The chemical composition of diamonds is carbon, which is the only single element in gems. It belongs to the equiaxed crystal system. The crystal forms are mostly octahedron, rhombic dodecahedron, tetrahedron and their aggregates. Pure diamond is colorless and transparent, showing different colors due to the mixing of trace elements. Strong diamond luster. The refractive index is 2.4 17 and the dispersion is moderate, which is 0.044. An isotropic object. The thermal conductivity is 0.35 calories/cm sec .. Tested by thermal conductivity meter, the response is the most sensitive. The hardness is 10, which is the hardest mineral known at present. The absolute hardness is 1000 times that of the time, and 150 times that of corundum. It is afraid of heavy blows, and it will be broken by cleavage after heavy blows. A set of cleavage is completed. The density is 3.52g/cm3. Diamonds are luminous, and after being irradiated by sunlight, they can emit light blue phosphorescence at night. X-ray irradiation emits sky blue fluorescence. The chemical properties of diamond are very stable, and it is not easy to dissolve in acid and alkali at room temperature, and acid and alkali will not affect it.
The difference between diamonds and similar precious stones and synthetic diamonds. Common substitutes or counterfeits in gem market include colorless gemstones, colorless spinel, cubic zirconia, strontium titanate, yttrium aluminum garnet, yttrium gallium garnet, artificial rutile and so on. Synthetic diamonds were first developed by Japan in 1955, but they were not mass-produced. Synthetic diamonds are rare in the market because they are more expensive than natural diamonds. Diamonds can be distinguished from similar gems by their unique hardness, density, dispersion and refractive index. For example, diamond-like cubic zirconia is colorless, with strong dispersibility (0.060), strong luster and high density of 5.8 g/cm3, which has obvious sense of gravity. Yttrium aluminum garnet has a soft dispersity, so it is difficult to distinguish it from diamonds with naked eyes.
In the past, people didn't ponder diamonds, but only used the original diamonds as ornaments. The time when diamond crystals really became diamonds and jewels was about 1450. At that time, diamonds had only 17 faces. The diamond ring worn by the Queen of England when she was in power from 1558 to 1603 was just an octahedral diamond crystal with a top worn off as a ring surface. Until 19 19, a Polish living in the United States named Tolkovsky designed 58 kinds of cutting techniques for turning diamonds, which are still in use today. This cut is accurately calculated according to the refractive index of the diamond and other factors, and cannot be changed at will, otherwise the polished diamond will lose its luster or leak light.
The history of human exploitation and utilization of diamonds has been thousands of years, but from ancient times to now, gem-grade diamonds larger than 20 carats are quite rare. Diamonds larger than 100 carat are regarded as national treasures. It is said that there are more than 1900 extra-large diamonds larger than 1000 carats found in the world at present, of which 21000 are larger than 500 carats, and only 2 are larger than1000 carats. Up to now, the largest diamond in the world was found in Premier, Zaire, South Africa on127 October, 1905+65438. This diamond is named Cullinan and weighs 3 106 carats. It is 100 mm long, 65 mm wide and 50 mm thick. Gem experts estimate Cullinan's value as high as $7.5 billion. 1907, the local government of transvaal province presented this giant diamond to King Edward VII of England. The king of England handed over the project of processing this giant diamond to the famous Dutch company Ascher, which once processed "noble" diamonds. After the company took over the project, it studied this giant diamond for several months. On February 1908 and 10, the giant diamond was cut into several large pieces and processed into 9 large diamonds and 98 small diamonds, leaving a rough stone (weighing 9.5 carats) unprocessed. The total amount of finished diamonds processed is 1063.65 carats, and the largest diamond processed is named "Cullinan No.1", also known as Africa Star, weighing 530.02 carats, which is a pear-shaped faceted diamond. "Cullinan II" is a chamfered rectangular drill, weighing 3 17.4 carats. Cullinan III is a pear-shaped diamond weighing 95 carats, Cullinan IV is a square diamond weighing 64 carats, a heart-shaped diamond weighing 19 carats, two horse-eye diamonds weighing l10.5 carats and 8.8 carats respectively, and the last two diamonds are rectangular diamonds (weighing 6.8 carats) and rugby diamonds (football diamonds).
