000♠1700 °C (7003197300000000000♠1973 K / 7003224592777777777♠3583 °F) in vacuum or oxygen-free atmosphere, diamond converts to graphite; in air, transformation starts at ~7002973150000000000♠700 °C.[32] Diamond's ignition point is 720–7003107315000000000♠800 °C in oxygen and 850–7003127315000000000♠1000 °C in air. Naturally occurring diamonds have a density ranging from 3.15 to 7003353000000000000♠3.53 g/cm3, with pure diamond close to 7003352000000000000♠3.52 g/cm3.[1] The chemical bonds that hold the carbon atoms in diamonds together are weaker than those in graphite. In diamonds, the bonds form an inflexible three-dimensional lattice, whereas in graphite, the atoms are tightly bonded into sheets, which can slide easily over one another, making the overall structure weaker.[33] In a diamond, each carbon atom is surrounded by neighboring four carbon atoms forming a tetrahedral shaped unit.

text: Crystal habit

text: Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles. As diamond's crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cube, octahedron, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron. The crystals can have rounded off and unexpressive edges and can be elongated. Diamonds (especially those with rounded crystal faces) are commonly found coated in nyf, an opaque gum-like skin.[34]

text: Some diamonds have opaque fibers. They are referred to as opaque if the fibers grow from a clear substrate or fibrous if they occupy the entire crystal. Their colors range from yellow to green or gray, sometimes with cloud-like white to gray impurities. Their most common shape is cuboidal, but they can also form octahedra, dodecahedra, macles or combined shapes. The structure is the result of numerous impurities with sizes between 1 and 5 microns. These diamonds probably formed in kimberlite magma and sampled the volatiles.[12]

text: Diamonds can also form polycrystalline aggregates. There have been attempts to classify them into groups with names such as boart, ballas, stewartite and framesite, but there is no widely accepted set of criteria.[12] Carbonado, a type in which the diamond grains were sintered (fused without melting by the application of heat and pressure), is black in color and tougher than single crystal diamond.[35] It has never been observed in a volcanic rock. There are many theories for its origin, including formation in a star, but no consensus.[12][36][37]

text: Hardness

text: Diamond is the hardest known natural material on both the Vickers scale and the Mohs scale. Diamond's great hardness relative to other materials has been known since antiquity, and is the source of its name.

text: Diamond hardness depends on its purity, crystalline perfection and orientation: hardness is higher for flawless, pure crystals oriented to the <111> direction (along the longest diagonal of the cubic diamond lattice).[38] Therefore, whereas it might be possible to scratch some diamonds with other materials, such as boron nitride, the hardest diamonds can only be scratched by other diamonds and nanocrystalline diamond aggregates.

text: The hardness of diamond contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, it maintains its polish extremely well. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in engagement or wedding rings, which are often worn every day.

text: The hardest natural diamonds mostly originate from the Copeton and Bingara fields located in the New England area in New South Wales, Australia. These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds. Their hardness is associated with the crystal growth form, which is single-stage crystal growth. Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice, all of which affect their hardness. It is possible to treat regular diamonds under a combination of high pressure and high temperature to produce diamonds that are harder than the diamonds used in hardness gauges.[39]

text: Somewhat related to hardness is another mechanical property toughness, which is a material's ability to resist breakage from forceful impact. The toughness of natural diamond has been measured as 7.5–10 MPa·m1/2.[40][41] This value is good compared to other ceramic materials, but poor compared to most engineering materials such as engineering alloys, which typically exhibit toughnesses over 100 MPa·m1/2. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamond has a cleavage plane and is therefore more fragile in some orientations than others. Diamond cutters use this attribute to cleave some stones, prior to faceting.[42] "Impact toughness" is one of the main indexes to measure the quality of synthetic industrial diamonds.

text: Pressure resistance

text: Used in so-called diamond anvil experiments to create high-pressure environments, diamonds are able to withstand crushing pressures in excess of 600 gigapascals (6 million atmospheres).[43]

text: Electrical conductivity

text: Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators.[44] The conductivity and blue color originate from boron impurity. Boron substitutes for carbon atoms in the diamond lattice, donating a hole into the valence band.[44]

text: Substantial conductivity is commonly observed in nominally undoped diamond grown by chemical vapor deposition. This conductivity is associated with hydrogen-related species adsorbed at the surface, and it can be removed by annealing or other surface treatments.[45][46]

text: Surface property

text: Diamonds are naturally lipophilic and hydrophobic, which means the diamonds' surface cannot be wet by water, but can be easily wet and stuck by oil. This property can be utilized to extract diamonds using oil when making synthetic diamonds. However, when diamond surfaces are chemically modified with certain ions, they are expected to become so hydrophilic that they can stabilize multiple layers of water ice at human body temperature.[47]

text: The surface of diamonds is partially oxidized. The oxidized surface can be reduced by heat treatment under hydrogen flow. That is to say, this heat treatment partially removes oxygen-containing functional groups. But diamonds (sp3C) are unstable against high temperature (above about 400 °C (752 °F)) under atmospheric pressure. The structure gradually changes into sp2C above this temperature. Thus, diamonds should be reduced under this temperature.[48]

text: Chemical stability

text: Diamonds are not very reactive. Under room temperature diamonds do not react with any chemical reagents including strong acids and bases. A diamond's surface can only be oxidized at temperatures above about 850 °C (1,560 °F) in air. Diamond also reacts with fluorine gas above about 700 °C (1,292 °F).

text: Color

text: Diamond has a wide bandgap of 6981881197067849999♠5.5 eV corresponding to the deep ultraviolet wavelength of 225 nanometers. This means that pure diamond should transmit visible light and appear as a clear colorless crystal. Colors in diamond originate from lattice defects and impurities. The diamond crystal lattice is exceptionally strong, and only atoms of nitrogen, boron and hydrogen can be introduced into diamond during the growth at significant concentrations (up to atomic percents). Transition metals nickel and cobalt, which are commonly used for growth of synthetic diamond by high-pressure high-temperature techniques, have been detected in diamond as individual atoms; the maximum concentration is 0.01% for nickel[49] and even less for cobalt. Virtually any element can be introduced to diamond by ion implantation.[50]

text: Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the yellow and brown color in diamonds. Boron is responsible for the blue color.[31] Color in diamond has two additional sources: irradiation (usually by alpha particles), that causes the color in green diamonds, and plastic deformation of the diamond crystal lattice. Plastic deformation is the cause of color in some brown[51] and perhaps pink and red diamonds.[52] In order of increasing rarity, yellow diamond is followed by brown, colorless, then by blue, green, black, pink, orange, purple, and red.[42] "Black", or Carbonado, diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the crystal lattice, known as a carbon flaw. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present.[42] The Gemological Institute of America (GIA) classifies low saturation yellow and brown diamonds as diamonds in the normal color range, and applies a grading scale from "D" (colorless) to "Z" (light yellow). Diamonds of a different color, such as blue, are called fancy colored diamonds and fall under a different grading scale.[42]

text: In 2008, the Wittelsbach Diamond, a 35.56-carat (7.112 g) blue diamond once belonging to the King of Spain, fetched over US$24 million at a Christie's auction.[53] In May 2009, a 7.03-carat (1.406 g) blue diamond fetched the highest price per carat ever paid for a diamond when it was sold at auction for 10.5 million Swiss francs (6.97 million euros, or US$9.5 million at the time).[54] That record was, however, beaten the same year: a 5-carat (1.0 g) vivid pink diamond was sold for $10.8 million in Hong Kong on December 1, 2009.[55]

text: Identification

text: Diamonds can be identified by their high thermal conductivity. Their high refractive index is also indicative, but other materials have similar refractivity. Diamonds cut glass, but this does not positively identify a diamond because other materials, such as quartz, also lie above glass on the Mohs scale and can also cut it. Diamonds can scratch other diamonds, but this can result in damage to one or both stones. Hardness tests are infrequently used in practical gemology because of their potentially destructive nature.[56] The extreme hardness and high value of diamond means that gems are typically polished slowly, using painstaking traditional techniques and greater attention to detail than is the case with most other gemstones;[10] these tend to result in extremely flat, highly polished facets with exceptionally sharp facet edges. Diamonds also possess an extremely high refractive index and fairly high dispersion. Taken together, these factors affect the overall appearance of a polished diamond and most diamantaires still rely upon skilled use of a loupe (magnifying glass) to identify diamonds "by eye".[57]

text: Industry

text: The diamond industry can be separated into two distinct categories: one dealing with gem-grade diamonds and another for industrial-grade diamonds. Both markets value diamonds differently.

