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
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
Sotheby's is a British-founded American multinational corporation headquartered in New York City. One of the world's largest brokers of fine and decorative art, real estate, collectibles, Sotheby's operation is divided into three segments: auction and dealer; the company's services range from corporate art services to private sales. It is named after one of John Sotheby. Sotheby's is the world's fourth oldest auction house in continuous operation, with 90 locations in 40 countries; as of December 2011, the company had 1,446 employees worldwide. It is the world's largest art business with global sales in 2011 totalling $5.8 billion. Sotheby's was established on 11 March 1744 in London; the American holding company was incorporated in August 1983 in Michigan. In June 2006, Sotheby's Holdings, Inc. reincorporated in the State of Delaware and was renamed Sotheby's. In July 2016, Chinese insurance company Taikang Life became Sotheby's largest shareholder. Sotheby's predecessor and Leigh, was founded in London on 11 March 1744, when Samuel Baker presided over the disposal of "several hundred scarce and valuable" books from the library of Rt Hon Sir John Stanley Bt. of Alderley.
Three Swedish auction houses are older and Sotheby's great rival in London and New York, Christie's, dates from 1759 or shortly after. The current business dates back to 1804, when two of the partners of the original business left to set up their own book dealership; the library Napoleon took with him into exile at St Helena, as well as the library collections of John Wilkes, Benjamin Heywood Bright and the Dukes of Devonshire and of Buckingham were sold through Samuel Baker's auctions. After Baker's death in 1778, his estate was divided between John Sotheby. George Leigh died unmarried in 1816, but not before endeavouring to secure his succession by recruiting Samuel E Leigh into the business. Under the Sotheby family, the auction house extended its activities to auctioning prints and coins. John Wilkinson, Sotheby's Senior Accountant, became the company's new CEO; the business did not seek to auction fine arts in general until much their first major success in this field being the sale of a Frans Hals painting for nine thousand guineas as late as 1913.
In 1917, Sotheby's relocated from 13 Wellington Street to 34-35 New Bond Street, which remains as its London base to this day. They soon came to rival Christie's as leaders of the London auction market, which had become the most important for art. In 1955, Sotheby's opened an office at New York City. In 1964, Sotheby's purchased Parke-Bernet the largest auctioneer of fine art in the United States. In the following year, Sotheby's moved to New York. With international popularity of fine art auction growing, Sotheby's opened offices in Paris and Los Angeles in 1967, became the first auction house to operate in Hong Kong in 1973, Moscow in 1988. Sotheby's became a U. K. public company in 1977. A 25 percent drop from the 1980–81 record of $610 million in sales contributed to Sotheby's decision to relocate its North American headquarters from Madison Avenue to a former cigar factory at 1334 York Avenue, New York, in 1982; the auction house closed its Madison Avenue galleries at East 76th Street. The Los Angeles galleries were sold and auctions of West Coast material moved to New York.
In the following year, a group of investors privatized Sotheby's. Sotheby's was incorporated as Sotheby's Holdings, Inc. in Michigan in August 1983. Taubman took Sotheby's public in 1988, listing the company's shares on the New York Stock Exchange, making Sotheby's the oldest publicly traded company on the NYSE under the ticker symbol "BID." In June 2006, Sotheby's Holdings, Inc. reincorporated in the State of Delaware and was renamed Sotheby's shortly after. With private transactions constituting an essential and profitable business segment, through the years Sotheby's has bought art galleries and helped dealers finance purchases, it has gone into partnership with dealers on private sales. In 1990, Sotheby's teamed up with dealer William Acquavella, to form Acquavella Modern Art, a Nevada general partnership and a subsidiary of Sotheby's Holding Company; the subsidiary paid $143 million for the contents of the Pierre Matisse Gallery in Manhattan, which included about 2,300 works by such artists as Miró, Jean Dubuffet, Alberto Giacometti, Marc Chagall, began selling the works both at auction and privately.
