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
Russia the Russian Federation, is a transcontinental country in Eastern Europe and North Asia. At 17,125,200 square kilometres, Russia is by far or by a considerable margin the largest country in the world by area, covering more than one-eighth of the Earth's inhabited land area, the ninth most populous, with about 146.77 million people as of 2019, including Crimea. About 77 % of the population live in the European part of the country. Russia's capital, Moscow, is one of the largest cities in the world and the second largest city in Europe. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a wide range of environments and landforms. From northwest to southeast, Russia shares land borders with Norway, Estonia, Latvia and Poland, Ukraine, Azerbaijan, China and North Korea, it shares maritime borders with Japan by the Sea of Okhotsk and the U. S. state of Alaska across the Bering Strait. However, Russia recognises two more countries that border it, Abkhazia and South Ossetia, both of which are internationally recognized as parts of Georgia.
The East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, the medieval state of Rus arose in the 9th century. In 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus' disintegrated into a number of smaller states; the Grand Duchy of Moscow reunified the surrounding Russian principalities and achieved independence from the Golden Horde. By the 18th century, the nation had expanded through conquest and exploration to become the Russian Empire, the third largest empire in history, stretching from Poland on the west to Alaska on the east. Following the Russian Revolution, the Russian Soviet Federative Socialist Republic became the largest and leading constituent of the Union of Soviet Socialist Republics, the world's first constitutionally socialist state; the Soviet Union played a decisive role in the Allied victory in World War II, emerged as a recognized superpower and rival to the United States during the Cold War.
The Soviet era saw some of the most significant technological achievements of the 20th century, including the world's first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the world's second largest economy, largest standing military in the world and the largest stockpile of weapons of mass destruction. Following the dissolution of the Soviet Union in 1991, twelve independent republics emerged from the USSR: Russia, Belarus, Uzbekistan, Azerbaijan, Kyrgyzstan, Tajikistan and the Baltic states regained independence: Estonia, Lithuania, it is governed as a federal semi-presidential republic. Russia's economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2018. Russia's extensive mineral and energy resources are the largest such reserves in the world, making it one of the leading producers of oil and natural gas globally; the country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction.
Russia is a great power as well as a regional power and has been characterised as a potential superpower. It is a permanent member of the United Nations Security Council and an active global partner of ASEAN, as well as a member of the Shanghai Cooperation Organisation, the G20, the Council of Europe, the Asia-Pacific Economic Cooperation, the Organization for Security and Co-operation in Europe, the World Trade Organization, as well as being the leading member of the Commonwealth of Independent States, the Collective Security Treaty Organization and one of the five members of the Eurasian Economic Union, along with Armenia, Belarus and Kyrgyzstan; the name Russia is derived from Rus', a medieval state populated by the East Slavs. However, this proper name became more prominent in the history, the country was called by its inhabitants "Русская Земля", which can be translated as "Russian Land" or "Land of Rus'". In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus' by modern historiography.
The name Rus itself comes from the early medieval Rus' people, Swedish merchants and warriors who relocated from across the Baltic Sea and founded a state centered on Novgorod that became Kievan Rus. An old Latin version of the name Rus' was Ruthenia applied to the western and southern regions of Rus' that were adjacent to Catholic Europe; the current name of the country, Россия, comes from the Byzantine Greek designation of the Rus', Ρωσσία Rossía—spelled Ρωσία in Modern Greek. The standard way to refer to citizens of Russia is rossiyane in Russian. There are two Russian words which are commonly
The Diamond Fund is a unique collection of gems and natural nuggets, which are stored and exhibited in the Kremlin Armoury in Russia. The Fund was opened in 1967 and its collection dates back to the Russian Crown treasury instituted by Emperor Peter I of Russia in 1719, it is a part of Moscow Kremlin Museums. The gem collection of Peter I, established in 1719, was stored in the Diamond Chamber in the Winter Palace. All succeeding monarchs added their contributions to the Chamber. A 1922 study by Alexander Fersman identified 85% of all exhibits to be from 1719–1855, to emperors Peter I through Nicholas I, only 15% attributed from the last three emperors. Catherine the Great exhibited a particular interest for expensive rocks naming her stallion "Diamond." The Diamond Fund received the most contributions from her than any other monarch. Preservation and looting of Imperial treasures after the Russian Revolution of 1917 are a matter of controversy and speculation; the Imperial collection was moved from Saint Petersburg to Moscow during World War I.