text: Gem-grade diamonds

text: A large trade in gem-grade diamonds exists. Although most gem-grade diamonds are sold newly polished, there is a well-established market for resale of polished diamonds (e.g. pawnbroking, auctions, second-hand jewelry stores, diamantaires, bourses, etc.). One hallmark of the trade in gem-quality diamonds is its remarkable concentration: wholesale trade and diamond cutting is limited to just a few locations; in 2003, 92% of the world's diamonds were cut and polished in Surat, India.[58] Other important centers of diamond cutting and trading are the Antwerp diamond district in Belgium, where the International Gemological Institute is based, London, the Diamond District in New York City, the Diamond Exchange District in Tel Aviv, and Amsterdam. One contributory factor is the geological nature of diamond deposits: several large primary kimberlite-pipe mines each account for significant portions of market share (such as the Jwaneng mine in Botswana, which is a single large-pit mine that can produce between 12,500,000 and 15,000,000 carats (2,500 and 3,000 kg) of diamonds per year[59]). Secondary alluvial diamond deposits, on the other hand, tend to be fragmented amongst many different operators because they can be dispersed over many hundreds of square kilometers (e.g., alluvial deposits in Brazil).

text: The production and distribution of diamonds is largely consolidated in the hands of a few key players, and concentrated in traditional diamond trading centers, the most important being Antwerp, where 80% of all rough diamonds, 50% of all cut diamonds and more than 50% of all rough, cut and industrial diamonds combined are handled.[60] This makes Antwerp a de facto "world diamond capital".[61] The city of Antwerp also hosts the Antwerpsche Diamantkring, created in 1929 to become the first and biggest diamond bourse dedicated to rough diamonds.[62] Another important diamond center is New York City, where almost 80% of the world's diamonds are sold, including auction sales.[60]

text: The De Beers company, as the world's largest diamond mining company, holds a dominant position in the industry, and has done so since soon after its founding in 1888 by the British imperialist Cecil Rhodes. De Beers is currently the world's largest operator of diamond production facilities (mines) and distribution channels for gem-quality diamonds. The Diamond Trading Company (DTC) is a subsidiary of De Beers and markets rough diamonds from De Beers-operated mines. De Beers and its subsidiaries own mines that produce some 40% of annual world diamond production. For most of the 20th century over 80% of the world's rough diamonds passed through De Beers,[63] but by 2001–2009 the figure had decreased to around 45%,[64] and by 2013 the company's market share had further decreased to around 38% in value terms and even less by volume.[65] De Beers sold off the vast majority of its diamond stockpile in the late 1990s – early 2000s[66] and the remainder largely represents working stock (diamonds that are being sorted before sale).[67] This was well documented in the press[68] but remains little known to the general public.

text: As a part of reducing its influence, De Beers withdrew from purchasing diamonds on the open market in 1999 and ceased, at the end of 2008, purchasing Russian diamonds mined by the largest Russian diamond company Alrosa.[69] As of January 2011, De Beers states that it only sells diamonds from the following four countries: Botswana, Namibia, South Africa and Canada.[70] Alrosa had to suspend their sales in October 2008 due to the global energy crisis,[71] but the company reported that it had resumed selling rough diamonds on the open market by October 2009.[72] Apart from Alrosa, other important diamond mining companies include BHP Billiton, which is the world's largest mining company;[73] Rio Tinto Group, the owner of the Argyle (100%), Diavik (60%), and Murowa (78%) diamond mines;[74] and Petra Diamonds, the owner of several major diamond mines in Africa.

text: Further down the supply chain, members of The World Federation of Diamond Bourses (WFDB) act as a medium for wholesale diamond exchange, trading both polished and rough diamonds. The WFDB consists of independent diamond bourses in major cutting centers such as Tel Aviv, Antwerp, Johannesburg and other cities across the USA, Europe and Asia.[42] In 2000, the WFDB and The International Diamond Manufacturers Association established the World Diamond Council to prevent the trading of diamonds used to fund war and inhumane acts. WFDB's additional activities include sponsoring the World Diamond Congress every two years, as well as the establishment of the International Diamond Council (IDC) to oversee diamond grading.

text: Once purchased by Sightholders (which is a trademark term referring to the companies that have a three-year supply contract with DTC), diamonds are cut and polished in preparation for sale as gemstones ('industrial' stones are regarded as a by-product of the gemstone market; they are used for abrasives).[75] The cutting and polishing of rough diamonds is a specialized skill that is concentrated in a limited number of locations worldwide.[75] Traditional diamond cutting centers are Antwerp, Amsterdam, Johannesburg, New York City, and Tel Aviv. Recently, diamond cutting centers have been established in China, India, Thailand, Namibia and Botswana.[75] Cutting centers with lower cost of labor, notably Surat in Gujarat, India, handle a larger number of smaller carat diamonds, while smaller quantities of larger or more valuable diamonds are more likely to be handled in Europe or North America. The recent expansion of this industry in India, employing low cost labor, has allowed smaller diamonds to be prepared as gems in greater quantities than was previously economically feasible.[60]

text: Diamonds prepared as gemstones are sold on diamond exchanges called bourses. There are 28 registered diamond bourses in the world.[76] Bourses are the final tightly controlled step in the diamond supply chain; wholesalers and even retailers are able to buy relatively small lots of diamonds at the bourses, after which they are prepared for final sale to the consumer. Diamonds can be sold already set in jewelry, or sold unset ("loose"). According to the Rio Tinto Group, in 2002 the diamonds produced and released to the market were valued at US$9 billion as rough diamonds, US$14 billion after being cut and polished, US$28 billion in wholesale diamond jewelry, and US$57 billion in retail sales.[77]

text: Cutting

text: Mined rough diamonds are converted into gems through a multi-step process called "cutting". Diamonds are extremely hard, but also brittle and can be split up by a single blow. Therefore, diamond cutting is traditionally considered as a delicate procedure requiring skills, scientific knowledge, tools and experience. Its final goal is to produce a faceted jewel where the specific angles between the facets would optimize the diamond luster, that is dispersion of white light, whereas the number and area of facets would determine the weight of the final product. The weight reduction upon cutting is significant and can be of the order of 50%.[78] Several possible shapes are considered, but the final decision is often determined not only by scientific, but also practical considerations. For example, the diamond might be intended for display or for wear, in a ring or a necklace, singled or surrounded by other gems of certain color and shape.[79] Some of them may be considered as classical, such as round, pear, marquise, oval, hearts and arrows diamonds, etc. Some of them are special, produced by certain companies, for example, Phoenix, Cushion, Sole Mio diamonds, etc.[80]

text: The most time-consuming part of the cutting is the preliminary analysis of the rough stone. It needs to address a large number of issues, bears much responsibility, and therefore can last years in case of unique diamonds. The following issues are considered:

