American Museum of Natural History
The American Museum of Natural History, located on the Upper West Side of Manhattan, New York City, is one of the largest natural history museums in the world. Located in Theodore Roosevelt Park across the street from Central Park, the museum complex comprises 28 interconnected buildings housing 45 permanent exhibition halls, in addition to a planetarium and a library; the museum collections contain over 33 million specimens of plants, fossils, rocks, human remains, human cultural artifacts, of which only a small fraction can be displayed at any given time, occupies more than 2 million square feet. The museum has a full-time scientific staff of 225, sponsors over 120 special field expeditions each year, averages about five million visits annually; the one mission statement of the American Museum of Natural History is: "To discover and disseminate—through scientific research and education—knowledge about human cultures, the natural world, the universe." Before construction of the present complex, the museum was housed in the Arsenal building in Central Park.
Theodore Roosevelt, Sr. the father of the 26th U. S. President, was one of the founders along with John David Wolfe, William T. Blodgett, Robert L. Stuart, Andrew H. Green, Robert Colgate, Morris K. Jesup, Benjamin H. Field, D. Jackson Steward, Richard M. Blatchford, J. P. Morgan, Adrian Iselin, Moses H. Grinnell, Benjamin B. Sherman, A. G. Phelps Dodge, William A. Haines, Charles A. Dana, Joseph H. Choate, Henry G. Stebbins, Henry Parish, Howard Potter; the founding of the museum realized the dream of naturalist Dr. Albert S. Bickmore. Bickmore, a one-time student of zoologist Louis Agassiz, lobbied tirelessly for years for the establishment of a natural history museum in New York, his proposal, backed by his powerful sponsors, won the support of the Governor of New York, John Thompson Hoffman, who signed a bill creating the American Museum of Natural History on April 6, 1869. In 1874, the cornerstone was laid for the museum's first building, now hidden from view by the many buildings in the complex that today occupy most of Manhattan Square.
The original Victorian Gothic building, opened in 1877, was designed by Calvert Vaux and J. Wrey Mould, both closely identified with the architecture of Central Park; the original building was soon eclipsed by the south range of the museum, designed by J. Cleaveland Cady, an exercise in rusticated brownstone neo-Romanesque, influenced by H. H. Richardson, it extends 700 feet with corner towers 150 feet tall. Its pink brownstone and granite, similar to that found at Grindstone Island in the St. Lawrence River, came from quarries at Picton Island, New York; the entrance on Central Park West, the New York State Memorial to Theodore Roosevelt, completed by John Russell Pope in 1936, is an overscaled Beaux-Arts monument. It leads to a vast Roman basilica, where visitors are greeted with a cast of a skeleton of a rearing Barosaurus defending her young from an Allosaurus; the museum is accessible through its 77th street foyer, renamed the "Grand Gallery" and featuring a suspended Haida canoe. The hall leads into the oldest extant exhibit in the hall of Northwest Coast Indians.
Since 1930, little has been added to the exterior of the original building. The architect Kevin Roche and his firm Roche-Dinkeloo have been responsible for the master planning of the museum since the 1990s. Various renovations to both the interior and exterior have been carried out. Renovations to the Dinosaur Hall were undertaken starting in 1991, the museum restored the mural in Roosevelt Memorial Hall in 2010. In 1992 the Roche-Dinkeloo firm designed the eight-story AMNH Library. However, the entirety of the master plan was not realized, by 2015, the museum consisted of 25 separate buildings that were poorly connected; the museum's south façade, spanning 77th Street from Central Park West to Columbus Avenue was cleaned, repaired and re-emerged in 2009. Steven Reichl, a spokesman for the museum, said that work would include restoring 650 black-cherry window frames and stone repairs; the museum's consultant on the latest renovation is Wiss, Elstner Associates, Inc. an architectural and engineering firm with headquarters in Northbrook, Illinois.
In 2014, the museum published plans for a $325 million, 195,000-square-foot annex, the Richard Gilder Center for Science and Innovation, on the Columbus Avenue side. Designed by Studio Gang, Higgins Quasebarth & Partners and landscape architects Reed Hilderbrand, the new building's pink Milford granite facade will have a textural, curvilinear design inspired by natural topographical elements showcased in the museum, including "geological strata, glacier-gouged caves, curving canyons, blocks of glacial ice," as a striking contrast to the museum's predominance of High Victorian Gothic, Richardson Romanesque and Beaux Arts architectural styles; the interior itself would contain a new entrance from Columbus Avenue north of 79th Street. This expansion was supposed to be located to the south of the existing museum, occupying parts of Theodore Roosevelt Park; the expansion was relocated to the west side of the existing museum, its footprint was reduced in size, due to opposition to construction in the park.
