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
Jewellery or jewelry consists of small decorative items worn for personal adornment, such as brooches, necklaces, pendants and cufflinks. Jewellery may be attached to the clothes. From a western perspective, the term is restricted to durable ornaments, excluding flowers for example. For many centuries metal combined with gemstones, has been the normal material for jewellery, but other materials such as shells and other plant materials may be used, it is one of the oldest type of archaeological artefact – with 100,000-year-old beads made from Nassarius shells thought to be the oldest known jewellery. The basic forms of jewellery vary between cultures but are extremely long-lived. Jewellery may be made from a wide range of materials. Gemstones and similar materials such as amber and coral, precious metals and shells have been used, enamel has been important. In most cultures jewellery can be understood as a status symbol, for its material properties, its patterns, or for meaningful symbols. Jewellery has been made to adorn nearly every body part, from hairpins to toe rings, genital jewellery.
The patterns of wearing jewellery between the sexes, by children and older people can vary between cultures, but adult women have been the most consistent wearers of jewellery. The word jewellery itself is derived from the word jewel, anglicised from the Old French "jouel", beyond that, to the Latin word "jocale", meaning plaything. In British English, Indian English, New Zealand English, Hiberno-English, Australian English, South African English it is spelled jewellery, while the spelling is jewelry in American English. Both are used in Canadian English. In French and a few other European languages the equivalent term, may cover decorated metalwork in precious metal such as objets d'art and church items, not just objects worn on the person. Humans have used jewellery for a number of different reasons: functional to fix clothing or hair in place as a marker of social status and personal status, as with a wedding ring as a signifier of some form of affiliation, whether ethnic, religious or social to provide talismanic protection as an artistic display as a carrier or symbol of personal meaning – such as love, mourning, or luckMost cultures at some point have had a practice of keeping large amounts of wealth stored in the form of jewellery.
Numerous cultures store wedding dowries in the form of jewellery or make jewellery as a means to store or display coins. Alternatively, jewellery has been used as a trade good. Many items of jewellery, such as brooches and buckles, originated as purely functional items, but evolved into decorative items as their functional requirement diminished. Jewellery can symbolise group membership or status. Wearing of amulets and devotional medals to provide protection or ward off evil is common in some cultures; these may take the form of symbols, plants, body parts, or glyphs. In creating jewellery, coins, or other precious items are used, they are set into precious metals. Platinum alloys range from 900 to 950; the silver used in jewellery is sterling silver, or 92.5% fine silver. In costume jewellery, stainless steel findings are sometimes used. Other used materials include glass, such as fused-glass or enamel. However, any inclusion of lead or lead solder will give a British Assay office the right to destroy the piece, however it is rare for the assay office to do so.
Beads are used in jewellery. These may be made of glass, metal, shells and polymer clay. Beaded jewellery encompasses necklaces, earrings and rings. Beads may be small. Seed beads are used in an embroidery technique where they are sewn onto fabric backings to create broad collar neck pieces and beaded bracelets. Bead embroidery, a popular type of handwork during the Victorian era, is enjoying a renaissance in modern jewellery making. Beading, or beadwork, is very popular in many African and indigenous North American cultures. Silversmiths and lapidaries methods include forging, soldering or welding, carving and "cold-joining". Diamonds were first mined in India. Pliny may have mentioned them, although there is some debate as to the exact nature of the stone he referred to as Adamas. Ther
Las Vegas the City of Las Vegas and known as Vegas, is the 28th-most populated city in the United States, the most populated city in the state of Nevada, the county seat of Clark County. The city anchors the Las Vegas Valley metropolitan area and is the largest city within the greater Mojave Desert. Las Vegas is an internationally renowned major resort city, known for its gambling, fine dining and nightlife; the Las Vegas Valley as a whole serves as the leading financial and cultural center for Nevada. The city bills itself as The Entertainment Capital of the World, is famous for its mega casino–hotels and associated activities, it is a top three destination in the United States for business conventions and a global leader in the hospitality industry, claiming more AAA Five Diamond hotels than any other city in the world. Today, Las Vegas annually ranks as one of the world's most visited tourist destinations; the city's tolerance for numerous forms of adult entertainment earned it the title of Sin City, has made Las Vegas a popular setting for literature, television programs, music videos.
