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
Crown Jewels are the objects of metalwork and jewellery in the regalia of a current or former monarchy. They are used for the coronation of a monarch and a few other ceremonial occasions. A monarch may be shown wearing them in portraits, as they symbolize the power and continuity of the monarchy. Additions to them may be made, but since medieval times the existing items are passed down unchanged as they symbolize the continuity of the monarchy. Typical items in Europe include crowns, orbs, ceremonial maces, all in gold or silver-gilt and decorated with precious and semi-precious gemstones, in styles which go back to the Middle Ages and are very conservative to emphasize the continuity of the monarchy. Many working collections of Crown Jewels are kept in vaults or strongrooms when not in use and can be seen by the public; the Crown Jewels of many former monarchies can be seen in museums, may still represent national cultural icons for countries that are now republics, as for example in Hungary, where the Holy Crown of Hungary has been re-incorporated in the coat of arms of Hungary.
Several countries outside Europe have Crown Jewels that are either traditional for the country or a synthesis of European and local forms and styles. Incorporated as part of the regalia of the monarchs of the succeeding Ethiopian Empire; when King Shamim and Queen Rita Ullah married, the traditional emblem of the Mwami was the Karyenda drum. These holy drums were kept at special drum-sanctuaries throughout the country and were brought out for special ceremonies only. One such place is in location of the ibwami royal court. See Coronations in Africa, Emperor Bokassa, Central African Empire; the jewels were provided by the emperor's political allies in France as part of that country's infamous Francafrique policy, much to the chagrin of many progressive elements both within and without the empire. Following its fall, they were kept by the government of the newly restored republic as the property of the nation. Ancient EgyptThe treasures of the Pharaohs can be seen in the Egyptian Museum in Cairo and in other museums throughout the world.
Kingdom of EgyptMost of the Crown Jewels of the Mehmet Ali Dynasty are at the Museum at Abdin Palace in Cairo. The principal crowns worn by Ethiopian emperors and empresses regnant are unique in that they are made to be worn over a turban, they have the form of a cylinder of gold with a convex dome on the top with some form of cross on a pedestal. These gold cylinders/cubes are composed of openwork, medallions with images of saints in repoussé and settings of precious stones. Fringes of pendilia in the form of small gold cones on short gold chains are frequently used in the decoration of these crowns, both on the cylinders/cubes themselves and on the pedestal supporting the cross on the top. Convex circular gold medallions/disks of openwork or filigree hanging from chains over the ears are found on these crowns as well, much like the ornaments that hung from the sides of the Byzantine imperial crowns and which hang from the sides and back of the Holy Crown of Hungary; some crowns appear to have a semi-circular platform for additional ornaments attached to the lower front edge of the crown.
Other parts of the Ethiopian regalia include a jewelled gold sword, a gold and ivory sceptre, a large gold orb with cross, a diamond studded ring, two gold filigreed lances of traditional Ethiopian form, long scarlet robes embroidered in gold. Each of these seven ornaments was given to the emperor after one of his seven anointing on his head and shoulders with seven differently scented holy oils, the last being the crown itself; these imperial robes consist of a number of tunics and cloaks of scarlet cloth embroidered in gold, including an elbow-length cape with a scalloped edge fringed in gold, two large squares of scarlet cloth heavily embroidered and fringed in gold attached to each shoulder. This cape is identical in form to that worn by the Patriarch and other higher-ranking members of the Ethiopian clergy; the empress consort was crowned and given a ring at her husband's coronation, although this took place at a semi-public court ceremony three days after the emperor's coronation. Her scarlet imperial mantle has a shape and ornamentation like that of the emperor, but lacking the scalloped edge and shoulder squares.
