Brazil the Federative Republic of Brazil, is the largest country in both South America and Latin America. At 8.5 million square kilometers and with over 208 million people, Brazil is the world's fifth-largest country by area and the fifth most populous. Its capital is Brasília, its most populated city is São Paulo; the federation is composed of the union of the 26 states, the Federal District, the 5,570 municipalities. It is the largest country to have Portuguese as an official language and the only one in the Americas. Bounded by the Atlantic Ocean on the east, Brazil has a coastline of 7,491 kilometers, it borders all other South American countries except Ecuador and Chile and covers 47.3% of the continent's land area. Its Amazon River basin includes a vast tropical forest, home to diverse wildlife, a variety of ecological systems, extensive natural resources spanning numerous protected habitats; this unique environmental heritage makes Brazil one of 17 megadiverse countries, is the subject of significant global interest and debate regarding deforestation and environmental protection.
Brazil was inhabited by numerous tribal nations prior to the landing in 1500 of explorer Pedro Álvares Cabral, who claimed the area for the Portuguese Empire. Brazil remained a Portuguese colony until 1808, when the capital of the empire was transferred from Lisbon to Rio de Janeiro. In 1815, the colony was elevated to the rank of kingdom upon the formation of the United Kingdom of Portugal and the Algarves. Independence was achieved in 1822 with the creation of the Empire of Brazil, a unitary state governed under a constitutional monarchy and a parliamentary system; the ratification of the first constitution in 1824 led to the formation of a bicameral legislature, now called the National Congress. The country became a presidential republic in 1889 following a military coup d'état. An authoritarian military junta came to power in 1964 and ruled until 1985, after which civilian governance resumed. Brazil's current constitution, formulated in 1988, defines it as a democratic federal republic. Due to its rich culture and history, the country ranks thirteenth in the world by number of UNESCO World Heritage Sites.
Brazil is considered an advanced emerging economy. It has the ninth largest GDP in the world by nominal, eight and PPP measures, it is one of the world's major breadbaskets, being the largest producer of coffee for the last 150 years. It is classified as an upper-middle income economy by the World Bank and a newly industrialized country, with the largest share of global wealth in Latin America. Brazil is a regional power and sometimes considered a great or a middle power in international affairs. On account of its international recognition and influence, the country is subsequently classified as an emerging power and a potential superpower by several analysts. Brazil is a founding member of the United Nations, the G20, BRICS, Union of South American Nations, Organization of American States, Organization of Ibero-American States and the Community of Portuguese Language Countries, it is that the word "Brazil" comes from the Portuguese word for brazilwood, a tree that once grew plentifully along the Brazilian coast.
In Portuguese, brazilwood is called pau-brasil, with the word brasil given the etymology "red like an ember", formed from brasa and the suffix -il. As brazilwood produces a deep red dye, it was valued by the European textile industry and was the earliest commercially exploited product from Brazil. Throughout the 16th century, massive amounts of brazilwood were harvested by indigenous peoples along the Brazilian coast, who sold the timber to European traders in return for assorted European consumer goods; the official Portuguese name of the land, in original Portuguese records, was the "Land of the Holy Cross", but European sailors and merchants called it the "Land of Brazil" because of the brazilwood trade. The popular appellation eclipsed and supplanted the official Portuguese name; some early sailors called it the "Land of Parrots". In the Guarani language, an official language of Paraguay, Brazil is called "Pindorama"; this was the name the indigenous population gave to the region, meaning "land of the palm trees".