Las Vegas was settled in 1905 and incorporated in 1911. At the close of the 20th century, it was the most populated American city founded within that century. Population growth has accelerated since the 1960s, between 1990 and 2000 the population nearly doubled, increasing by 85.2%. Rapid growth has continued into the 21st century, according to a 2018 estimate, the population is 648,224 with a regional population of 2,227,053; as with most major metropolitan areas, the name of the primary city is used to describe areas beyond official city limits. In the case of Las Vegas, this applies to the areas on and near the Las Vegas Strip, located within the unincorporated communities of Paradise and Winchester; the earliest visitors to the Las Vegas area were nomadic Paleo-Indians, who traveled there 10,000 years ago, leaving behind petroglyphs. Anasazi and Paiute tribes followed at least 2,000 years ago. A young Mexican scout named Rafael Rivera is credited as the first non-Native American to encounter the valley, in 1829.
Trader Antonio Armijo led a 60-man party along the Spanish Trail to Los Angeles, California in 1829. The area was named Las Vegas, Spanish for "the meadows," as it featured abundant wild grasses, as well as the desert spring waters needed by westward travelers; the year 1844 marked the arrival of John C. Frémont, whose writings helped lure pioneers to the area. Downtown Las Vegas's Fremont Street is named after him. Eleven years members of the LDS Church chose Las Vegas as the site to build a fort halfway between Salt Lake City and Los Angeles, where they would travel to gather supplies; the fort was abandoned several years afterward. The remainder of this Old Mormon Fort can still be seen at the intersection of Las Vegas Boulevard and Washington Avenue. Las Vegas was founded as a city in 1905, when 110 acres of land adjacent to the Union Pacific Railroad tracks were auctioned in what would become the downtown area. In 1911, Las Vegas was incorporated as a city. 1931 was a pivotal year for Las Vegas.
At that time, Nevada legalized casino gambling and reduced residency requirements for divorce to six weeks. This year witnessed the beginning of construction on nearby Hoover Dam; the influx of construction workers and their families helped Las Vegas avoid economic calamity during the Great Depression. The construction work was completed in 1935. In 1941, the Las Vegas Army Air Corps Gunnery School was established. Known as Nellis Air Force Base, it is home to the aerobatic team called the Thunderbirds. Following World War II, lavishly decorated hotels, gambling casinos, big-name entertainment became synonymous with Las Vegas. In the 1950s the Moulin Rouge opened and became the first racially integrated casino-hotel in Las Vegas. In 1951, nuclear weapons testing began at the Nevada Test Site, 65 miles northwest of Las Vegas. During this time the city was nicknamed the "Atomic City". Residents and visitors were able to witness the mushroom clouds until 1963, when the limited Test Ban Treaty required that nuclear tests be moved underground.
The iconic "Welcome to Las Vegas" sign, never located within municipal limits, was created in 1959 by Betty Willis. During the 1960s, corporations and business powerhouses such as Howard Hughes were building and buying hotel-casino properties. Gambling was referred to as "gaming"; the year 1995 marked the opening of the Fremont Street Experience in Las Vegas's downtown area. This canopied five-block area features 12.5 million LED lights and 550,000 watts of sound from dusk until midnight during shows held on the top of each hour. Due to the realization of many revitalization efforts, 2012 was dubbed "The Year of Downtown." Hundreds of millions of dollars' worth of projects made their debut at this time. They included The Smith Center for the Performing Arts and DISCOVERY Children's Museum, Mob Museum, Neon Museum, a new City Hall complex and renovations for a new Zappos.com corporate headquarters in the old City Hall building. Las Vegas is situated within Clark County in a basin on the floor of the Mojave Desert and is surrounded by mountain ranges on all sides.
Much of the landscape is arid with desert vegetation and wildlife. It can be subjected to torrential flash floods, although much has been done to mitigate the effects of flash floods through improved drainage systems; the peaks surrounding Las Vegas reach elevations of o
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
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