text:
The hardness of diamond and its ability to cleave strongly depend on the crystal orientation. Therefore, the crystallographic structure of the diamond to be cut is analyzed using X-ray diffraction to choose the optimal cutting directions.
Most diamonds contain visible non-diamond inclusions and crystal flaws. The cutter has to decide which flaws are to be removed by the cutting and which could be kept.
The diamond can be split by a single, well calculated blow of a hammer to a pointed tool, which is quick, but risky. Alternatively, it can be cut with a diamond saw, which is a more reliable but tedious procedure.[79][81]

text: After initial cutting, the diamond is shaped in numerous stages of polishing. Unlike cutting, which is a responsible but quick operation, polishing removes material by gradual erosion and is extremely time consuming. The associated technique is well developed; it is considered as a routine and can be performed by technicians.[82] After polishing, the diamond is reexamined for possible flaws, either remaining or induced by the process. Those flaws are concealed through various diamond enhancement techniques, such as repolishing, crack filling, or clever arrangement of the stone in the jewelry. Remaining non-diamond inclusions are removed through laser drilling and filling of the voids produced.[56]

text: Marketing

text: Marketing has significantly affected the image of diamond as a valuable commodity.

text: N. W. Ayer & Son, the advertising firm retained by De Beers in the mid-20th century, succeeded in reviving the American diamond market. And the firm created new markets in countries where no diamond tradition had existed before. N. W. Ayer's marketing included product placement, advertising focused on the diamond product itself rather than the De Beers brand, and associations with celebrities and royalty. Without advertising the De Beers brand, De Beers was advertising its competitors' diamond products as well,[83] but this was not a concern as De Beers dominated the diamond market throughout the 20th century. De Beers' market share dipped temporarily to 2nd place in the global market below Alrosa in the aftermath of the global economic crisis of 2008, down to less than 29% in terms of carats mined, rather than sold.[84] The campaign lasted for decades but was effectively discontinued by early 2011. De Beers still advertises diamonds, but the advertising now mostly promotes its own brands, or licensed product lines, rather than completely "generic" diamond products.[84] The campaign was perhaps best captured by the slogan "a diamond is forever".[7] This slogan is now being used by De Beers Diamond Jewelers,[85] a jewelry firm which is a 50%/50% joint venture between the De Beers mining company and LVMH, the luxury goods conglomerate.

text: Brown-colored diamonds constituted a significant part of the diamond production, and were predominantly used for industrial purposes. They were seen as worthless for jewelry (not even being assessed on the diamond color scale). After the development of Argyle diamond mine in Australia in 1986, and marketing, brown diamonds have become acceptable gems.[86][87] The change was mostly due to the numbers: the Argyle mine, with its 35,000,000 carats (7,000 kg) of diamonds per year, makes about one-third of global production of natural diamonds;[88] 80% of Argyle diamonds are brown.[89]

text: Industrial-grade diamonds

text: Industrial diamonds are valued mostly for their hardness and thermal conductivity, making many of the gemological characteristics of diamonds, such as the 4 Cs, irrelevant for most applications. 80% of mined diamonds (equal to about 135,000,000 carats (27,000 kg) annually) are unsuitable for use as gemstones and are used industrially.[90] In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; another 570,000,000 carats (114,000 kg) of synthetic diamond is produced annually for industrial use (in 2004; in 2014 it is 4,500,000,000 carats (900,000 kg), 90% of which is produced in China). Approximately 90% of diamond grinding grit is currently of synthetic origin.[91]

text: The boundary between gem-quality diamonds and industrial diamonds is poorly defined and partly depends on market conditions (for example, if demand for polished diamonds is high, some lower-grade stones will be polished into low-quality or small gemstones rather than being sold for industrial use). Within the category of industrial diamonds, there is a sub-category comprising the lowest-quality, mostly opaque stones, which are known as bort.[92]

text: Industrial use of diamonds has historically been associated with their hardness, which makes diamond the ideal material for cutting and grinding tools. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial applications of this property include diamond-tipped drill bits and saws, and the use of diamond powder as an abrasive. Less expensive industrial-grade diamonds, known as bort, with more flaws and poorer color than gems, are used for such purposes.[93] Diamond is not suitable for machining ferrous alloys at high speeds, as carbon is soluble in iron at the high temperatures created by high-speed machining, leading to greatly increased wear on diamond tools compared to alternatives.[94]

text: Specialized applications include use in laboratories as containment for high-pressure experiments (see diamond anvil cell), high-performance bearings, and limited use in specialized windows.[92] With the continuing advances being made in the production of synthetic diamonds, future applications are becoming feasible. The high thermal conductivity of diamond makes it suitable as a heat sink for integrated circuits in electronics.[95]

text: Mining

text: Approximately 130,000,000 carats (26,000 kg) of diamonds are mined annually, with a total value of nearly US$9 billion, and about 100,000 kg (220,000 lb) are synthesized annually.[96]

text: Roughly 49% of diamonds originate from Central and Southern Africa, although significant sources of the mineral have been discovered in Canada, India, Russia, Brazil, and Australia.[91] They are mined from kimberlite and lamproite volcanic pipes, which can bring diamond crystals, originating from deep within the Earth where high pressures and temperatures enable them to form, to the surface. The mining and distribution of natural diamonds are subjects of frequent controversy such as concerns over the sale of blood diamonds or conflict diamonds by African paramilitary groups.[97] The diamond supply chain is controlled by a limited number of powerful businesses, and is also highly concentrated in a small number of locations around the world.

text: Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care is required not to destroy larger diamonds, and then sorted by density. Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence, after which the final sorting steps are done by hand. Before the use of X-rays became commonplace,[78] the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.[42]

text: Historically, diamonds were found only in alluvial deposits in Guntur and Krishna district of the Krishna River delta in Southern India.[98] India led the world in diamond production from the time of their discovery in approximately the 9th century BC[4][99] to the mid-18th century AD, but the commercial potential of these sources had been exhausted by the late 18th century and at that time India was eclipsed by Brazil where the first non-Indian diamonds were found in 1725.[4] Currently, one of the most prominent Indian mines is located at Panna.[100]

text: Diamond extraction from primary deposits (kimberlites and lamproites) started in the 1870s after the discovery of the Diamond Fields in South Africa.[101] Production has increased over time and now an accumulated total of 4,500,000,000 carats (900,000 kg) have been mined since that date.[102] Twenty percent of that amount has been mined in the last five years, and during the last 10 years, nine new mines have started production; four more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.[102]

text: In the U.S., diamonds have been found in Arkansas, Colorado, New Mexico, Wyoming, and Montana.[103][104] In 2004, the discovery of a microscopic diamond in the U.S. led to the January 2008 bulk-sampling of kimberlite pipes in a remote part of Montana. The Crater of Diamonds State Park in Arkansas is open to the public, and is the only mine in the world where members of the public can dig for diamonds.[104]

text: Today, most commercially viable diamond deposits are in Russia (mostly in Sakha Republic, for example Mir pipe and Udachnaya pipe), Botswana, Australia (Northern and Western Australia) and the Democratic Republic of the Congo.[105] In 2005, Russia produced almost one-fifth of the global diamond output, according to the British Geological Survey. Australia boasts the richest diamantiferous pipe, with production from the Argyle diamond mine reaching peak levels of 42 metric tons per year in the 1990s.[103][106] There are also commercial deposits being actively mined in the Northwest Territories of Canada and Brazil.[91] Diamond prospectors continue to search the globe for diamond-bearing kimberlite and lamproite pipes.

