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. Thermal conductivity 0.35 calories/cm? Second degree. 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. Therefore, the identification characteristics of diamonds should be kept in mind when purchasing, so as to avoid unnecessary losses.
Mosan diamond: very similar to diamond, it is the latest diamond imitation-synthetic silicon carbide. It is a world patent product developed by C3 Company of the United States with an investment of US$ 45 million. It was listed on1June, 998. Its chemical composition is SiC, almost colorless, with refractive index of 2.56-2.69, dispersion of 0. 104, birefringence of 0.043, hardness of 9.25 and density of 3.22g/cm3. Detection method: The thermal conductivity meter can't distinguish diamond from Mosan diamond, so it must be identified by the 590 colorless silicon carbide/diamond detector of C3 company in the United States. Using diiodomethane (density: 3.32g/cm3) liquid, it was found that mosan stone floated and diamond sank. You can also use a magnifying glass to observe inclusions and fire method for auxiliary identification.
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.
Diamonds rank first among the five precious and high-grade gems in the world, and are known as "the king of gems" and "priceless treasures". International Gems defines diamonds as "the birthstone of April". The first country to discover diamonds in the world is India, one of the four ancient civilizations. The largest diamond in the world is the Cullinan diamond found in Pretoria, South Africa on June1905+1October 2/KLOC-0. It is light sky blue and weighs 3 106 carats, which is similar to a man's fist. Polished into 105 diamonds of different sizes, the largest of which, the "Star of Africa", weighs 530.2 carats and is embedded in the scepter of King Edward VII of England. The most famous big diamond in China is called "Chang Lin Diamond", which weighs 158.78 carats,1977 65438+February 2 1. Wei, a female member of Changlin Village, Jishan Town, Linshu County, Shandong Province, found it while farming.
Gemstone diamonds are mostly concentrated in placer or kimberlite and lamprophyre cones. The most famous diamond producing areas in the world are Australia, South Africa, Zaire, Botswana, Russia and other countries. China's Liaoning, Shandong, Hunan and other provinces have output.
Rough diamonds, even if they reach gem level, are not very beautiful and pleasing to the eye. Gemstones and diamonds can only become dazzling diamonds after careful design and pondering.
Diamond cutting includes cutting ratio, pavilion angle, facet polishing and so on.
Depth: the height from the bottom of the gem to the table.
The cutting quality has an important influence on the appearance of diamonds. Excellent cutting can make all the light entering the diamond radiate from the table and make the diamond look radiant. If the cutting is not good, part of the light entering the diamond will be refracted from the pavilion, causing light leakage, while the diamond is "dull and depressed". When the diamond is cut too deep, the light will escape from its bottom, so the brightness of the diamond will be damaged and its center will become dark. If the diamond is cut too shallow, the light will escape from its pavilion, and the brightness of the diamond will be damaged, losing its luster and becoming dim.
At present, some people not only show their brilliance to the maximum extent, but also want to give full play to their advantages of high dispersion to make diamonds look more colorful and brighter. So there are 78 "Macmillan" slices (also known as European style). In addition, the cutting workers tried to embody the beauty of diamonds and maintain the quality of diamonds as much as possible, which led to fancy cutting such as heart-shaped, square, olive tip and fire rose.
The color of diamonds
The main colors of diamonds are colorless, white and light yellow. Yellow is a taboo for diamonds, and its fading directly affects the quality and value of diamonds. Therefore, the color of diamond is the primary factor in its economic evaluation. The classification of diamond color is very strict in the international jewelry industry, and all countries have their own corresponding evaluation standards.
Hong Kong's evaluation of diamond color is that colorless to yellow is divided into 100 colors by colorimeter, so it is called "Baise Grade", which is adopted in China. American Gemological Institute is colorless to yellow, and it is divided into D, E, F, …, U, V, W and other color grades.
At present, the evaluation of diamond color grading mostly adopts the comparison method, that is, under the standard white diamond lamp, the diamond to be graded is compared with the "standard diamond sample". Since this classification is based on the scheme of American Gemological Institute, it is best for the standard diamonds used for comparison to be appraised by American Gemological Institute with certificates attached.