Some of the earliest human remains found in the Americas, Luzia Woman, were found in the area of Pedro Leopoldo, Minas Gerais and provide evidence of human habitation going back at least 11,000 years. The earliest pottery found in the Western Hemisphere was excavated in the Amazon basin of Brazil and radiocarbon dated to 8,000 years ago; the pottery was found near Santarém and provides evidence that the tropical forest region supported a complex prehistoric culture. The Marajoara culture flourished on Marajó in the Amazon delta from 800 CE to 1400 CE, developing sophisticated pottery, social stratification, large populations, mound building, complex social formations such as chiefdoms. Around the time of the Portuguese arrival, the territory of current day Brazil had an estimated indigenous population of 7 million people semi-nomadic who subsisted on hunting, fishing and migrant agriculture; the indigenous population of Brazil comprised several large indigenous ethnic groups. The Tupí people were subdivided into the Tupiniquins and Tupinambás, there were many subdivisions of the other gro
Haaretz is an Israeli newspaper. It was founded in 1918, making it the longest running newspaper in print in Israel, is now published in both Hebrew and English in the Berliner format; the English edition is sold together with the International New York Times. Both Hebrew and English editions can be read on the Internet. In North America, it is published as a weekly newspaper, combining articles from the Friday edition with a roundup from the rest of the week, it is known for its liberal stances on domestic and foreign issues. As of 2016, the newspaper had a weekday exposure rate of 3.9% in Israel. According to the Center for Research Libraries, among Israel's daily newspapers, "Haaretz is considered the most influential and respected for both its news coverage and its commentary." Haaretz was first published in 1918 as a newspaper sponsored by the British military government in Palestine. In 1919, it was taken over by a group of socialist-oriented Zionists from Russia; the newspaper was established on 18 June 1919 by a group of businessmen including the philanthropist Isaac Leib Goldberg, it was called Hadashot Ha'aretz.
The name was shortened to Haaretz. The literary section of the paper attracted leading Hebrew writers of the time; the newspaper was published in Jerusalem. From 1919 to 1922, the paper was headed among them Leib Yaffe, it was closed due to a budgetary shortfall and reopened in Tel Aviv at the beginning of 1923 under the editorship of Moshe Glickson, who held the post for 15 years. The Tel Aviv municipality granted the paper financial support by paying in advance for future advertisements. Salman Schocken, a Jewish businessman who left Germany in 1934 after the Nazis had come to power, bought the paper in December 1935. Schocken was active in Brit Shalom known as the Jewish–Palestinian Peace Alliance, a body supporting co-existence between Jews and Arabs, sympathetic to a homeland for both peoples, his son, Gershom Schocken, became the chief editor in 1939 and held that position until his death in 1990. The Schocken family were the sole owners of the Haaretz Group until August 2006, when they sold a 25% stake to German publisher M. DuMont Schauberg.
The deal was negotiated with the help of the former Israeli ambassador to Avi Primor. This deal was seen as controversial in Israel as DuMont Schauberg's father, Kurt Neven DuMont, was member of the Nazi party and his publishing house promoted Nazi ideology. On 12 June 2011, it was announced that Russian-Israeli businessman Leonid Nevzlin had purchased a 20% stake in the Haaretz Group, buying 15% from the family and 5% from M. DuMont Schauberg. In October 2012, a union strike mobilized to protest planned layoffs by the Haaretz management, causing a one-day interruption of Haaretz and its TheMarker business supplement. According to Israel Radio, it was the first time since 1965 that a newspaper did not go to press on account of a strike; the newspaper's editorial policy was defined by Gershom Schocken, editor-in-chief from 1939 to 1990. Schocken was succeeded as editor-in-chief by Hanoch Marmari. In 2004 David Landau replaced Marmari and was succeeded by Dov Alfon in 2008; the current editor-in-chief of the newspaper is Aluf Benn, who replaced Alfon in August 2011.