text: Political issues

text: In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines, using proceeds from diamond sales to finance their operations. Diamonds sold through this process are known as conflict diamonds or blood diamonds.[97]

text: In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central and western Africa, the United Nations, the diamond industry and diamond-trading nations introduced the Kimberley Process in 2002.[107] The Kimberley Process aims to ensure that conflict diamonds do not become intermixed with the diamonds not controlled by such rebel groups. This is done by requiring diamond-producing countries to provide proof that the money they make from selling the diamonds is not used to fund criminal or revolutionary activities. Although the Kimberley Process has been moderately successful in limiting the number of conflict diamonds entering the market, some still find their way in. According to the International Diamond Manufacturers Association, conflict diamonds constitute 2–3% of all diamonds traded.[108] Two major flaws still hinder the effectiveness of the Kimberley Process: (1) the relative ease of smuggling diamonds across African borders, and (2) the violent nature of diamond mining in nations that are not in a technical state of war and whose diamonds are therefore considered "clean".[107]

text: The Canadian Government has set up a body known as the Canadian Diamond Code of Conduct[109] to help authenticate Canadian diamonds. This is a stringent tracking system of diamonds and helps protect the "conflict free" label of Canadian diamonds.[110]

text: Synthetics, simulants, and enhancements

text: Synthetics

text: Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth. The gemological and industrial uses of diamond have created a large demand for rough stones. This demand has been satisfied in large part by synthetic diamonds, which have been manufactured by various processes for more than half a century. However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size.[13] It is possible to make colorless synthetic gemstones that, on a molecular level, are identical to natural stones and so visually similar that only a gemologist with special equipment can tell the difference.[111]

text: The majority of commercially available synthetic diamonds are yellow and are produced by so-called high-pressure high-temperature (HPHT) processes.[112] The yellow color is caused by nitrogen impurities. Other colors may also be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation after synthesis.[113]

text: Another popular method of growing synthetic diamond is chemical vapor deposition (CVD). The growth occurs under low pressure (below atmospheric pressure). It involves feeding a mixture of gases (typically 1 to 99 methane to hydrogen) into a chamber and splitting them to chemically active radicals in a plasma ignited by microwaves, hot filament, arc discharge, welding torch or laser.[114] This method is mostly used for coatings, but can also produce single crystals several millimeters in size (see picture).[96]

text: As of 2010, nearly all 5,000 million carats (1,000 tonnes) of synthetic diamonds produced per year are for industrial use. Around 50% of the 133 million carats of natural diamonds mined per year end up in industrial use.[111][115] Mining companies' expenses average $40 to $60 per carat for natural colorless diamonds, while synthetic manufacturers' expenses average $2,500 per carat for synthetic, gem-quality colorless diamonds.[111]:79 However, a purchaser is more likely to encounter a synthetic when looking for a fancy-colored diamond because nearly all synthetic diamonds are fancy-colored, while only 0.01% of natural diamonds are.[116]

text: Simulants

text: A diamond simulant is a non-diamond material that is used to simulate the appearance of a diamond, and may be referred to as diamante. Cubic zirconia is the most common. The gemstone moissanite (silicon carbide) can be treated as a diamond simulant, though more costly to produce than cubic zirconia. Both are produced synthetically.[117]

text: Enhancements

text: Diamond enhancements are specific treatments performed on natural or synthetic diamonds (usually those already cut and polished into a gem), which are designed to better the gemological characteristics of the stone in one or more ways. These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond.[118]

text: Coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance is diamond-like carbon—an amorphous carbonaceous material that has some physical properties similar to those of the diamond. Advertising suggests that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant. Techniques such as Raman spectroscopy should easily identify such a treatment.[119]

text: Identification

text: Early diamond identification tests included a scratch test relying on the superior hardness of diamond. This test is destructive, as a diamond can scratch another diamond, and is rarely used nowadays. Instead, diamond identification relies on its superior thermal conductivity. Electronic thermal probes are widely used in the gemological centers to separate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop. This test takes about 2–3 seconds.[120]

text: Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between various types of diamond, for example synthetic or natural, irradiated or non-irradiated, etc., requires more advanced, optical techniques. Those techniques are also used for some diamonds simulants, such as silicon carbide, which pass the thermal conductivity test. Optical techniques can distinguish between natural diamonds and synthetic diamonds. They can also identify the vast majority of treated natural diamonds.[121] "Perfect" crystals (at the atomic lattice level) have never been found, so both natural and synthetic diamonds always possess characteristic imperfections, arising from the circumstances of their crystal growth, that allow them to be distinguished from each other.[122]

text: Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to determine a diamond's origin.[121] They also use specially made instruments to aid them in the identification process. Two screening instruments are the DiamondSure and the DiamondView, both produced by the DTC and marketed by the GIA.[123]

text: Several methods for identifying synthetic diamonds can be performed, depending on the method of production and the color of the diamond. CVD diamonds can usually be identified by an orange fluorescence. D-J colored diamonds can be screened through the Swiss Gemmological Institute's[124] Diamond Spotter. Stones in the D-Z color range can be examined through the DiamondSure UV/visible spectrometer, a tool developed by De Beers.[122] Similarly, natural diamonds usually have minor imperfections and flaws, such as inclusions of foreign material, that are not seen in synthetic diamonds.

text: Screening devices based on diamond type detection can be used to make a distinction between diamonds that are certainly natural and diamonds that are potentially synthetic. Those potentially synthetic diamonds require more investigation in a specialized lab. Examples of commercial screening devices are D-Screen (WTOCD / HRD Antwerp) and Alpha Diamond Analyzer (Bruker / HRD Antwerp).

text: Stolen diamonds

text: Occasionally large thefts of diamonds take place. In February 2013 armed robbers carried out a raid at Brussels Airport and escaped with gems estimated to be worth $50m (£32m; 37m euros). The gang broke through a perimeter fence and raided the cargo hold of a Swiss-bound plane. The gang have since been arrested and large amounts of cash and diamonds recovered.[125]

text: The identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctive shape depending on whether their source is a mine or from an alluvial environment such as a beach or river—alluvial diamonds have smoother surfaces than those that have been mined. Determining the provenance of cut and polished stones is much more complex.

text: The Kimberley Process was developed to monitor the trade in rough diamonds and prevent their being used to fund violence. Before exporting, rough diamonds are certificated by the government of the country of origin. Some countries, such as Venezuela, are not party to the agreement. The Kimberley Process does not apply to local sales of rough diamonds within a country.

text: Diamonds may be etched by laser with marks invisible to the naked eye. Lazare Kaplan, a US-based company, developed this method. However, whatever is marked on a diamond can readily be removed.[126][127]


document_title: Nuclear weapons and the United States

question_text: when did the nuclear stockpile of the united states peak

root

text: Nuclear weapons and the United States

text: Development history[edit]

text: Manhattan Project[edit]

text: The United States first began developing nuclear weapons during World War II under the order of President Franklin Roosevelt in 1939, motivated by the fear that they were engaged in a race with Nazi Germany to develop such a weapon. After a slow start under the direction of the National Bureau of Standards, at the urging of British scientists and American administrators, the program was put under the Office of Scientific Research and Development, where in 1942 it was officially transferred under the auspices of the United States Army and became known as the Manhattan Project, an American, British and Canadian joint venture. Under the direction of General Leslie Groves, over thirty different sites were constructed for the research, production, and testing of components related to bomb making. These included the Los Alamos National Laboratory at Los Alamos, New Mexico, under the direction of physicist Robert Oppenheimer, the Hanford plutonium production facility in Washington, and the Y-12 National Security Complex in Tennessee.