The annex would instead replace three existing buildings along Columbus Avenue's east side, with more than 30 connections to the existing museum, it would be six stories high, the same height as the existing buildings. The plans for the expansion wer
New York City
The City of New York called either New York City or New York, is the most populous city in the United States. With an estimated 2017 population of 8,622,698 distributed over a land area of about 302.6 square miles, New York is the most densely populated major city in the United States. Located at the southern tip of the state of New York, the city is the center of the New York metropolitan area, the largest metropolitan area in the world by urban landmass and one of the world's most populous megacities, with an estimated 20,320,876 people in its 2017 Metropolitan Statistical Area and 23,876,155 residents in its Combined Statistical Area. A global power city, New York City has been described as the cultural and media capital of the world, exerts a significant impact upon commerce, research, education, tourism, art and sports; the city's fast pace has inspired the term New York minute. Home to the headquarters of the United Nations, New York is an important center for international diplomacy.
Situated on one of the world's largest natural harbors, New York City consists of five boroughs, each of, a separate county of the State of New York. The five boroughs – Brooklyn, Manhattan, The Bronx, Staten Island – were consolidated into a single city in 1898; the city and its metropolitan area constitute the premier gateway for legal immigration to the United States. As many as 800 languages are spoken in New York, making it the most linguistically diverse city in the world. New York City is home to more than 3.2 million residents born outside the United States, the largest foreign-born population of any city in the world. In 2017, the New York metropolitan area produced a gross metropolitan product of US$1.73 trillion. If greater New York City were a sovereign state, it would have the 12th highest GDP in the world. New York is home to the highest number of billionaires of any city in the world. New York City traces its origins to a trading post founded by colonists from the Dutch Republic in 1624 on Lower Manhattan.
The city and its surroundings came under English control in 1664 and were renamed New York after King Charles II of England granted the lands to his brother, the Duke of York. New York served as the capital of the United States from 1785 until 1790, it has been the country's largest city since 1790. The Statue of Liberty greeted millions of immigrants as they came to the U. S. by ship in the late 19th and early 20th centuries and is an international symbol of the U. S. and its ideals of liberty and peace. In the 21st century, New York has emerged as a global node of creativity and entrepreneurship, social tolerance, environmental sustainability, as a symbol of freedom and cultural diversity. Many districts and landmarks in New York City are well known, with the city having three of the world's ten most visited tourist attractions in 2013 and receiving a record 62.8 million tourists in 2017. Several sources have ranked New York the most photographed city in the world. Times Square, iconic as the world's "heart" and its "Crossroads", is the brightly illuminated hub of the Broadway Theater District, one of the world's busiest pedestrian intersections, a major center of the world's entertainment industry.
The names of many of the city's landmarks and parks are known around the world. Manhattan's real estate market is among the most expensive in the world. New York is home to the largest ethnic Chinese population outside of Asia, with multiple signature Chinatowns developing across the city. Providing continuous 24/7 service, the New York City Subway is the largest single-operator rapid transit system worldwide, with 472 rail stations. Over 120 colleges and universities are located in New York City, including Columbia University, New York University, Rockefeller University, which have been ranked among the top universities in the world. Anchored by Wall Street in the Financial District of Lower Manhattan, New York has been called both the most economically powerful city and the leading financial center of the world, the city is home to the world's two largest stock exchanges by total market capitalization, the New York Stock Exchange and NASDAQ. In 1664, the city was named in honor of the Duke of York.
James's older brother, King Charles II, had appointed the Duke proprietor of the former territory of New Netherland, including the city of New Amsterdam, which England had seized from the Dutch. During the Wisconsinan glaciation, 75,000 to 11,000 years ago, the New York City region was situated at the edge of a large ice sheet over 1,000 feet in depth; the erosive forward movement of the ice contributed to the separation of what is now Long Island and Staten Island. That action left bedrock at a shallow depth, providing a solid foundation for most of Manhattan's skyscrapers. In the precolonial era, the area of present-day New York City was inhabited by Algonquian Native Americans, including the Lenape, whose homeland, known as Lenapehoking, included Staten Island; the first documented visit into New York Harbor by a European was in 1524 by Giovanni da Verrazzano, a Florentine explorer in the service of the French crown. He named it Nouvelle Angoulême. A Spanish expedition led by captain Estêvão Gomes, a Portuguese sailing for Emperor Charles V, arrived in New York Harbor in January 1525 and charted the mouth of the Hudson River, which he named Río de San Antonio.