Charlotte Halle became editor of the English print edition in February 2008. Haaretz describes itself as having "a broadly liberal outlook both on domestic issues and on international affairs". Others describe it alternatively centre-left, or left-wing; the newspaper opposes retaining control of the territories and supports peace initiatives. The Haaretz editorial line is supportive of weaker elements in Israeli society, such as sex workers, foreign laborers, Israeli Arabs, Ethiopian immigrants, Russian immigrants. In 2006, the BBC said that Haaretz takes a moderate stance on foreign security. David Remnick in The New Yorker described Haaretz as "easily the most liberal newspaper in Israel", its ideology as left-wing and its temper as "insistently oppositional". According to Ira Sharkansky, Haaretz's op-ed pages are open to a variety of opinions. J. J. Goldberg, the editor of the American The Jewish Daily Forward, describes Haaretz as "Israel's most vehemently anti-settlement daily paper". Stephen Glain of The Nation described Haaretz as "Israel's liberal beacon", citing its editorials voicing opposition to the occupation, the discriminatory treatment of Arab citizens, the mindset that led to the Second Lebanon War.
A 2003 study in The International Journal of Press/Politics concluded that Haaretz's reporting of the Israeli–Palestinian conflict was more favorable to Israelis than to Palestinians, but less so than that of The New York Times. In 2016, Jeffrey Goldberg, the editor-in-chief of The Atlantic, wrote "I like a lot of the people at Haaretz, many of its positions, but the cartoonish anti-Israelism and anti-Semitism can be grating". In 2016, the newspaper's readership fell to an all-time low of 3.9% on weekdays, far behind other national newspapers in Israel: Israel Hayom had an exposure rate of 39.7%, Yedioth Ahronoth 34.9%, Israel Post 7.2%, Globes 4.6%. Haaretz uses smaller headlines and print than other mass circulation papers in Israel. Less space is devoted to pictures, more to political analysis. Opinion columns are written by regular commentators rather than guest writers, its editorial pages are considered influential among government leaders. Apart from the news, Haaretz publishes feature articles on social and environmental issues, as well as book reviews, investigat
William Goldberg (diamond dealer)
William Goldberg was an American diamond dealer and the founder of the William Goldberg Diamond Corporation. Goldberg was born in New York City, he started cutting diamonds in 1948, but found that his aptitude lay with buying and selling diamonds rather than cutting them. In 1952 he founded Weiss with diamond cutter Irving Weiss. In 1973 he formed the William Goldberg Diamond Corporation, located on 48th Street in New York City's Diamond District. In 1978 he served three terms, he traded well known diamonds including the Queen of Holland diamond, the Premier Rose diamond, the Red Shield diamond and the Pumpkin diamond. He died of pancreatic cancer, aged 77. Following his death, members of Goldberg's family created the William Goldberg Endowed Scholarship Fund at the Gemological Institute of America
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
Shlomo Moussaieff (businessman)
Shlomo Moussaieff was an Israeli jeweler, of Bukharan Jewish descent, the grandson of the wealthy gemstone trader Rabbi Moussaieff from Uzbekistan. Founder of Moussaieff Jewellers Ltd. he and his wife and business partner, were ranked No. 315 on the Sunday Times Rich List 2011, with a fortune estimated at £220 million. Moussaieff produced precious jewellery for international royalty and high society, including Western royalty as well as those from Saudi Arabia and Persian Gulf states, he spoke Arabic fluently. In addition, Moussaieff was regarded as one of the world's top private collectors of antiquities associated with the Bible and ancient Near East, with a collection of 60,000 artefacts. Shlomo Moussaieff was the second of 12 children of Rehavia Moussaieff, a Jerusalem-born jewellery dealer, he was named after his grandfather, Shlomo Moussaieff, a wealthy Bukharan merchant, one of the founders of the Bukharim neighbourhood in Jerusalem in 1891. Rehavia, who traded in fine gems in Paris, introduced Shlomo to the jewellery trade at a young age.
Shlomo's youngest brother, Alon became a Jerusalem jewellery dealer. Several of his sisters own jewellery stores: Hannah in Jerusalem's King David Hotel, Naomi in London and Aviva in Geneva, his father, a strict disciplinarian, threw him out of the house at the age of 12 because he refused to apply himself to his studies. Moussaieff claims he was unable to read and write, he began sleeping in synagogues and the street, worked for a carpenter in Sanhedria. After hours, he hung around the Second Temple-era Tombs of the Sanhedrin in the nearby park. Inside the caves, which were open to the public, he discovered ancient coins that he sold to traders, he carved up lead coffins and sold the lead in the Armenian Quarter. Apprehended and beaten by an Arab policeman, he was brought before an Arab judge and sentenced to nine months in a reform school in Tulkarm, he asked to learn in a madrassa, where he found it easy to learn the Koran by heart, became familiar with Arab culture. In 1940 Moussaieff joined the Etzel.