tag: p

text: By investing heavily in breeding plutonium in early nuclear reactors and in the electromagnetic and gaseous diffusion enrichment processes for the production of uranium-235, the United States was able to develop three usable weapons by mid-1945. The Trinity test was a plutonium implosion-design weapon tested on 16 July 1945, with around a 20 kiloton yield. Faced with an imminent invasion of the Japanese home islands and with Japan not surrendering, President Harry S. Truman ordered the atomic raids on enemy cities. On 6 August, a uranium-gun design bomb, Little Boy, was detonated over the Japanese city of Hiroshima with an energy of about 15 kilotons of TNT, destroying nearly 50,000 buildings (including the 2nd General Army and Fifth Division headquarters) and killing approximately 70,000 people, among them 20,000 Japanese combatants and 20,000 Korean slave laborers. On 9 August, a plutonium implosion-design bomb, Fat Man, was used against the Japanese city of Nagasaki with the explosion equivalent to about 20 kilotons of TNT, destroying 60% of the city and killing approximately 35,000 people, among them 23,200–28,200 Japanese munitions workers, 2,000 Korean slave laborers, and 150 Japanese combatants.[12]

text: During the Cold War[edit]

text: Between 1945 and 1990, more than 70,000 total warheads were developed, in over 65 different varieties, ranging in yield from around .01 kilotons (such as the man-portable Davy Crockett shell) to the 25 megaton B41 bomb.[10] Between 1940 and 1996, the U.S. spent at least $8.89 trillion in present-day terms[6] on nuclear weapons development. Over half was spent on building delivery mechanisms for the weapon. $557 billion in present-day terms was spent on nuclear waste management and environmental remediation.[7]

text: Richland, Washington was the first city established to support plutonium production at the nearby Hanford nuclear site, to power the American nuclear weapons arsenals. It produced plutonium for use in cold war atomic bombs.[13]

text: Post–Cold War[edit]

text: After the end of the Cold War following the dissolution of the Soviet Union in 1991, the U.S. nuclear program was heavily curtailed, halting its program of nuclear testing, ceasing production of new nuclear weapons, and reducing its stockpile by half by the mid-1990s under President Bill Clinton. Many of its former nuclear facilities were shut down, and their sites became targets of extensive environmental remediation. Much of the former efforts towards the production of weapons became involved in the program of stockpile stewardship, attempting to predict the behavior of aging weapons without using full-scale nuclear testing. Increased funding was also put into anti-nuclear proliferation programs, such as helping the states of the former Soviet Union eliminate their former nuclear sites, and assist Russia in their efforts to inventory and secure their inherited nuclear stockpile. By February 2006, over $1.2 billion had been paid under the Radiation Exposure Compensation Act of 1990 to U.S. citizens exposed to nuclear hazards as a result of the U.S. nuclear weapons program, and by 1998 at least $759 million had been paid to the Marshall Islanders in compensation for their exposure to U.S. nuclear testing, and over $15 million was paid to the Japanese government following the exposure of its citizens and food supply to nuclear fallout from the 1954 "Bravo" test.[10][11] In 1998, the country spent an estimated total of $35.1 billion on its nuclear weapons and weapons-related programs.[10]

text: In the 2013 book Plutopia: Nuclear Families, Atomic Cities, and the Great Soviet and American Plutonium Disasters (Oxford), Kate Brown explores the health of affected citizens in the United States, and the “slow-motion disasters” that still threaten the environments where the plants are located. According to Brown, the plants at Hanford, over a period of four decades, released millions of curies of radioactive isotopes into the surrounding environment.[13] Brown says that most of this radioactive contamination over the years at Hanford were part of normal operations, but unforeseen accidents did occur and plant management kept this secret, as the pollution continued unabated. Even today, as pollution threats to health and the environment persist, the government keeps knowledge about the associated risks from the public.[13]

text: During the presidency of George W. Bush, and especially after the 11 September terrorist attacks of 2001, rumors have circulated in major news sources that the U.S. has been considering design of new nuclear weapons ("bunker-busting nukes"), and the resumption of nuclear testing for reasons of stockpile stewardship. Statements by the U.S. government in 2004, however, indicated that the arsenal will drop to around 5,500 total warheads by 2012.[14] According to recent reports, much of that reduction was already accomplished by January 2008.[15]

text: Nuclear weapons testing[edit]

text: Between 16 July 1945 and 23 September 1992, the United States maintained a program of vigorous nuclear testing, with the exception of a moratorium between November 1958 and September 1961. By official count, a total of 1,054 nuclear tests and two nuclear attacks were conducted, with over 100 of them taking place at sites in the Pacific Ocean, over 900 of them at the Nevada Test Site, and ten on miscellaneous sites in the United States (Alaska, Colorado, Mississippi, and New Mexico).[5] Until November 1962, the vast majority of the U.S. tests were atmospheric (that is, above-ground); after the acceptance of the Partial Test Ban Treaty all testing was relegated underground, in order to prevent the dispersion of nuclear fallout.

text: The U.S. program of atmospheric nuclear testing exposed a number of the population to the hazards of fallout. Estimating exact numbers, and the exact consequences, of people exposed has been medically very difficult, with the exception of the high exposures of Marshall Islanders and Japanese fishers in the case of the Castle Bravo incident in 1954. A number of groups of U.S. citizens—especially farmers and inhabitants of cities downwind of the Nevada Test Site and U.S. military workers at various tests—have sued for compensation and recognition of their exposure, many successfully. The passage of the Radiation Exposure Compensation Act of 1990 allowed for a systematic filing of compensation claims in relation to testing as well as those employed at nuclear weapons facilities. By June 2009 over $1.4 billion total has been given in compensation, with over $660 million going to "downwinders".[11]

text: A few notable U.S. nuclear tests include:

text:
Trinity test on 16 July 1945, was the world's first test of a nuclear weapon (yield of around 20 kt).
Operation Crossroads series in July 1946, was the first postwar test series and one of the largest military operations in U.S. history.
Operation Greenhouse shots of May 1951 included the first boosted fission weapon test ("Item") and a scientific test that proved the feasibility of thermonuclear weapons ("George").
Ivy Mike shot of 1 November 1952, was the first full test of a Teller-Ulam design "staged" hydrogen bomb, with a yield of 10 megatons. It was not a deployable weapon, however—with its full cryogenic equipment it weighed some 82 tons.
Castle Bravo shot of 1 March 1954, was the first test of a deployable (solid fuel) thermonuclear weapon, and also (accidentally) the largest weapon ever tested by the United States (15 megatons). It was also the single largest U.S. radiological accident in connection with nuclear testing. The unanticipated yield, and a change in the weather, resulted in nuclear fallout spreading eastward onto the inhabited Rongelap and Rongerik atolls, which were soon evacuated. Many of the Marshall Islanders have since suffered from birth defects and have received some compensation from the federal government. A Japanese fishing boat, Daigo Fukuryū Maru, also came into contact with the fallout, which caused many of the crew to grow ill; one eventually died.
Shot Argus I of Operation Argus, on 27 August 1958, was the first detonation of a nuclear weapon in outer space when a 1.7-kiloton warhead was detonated at an altitude of 200 kilometres (120 mi) during a series of high altitude nuclear explosions.
Shot Frigate Bird of Operation Dominic I on 6 May 1962, was the only U.S. test of an operational submarine-launched ballistic missile (SLBM) with a live nuclear warhead (yield of 600 kilotons), at Christmas Island. In general, missile systems were tested without live warheads and warheads were tested separately for safety concerns. In the early 1960s, however, there mounted technical questions about how the systems would behave under combat conditions (when they were "mated", in military parlance), and this test was meant to dispel these concerns. However, the warhead had to be somewhat modified before its use, and the missile was a SLBM (and not an ICBM), so by itself it did not satisfy all concerns.[16]
Shot Sedan of Operation Storax on 6 July 1962 (yield of 104 kilotons), was an attempt to show the feasibility of using nuclear weapons for "civilian" and "peaceful" purposes as part of Operation Plowshare. In this instance, a 1,280-foot (390 m) diameter 320-foot (98 m) deep crater was created at the Nevada Test Site.