The Padrón Rea
A chemically pure and structurally perfect diamond is transparent with no hue, or color. However, in reality no gem-sized natural diamonds are perfect; the color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice. Depending on the hue and intensity of a diamond's coloration, a diamond's color can either detract from or enhance its value. For example, most white diamonds are discounted in price when more yellow hue is detectable, while intense pink diamonds or blue diamonds can be more valuable. Of all colored diamonds, red diamonds are the rarest; the Aurora Pyramid of Hope displays a spectacular array of colored diamonds, including red diamonds. Diamonds occur in a variety of colors—steel gray, blue, orange, green, pink to purple and black. Colored diamonds contain interstitial impurities or structural defects that cause the coloration, pure diamonds are transparent and colorless. Diamonds are scientifically classed into two main types and several subtypes, according to the nature of impurities present and how these impurities affect light absorption: Type I diamonds have nitrogen atoms as the main impurity at a concentration of 0.1%.
If the nitrogen atoms are in pairs they do not affect the diamond's color. If the nitrogen atoms are in large even-numbered aggregates they impart a yellow to brown tint. About 98% of gem diamonds are type Ia, most of these are a mixture of IaA and IaB material: these diamonds belong to the Cape series, named after the diamond-rich region known as Cape Province in North Africa, whose deposits are Type Ia. If the nitrogen atoms are dispersed throughout the crystal in isolated sites, they give the stone an intense yellow or brown tint. Synthetic diamond containing nitrogen is Type Ib. Type I diamonds absorb from 320 nm, they have a characteristic fluorescence and visible absorption spectrum. Type II diamonds have no measurable nitrogen impurities. Type II diamonds absorb in a different region of the infrared, transmit in the ultraviolet below 225 nm, unlike Type I diamonds, they have differing fluorescence characteristics, but no discernible visible absorption spectrum. Type IIa diamond can be colored pink, red, or brown due to structural anomalies arising through plastic deformation during crystal growth—these diamonds are rare, but constitute a large percentage of Australian production.
Type IIb diamonds, which account for 0.1% of gem diamonds, are light blue due to scattered boron within the crystal matrix. However, a blue-grey color may occur in Type Ia diamonds and be unrelated to boron. Not restricted to type are green diamonds, whose color is caused by GR1 color centers in the crystal lattice produced by exposure to varying quantities of radiation. Pink and red are caused by plastic deformation of the crystal lattice from pressure. Black diamonds are caused by microscopic black or gray inclusions of other materials such as graphite or sulfides and/or microscopic fractures. Opaque or opalescent white diamonds are caused by microscopic inclusions. Purple diamonds are caused by a combination of high hydrogen content; the majority of diamonds that are mined are in a range of pale yellow or brown color, termed the normal color range. Diamonds that are of intense yellow or brown, or any other color are called fancy color diamonds. Diamonds that are of the highest purity are colorless, appear a bright white.
The degree to which diamonds exhibit body color is one of the four value factors by which diamonds are assessed. Diamonds have a color grading system; this system goes from D to Z. The more colorless a diamond is, the rarer and more valuable it is because it appears white and brighter to the eye. Color grading of diamonds was performed as a step of sorting rough diamonds for sale by the London Diamond Syndicate; as the diamond trade developed, early diamond grades were introduced by various parties in the diamond trade. Without any co-operative development these early grading systems lacked standard nomenclature, consistency; some early grading scales were. Numerous terms developed to describe diamonds of particular colors: golconda, jagers, blue white, fine white, gem blue, etc. Refers to a grading scale for diamonds in the normal color range used by internationally recognized laboratories; the scale ranges from D, colorless to Z, a pale yellow or brown color. Brown diamonds darker than K color are described using their letter grade, a descriptive phrase, for example M Faint Brown.