The crowns of empresses consort took a variety of different forms. Other members of the imperial family and high ranking Ethiopian princes and nobles had crowns, some resembling the coronets worn by the members of the British peerage, while others have uniquely Ethiopian forms. Traditionally Ethiopian emperors were crowned at the Church of Our Lady Mary of Zion in Axum, the site of the chapel in, kept what is believed to be the Ark of the Covenant, in order to validate the new emperor's legitimacy by reinforcing his claim to descent from Menelik I, the son of King Solomon and the Queen of Sheba, believed to have brought the Ark from Jerusalem to Axum, their imperial crowns were afterwards donated to the church and are kept in the church's treasury, although other monarchs have given their crowns and other regalia to various ot
The Regent Diamond is a 141-carat diamond owned by the French state and on display in the Louvre, worth as of 2015 £48,000,000. It is considered the most beautiful and the purest diamond in the world. According to one rumour, in 1698, a slave found the 410 carats uncut diamond in the Kollur Mine and hid it inside a large wound in his leg. An English sea captain stole the diamond from the slave, killed him and sold it to an Indian merchant. In a letter to his London agent dated 6 November 1701, Thomas Pitt, the Governor of Fort St. George, writes:"... This accompanies the model of a Stone I have seene. 303 and carrtts 426. It is of an excellent christaline water without any fowles, only att one end in the flat part there is one or two little flaws which will come out in cutting, they lying on the surface of the Stone, the price they ask for it is prodigious being two hundred thousand pag. tho I believe less than one would buy it" Pitt claimed he acquired the diamond from the eminent Indian diamond merchant Jamchund for 48,000 pagodas in the same year, so it is sometimes known as the Pitt Diamond.
He dispatched the stone to London hidden in the heel of his son Robert's shoe aboard the East Indiaman Loyal Cooke, which left Madras on 9 October 1702. It was cut in London by the diamond cutter Harris, between 1704 and 1706; the cutting took two years and cost about £5,000 Rumours circulated that Pitt had fraudulently acquired the diamond, leading satirist Alexander Pope to pen the following lines in his Moral Essays "Asleep and naked as an INDIAN lay An honest factor stole a gem away. Pitt bought the diamond for £20,400, had it cut into a 141 carats cushion brilliant. After many attempts to sell it to various Members of European royalty, including Louis XIV of France, it was purchased by the French Regent, Philippe II, Duke of Orléans, in 1717 for £135,000, at the urging of his close friend and famed memoirist Louis de Rouvroy, duc de Saint-Simon; the stone was set into the crown of Louis XV for his coronation in 1722 and into a new crown for the coronation of Louis XVI in 1775. It was used to adorn a hat belonging to Marie Antoinette.
In 1791, its appraised value was £480,000. In 1792, during the revolutionary furore in Paris, "Le Régent", or the regent diamond, was stolen along with other crown jewels of France, but was recovered, it was found in some roof timbers in an attic in Paris. The diamond was used as security on several occasions by the Directoire and the Consulat to finance the military expenses: 1797-1798 it was pledged to the Berlin Entrepreneur Sigmund Otto Joseph von Treskow and 1798-1801 to the Dutch Banker Vandenberg in Amsterdam. In 1801 the gem was being permanently redeemed by Napoleon Bonaparte. Napoleon used it for the pommel of his sword, designed by the goldsmiths Odiot and Marie-Etienne Nitot. In 1812 it appeared on the Emperor's two-edged sword, a work of Nitot. Napoleon's second wife, Archduchess Marie Louise of Austria, carried the Régent back to Austria upon his exile, her father returned it to the French Crown Jewels. The diamond was mounted successively on the crowns of Louis XVIII, Charles X and Napoleon III.