tag: ul

text: A summary table of each of the American operational series may be found at United States' nuclear test series.

text: Delivery systems[edit]

text: This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (August 2013) (Learn how and when to remove this template message)

tag: table

text: The original Little Boy and Fat Man weapons, developed by the United States during the Manhattan Project, were relatively large (Fat Man had a diameter of 5 feet (1.5 m)) and heavy (around 5 tons each) and required specially modified bomber planes to be adapted for their bombing missions against Japan. Each modified bomber could only carry one such weapon and only within a limited range. After these initial weapons were developed, a considerable amount of money and research was conducted towards the goal of standardizing nuclear warheads so that they did not require highly specialized experts to assemble them before use, as in the case with the idiosyncratic wartime devices, and miniaturization of the warheads for use in more variable delivery systems.

text: Through the aid of brainpower acquired through Operation Paperclip at the tail end of the European theater of World War II, the United States was able to embark on an ambitious program in rocketry. One of the first products of this was the development of rockets capable of holding nuclear warheads. The MGR-1 Honest John was the first such weapon, developed in 1953 as a surface-to-surface missile with a 15-mile (24 km) maximum range. Because of their limited range, their potential use was heavily constrained (they could not, for example, threaten Moscow with an immediate strike).

text: Development of long-range bombers, such as the B-29 Superfortress during World War II, was continued during the Cold War period. In 1946, the Convair B-36 Peacemaker became the first purpose-built nuclear bomber; it served with the USAF until 1959. The Boeing B-52 Stratofortress was able by the mid-1950s to carry a wide arsenal of nuclear bombs, each with different capabilities and potential use situations. Starting in 1946, the U.S. based its initial deterrence force on the Strategic Air Command, which, by the late 1950s, maintained a number of nuclear-armed bombers in the sky at all times, prepared to receive orders to attack the USSR whenever needed. This system was, however, tremendously expensive, both in terms of natural and human resources, and raised the possibility of an accidental nuclear war.

text: During the 1950s and 1960s, elaborate computerized early warning systems such as Defense Support Program were developed to detect incoming Soviet attacks and to coordinate response strategies. During this same period, intercontinental ballistic missile (ICBM) systems were developed that could deliver a nuclear payload across vast distances, allowing the U.S. to house nuclear forces capable of hitting the Soviet Union in the American Midwest. Shorter-range weapons, including small tactical weapons, were fielded in Europe as well, including nuclear artillery and man-portable Special Atomic Demolition Munition. The development of submarine-launched ballistic missile systems allowed for hidden nuclear submarines to covertly launch missiles at distant targets as well, making it virtually impossible for the Soviet Union to successfully launch a first strike attack against the United States without receiving a deadly response.

text: Improvements in warhead miniaturization in the 1970s and 1980s allowed for the development of MIRVs—missiles which could carry multiple warheads, each of which could be separately targeted. The question of whether these missiles should be based on constantly rotating train tracks (to avoid being easily targeted by opposing Soviet missiles) or based in heavily fortified silos (to possibly withstand a Soviet attack) was a major political controversy in the 1980s (eventually the silo deployment method was chosen). MIRVed systems enabled the U.S. to render Soviet missile defenses economically unfeasible, as each offensive missile would require between three and ten defensive missiles to counter.

text: Additional developments in weapons delivery included cruise missile systems, which allowed a plane to fire a long-distance, low-flying nuclear-tipped missile towards a target from a relatively comfortable distance.

text: The current delivery systems of the U.S. make virtually any part of the Earth's surface within the reach of its nuclear arsenal. Though its land-based missile systems have a maximum range of 10,000 kilometres (6,200 mi) (less than worldwide), its submarine-based forces extend its reach from a coastline 12,000 kilometres (7,500 mi) inland. Additionally, in-flight refueling of long-range bombers and the use of aircraft carriers extends the possible range virtually indefinitely.

text: Command and control[edit]

text: Command and control procedures in case of nuclear war were given by the Single Integrated Operational Plan (SIOP) until 2003, when this was superseded by Operations Plan 8044.

text: A nuclear strike must be authorized by the President or, if he or she has been killed, by a surviving member of the nuclear chain of command.[17] The President can give the order using his nuclear briefcase (called the nuclear football in the case of the United States), or can use command centers such as the White House Situation Room. The command would be carried out by a Nuclear and Missile Operations Officer (a member of a missile combat crew, also called a "missileer") at a missile launch control center. A two-man rule applies to the launch of missiles, meaning that two officers must turn keys simultaneously (far enough apart that this cannot be done by one man).

text: When President Reagan was shot in 1981 there was confusion about where the "nuclear football" was, and who was in charge.[18]

text: In 1975 a launch crew member, Harold Hering, was dismissed from the Air Force for asking how he could know whether the order to launch his missiles came from a sane president.

text: It has been claimed that the system is not foolproof.[17]

text: Accidents[edit]

text: The United States nuclear program since its inception has experienced accidents of varying forms, ranging from single-casualty research experiments (such as that of Louis Slotin during the Manhattan Project), to the nuclear fallout dispersion of the Castle Bravo shot in 1954, to the accidental dropping of nuclear weapons from aircraft (broken arrows). How close any of these accidents came to being major nuclear disasters is a matter of technical and scholarly debate and interpretation.

text: Weapons accidentally dropped by the United States include incidents near Atlantic City, New Jersey (1957), Savannah, Georgia (1958) (see Tybee Bomb), Goldsboro, North Carolina (1961) (see 1961 Goldsboro B-52 crash), off the coast of Okinawa (1965), in the sea near Palomares, Spain (1966, see 1966 Palomares B-52 crash), and near Thule Air Base, Greenland (1968) (see 1968 Thule Air Base B-52 crash). In some of these cases (such as Palomares), the explosive system of the fission weapon discharged, but did not trigger a nuclear chain reaction (safety features prevent this from easily happening), but did disperse hazardous nuclear materials across wide areas, necessitating expensive cleanup endeavors. Eleven American nuclear warheads are thought[10] to be lost and unrecovered, primarily in submarine accidents.

text: The nuclear testing program resulted in a number of cases of fallout dispersion onto populated areas. The most significant of these was the Castle Bravo test, which spread radioactive ash over an area of over 100 square miles (260 km2), including a number of populated islands.[19] The populations of the islands were evacuated but not before suffering radiation burns.[19] They would later suffer long-term effects, such as birth defects and increased cancer risk. There were also instances during the nuclear testing program in which soldiers were exposed to overly high levels of radiation, which grew into a major scandal in the 1970s and 1980s, as many soldiers later suffered from what were claimed to be diseases caused by their exposures.

text: Many of the former nuclear facilities (see next section) produced significant environmental damages during their years of activity, and since the 1990s have been Superfund sites of cleanup and environmental remediation. The Radiation Exposure Compensation Act of 1990 allows for U.S. citizens exposed to radiation or other health risks through the U.S. nuclear program to file for compensation and damages.