The treasure was first exhibited to the public in November 1967. A short-term show, it became a permanent exhibition in 1968. During the late Soviet period, the value of the Fund's collection was estimated to be $7 billion; the Russian State retains the monopoly for mining and distribution of gemstones, as set by the 1998 law "On precious metals and precious stones". Diamond Fund operations are regulated by the 1999 presidential decree; the Diamond Fund is part of a larger State Fund of Precious Stones, managed by the Ministry of Finance, accumulates the most valuable items, in particular All raw diamonds exceeding 50 carats All cut diamonds exceeding 20 carats, cut diamonds of exceptional quality exceeding 6 carats All raw emeralds, sapphires exceeding 30 carats raw or 20 carats cut Unique nuggets, amber and jewellery 2006 – "The Creator", mined in Yakutia in 2004. Third largest raw diamond in the Fund, 298.48 carats 2003 – golden nugget, 33 kg 1989 – "Alexander Pushkin", second-largest raw diamond, 320.65 carats 1980 – "XXVI Congress of CPSU", largest raw diamond, 342.57 carats Orlov diamond, 189.62 carats Shah diamond, 88.7 carats, first inscription dated 1591, a gift from the Shah of Persia in 1829 Flat portrait diamond, 25 carats Red spinel, set in the Imperial Crown of Russia, 398.72 carats, purchased in China in 1676 Sapphire, 260.37 carats Colombian emerald, 136.25 carats Olive-green chrysolite, 192.6 carats Imperial Crown of Russia made for Catherine II, 1762 The Daffodil Bouquet The Blue Fountain "The Great Triangle", gold, 36.2 kg "The Camel", gold, 9.28 kg "Mephisto", gold, 20.25 g The Diamond Fund is exhibited in the Kremlin Armoury building.
For visitors, it is accessible only through tours of fixed duration due to the limited space inside the Fund. Tours in Russian are organized daily, at twenty-minute intervals. Foreign visitors can receive an audioguide in English, French, Italian, Chinese or Japanese. List of diamonds Alrosa Pink diamond Official website of the Diamond Fund Information for visitors History of the Diamond Fund from the Alexander Palace website
The Republic of Sakha is a federal Russian republic. It had a population of 958,528 at the 2010 Census ethnic Yakuts and Russians. Comprising half the Far Eastern Federal District, it is the largest subnational governing body by area in the world at 3,083,523 square kilometers, its capital is the city of Yakutsk. It is known for its extreme and severe climate, with the lowest temperatures in the Northern Hemisphere being recorded in Verkhoyansk and Delyankir, regular winter averages being below −35 °C in Yakutsk; the hypercontinental tendencies result in warm summers for much of the republic. Borders: internal: Chukotka Autonomous Okrug, Magadan Oblast, Khabarovsk Krai, Amur Oblast, Zabaykalsky Krai, Irkutsk Oblast, Krasnoyarsk Krai. Water: Arctic Ocean. Highest point: Peak Pobeda, Mus-Khaya Mountain Peak Maximum N->S distance: 2,500 km Maximum E->W distance: 2,000 km Sakha stretches to the Henrietta Island in the far north and is washed by the Laptev and Eastern Siberian Seas of the Arctic Ocean.
These waters, the coldest and iciest of all seas in the Northern Hemisphere, are covered by ice for 9–10 months of the year. New Siberian Islands are a part of the republic's territory. After Nunavut was separated from Canada's Northwest Territories, Sakha became the largest subnational entity in the world, with an area of 3,083,523 square kilometers smaller than the territory of India. Sakha can be divided into three great vegetation belts. About 40% of Sakha lies above the Arctic circle and all of it is covered by permafrost which influences the region's ecology and limits forests in the southern region. Arctic and subarctic tundra define the middle region, where lichen and moss grow as great green carpets and are favorite pastures for reindeer. In the southern part of the tundra belt, scattered stands of dwarf Siberian pine and larch grow along the rivers. Below the tundra is the vast taiga forest region. Larch trees dominate in the north and stands of fir and pine begin to appear in the south.
Taiga forests cover about 47% of Sakha and 90% of the cover is larch. The Sakha Republic is the site of Pleistocene Park, a project directed at recreating Pleistocene tundra grasslands by stimulating the growth of grass with the introduction of animals which thrived in the region during the late Pleistocene — early Holocene period. Sakha Republic is the only subject of Russia. Sakha spans three time zones: Yakutsk Time Zone. Covers the republic's territory to the west of the Lena River as well as the territories of the districts located on both sides of the Lena River. Vladivostok Time Zone. Covers most of the republic's territory located between 140 ° E longitude. Districts: Oymyakonsky, Ust-Yansky, Verkhoyansky. Magadan Time Zone. Covers most of the republic's territory located east of 140°E longitude. Districts: Abyysky, Momsky, Srednekolymsky, Verkhnekolymsky. Navigable Lena River, as it moves northward, includes hundreds of small tributaries located in the Verkhoyansk Range. Other major rivers include: Vilyuy River Lena River tributary Olenyok River Aldan River Lena River tributary Kolyma River Indigirka River Alazeya River Amga River Aldan River tributary Olyokma River Lena River tributary Markha River Vilyuy River tributary Tyung River Vilyuy River tributary Maya River Aldan River tributary Anabar River Yana River Morkoka River Markha River tributary Uchur River Aldan River tributary Linde River Lena River tributary Nyuya River Lena River tributary Selennyakh River Indigirka River tributary There are over 800,000 lakes in the republic.