Diamonds with more depth of color than Z color fall into the fancy color diamond range. Diamond color is graded by comparing a sample stone to a master stone set of diamonds; each master stone is known to exhibit the least amount of body color that a diamond in that color grade may exhibit. A trained diamond grader compares a diamond of unknown grade against the series of master stones, assessing where in the range of color the diamond resides; this process occurs in a lighting box, fitted with daylight equivalent lamps. Accurate color grading can only be performed with diamond unset, as the comparison with master
A diamond cut is a style or design guide used when shaping a diamond for polishing such as the brilliant cut. Cut does not refer to shape, but the symmetry and polish of a diamond; the cut of a diamond affects a diamond's brilliance. In order to best use a diamond gemstone's material properties, a number of different diamond cuts have been developed. A diamond cut constitutes a more or less symmetrical arrangement of facets, which together modify the shape and appearance of a diamond crystal. Diamond cutters must consider several factors, such as the shape and size of the crystal, when choosing a cut; the practical history of diamond cuts can be traced back to the Middle Ages, while their theoretical basis was not developed until the turn of the 20th century. Design creation and innovation continue to the present day: new technology—notably laser cutting and computer-aided design—has enabled the development of cuts whose complexity, optical performance, waste reduction were hitherto unthinkable.
The most popular of diamond cuts is the modern round brilliant, whose facet arrangements and proportions have been perfected by both mathematical and empirical analysis. Popular are the fancy cuts, which come in a variety of shapes, many of which were derived from the round brilliant. A diamond's cut is evaluated by trained graders, with higher grades given to stones whose symmetry and proportions most match the particular "ideal" used as a benchmark; the strictest standards are applied to the round brilliant. Different countries base their cut grading on different ideals: one may speak of the American Standard or the Scandinavian Standard, to give but two examples; the history of diamond cuts can be traced to the late Middle Ages, before which time diamonds were employed in their natural octahedral state—anhedral diamonds were not used in jewelry. The first "improvements" on nature's design involved a simple polishing of the octahedral crystal faces to create and unblemished facets, or to fashion the desired octahedral shape out of an otherwise unappealing piece of rough.
This was called the point cut and dates from the mid 14th century. By the mid 15th century, the point cut began to be improved upon: a little less than one half of the octahedron would be sawn off, creating the table cut; the importance of a culet was realised, some table-cut stones may possess one. The addition of four corner facets created the old single cut. Neither of these early cuts would reveal. At the time, diamond was valued chiefly for its adamantine superlative hardness. For this reason, colored gemstones such as ruby and sapphire were far more popular in jewelry of the era. In or around 1476, Lodewyk van Berquem, a Flemish polisher of Bruges, introduced the technique of absolute symmetry in the disposition of facets using a device of his own invention, the scaif, he cut stones in the shape known as briolette. About the middle of the 16th century, the rose or rosette was introduced in Antwerp: it consisted of triangular facets arranged in a symmetrical radiating pattern, but with the bottom of the stone left flat—essentially a crown without a pavilion.
Many large, famous Indian diamonds of old feature a rose-like cut. However, Indian "rose cuts" were far less symmetrical as their cutters had the primary interest of conserving carat weight, due to the divine status of diamond in India. In either event, the rose cut continued to evolve, with its depth and arrangements of facets being tweaked; the first brilliant cuts were introduced in the middle of the 17th century. Known as Mazarins, they had 17 facets on the crown, they are called double-cut brilliants as they are seen as a step up from old single cuts. Vincent Peruzzi, a Venetian polisher increased the number of crown facets from 17 to 33, thereby increasing the fire and brilliance of the cut gem, properties that in the Mazarin were incomparably better than in the rose, yet Peruzzi-cut diamonds, when seen nowadays, seem exceedingly dull compared to modern-cut brilliants. Because the practice of bruting had not yet been developed, these early brilliants were all rounded squares or rectangles in cross-section.