In 1996, Sotheby's acquired Andre Emmerich Gallery to operate a division called Emmerich/Sotheby's, in 1997 it purchased a 50% interest in Deitch Projects. As a consequence, the Josef and Anni Albers Foundation, the main beneficiary of the artists' estates, as well as the estates of Morris Louis and Milton Avery announced that they would not renew their Emmerich contracts; that decision came right after it was disclosed that Sotheby's had decided to close Emmerich's prime space at 41 East 57th Street, that its artists would be handled out of Deitch Projects. Sotheby's subsequently closed Andre Emmerich in 1998 and sold its share in Deitch Projects back to Jeffrey Deitch. In 2006, Sotheby's acquired a Dutch dealership, Noortman Master Paintings, from its owner, Robert Noortman, for $82.5 million. Sotheby's and Noortman had collaborated before in 1995, when the sales of Dutch plastic millionaire Joost Ritman were divided between the two companies. In 1990, Sotheby's New
Christie's is a British auction house. It was founded in 1766 by James Christie, its main premises are on King Street, St James's, in London and in the Rockefeller Center in New York City. The company is owned by the holding company of François-Henri Pinault. Sales in 2015 totalled £4.8 billion. In 2017 the Salvator Mundi was sold for $450.3 million at Christie's, which at that time was the highest price paid for a single painting at an auction. The official company literature states that founder James Christie conducted the first sale in London, England, on 5 December 1766, the earliest auction catalogue the company retains is from December 1766. However, other sources note that James Christie rented auction rooms from 1762, newspaper advertisements for Christie's sales dating from 1759 have been traced. Christie's was a public company, listed on the London Stock Exchange, from 1973 to 1999. In 1974, Jo Floyd was appointed chairman of Christie's, he served as chairman of Christie's International plc from 1976 to 1988, until handing over to Lord Carrington, was a non-executive director until 1992.
Christie's International Inc. held its first sale in the United States in 1977. Christie's growth was steady since 1989, when it had 42 % of the auction market. In 1990, the company reversed a long-standing policy and guaranteed a minimum price for a collection of artworks in its May auctions. In 1996, sales exceeded those of Sotheby's for the first time since 1954. However, profits did not grow at the same pace. In 1993, Christie's paid $12.7 million for the London gallery Spink & Son, which specialised in Oriental art and British paintings. The company bought Leger Gallery for $3.3 million in 1996, merged it with Spink to become Spink-Leger. Spink-Leger closed in 2002. To make itself competitive with Sotheby's in the property market, Christie's bought Great Estates in 1995 the largest network of independent estate agents in North America, changing its name to Christie's Great Estates Inc. In December 1997, under the chairmanship of Lord Hindlip, Christie's put itself on the auction block, but after two months of negotiations with the consortium-led investment firm SBC Warburg Dillon Read it did not attract a bid high enough to accept.
In May 1998, François Pinault's holding company, Groupe Artémis S. A. first bought 29.1 percent of the company for $243.2 million, subsequently purchased the rest of it in a deal that valued the entire company at $1.2 billion. The company has since not been reporting profits, its policy, in line with UK accounting standards, is to convert non-UK results using an average exchange rate weighted daily by sales throughout the year. In 2002, Christie's France held its first auction in Paris. Like Sotheby's, Christie's became involved in high-profile private transactions. In 2006, Christie's offered a reported $21 million guarantee to the Donald Judd Foundation and displayed the artist's works for five weeks in an exhibition that won an AICA award for "Best Installation in an Alternative Space". In 2007 it brokered a $68 million deal that transferred Thomas Eakins's The Gross Clinic from the Jefferson Medical College at the Thomas Jefferson University in Philadelphia to joint ownership by the Philadelphia Museum of Art and the Pennsylvania Academy of the Fine Arts.
In the same year, the Haunch of Venison gallery became a subsidiary of the company. On 28 December 2008, The Sunday Times reported that Pinault's debts left him "considering" the sale of Christie's and that a number of "private equity groups" were thought to be interested in its acquisition. In January 2009, the company employed 2,100 people worldwide, though an unspecified number of staff and consultants were soon to be cut due to a worldwide downturn in the art market. With sales for premier Impressionist and contemporary artworks tallying only US$248.8 million in comparison to US$739 million just a year before, a second round of job cuts began after May 2009. Guy Bennett resigned just before to the beginning of the summer 2009 sales season. Although the economic downturn has encouraged some collectors to sell art, others are unwilling to sell in a market which may yield only bargain prices. On 1 January 2017, Guillaume Cerutti was appointed chief executive officer. Patricia Barbizet was appointed chief executive officer of Christie's in 2014, the first female CEO of the company.