Major lakes and reservoirs include: Lake Mogotoyevo Lake Nedzheli Lake Nerpichye Vilyuyskoye Reservoir Sakha's greatest mountain range, the Verkhoyansk Range, runs parallel and east of the Lena River, forming a great arc that begins in the Sea of Okhotsk and ends in the Laptev Sea. The Chersky Range has the highest peak in Sakha, Peak Pobeda; the second highest peak is Peak Mus-Khaya reaching 3,011 m. The Stanovoi Range borders Sakha in the south; the Republic's extensive coastline contains a number of peninsulas. The soil contains large reserves of oil, coal, gold, tin and many others. Sakha p
The Moscow Kremlin, or the Kremlin, is a fortified complex in the center of Moscow, overlooking the Moskva River to the south, Saint Basil's Cathedral and Red Square to the east, the Alexander Garden to the west. It is the best known of the kremlins and includes five palaces, four cathedrals, the enclosing Kremlin Wall with Kremlin towers. In addition, within this complex is the Grand Kremlin Palace, the Tsar's Moscow residence; the complex now serves as the official residence of the President of the Russian Federation and as a museum with 2,746,405 visitors in 2017. The name "Kremlin" means "fortress inside a city", is also used metonymically to refer to the government of the Russian Federation in a similar sense to how "White House" refers to the Executive Office of the President of the United States, it referred to the government of the Soviet Union and its highest members. The term "Kremlinology" refers to the study of Russian politics; the site had been continuously inhabited by Finno-Ugric peoples since the 2nd century BC.
The Slavs occupied the south-western portion of Borovitsky Hill as early as the 11th century, as evidenced by a metropolitan seal from the 1090s, unearthed by Soviet archaeologists in the area. The Vyatichi built a fortified structure on the hill where the Neglinnaya River flowed into the Moskva River. Up to the 14th century, the site was known as the'grad of Moscow'; the word "Kremlin" was first recorded in 1331. The grad was extended by Prince Yuri Dolgorukiy in 1156, destroyed by the Mongols in 1237 and rebuilt in oak in 1339. Dmitri Donskoi replaced the oak walls with a strong citadel of white limestone in 1366–1368 on the basic foundations of the current walls. Dmitri's son Vasily I resumed construction of cloisters in the Kremlin; the newly built Cathedral of the Annunciation was painted by Theophanes the Greek, Andrei Rublev, Prokhor in 1406. The Chudov Monastery was founded by Metropolitan Alexis. Grand Prince Ivan III organised the reconstruction of the Kremlin, inviting a number of skilled architects from Renaissance Italy, including Petrus Antonius Solarius, who designed the new Kremlin wall and its towers, Marcus Ruffus who designed the new palace for the prince.
It was during his reign that three extant cathedrals of the Kremlin, the Deposition Church, the Palace of Facets were constructed. The highest building of the city and Muscovite Russia was the Ivan the Great Bell Tower, built in 1505–08 and augmented to its present height in 1600; the Kremlin walls as they now appear were built between 1485 and 1495. Spasskie gates of the wall still bear a dedication in Latin praising Petrus Antonius Solarius for the design. After construction of the new kremlin walls and churches was complete, the monarch decreed that no structures should be built in the immediate vicinity of the citadel; the Kremlin was separated from the walled merchant town by a 30-meter-wide moat, over which Saint Basil's Cathedral was constructed during the reign of Ivan the Terrible. The same tsar renovated some of his grandfather's palaces, added a new palace and cathedral for his sons, endowed the Trinity metochion inside the Kremlin; the metochion was administrated by the Trinity Monastery and contained the graceful tower church of St. Sergius, described by foreigners as one of the finest in the country.
During the Time of Troubles, the Kremlin was held by the Polish forces for two years, between 21 September 1610 and 26 October 1612. The Kremlin's liberation by the volunteer army of prince Dmitry Pozharsky and Kuzma Minin paved the way for the election of Mikhail Romanov as the new tsar. During his reign and that of his son Alexis and grandson Feodor, the eleven-domed Upper Saviour Cathedral, Armorial Gate, Terem Palace, Amusement Palace and the palace of Patriarch Nikon were built. Following the death of Alexis's son and the Moscow Uprising of 1682, Tsar Peter escaped with much difficulty from the Kremlin and as a result developed a dislike for it. Three decades Peter abandoned the residence of his forefathers for his new capital, Saint Petersburg. Although still used for coronation ceremonies, the Kremlin was abandoned and neglected until 1773, when Catherine the Great engaged Vasili Bazhenov to build her new residence there. Bazhenov produced a bombastic Neoclassical design on a heroic scale, which involved the demolition of several churches and palaces, as well as a portion of the Kremlin wall.
After the preparations were over, construction was delayed due to lack of funds. Several years the architect Matvey Kazakov supervised the reconstruction of the dismantled sections of the wall and of some structures of the Chudov Monastery, built the spacious and luxurious Offices of the Senate, since adapted for use as the principal workplace of the President of Russia. During the Imperial period, from the early 18th and until the late 19th century, the Kremlin walls were traditionally painted white, in accordance with fashion. French forces occupied the Kremlin from 2 September to 11 October 1812, following the French invasion of Russia; when Napoleon retreated from Moscow, he ordered the whole Kremlin to be blown up. The Kremlin Arsenal, several portions of the Kremlin Wall and several wall towers were destroyed by explosions and the Faceted Chamber and other churches were damaged by fire. Explosions continued for
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 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