Upon the recommendation of his Etzel leader, he joined the British Army at age 17 to fight Nazi Germany during World War II. Stationed in the Egyptian desert and Livorno, Italy, he searched through synagogue genizot during his free time and bought old Kabbalah manuscripts and marriage contracts written by well-known rabbis. In 1947 he rejoined the Etzel to battle the Arab Legion in the Old City of Jerusalem; when the city fell to the Jordanians in 1948, he was taken captive and imprisoned for one year in Transjordan. He married Alisa, an Austrian native, two weeks before he went into captivity. After his release, Moussaieff worked in his family's jewellery store and opened his own antique jewellery shop in downtown Jerusalem, he supplemented his income by smuggling "gold and antiquities from Jordan to Israel" in the 1950s. During this time he came in contact with Moshe Dayan, another confirmed antiquities smuggler, provided Dayan with artefacts in exchange for the use of Dayan's car for transporting smuggled goods.
In 1954 he was detained under suspicion of stealing 1,000 coins and other antiquities from the Hebrew University of Jerusalem. Moussaieff claimed he would not disclose the seller, he was released. In 1963 he moved to London and opened his first jewellery shop in the lobby of the London Hilton on Park Lane, he opened another store on London's Bond Street. Sales increased in 1967 when wealthy Arabs from Saudi Arabia and the Persian Gulf began to buy jewelry in London, he and his wife operated the business in partnership. In addition to diamonds, coloured gemstones, natural pearls, Moussaieff re-set stones and pearls that he acquired at antique jewellery auctions into new jewellery designs. Today Moussaieff Jewellers Ltd. has two London stores and a shop at the Grand Hotel Kempinski Geneve in Switzerland. Moussaieff's clients included government figures such as Imelda Marcos and Princess Ashraf and Princess Shams of Iran, celebrities such as, Richard Burton, Elizabeth Taylor, Stavros Niarchos, Zsa Zsa Gabor, Joan Collins, Bob Cummings, Shirley MacLaine, George Raft, Peter Sellers and Frank Sinatra.
In the late 1990s he developed a following among affluent Israelis. Moussaieff's collection included rare stones such as the Moussaieff Blue Diamond, a flawless 6.04 carat stone that Alisa purchased at a 2007 Sotheby's auction in Hong Kong for $7.98 million, setting a world record in price per carat, with a final bid of $1.32 million per carat. The Moussaieff Red Diamond, a trilliant cut, 5.11 carat red diamond purchased in 2001 or 2002, is the world's largest known red diamond. Moussaieff retired from the business in 2004 while his wife continued to oversee sales and acquisitions. Moussaieff was regarded as one of the foremost private collectors of antiquities of the Bible and ancient Near East. According to his own estimate, he owned 60,000 artefacts, specialising in ancient manuscripts and personal seals from the First and Second Temple periods. Since he was willing to pay large sums for antiquities that proved the historical authenticity of the Bible, antiquities experts believe that some fakes and forgeries crept into in his collection.
In 2004 Moussaieff testified as a victim in a forgery trial involving the James Ossuary and the Jehoash Inscription. Moussaieff had bought two ostracons from one of the defendants in the trial. In March 2012 the defendants were acquitted of the forg
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
Brilliant (diamond cut)
A brilliant is a diamond or other gemstone cut in a particular form with numerous facets so as to have exceptional brilliance. The shape resembles that of a cone and provides maximized light return through the top of the diamond. With modern techniques, the cutting and polishing of a diamond crystal always results in a dramatic loss of weight; the round brilliant cut is preferred when the crystal is an octahedron, as two stones may be cut from one such crystal. Oddly shaped crystals such as macles are more to be cut in a fancy cut—that is, a cut other than the round brilliant—which the particular crystal shape lends itself to; the original round brilliant-cut was developed by Marcel Tolkowsky in 1919. The modern round brilliant consists of 58 facets, ordinarily today cut in two pyramids placed base to base: 33 on the crown, truncated comparatively near its base by the table, 25 on the pavilion, which has only the apex cut off to form the culet, around which 8 extra facets are sometimes added.