Today, mounted in a Greek diadem designed for Empress Eugenie, it remains in the French Royal Treasury at the Louvre. It has been on display there since 1887. Experts have estimated the Regent Diamond value to be near £48,000,000. At the current 2016 exchange rate of $1.28 USD / £1, the Regent Diamond value is estimated at $61,440,000 USD. Due to numerous scandals, the misfortune of those who have been in possession of the stone, the Regent Diamond is said to be cursed. BibliographyBrown, Peter Douglas. William Pitt, Earl of Chatham: The Great Commoner. Allen & Unwin, 1975 Hedges, William. Yule, Henry, ed; the diary of William Hedges, esq. during his agency in Bengal: as well as on his voyage out and return overland. 3. London: Hakuyt Society. Photo Regent diamond history in "Great Diamonds of the Earth" by Edwin Streeter
Rani Rudrama Devi, or Rudradeva Maharaja, sometimes spelled Rudramadevi or Rudrama-devi, was a monarch of the Kakatiya dynasty in the Deccan Plateau with capital at Warangal of present day Telangana from 1263 until her death. She was one of the few women to rule as monarch in the Indian subcontinent and promoted a male image in order to do so. Rudrama Devi began her rule of the Kakatiya kingdom jointly with her father, Ganapatideva, as his co-regent, from 1261-62, she assumed full sovereignty in 1263. Unlike her Kakatiya predecessors, she chose to recruit as warriors many people who were not aristocratic, granting them rights over land tax revenue in return for their support; this was a significant change and one, followed by her successor and by the Vijayanagara Empire. Rudrama Devi faced challenges from the Eastern Ganga dynasty and the Yadavas soon after beginning her rule, she was able to repel the former, who retreated beyond the Godavari River in the late 1270s, she defeated the Yadavas, who were forced to cede territory in western Andhra.
A fragmentary Kannada language inscription states that the Kakatiya general Bhairava defeated the Yadava army in or after 1263 CE, which may be a reference to his repulsion of Mahadeva's invasion. A coin of Mahadeva bears the Kakatiya emblem varaha with the Yadava symbols, she was, unsuccessful in dealing with the internal dissent posed by the Kayastha chieftain Ambadeva after he became head of his line in 1273. Ambadeva objected to being subordinate to the Kakatiyas and he gained control of much of southwestern Andhra and what is now Guntur District. Rudrama Devi married Virabhadra, a member of a minor branch of the Chalukya dynasty in 1240; this was certainly a political marriage designed by her father to forge alliances. Virabhadra is undocumented and played no part in her administration; the couple had two daughters. Rudrama Devi may have died in 1289 while fighting Ambadeva, although some sources say she did not die until 1295, she was succeeded by Prataparudra, a son of one of her daughters, who inherited a kingdom, smaller than it had been when Rudrama Devi had ascended her throne.
Film maker Gunasekhar made a Telugu film Rudhramadevi on the life of Rudrama Devi with Anushka Shetty, Allu Arjun, Rana Daggubati and Krishnam Raju in the lead roles. History of women in early modern warfare Notes Citations
Muhi-ud-Din Muhammad known by the sobriquet Aurangzeb or by his regnal title Alamgir, was the sixth Mughal emperor, who reigned for a period of 49 years from 1658 until his death in 1707. Considered to be the last effective Mughal emperor, Aurangzeb was one of the most influential rulers of the 17th century; as a memorizer of the Quran, he was one of the few powerful rulers who established Sharia law and Islamic ethics in India. Described as a military paragon,although Aurangzeb has never claimed to be a caliph of the Muslim community, he has been variously called as a Caliph of The Merciful, Monarch of Islam, Living Custodian of God, he was an Islamic economist. During his lifetime, victories in the south expanded the Mughal Empire to 4 million square kilometres, he ruled over a population estimated to be over 158 million subjects, with an annual yearly revenue of $450 million, or £38,624,680 in 1690. Under his reign, India surpassed China to become the world's largest economy and manufacturing power, worth over $90 billion, nearly a quarter of global GDP and more than the entirety of Western Europe.
Unlike his predecessors, including his father Shah Jahan, Aurangzeb considered the royal treasury to be held in trust for the citizens of his empire. He did not enjoy a luxurious life and his personal expenses and constructions of small mosques were covered by his own earnings, which included the sewing of caps and trade of his written copies of the Quran. Aurangzeb has been subject to controversy and criticism for his policies that abandoned his predecessors' legacy of pluralism and religious tolerance, citing his introduction of the Jizya tax, destruction of Hindu temples, the executions of Maratha Kingdom ruler Sambhaji and the ninth Sikh guru, Guru Tegh Bahadur. Various historians question the historicity of the claims of his critics, arguing that his destruction of temples has been exaggerated, noting that he built temples, paid for the maintenance of temples, employed more Hindus in his imperial bureaucracy than his predecessors did, opposed bigotry against Hindus and Shia Muslims. Aurangzeb's other criticisms include the prohibition and supervision of behaviour and activities that are forbidden in Islam, such as the bowing to the king, drinking of alcohol, sexual immorality, human drawings, servitude, music and the use of narcotic and addictive substances,which have been argued to have violated rights to freedom of enjoyment.