Given the general name of cushion—what are known today as old mine cuts—these were common by the early 18th century. Sometime the old European cut was developed, which had a shallower pavilion, more rounded shape, different arrangement of facets; the old European cut was the forerunner of modern brilliants and was the most advanced in use during the 19th century. Around 1900, the development of diamond saws and good jewelry lathes enabled the development of modern diamond cutting and diamond cuts, chief among them the round brilliant cut. In 1919, Marcel Tolkowsky analyzed this cut: his calculations took both brilliance and fire into consideration, creating a delicate balance between the two. Tolkowsky's calculations would serve as the basis for all future brilliant cut modifications and standards. Tolkowsky's model of the "ideal" cut is not perfect; the original mo
Fifth Avenue is a major thoroughfare in the borough of Manhattan in New York City. It stretches north from Washington Square Park in Greenwich Village to West 143rd Street in Harlem, it is considered one of the most elegant streets in the world. A narrower thoroughfare, much of Fifth Avenue south of Central Park was widened in 1908, sacrificing its wide sidewalks to accommodate the increasing traffic; the midtown blocks, now famously commercial, were a residential district until the start of the 20th century. The first commercial building on Fifth Avenue was erected by Benjamin Altman who bought the corner lot on the northeast corner of 34th Street in 1896, demolished the "Marble Palace" of his arch-rival, A. T. Stewart. In 1906 his department store, B. Altman and Company, occupied the whole of its block front; the result was the creation of a high-end shopping district that attracted fashionable women and the upscale stores that wished to serve them. Lord & Taylor's flagship store was once located on Fifth Avenue near the Empire State Building and the New York Public Library, but has since closed.
In the 1920s, traffic towers controlled important intersections from 14th to 59th Streets. Fifth Avenue originates at Washington Square Park in Greenwich Village and runs northwards through the heart of Midtown, along the eastern side of Central Park, where it forms the boundary of the Upper East Side and through Harlem, where it terminates at the Harlem River at 142nd Street. Traffic crosses the river on the Madison Avenue Bridge. Fifth Avenue serves as the dividing line for house numbering and west-east streets in Manhattan, just as Jerome Avenue does in the Bronx, it separates, for example, East 59th Street from West 59th Street. From this zero point for street addresses, numbers increase in both directions as one moves away from Fifth Avenue, The building lot numbering system worked on the East Side as well, before Madison & Lexington Aves. were retrofitted into the street grid, confusing the building numbers. Confusingly, an address on a cross street cannot be predicted at the intersection of Madison Ave. or Lexington Ave. as these were added decades after the building numbers.
It's. The "most expensive street in the world" moniker changes depending on currency fluctuations and local economic conditions from year to year. For several years starting in the mid-1990s, the shopping district between 49th and 57th Streets was ranked as having the world's most expensive retail spaces on a cost per square foot basis. In 2008, Forbes magazine ranked Fifth Avenue as being the most expensive street in the world; some of the most coveted real estate on Fifth Avenue are the penthouses perched atop the buildings. The American Planning Association compiled a list of "2012 Great Places in America" and declared Fifth Avenue to be one of the greatest streets to visit in America; this historic street has many world-renowned museums and stores, luxury apartments, historical landmarks that are reminiscent of its history and vision for the future. By 2018 portions of Fifth Avenue had large numbers of vacant store fronts for long periods, part of a citywide trend of vacant store fronts attributed to high rental costs.
Fifth Avenue from 142nd Street to 135th Street carries two-way traffic. Fifth Avenue carries one-way traffic southbound from 135th Street to Washington Square North; the changeover to one-way traffic south of 135th Street took place on January 14, 1966, at which time Madison Avenue was changed to one way uptown. From 124th Street to 120th Street, Fifth Avenue is cut off by Marcus Garvey Park, with southbound traffic diverted around the park via Mount Morris Park West. Fifth Avenue is the traditional route for many celebratory parades in New York City; the longest running parade is the annual St. Patrick's Day Parade. Parades held are distinct from the ticker-tape parades held on the "Canyon of Heroes" on lower Broadway, the Macy's Thanksgiving Day Parade held on Broadway from the Upper West Side downtown to Herald Square. Fifth Avenue parades proceed from south to north, with the exception of the LGBT Pride March, which goes north to south to end in Greenwich Village; the Latino literary classic by New Yorker Giannina Braschi, entitled "Empire of Dreams," takes place on the Puerto Rican Day Parade on Fifth Avenue.
Bicycling on Fifth Avenue ranges from segregated with a bike lane south of 23rd Street, to scenic along Central Park, to dangerous through Midtown with heavy traffic during rush hours. There is no dedicated bike lane along Fifth Avenue. In July 1987 New York City Mayor Edward Koch proposed banning bicycling on Fifth and Madison Avenues during weekdays, but many bicyclists protested and had the ban overturned; when the trial was started on Monday, August 24, 1987 for 90 days to ban bicyclists from these three avenues from 31st Street to 59th Street between 10 a.m. and 4 p.m. on weekdays, mopeds would not be banned. On Monday, August 31, 1987, a state appeals court judge halted the ban for at least a week pending a ruling after opponents against the ban brought a lawsuit. Fifth Avenue is one of the few major streets in Manhattan along. Instead, Fifth Avenue Coach offered a service more to the taste of fashionable gentlefolk, at twice the fare. Double-decker buses were operated by the Fifth Avenue Coach Company until 1953, again by MTA Regional Bus Operations from 1976 to 1978.