In recent decades, most girdles are faceted. Many girdles have 64, 80, or 96 facets. While the facet count is standard, the actual proportions are not universally agreed upon; some gem cutters refer to a Scandinavian brilliant cut. Quoting Green et al. 2001: Because every facet has the potential to change a light ray's plane of travel, every facet must be considered in any complete calculation of light paths. Just as a two-dimensional slice of a diamond provides incomplete information about the three-dimensional nature of light behavior inside a diamond, this two-dimensional slice provides incomplete information about light behavior outside the diamond. A diamond's panorama is three-dimensional. Although diamonds are symmetrical, light can enter a diamond from many directions and many angles; this factor further highlights the need to reevaluate Tolkowsky's results, to recalculate the effects of a diamond's proportions on its appearance aspects. Another important point to consider is that Tolkowsky did not follow the path of a ray, reflected more than twice in the diamond.
However, we now know that a diamond's appearance is composed of many light paths that reflect more than two times within that diamond. Once again, we can see that Tolkowsky's predictions are helpful in explaining optimal diamond performance, but they are incomplete by today's technological standards. Figures 1 and 2 show the facets of a round brilliant diamond. Figure 1 assumes that the "thick part of the girdle" is the same thickness at all 16 "thick parts", it does not consider the effects of indexed upper girdle facets. Figure 2 is adapted from Figure 37 of Marcel Tolkowsky's Diamond Design, published in 1919. Since 1919, the lower girdle facets have become longer; as a result, the pavilion main facets have become narrower. The relationship between the crown angle and the pavilion angle has the greatest effect on the look of the diamond. A steep pavilion angle can sometimes be complemented by a shallower crown angle, vice versa. Other proportions affect the look of the diamond: The table ratio is significant.
The length of the lower girdle facets affects whether Hearts and arrows can be seen in the stone, under certain viewers. Most round brilliant diamonds have the same girdle thickness at all 16 "thick parts". So-called "cheated" girdles have thicker girdles where the main facets touch the girdle than where adjacent upper girdle facets touch the girdle; these stones weigh more, have worse optical performance. So-called "painted" girdles have thinner girdles where the main facets touch the girdle than where adjacent upper girdle facets touch the girdle; these stones have less light leakage at the edge of the stone. Some diamonds with painted girdles receive lower grades in the GIA's cut grading system, for reasons given in a 2005 GIA article. Several groups have developed diamond cut grading standards, they all disagree somewhat on. There are certain proportions; the AGA standards may be the strictest. David Atlas has suggested; the HCA changed several times between 2001 and 2004. As of 2004, an HCA score below two represented an excellent cut.
The HCA distinguishes between brilliant and fiery cuts. The American Gem Society standards changed in 2005 to better match Tolkowsky's model and Octonus' ray tracing results; the 2005 AGS standards penalize stones with "cheated" girdles. They grade from 0 to 10; the GIA began grading cut on every grading report beginning 2006 based on their comprehensive study of 20,000 proportions with 70,000 observations of 2,000 diamonds. The single descriptive words are as follows: Excellent, Very Good, Good and Poor; the distance from the viewer's eye to the diamond is important. The 2005 AGS cut standards are based on a distance of 25 centimeters; the 2004 HCA cut standards are based on a distance of 40 centimeters. Polish and symmetry are two important aspects of the cut; the polish grade describes the smoothness of the diamond's facets, the symmetry grade refers to alignment of the facets. With