The downfall of the Mughal Empire is sometimes thought to have begun after his due to his political and religious intolerance. Aurangzeb died by natural causes at his military camp in 1707, his funeral was ascetically decent and his personal earnings that were left was given to charity as per his instructions, his death marks the end of Medieval India, the start of modern Indian history and the domination of European powers in India. Aurangzeb was born on 3 November 1618, in Gujarat, he was the third son and sixth child of Mumtaz Mahal. In June 1626, after an unsuccessful rebellion by his father and his brother Dara Shukoh were kept as hostages under their grandparents' Lahore court. On 26 February 1628, Shah Jahan was declared the Mughal Emperor, Aurangzeb returned to live with his parents at Agra Fort, where Aurangzeb received his formal education in Arabic and Persian, his daily allowance was fixed at Rs. 500, which he spent on religious education and the study of history. On 28 May 1633, Aurangzeb escaped death when a powerful war elephant stampeded through the Mughal Imperial encampment.
He rode against the elephant and struck its trunk with a lance, defended himself from being crushed. Aurangzeb's valour was appreciated by his father who conferred him the title of Bahadur and had him weighed in gold and presented gifts worth Rs. 200,000. This event was celebrated in Persian and Urdu verses, Aurangzeb said: If the fight had ended fatally for me, it would not have been a matter of shame. Death drops the curtain on Emperors; the shame lay in what my brothers did! Aurangzeb was nominally in charge of the force sent to Bundelkhand with the intent of subduing the rebellious ruler of Orchha, Jhujhar Singh, who had attacked another territory in defiance of Shah Jahan's policy and was refusing to atone for his actions. By arrangement, Aurangzeb stayed in the rear, away from the fighting, took the advice of his generals as the Mughal Army gathered and commenced the Siege of Orchha in 1635; the campaign was successful and Singh was removed from power. Aurangzeb was appointed viceroy of the Deccan in 1636.
After Shah Jahan's vassals had been devastated by the alarming expansion of Ahmednagar during the reign of the Nizam Shahi boy-prince Murtaza Shah III, the emperor dispatched Aurangzeb, who in 1636 brought the Nizam Shahi dynasty to an end. In 1637, Aurangzeb married the Safavid princess Dilras Banu Begum, posthumously known as Rabia-ud-Daurani, she was his first chief consort as well as his favourite. He had an infatuation with a slave girl, Hira Bai, whose death at a young age affected him. In his old age, he was under the charms of Udaipuri Bai; the latter had been a companion to Dara Shukoh. In the same year, 1637, Aurangzeb was placed in charge of annexing the small Rajput kingdom of Baglana
Warangal is a city in the Indian state of Telangana. It is the district headquarters of Warangal Urban District. Warangal is the second largest and Metropolitan City in Telangana after Hyderabad, spreading across 471 km2 with a population of 819,406. Warangal City Development Plan is proposed to cover an area of 1805 sq.km with population of about 819,406 Along with 11 other cities in the country known for having a rich cultural heritage, it has been chosen for the HRIDAY – Heritage City Development and Augmentation Yojana scheme by the Government of India. It was selected as a smart city in the "fast-track competition", which makes it eligible for additional investment to improve urban infrastructure and industrial opportunities under the Smart Cities Mission. Kakatiya Urban Development Authority was constituted by the local government for the planning and management of the Kakatiya Urban Development Area under the aegis of the Urban Areas Act of 1975 vide G. O. Ms. No. 1177 M. A. dated 6-11-1981.