She replaced Steven Murphy, hired in 2010 to develop their online presence and launch in new markets, such as China. In 2012, Impressionist works, which dominated the market during the 1980s boom, were replaced by contemporary art as Christie's top category. Asian art was the third most-lucrative area. With income from classic auctioneering falling, treaty sales made £413.4 million in the first half of 2012, an increase of 53% on the same period last year. The company has promoted curated events, centred on a theme rather than an art classification or time period; as part of a companywide review in 2017, Christie's announced the layoffs of 250 employees, or 12 percent of the total work force, based in Britain and Europe. From 2008 until 2013, Christie's charged 25 percent for the first $50,000. From 2013, it charged 25 percent for the first $75,000. Christie's main London salesroom is on
United States dollar
The United States dollar is the official currency of the United States and its territories per the United States Constitution since 1792. In practice, the dollar is divided into 100 smaller cent units, but is divided into 1000 mills for accounting; the circulating paper money consists of Federal Reserve Notes that are denominated in United States dollars. Since the suspension in 1971 of convertibility of paper U. S. currency into any precious metal, the U. S. dollar is, de facto, fiat money. As it is the most used in international transactions, the U. S. dollar is the world's primary reserve currency. Several countries use it as their official currency, in many others it is the de facto currency. Besides the United States, it is used as the sole currency in two British Overseas Territories in the Caribbean: the British Virgin Islands and Turks and Caicos Islands. A few countries use the Federal Reserve Notes for paper money, while still minting their own coins, or accept U. S. dollar coins. As of June 27, 2018, there are $1.67 trillion in circulation, of which $1.62 trillion is in Federal Reserve notes.
Article I, Section 8 of the U. S. Constitution provides that the Congress has the power "To coin money". Laws implementing this power are codified at 31 U. S. C. § 5112. Section 5112 prescribes the forms; these coins are both designated in Section 5112 as "legal tender" in payment of debts. The Sacagawea dollar is one example of the copper alloy dollar; the pure silver dollar is known as the American Silver Eagle. Section 5112 provides for the minting and issuance of other coins, which have values ranging from one cent to 100 dollars; these other coins are more described in Coins of the United States dollar. The Constitution provides that "a regular Statement and Account of the Receipts and Expenditures of all public Money shall be published from time to time"; that provision of the Constitution is made specific by Section 331 of Title 31 of the United States Code. The sums of money reported in the "Statements" are being expressed in U. S. dollars. The U. S. dollar may therefore be described as the unit of account of the United States.
The word "dollar" is one of the words in the first paragraph of Section 9 of Article I of the Constitution. There, "dollars" is a reference to the Spanish milled dollar, a coin that had a monetary value of 8 Spanish units of currency, or reales. In 1792 the U. S. Congress passed a Coinage Act. Section 9 of that act authorized the production of various coins, including "DOLLARS OR UNITS—each to be of the value of a Spanish milled dollar as the same is now current, to contain three hundred and seventy-one grains and four sixteenth parts of a grain of pure, or four hundred and sixteen grains of standard silver". Section 20 of the act provided, "That the money of account of the United States shall be expressed in dollars, or units... and that all accounts in the public offices and all proceedings in the courts of the United States shall be kept and had in conformity to this regulation". In other words, this act designated the United States dollar as the unit of currency of the United States. Unlike the Spanish milled dollar, the U.
S. dollar is based upon a decimal system of values. In addition to the dollar the coinage act established monetary units of mill or one-thousandth of a dollar, cent or one-hundredth of a dollar, dime or one-tenth of a dollar, eagle or ten dollars, with prescribed weights and composition of gold, silver, or copper for each, it was proposed in the mid-1800s that one hundred dollars be known as a union, but no union coins were struck and only patterns for the $50 half union exist. However, only cents are in everyday use as divisions of the dollar. XX9 per gallon, e.g. $3.599, more written as $3.599⁄10. When issued in circulating form, denominations equal to or less than a dollar are emitted as U. S. coins while denominations equal to or greater than a dollar are emitted as Federal Reserve notes. Both one-dollar coins and notes are produced today, although the note form is more common. In the past, "paper money" was issued in denominations less than a dollar and gold coins were issued for circulation up to the value of $20.
The term eagle was used in the Coinage Act of 1792 for the denomination of ten dollars, subsequently was used in naming gold coins. Paper currency less than one dollar in denomination, known as "fractional currency", was sometimes pejoratively referred to as "shinplasters". In 1854, James Guthrie Secretary of the Treasury, proposed creating $100, $50 and $25 gold coins, which were referred to as a "Union", "Half Union", "Quarter Union", thus implying a denomination of 1 Union = $100. Today, USD notes are made from cotton fiber paper, unlike most common paper, made of wood fiber. U. S. coins are produced by the United States Mint. U. S. dollar banknotes are printed by the Bureau of Engraving and Printing and, since 1914, have been issued by t
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
Geneva is the second-most populous city in Switzerland and the most populous city of Romandy, the French-speaking part of Switzerland. Situated where the Rhône exits Lake Geneva, it is the capital of the Canton of Geneva; the municipality has a population of 200,548, the canton has 495,249 residents. In 2014, the compact agglomération du Grand Genève had 946,000 inhabitants in 212 communities in both Switzerland and France. Within Swiss territory, the commuter area named "Métropole lémanique" contains a population of 1.26 million. This area is spread east from Geneva towards the Riviera area and north-east towards Yverdon-les-Bains, in the neighbouring canton of Vaud. Geneva is a global city, a financial centre, a worldwide centre for diplomacy due to the presence of numerous international organizations, including the headquarters of many agencies of the United Nations and the Red Cross. Geneva hosts the highest number of international organizations in the world, it is where the Geneva Conventions were signed, which chiefly concern the treatment of wartime non-combatants and prisoners of war.