Today, local bus service along Fifth Avenue is provided by the MTA's M1, M2, M3, M4 buses. The M5 and Q32 run on Fifth Avenue in Midtown, while the M55 runs on Fifth Avenue south of 44th Street
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form, but diamond never converts to it. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are utilized in major industrial applications such as cutting and polishing tools, they are the reason that diamond anvil cells can subject materials to pressures found deep in the Earth. Because the arrangement of atoms in diamond is rigid, few types of impurity can contaminate it. Small numbers of defects or impurities color diamond blue, brown, purple, orange or red. Diamond has high optical dispersion. Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths between 150 and 250 kilometers in the Earth's mantle, although a few have come from as deep as 800 kilometers. Under high pressure and temperature, carbon-containing fluids dissolved minerals and replaced them with diamonds.
Much more they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites. Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures or from hydrocarbon gas by chemical vapor deposition. Imitation diamonds can be made out of materials such as cubic zirconia and silicon carbide. Natural and imitation diamonds are most distinguished using optical techniques or thermal conductivity measurements. Diamond is a solid form of pure carbon with its atoms arranged in a crystal. Solid carbon comes in different forms known as allotropes depending on the type of chemical bond; the two most common allotropes of pure carbon are graphite. In graphite the bonds are sp2 orbital hybrids and the atoms form in planes with each bound to three nearest neighbors 120 degrees apart. In diamond they are sp3 and the atoms form tetrahedra with each bound to four nearest neighbors. Tetrahedra are rigid, the bonds are strong, of all known substances diamond has the greatest number of atoms per unit volume, why it is both the hardest and the least compressible.
It has a high density, ranging from 3150 to 3530 kilograms per cubic metre in natural diamonds and 3520 kg/m³ in pure diamond. In graphite, the bonds between nearest neighbors are stronger but the bonds between planes are weak, so the planes can slip past each other. Thus, graphite is much softer than diamond. However, the stronger bonds make graphite less flammable. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness and thermal conductivity, as well as wide bandgap and high optical dispersion. Diamond's ignition point is 720 -- 800 °C in 850 -- 1000 °C in air; the equilibrium pressure and temperature conditions for a transition between graphite and diamond is well established theoretically and experimentally. The pressure changes linearly between 1.7 GPa at 0 K and 12 GPa at 5000 K. However, the phases have a wide region about this line where they can coexist. At normal temperature and pressure, 20 °C and 1 standard atmosphere, the stable phase of carbon is graphite, but diamond is metastable and its rate of conversion to graphite is negligible.
However, at temperatures above about 4500 K, diamond converts to graphite. Rapid conversion of graphite to diamond requires pressures well above the equilibrium line: at 2000 K, a pressure of 35 GPa is needed. Above the triple point, the melting point of diamond increases with increasing pressure. At high pressures and germanium have a BC8 body-centered cubic crystal structure, a similar structure is predicted for carbon at high pressures. At 0 K, the transition is predicted to occur at 1100 GPa; the most common crystal structure of diamond is called diamond cubic. It is formed of unit cells stacked together. Although there are 18 atoms in the figure, each corner atom is shared by eight unit cells and each atom in the center of a face is shared by two, so there are a total of eight atoms per unit cell; each side of the unit cell is 3.57 angstroms in length. A diamond cubic lattice can be thought of as two interpenetrating face-centered cubic lattices with one displaced by 1/4 of the diagonal along a cubic cell, or as one lattice with two atoms associated with each lattice point.