text: Deliberate attacks on weapons facilities[edit]

text: In 1972 three hijackers took control of a domestic passenger flight along the east coast of the U.S. and threatened to crash the plane into a U.S. nuclear weapons plant in Oak Ridge, Tennessee. The plane got as close as 8,000 feet above the site before the hijackers’ demands were met.[20][21]

text: Various acts of civil disobedience since 1980 by the peace group Plowshares have shown how nuclear weapons facilities can be penetrated, and the group's actions represent extraordinary breaches of security at nuclear weapons plants in the United States. The National Nuclear Security Administration has acknowledged the seriousness of the 2012 Plowshares action. Non-proliferation policy experts have questioned "the use of private contractors to provide security at facilities that manufacture and store the government's most dangerous military material".[22] Nuclear weapons materials on the black market are a global concern,[23][24] and there is concern about the possible detonation of a small, crude nuclear weapon by a militant group in a major city, with significant loss of life and property.[25][26]

text: Stuxnet is a computer worm discovered in June 2010 that is believed to have been created by the United States and Israel to attack Iran's nuclear facilities.[27]

text: Development agencies[edit]

text: The initial U.S. nuclear program was run by the National Bureau of Standards starting in 1939 under the edict of President Franklin Delano Roosevelt. Its primary purpose was to delegate research and dispense funds. In 1940 the National Defense Research Committee (NDRC) was established, coordinating work under the Committee on Uranium among its other wartime efforts. In June 1941, the Office of Scientific Research and Development (OSRD) was established, with the NDRC as one of its subordinate agencies, which enlarged and renamed the Uranium Committee as the Section on Uranium. In 1941, NDRC research was placed under direct control of Vannevar Bush as the OSRD S-1 Section, which attempted to increase the pace of weapons research. In June 1942, the U.S. Army Corps of Engineers took over the project to develop atomic weapons, while the OSRD retained responsibility for scientific research.[28]

text: This was the beginning of the Manhattan Project, run as the Manhattan Engineering District (MED), an agency under military control that was in charge of developing the first atomic weapons. After World War II, the MED maintained control over the U.S. arsenal and production facilities and coordinated the Operation Crossroads tests. In 1946 after a long and protracted debate, the Atomic Energy Act of 1946 was passed, creating the Atomic Energy Commission (AEC) as a civilian agency that would be in charge of the production of nuclear weapons and research facilities, funded through Congress, with oversight provided by the Joint Committee on Atomic Energy. The AEC was given vast powers of control over secrecy, research, and money, and could seize lands with suspected uranium deposits. Along with its duties towards the production and regulation of nuclear weapons, it was also in charge of stimulating development and regulating civilian nuclear power. The full transference of activities was finalized in January 1947.[29]

text: In 1975, following the "energy crisis" of the early 1970s and public and congressional discontent with the AEC (in part because of the impossibility to be both a producer and a regulator), it was disassembled into component parts as the Energy Research and Development Administration (ERDA), which assumed most of the AEC's former production, coordination, and research roles, and the Nuclear Regulatory Commission, which assumed its civilian regulation activities.[30]

text: ERDA was short-lived, however, and in 1977 the U.S. nuclear weapons activities were reorganized under the Department of Energy,[31] which maintains such responsibilities through the semi-autonomous National Nuclear Security Administration. Some functions were taken over or shared by the Department of Homeland Security in 2002. The already-built weapons themselves are in the control of the Strategic Command, which is part of the Department of Defense.

text: In general, these agencies served to coordinate research and build sites. They generally operated their sites through contractors, however, both private and public (for example, Union Carbide, a private company, ran Oak Ridge National Laboratory for many decades; the University of California, a public educational institution, has run the Los Alamos and Lawrence Livermore laboratories since their inception, and will jointly manage Los Alamos with the private company Bechtel as of its next contract). Funding was received both through these agencies directly, but also from additional outside agencies, such as the Department of Defense. Each branch of the military also maintained its own nuclear-related research agencies (generally related to delivery systems).

text: Weapons production complex[edit]

text: This table is not comprehensive, as numerous facilities throughout the United States have contributed to its nuclear weapons program. It includes the major sites related to the U.S. weapons program (past and present), their basic site functions, and their current status of activity. Not listed are the many bases and facilities at which nuclear weapons have been deployed. In addition to deploying weapons on its own soil, during the Cold War, the United States also stationed nuclear weapons in 27 foreign countries and territories, including Okinawa, Japan (during the occupation immediately following World War II), Greenland, Germany, Taiwan, and French Morocco then independent Morocco.[32]

text:
Site name
Location
Function
Status

Los Alamos National Laboratory
Los Alamos, New Mexico
Research, Design, Pit Production
Active

Lawrence Livermore National Laboratory
Livermore, California
Research and design
Active

Sandia National Laboratories
Livermore, California; Albuquerque, New Mexico
Research and design
Active

Hanford Site
Richland, Washington
Material production (Plutonium)
Not active, in remediation

Oak Ridge National Laboratory
Oak Ridge, Tennessee
Material production (Uranium-235, fusion fuel), research
Active to some extent

Y-12 National Security Complex
Oak Ridge, Tennessee
Component fabrication, stockpile stewardship, uranium storage
Active

Nevada Test Site
Near Las Vegas, Nevada
Nuclear testing and nuclear waste disposal
Active; no tests since 1992, now engaged in waste disposal

Yucca Mountain
Nevada Test Site
Waste disposal (primarily power reactor)
Pending

Waste Isolation Pilot Plant
East of Carlsbad, New Mexico
Radioactive waste from nuclear weapons production
Active

Pacific Proving Grounds
Marshall Islands
Nuclear testing
Not active, last test in 1962

Rocky Flats Plant
Near Denver, Colorado
Components fabrication
Not active, in remediation

Pantex
Amarillo, Texas
Weapons assembly, disassembly, pit storage
Active, esp. disassembly

Fernald Site
Near Cincinnati, Ohio
Material fabrication (Uranium-235)
Not active, in remediation

Paducah Plant
Paducah, Kentucky
Material production (Uranium-235)
Active (commercial use)

Portsmouth Plant
Near Portsmouth, Ohio
Material fabrication (Uranium-235)
Active, (centrifuge), but not for weapons production

Kansas City Plant
Kansas City, Missouri
Component production
Active

Mound Plant
Miamisburg, Ohio
Research, component production, Tritium purification
Not active, in remediation

Pinellas Plant
Largo, Florida
Manufacture of electrical components
Active, but not for weapons production

Savannah River Site
Near Aiken, South Carolina
Material production (Plutonium, Tritium)
Active (limited operation), in remediation

text: Proliferation[edit]

text: Early on in the development of its nuclear weapons, the United States relied in part on information-sharing with both the United Kingdom and Canada, as codified in the Quebec Agreement of 1943. These three parties agreed not to share nuclear weapons information with other countries without the consent of the others, an early attempt at nonproliferation. After the development of the first nuclear weapons during World War II, though, there was much debate within the political circles and public sphere of the United States about whether or not the country should attempt to maintain a monopoly on nuclear technology, or whether it should undertake a program of information sharing with other nations (especially its former ally and likely competitor, the Soviet Union), or submit control of its weapons to some sort of international organization (such as the United Nations) who would use them to attempt to maintain world peace. Though fear of a nuclear arms race spurred many politicians and scientists to advocate some degree of international control or sharing of nuclear weapons and information, many politicians and members of the military believed that it was better in the short term to maintain high standards of nuclear secrecy and to forestall a Soviet bomb as long as possible (and they did not believe the USSR would actually submit to international controls in good faith).