In 2017, Geneva was ranked as the world's fifteenth most important financial centre for competitiveness by the Global Financial Centres Index, fifth in Europe behind London, Zürich and Luxembourg. In 2019 Geneva was ranked among the ten most liveable cities in the world by Mercer together with Zürich and Basel; the city has been referred to as the world's most compact metropolis and the "Peace Capital". In 2017, Geneva was ranked as the seventh most expensive city in the world. Geneva was ranked third in purchasing power in a global cities ranking by UBS in 2018; the city was mentioned in Latin texts, by Caesar, with the spelling Genava from the Celtic *genawa- from the stem *genu-, in the sense of a bending river or estuary. The medieval county of Geneva in Middle Latin was known as pagus major Genevensis or Comitatus Genevensis. After 1400 it became the Genevois province of Savoy; the name takes various forms in modern languages, Geneva in English, French: Genève, German: Genf, Italian: Ginevra, Romansh: Genevra.
The city shares the origin of * genawa "estuary", with the Italian port city of Genoa. Geneva was an Allobrogian border town, fortified against the Helvetii tribe, when the Romans took it in 121 BC, it became Christian under the Late Roman Empire, acquired its first bishop in the 5th century, having been connected to the Bishopric of Vienne in the 4th. In the Middle Ages, Geneva was ruled by a count under the Holy Roman Empire until the late 14th century, when it was granted a charter giving it a high degree of self-governance. Around this time, the House of Savoy came to at least nominally dominate the city. In the 15th century, an oligarchic republican government emerged with the creation of the Grand Council. In the first half of the 16th century, the Protestant Reformation reached the city, causing religious strife, during which Savoy rule was thrown off and Geneva allied itself with the Swiss Confederacy. In 1541, with Protestantism on the rise, John Calvin, the Protestant Reformer and proponent of Calvinism, became the spiritual leader of the city and established the Republic of Geneva.
By the 18th century, Geneva had come under the influence of Catholic France, which cultivated the city as its own. France tended to be at odds with the ordinary townsfolk, which inspired the failed Geneva Revolution of 1782, an attempt to win representation in the government for men of modest means. In 1798, revolutionary France under the Directory annexed Geneva. At the end of the Napoleonic Wars, on 1 June 1814, Geneva was admitted to the Swiss Confederation. In 1907, the separation of Church and State was adopted. Geneva flourished in the 19th and 20th centuries, becoming the seat of many international organizations. Geneva is located at 46°12' North, 6°09' East, at the south-western end of Lake Geneva, where the Rhône flows out, it is surrounded by three mountain chains, each belonging to the Jura: the Jura main range lies north-westward, the Vuache southward, the Salève south-eastward. The city covers an area of 15.93 km2, while the area of the canton is 282 km2, including the two small exclaves of Céligny in Vaud.
The part of the lake, attached to Geneva has an area of 38 km2 and is sometimes referred to as petit lac. The canton has only a 4.5-kilometre-long border with the rest of Switzerland. Of 107.5 km of border, 103 are shared with France, the Département de l'Ain to the north and west and the Département de la Haute-Savoie to the south and east. Of the land in the city, 0.24 km2, or 1.5%, is used for agricultural purposes, while 0.5 km2, or 3.1%, is forested. The rest of the land, 14.63 km2, or 91.8%, is built up, 0.49 km2, or 3.1%, is either rivers or lakes and 0.02 km2, or 0.1%, is wasteland. Of the built up area, industrial buildings made up 3.4%, housing and buildings made up 46.2% and transportation infrastructure 25.8%, while parks, green belts and sports fields made up 15.7%. Of the agricultural land, 0.3% is used for growing crops. Of the water in the municipality, 0.2 % is composed of lakes and 2.9 % streams. The altitude of Geneva is 373.6 metres, corresponds to the altitude of