Looked at from a <1 1 1> crystallographic direction, it is formed of layers stacked in a repeating ABCABC... pattern. Diamonds can form an ABAB... structure, known as hexagonal diamond or lonsdaleite, but this is far less common and is formed under different conditions from cubic carbon. Diamonds occur most 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, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron. The crystals can be elongated. Diamonds are found coated in nyf, an opaque gum-like skin; some diamonds have opaque fibers. They are referred to as opaque if the fibers
Crater of Diamonds State Park
Crater of Diamonds State Park is a 911-acre Arkansas state park in Pike County, Arkansas, in the United States. The park features a 37.5-acre plowed field, the world's only diamond-bearing site accessible to the public. Diamonds have continuously been discovered in the field since 1906, including the Strawn-Wagner Diamond; the site became a state park in 1972 after the Arkansas Department of Parks and Tourism purchased the site from the Arkansas Diamond Company and Ozark Diamond Mines Corporation, who had operated the site as a tourist attraction previously. In August 1906, John Huddleston found two strange crystals on the surface of his 243-acre farm near Murfreesboro and soon became known as the first person outside South Africa to find diamonds at their original source; the following month and his wife, sold an option on the 243 acres to a group of Little Rock investors headed by banker-attorney Samuel F. Reyburn, who undertook a careful, deliberate test of the property. After 1906, several attempts at commercial diamond mining failed.
The only significant yields came from the original surface layer, where erosion over a long period of time had concentrated diamonds. In the early period, 1907–1932, yields from this "black gumbo" surface material exceeded thirty carats per hundred loads. Highest yields from the undisturbed subsurface material were two carats per hundred loads in 1908 and about two carats per hundred short tons in 1943−1944; because equipment of the early period included bottom screens with mesh larger than 1/16 inch, thousands of smaller diamonds were allowed to pass through. The bulk of these ended up in drainage cuts of varying depths all over the field and in the big natural drains on the east and west edges of the diamond-bearing section of the volcanic deposit. In recent decades, those small diamonds have been the bread-and-butter of recreational diamond digging. Soon after the first diamond was found, a "diamond rush" created a boomtown atmosphere around Murfreesboro. According to old tales, hotels in Murfreesboro turned away 10,000 people in the space of a year.
These aspiring diamond miners formed a tent city near the mine, named "Kimberly" in honor of the famous Kimberley diamond district in South Africa. On the other hand, all available evidence indicates that the Town of Kimberly originated as a land-development venture in 1909, initiated by Mallard M. Mauney and his oldest son, Walter, on their land south of Murfreesboro; the project failed soon afterward as the speculative boom generated by the diamond discovery collapsed. Today, the Kimberly area is all cow pasture, owned by Mauney's descendants. During the Second World War, the U. S. government took over the mine and granted a contract to Glen Martin to extract this rare war material. Although diamonds were obtained, the concentration of diamonds similar to other producing mines, this was not successful as a venture due to the large costs involved with U. S. labor. After the war, the property was returned to the previous owners. From 1951 to 1972, the crater hosted several private tourist attractions.
The first, The Diamond Preserve of the United States, lasted only about one year. In late 1951, Howard A. Millar salvaged the infant tourist industry. In April 1952, Millar and his wife, launched their Crater of Diamonds attraction. Howard Millar, an accomplished writer and promoter, stirred unprecedented national publicity and drew enough visitors to sustain the operation. In March 1956, a visitor found the Star of Arkansas on the cleared surface; the rare beauty weighed 15.33 carats. Roscoe Johnston opened a rival tourist attraction, the Arkansas Diamond Mine, on the main part of the diamond field; the rivalry between the two tourist operations left both in a weakened position. In 1970, the entire volcanic formation was consolidated by a private partnership, which reassigned the property to General Earth Minerals of Dallas, Texas. GEM expected to turn the property over for a profit, but ended up indebted to GF Industries of Dallas. Upon default, GFI took the property in July 1971. GEM consolidated the tourist operation as well as the property.
GFI continued the attraction until it sold the 80-acre volcanic formation and some 800 acres to the State of Arkansas in March 1972 for $750,000. The tourist operation continued as the centerpiece of Crater of Diamonds State Park. Due in part to the park, because Arkansas was the first place outside South Africa where diamonds were found at their original volcanic source, this special gem has come to be associated with the Natural State. A large diamond symbol has dominated the state flag since 1912; the Arkansas State Quarter, released in 2003, bears a diamond on its face. The Crater of Diamonds volcanic pipe is part of a 95-million-year-old eroded volcano; the sourced lamproite magma, from the upper mantle, brought the diamonds to the surface. The diamonds had crystallized in the cratonic root of the continent long before and were sampled by the magma as it rose to the surface; the geology of the area and the diamond formation process itself were the subjects of the Ph. D. dissertation of Roland Everett Langford in 1973 from the University of Georgia.
The dissertation was on display at the state park for many years. The lamproite diamond sour