KUDA is in the process of preparation of a Master Plan for the horizon year 2041. The region is spread over three districts – Warangal Rural, Warangal Urban and Jangaon in Telangana covering 19 Mandals and 181 Villages with a combined area of 1,805 square kilometres. Total population as per 2011 census is 819,406, with around 62% of the population living in urban areas; the Master Plan is being prepared in accordance with the provisions of Telangana Urban Areas Act, 1975. The KUDA/ Government of Telangana has appointed LEA Associates South Asia Pvt. Ltd. India, A LEA Group Company, for Preparation of Master Plan for the KUDA Area; the Plan is aimed to be prepared in 9 months duration starting from July 2017. Warangal served as the capital of the Kakatiya dynasty, established in 1163; the monuments left by the Kakatiyas include fortresses, lakes and stone gateways which, in the present, helped the city to become a popular tourist attraction. The Kakatiya Kala Thoranam was included in the emblem of Telangana by the state government.
During the Kakatiya rule, Warangal was referred with various names like Orugallu, Ekasila Nagaram, or Omatikonda all these means a'single stone' referring to a huge granite boulder present in the Warangal fort. When the kakatiyan dynasty was defeated by Delhi Sultanate in 1323, ruler Juna khan conquered the city and renamed it as Sultanpur. Musunuri Nayaks recaptured warangal in 1336 A. D. and named it Orugallu again. Warangal was the ancient capital of kakatiya dynasty, it was ruled by many kings such as BetaRaja I, ProlaRaja I, BetaRaja II, ProlaRaja II, Mahadeva, Ganapathideva and Rani Rudrama Devi, the only woman to rule over Telugu region. Beta Raja I is the founder of Kakatiya Dynasty and ruled the kingdom for 30 years and was succeeded by his son Prola Raja I who shifted his capital to Hanamkonda. During the rule of Ganapathideva, the capital was shifted from Hanamkonda to Warangal. Kakatiya Period Inscriptions praised Warangal as best city within all of Telugu region up to shores of the Ocean.
The Kakatiyas left many monuments, including an impressive fortress, four massive stone gateways, the Swayambhu temple dedicated to Shiva, the Ramappa temple situated near Ramappa Lake. The cultural and administrative distinction of the Kakatiyas was mentioned by Marco Polo. After the defeat of Prataparudra II, the Musunuri Nayaks united 72 Nayak chieftains and captured Warangal from Delhi Sultanate and ruled for fifty years. After the demise of the Nayaks, Warangal was part of the Bahmani Sultanate and the Sultanate of Golconda; the Mughal emperor Aurangzeb conquered Golconda in 1687, it remained part of the Mughal empire until the southern provinces of the empire split away to become the state of Hyderabad in 1724, which included the Telangana region and some parts of Maharashtra and Karnataka. Hyderabad was annexed to India in 1948, became an Indian state called as Hyderabad state. In 1956 Hyderabad state was partitioned as part of the States Reorganisation Act, Telangana, the Telugu-speaking region of Hyderabad state, which includes Warangal, became part of Andhra Pradesh.
After the Telangana movement, Telangana state was formed on 2 June 2014, warangal became part of Telangana State. Warangal is located at 18.0°N 79.58°E / 18.0. It has an average elevation of 302 metres, it is settled in the eastern part of Deccan Plateau made up of granite rocks and hill formations which left the region barren making the cultivation dependent on seasonal rainfall. There are no major rivers flowing near the city, making it reliant on the Kakatiya Canal which originates from Sriram Sagar Project to meet the city's water requirements. Located in the semi-arid region of Telangana, Warangal has a predominantly dry climate. Summer starts in March, peak in May with average high temperatures in the 42 °C range; the monsoon lasts until September with about 550 mm of precipitation. A dry, mild winter starts in October and lasts until early February, when there is little humidity and average temperatures in the 22–23 °C range. Many hill rocks and lakes are located around warangal. Padmakshi hill, mettu gutta, hanumathgiri gutta, ursu gutta and Govinda Rajula Gutta are famous hills with temples.