text: Since this path was chosen, the United States was, in its early days, essentially an advocate for the prevention of nuclear proliferation, though primarily for the reason of self-preservation. A few years after the USSR detonated its first weapon in 1949, though, the U.S. under President Dwight D. Eisenhower sought to encourage a program of sharing nuclear information related to civilian nuclear power and nuclear physics in general. The Atoms for Peace program, begun in 1953, was also in part political: the U.S. was better poised to commit various scarce resources, such as enriched uranium, towards this peaceful effort, and to request a similar contribution from the Soviet Union, who had far fewer resources along these lines; thus the program had a strategic justification as well, as was later revealed by internal memos. This overall goal of promoting civilian use of nuclear energy in other countries, while also preventing weapons dissemination, has been labeled by many critics as contradictory and having led to lax standards for a number of decades which allowed a number of other nations, such as China and India, to profit from dual-use technology (purchased from nations other than the U.S.).

text: The United States is one of the five nuclear weapons states permitted to maintain a nuclear arsenal under the Treaty on the Non-Proliferation of Nuclear Weapons, of which it was an original drafter and signatory on 1 July 1968 (ratified 5 March 1970).

text: The Cooperative Threat Reduction program of the Defense Threat Reduction Agency was established after the breakup of the Soviet Union in 1991 to aid former Soviet bloc countries in the inventory and destruction of their sites for developing nuclear, chemical, and biological weapons, and their methods of delivering them (ICBM silos, long-range bombers, etc.). Over $4.4 billion has been spent on this endeavor to prevent purposeful or accidental proliferation of weapons from the former Soviet arsenal.[33]

text: After India and Pakistan tested nuclear weapons in 1998, President Bill Clinton imposed economic sanctions on the countries. In 1999, however, the sanctions against India were lifted; those against Pakistan were kept in place as a result of the military government that had taken over. Shortly after the September 11 attacks in 2001, President George W. Bush lifted the sanctions against Pakistan as well, in order to get the Pakistani government's help as a conduit for US and NATO forces for operations in Afghanistan.

text: The U.S. government has officially taken a silent policy towards the nuclear weapons ambitions of the state of Israel, while being exceedingly vocal against proliferation of such weapons in the countries of Iran and North Korea. Until 2005 when the program was cancelled, it was violating its own non-proliferation treaties in the pursuit of so-called nuclear bunker busters. The 2003 invasion of Iraq by the U.S. was done, in part, on indications that Weapons of Mass Destruction were being stockpiled (lately, stockpiles of previously undeclared nerve agent and mustard gas shells have been located in Iraq),[34] and the Bush administration said that its policies on proliferation were responsible for the Libyan government's agreement to abandon its nuclear ambitions.[35]

text: The International Atomic Energy Agency (IAEA) proposed a 2005 ban on fissile material that would greatly limit the production of weapons of mass destruction. 147 countries voted for this proposal but the United States voted against.

text: International relations and nuclear weapons[edit]

text: In 1958, the United States Air Force had considered a plan to drop nuclear bombs on China during a confrontation over Taiwan but it was overruled, previously secret documents showed after they were declassified due to the Freedom of Information Act in April 2008. The plan included an initial plan to drop 10–15 kiloton bombs on airfields in Amoy (now called Xiamen) in the event of a Chinese blockade against Taiwan's Offshore Islands.[36][37]

text: Occupational illness[edit]

text: The Energy Employees Occupational Illness Compensation Program (EEOICP) began on 31 July 2001. The program provides compensation and health benefits to Department of Energy nuclear weapons workers (employees, former employees, contractors and subcontractors) as well as compensation to certain survivors if the worker is already deceased.[38] By 14 August 2010, the program had already identified 45,799 civilians who lost their health (including 18,942 who developed cancer) due to exposure to radiation and toxic substances while producing nuclear weapons for the United States.[39]

text: Current status[edit]

text: The United States is one of the five recognized nuclear powers by the signatories of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). As of 2017, the US has an estimated 4,018 nuclear weapons in either deployment or storage.[40] This figure compares to a peak of 31,225 total warheads in 1967 and 22,217 in 1989, and does not include "several thousand" warheads that have been retired and scheduled for dismantlement. The Pantex Plant near Amarillo, Texas, is the only location in the United States where weapons from the aging nuclear arsenal can be refurbished or dismantled.[9]

text: In 2009 and 2010, the administration of President Barack Obama declared policies that would invalidate the Bush-era policy for use of nuclear weapons and its motions to develop new ones. First, in a prominent 2009 speech, U.S. President Barack Obama outlined a goal of "a world without nuclear weapons".[41] To that goal, U.S. President Barack Obama and Russian Prime Minister Dmitry Medvedev signed a new START treaty on April 8, 2010, to reduce the number of active nuclear weapons from 2,200 to 1,550.[42][43] That same week Obama also revised U.S. policy on the use of nuclear weapons in a Nuclear Posture Review required of all presidents, declaring for the first time that the U.S. would not use nuclear weapons against nonnuclear, NPT-compliant states. The policy also renounces development of any new nuclear weapons.[44]

text: The Obama Administration, in its release of the 2012 defense budget, included plans to modernize, as well as maintain, the nation's nuclear weapons arsenal.[45]

text: Nuclear disarmament movement[edit]

text: In the early 1980s, the revival of the nuclear arms race triggered large protests about nuclear weapons.[46] On June 12, 1982, one million people demonstrated in New York City's Central Park against nuclear weapons and for an end to the cold war arms race. It was the largest anti-nuclear protest and the largest political demonstration in American history.[47][48] International Day of Nuclear Disarmament protests were held on June 20, 1983 at 50 sites across the United States.[49][50] There were many Nevada Desert Experience protests and peace camps at the Nevada Test Site during the 1980s and 1990s.[51][52]

text: There have also been protests by anti-nuclear groups at the Y-12 Nuclear Weapons Plant,[53] the Idaho National Laboratory,[54] Yucca Mountain nuclear waste repository proposal,[55] the Hanford Site, the Nevada Test Site,[56] Lawrence Livermore National Laboratory,[57] and transportation of nuclear waste from the Los Alamos National Laboratory.[58]

text: On May 1, 2005, 40,000 anti-nuclear/anti-war protesters marched past the United Nations in New York, 60 years after the atomic bombings of Hiroshima and Nagasaki.[59][60] This was the largest anti-nuclear rally in the U.S. for several decades.[46] In May 2010, some 25,000 people, including members of peace organizations and 1945 atomic bomb survivors, marched from downtown New York to the United Nations headquarters, calling for the elimination of nuclear weapons.[61]

text: Some scientists and engineers have opposed nuclear weapons, including Paul M. Doty, Hermann Joseph Muller, Linus Pauling, Eugene Rabinowitch, M.V. Ramana and Frank N. von Hippel. In recent years, many elder statesmen have also advocated nuclear disarmament. Sam Nunn, William Perry, Henry Kissinger, and George Shultz—have called upon governments to embrace the vision of a world free of nuclear weapons, and in various op-ed columns have proposed an ambitious program of urgent steps to that end. The four have created the Nuclear Security Project to advance this agenda. Organisations such as Global Zero, an international non-partisan group of 300 world leaders dedicated to achieving nuclear disarmament, have also been established.

text: United States strategic nuclear weapons arsenal[edit]

text: Operational American strategic nuclear forces, July 1, 2016 [62]

text:
Delivery Vehicles
Warheads

Minuteman III W78/Mk12A ; W87/Mk21
431
481

ICBM (total)
431
481

UGM-133A Trident II D-5 W76-0/Mk4
230
N/A

UGM-133A Trident II D-5 W76-1/Mk4A
N/A

UGM-133A Trident II D-5 W88/Mk5
N/A

SLBM (total)
230
920

B-2
12
N/A

B-52H
68
N/A

B61-7
N/A
N/A

B61-11
N/A
N/A

B83
N/A
N/A

AGM-86 ALCM W80-1
N/A
N/A

Bomber force (total)
80
*

Strategic forces (total)
741
1481+

text: * Each heavy bomber is counted as one warhead (The New START Treaty)[63]