/kloc-At the beginning of the 7th century, a rough diamond weighing 309 carats was found in the diamond placer in Golconda, India, and was later named Orlov Diamond. At that time, a famous diamond processing expert planned to process it into the shape of "Indian Rose" according to Shah Han Zhe's will, but failed to do it completely, and the weight was reduced a lot (only 189.62 carats). According to legend, this wonderful, rare and flawless diamond was later made into the eyes of an idol in the Seringa temple in India. After Delhi was captured by the Persian king Nader Gil in 1739, this diamond was decorated on Nader Gil's throne and named "Gil onur". Then the diamond was stolen and fell into the hands of an Armenian. 1767, he deposited the diamonds in a bank in Amsterdam. 1772, he sold diamonds to Ivan, a jeweler, and Ivan bought them for 400,000 rubles to Count orlov in 1773. In the same year, orlov presented this diamond to Catherine II as a gift for her naming day. Later, it was welded into a carved silver base and inlaid on the top of the Russian scepter. Orlov diamonds are perfect and very rare. Slightly blue-green, there are several tiny yellowish inclusions in the crystal. This diamond is 22 mm thick, 3 1-32 mm wide and 35 mm long. At present, this diamond is treasured in the Diamond Foundation of the former Soviet Union, and another famous diamond "Shah" was presented to the czar's government by Persian Prince Mirza on 1829, aiming at repairing the relations between the two countries deteriorated by the murder of the Russian embassy in Persia. The Shah diamond weighs 88.7 carats. It is light yellow and flawless, except for some small cracks in the deep crystal. The three polished surfaces are engraved with Persian characters, meaning "Burhan-nizam-Shah II, 1000 (A.D. 159 1 year)". This diamond fell into their hands after India was occupied by the Great Mughal Dynasty 2. The second inscription means "Han Zhe Shah, son of Han Zhe Gil Shah, 105 1 year (A.D. 164 1 year)". The third paragraph means "ruler Kadzar-Faget-Ali-Shah Sultan, 1242. (King of Persia, 1842). This diamond was occupied by Shah of Nadjir in about 1739 when the great Mughal dynasty was occupied. No one knows where this diamond was collected. It is inferred that it may find Kangda placer in Hugele. Being able to carve an inscription on the incredibly hard "Shah" diamond shows that the skills of Persian artists at that time were unimaginable. The Archon of the Great Mughal Empire mentioned in the inscription, Shah Han Zhe, was in office from 1627 to 1666, and was captured by Jeb and spent the rest of his life in prison. Shah Hezhe rarely worships great gems. He has a special studio and even goes there to sort out and ponder gems. His son Jeb not only usurped the throne, but also seized his father's treasure. 1665, a famous traveler made a fascinating description of the throne of the Great Mughal Dynasty, which was decorated with a lot of precious stones. A diamond weighing 80-90 carats hangs on the canopy of the throne at the side of the audience, surrounded by many emeralds and rubies. This may be "Shah", hanging between the big Mughal and the worshippers as a treasure of protection. There is also a very beautiful diamond, named "Sangxi" diamond, which weighs 55 carats. It is said that this diamond was embedded in the helmet of the warrior Carl and was lost in a battle.
1589, "Sansi" appeared in the treasure house of Portuguese king Anton. Later, it was sold to France's Scud Sanxi for 65,438+10,000 old francs. "Sangxi" diamond has a long history as a family heirloom. Later, it was presented to King Genglihe II of France and included in the list of treasures in France. On 1792, this diamond was looted. 1830, "Sangxi" was bought by Demidoff, the descendant of a Ukrainian factory owner, and the transaction price was 500,000 francs. The French government fought a lawsuit on this matter, and five years later the diamond was awarded to Demidoff. There is also a touching story about the 4 10 carat "regent" diamond. It is said that it was picked up by an Indian slave in the well-known Golconda mine in 170 1 year. He wanted to use this diamond to change his life and be free, so he took advantage of people's inattention to raise a T-pick and hit it on his thigh, bleeding profusely. The Indians endured great pain, hiding diamonds in the depths of the wound and wrapping the wound with leaves as bandages. He found an English sailor and prepared to exchange his freedom. After seeing this huge diamond, the sailor hoped that he couldn't get it right away, so he was prepared to pay everything for it. Sailors and slaves soon settled down, and the sailors hid the Indians in jute and in the cabin without telling the captain. When the ships sailed into the high seas, the sailors gave the slaves food at night, killed them with daggers, and threw the victims into the sea while they were eating. After the ship landed in Madras, the sailors sold the diamonds to Sir Peter, the British governor of the city, for 20,000 pounds. When the sailor got the money, he quickly squandered it and finally hanged himself. 17 17 Peter sold the diamonds to the French regent Oranski for 3.4 million gold francs. The duke ordered the diamond to be processed, and the diamond "Regent" was born. The birth of this diamond is hard. It took two years to polish and polish. The processed weight is 140.5 carats. When Ludovici XIV was crowned in 65,438+0722, diamonds were embedded in his crown. In the early days of the French Revolution, just like the king. Later, a German jeweler sold it to Napoleon. /kloc-In the 1990s of 0/8, it was used as collateral by Napoleon to launch an expedition. 1940 When Hitler captured Paris, diamonds were hidden in the partition of the marble fireplace in Shambo. This diamond is currently on display in the Louvre. The particle size of diamond is 30 X 29 X 19mm. The cutting of diamond is dazzling and exquisite, and its luster has different repercussions from "fire". 1762, Ye, a talented court jeweler, won praise for the gorgeous and exquisite jewelry made by the king at the coronation ceremony of Catherine II. He created a new world with brilliant diamonds. The crown is always inlaid with 4936 diamonds, weighing 2858 carats. The whole crown weighs1907g, and the "spinel" diamond decorating the crown weighs 398.72 carats.
The evaluation and purchase of diamonds should be considered from the following four aspects:
(1) color: colorless is the best, and the darker the tone, the worse the quality. Colored diamonds, such as red, pink, green and blue. , which belongs to the treasures of diamonds and is expensive.
(2) Defects: The cleanliness of diamonds should be carefully observed under a ten-fold microscope. The more defects, the more obvious the location, the worse the quality and the lower the price.
(3) Weight: The price of diamonds is directly proportional to the square of weight. The greater the weight, the higher the value.
(4) Cutting: cutting and grinding according to the standard proportion to form a standard round drill type. If the proportion is not appropriate, the diamond will not be "hot" and the price will fall. If there are fine lines and man-made injuries on the surface, its price will also drop.