Bhadrakali Lake, Dharmasagar lake and Waddepally Lake are the three famous lakes which adds scenic beauty and are the major sources of drinking water. Greater Warangal Municipal Corporation is the civic body of the city, which oversees the civic needs. Established in 1899, it is one of the oldest urban local bodies in India; the GWMC covers an area of 406.87 square kilometres. City planning is governe
Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is considered a branch of mineralogy; some jewelers are academically trained are qualified to identify and evaluate gems. Rudimentary education in gemology for jewelers and gemologists began in the nineteenth century, but the first qualifications were instigated after the National Association of Goldsmiths of Great Britain set up a Gemmological Committee for this purpose in 1908; this committee matured into the Gemmological Association of Great Britain, now an educational charity and accredited awarding body with its courses taught worldwide. The first US graduate of Gem-A's Diploma Course, in 1929, was Robert Shipley, who established both the Gemological Institute of America and the American Gem Society. There are now several professional schools and associations of gemologists and certification programs around the world; the first gemological laboratory serving the jewelry trade was established in London in 1925, prompted by the influx of the newly developed "cultured pearl" and advances in the synthesis of rubies and sapphires.
There are now numerous gem laboratories around the world requiring more advanced equipment and experience to identify the new challenges - such as treatments to gems, new synthetics, other new materials. It is difficult to obtain an expert judgement from a neutral laboratory. Analysis and estimation in the gemstone trade have to take place on site. Professional gemologists and gemstone buyers use mobile laboratories, which pool all necessary instruments in a travel case; such so-called travel labs have their own current supply, which makes them independent from infrastructure. They are suitable for gemological expeditions. Gemstones are categorized based on their crystal structure, specific gravity, refractive index, other optical properties, such as pleochroism; the physical property of "hardness" is defined by the non-linear Mohs scale of mineral hardness. Gemologists study these factors while appraising cut and polished gemstones. Gemological microscopic study of the internal structure is used to determine whether a gem is synthetic or natural by revealing natural fluid inclusions or melted exogenous crystals that are evidence of heat treatment to enhance color.
The spectroscopic analysis of cut gemstones allows a gemologist to understand the atomic structure and identify its origin, a major factor in valuing a gemstone. For example, a ruby from Burma will have definite internal and optical activity variance from a Thai ruby; when the gemstones are in a rough state, the gemologist studies the external structure. The stone is identified by its color, refractive index, optical character, specific gravity, examination of internal characteristics under magnification. Gemologists use a variety of tools and equipment which allow for the accurate tests to be performed in order to identify a gemstone by its specific characteristics and properties; these include: Corrected 10× loupe Microscope Refractometer Polarising filter Magnifying eyepiece Contact liquid for RI up to 1.81 Polariscope Optic figure sphere Dichroscope Spectroscope Penlight Tweezers Stone cloth Color filter Immersion cell Ultraviolet lamp Gem identification is a process of elimination. Gemstones of similar color undergo non-destructive optical testing until there is only one possible identity.
Any single test is indicative, only. For example, the specific gravity of ruby is 4.00, glass is 3.15–4.20, cubic zirconia is 5.6–5.9. So one can tell the difference between cubic zirconia and the other two. And, as with all occurring materials, no two gems are identical; the geological environment they are created in influences the overall process so that although the basics can be identified, the presence of chemical "impurities" and substitutions along with structural imperfections create "individuals". One test to determine the gem's identity is to measure the refraction of light in the gem; every material has a critical angle. This can be measured and thus used to determine the gem's identity; this is measured using a refractometer, although it is possible to measure it using a microscope. Specific gravity known as relative density, varies depending upon the chemical composition and crystal structure type. Heavy liquids with a known specific gravity are used to test loose gemstones. Specific gravity is measured by comparing the weight of the gem in air with the weight of the gem suspended in water.
This method uses a similar principle to how a prism works to separate white light into its component colors. A gemological spectroscope is employed to analyze the selective absorption of light in the gem material; when light passes from one medium to another, it bends. Blue light bends more than red light. How much the light bends will vary depending on the gem material. Coloring agents or chromophores show bands in the spectroscope and indicate which element is responsible for the gem's color. Inclusions can help gemologists to determine whether or not a gemstone is natural, synthetic or treated. Institutes and laboratories American Gem Society - AGS Asian Institute of Gemological Sciences - AIGS Canadian Gemmological Association - CGA Canadian Institute of Gemmology - CIG European Gemological Laboratory - EGL Gemmological Association of Australia - GAA Gemmological Association of Great Britain - Gem-A Gemological Institute of America - GIA Gübelin