For other colors beyond the grading standard, such as red, blue, purple, etc. Because it is extremely rare, diamonds of this color are all treasures in diamonds, and their prices are far higher than the pricing standards of ordinary diamonds. For example,1On April 28th, 987, at a gem auction at Christie's in London, the weight of a stone was only 0. The transaction price of 95 carats of fuchsia diamonds was as high as $880,000.
According to different colors, precious diamonds have the following varieties:
1. water purification diamond: a colorless and transparent diamond, as pure as water, especially with a light blue color. The world's super-large diamonds and world-famous diamonds are mainly of this variety, such as "Jonkel".
2. Red diamond: a transparent diamond from pink to bright red, in which "pigeon blood red" is a rare treasure. For example, Australia is the main source of the world-famous diamond "Rose Red".
3. Blue diamond: A transparent diamond with sky blue and blue to dark blue, in which dark blue is the best. This diamond is different from all other colors. It has semiconductor characteristics. Because it is extremely rare, it is a rare treasure. For example, the world-famous diamond "Hope", the Premel mine in South Africa is its main source.
4. Green diamonds: light green to green transparent diamonds, of which bright green is the best. Such as the world-famous diamond "Dresden Green". Zimbabwe (Rhodesia) is its main source.
5. Purple diamond: a kind of transparent diamond from lavender to purple, especially the bright purple one is a rare treasure, and the former Soviet Union is its main source.
6. Golden diamond: a kind of golden transparent diamond, which is a common variety in colored diamond.
7. Black diamonds: Black diamonds can't be used as diamonds, but large black transparent diamonds can also be precious diamonds, such as the world-famous diamond "Africa Star".
Clarity of diamond
The cleanliness of diamonds is based on the observation results of diamonds under 10 times magnifying glass. It includes two aspects, that is, the original defects of gemstones and the damage to the diamond surface during processing. Clarity can be divided into the following six levels:
1. FLawless, referred to as fl. There are no flaws inside or outside the diamond. Some glitches can also be included in the FL level. This level allows additional facets in the pavilion, but these facets are not visible on the table; Visible natural primary facet or cleavage plane, its size does not exceed the waist width, or does not make the waist round; There are small spots inside, because it is colorless and does not affect the perspective.
2. Internal cleanliness, referred to as IF. There is no flaw inside, but there is a little flaw on the surface.
3. Including very, very subtle internal defects, as well as very tiny defects, which can only be observed from the pavilion or have very small defects on the surface. The difference between VVS 1 and VVS2 is that the cotton spot of VVS2 is very small, with very small stubble (basically no internal defects).
4. Very slight inclusion, referred to as VS 1 or VS2. You can see very tiny flaws, and you can clearly see the size and position. The difference between VS 1 and VS2 is that VS2 may have fine cotton wool and stubble.
5. Slightly contained, referred to as SI 1 and SI2. You can clearly see the defects, probably in the center of the table, especially VS2, which is very easy to see.
6.Inperfect, abbreviated as I 1, I2 and I3. You can clearly see the flaws, and sometimes you can clearly see the obvious cleavage.
There is a uniform mark on the cleanliness of diamonds in the world, which is generally marked in the corresponding position of the diamond morphology map of the appraisal certificate.
Diamond carat
Carat, as a unit of weight, originated from the seeds of Oryza sativa L. on the Mediterranean coast of Europe, with red flowers and brown nuts in pods, about 15cm long, which can be used to make glue. There is a strange phenomenon in carob trees. No matter where it grows, it bears the same weight of nuts. Historically, this fruit has been used as a weight to measure weight. Over time, it has become a unit of weight for weighing precious and subtle substances. It was not until 1907 that it was internationally recognized as a unit of measurement for gems, and it is still in use today.
Diamonds are generally very small, weighing 0. 1 ~ 0.24 carats, and are mainly used for setting clothes or other gem ring groups. Those with a weight of 0.25 ~ 1 carat are called medium diamonds, which are mainly used as necklaces, bracelets and brooches. Those weighing more than 1 carat are called big diamonds, which are mainly used as rings. The second unit of diamond weight unit is minute, 100 minute 1 carat; A 0. 1 carat diamond is 10 cent.
Because large diamonds are very rare, carat weight has become a very important factor in diamond economic evaluation. In general, the value of a diamond is directly proportional to the square of its carat weight, that is, the price of a diamond = the square of one carat × the basic price of one carat.
The shape of a diamond
Round is the most common and common shape of diamond, but besides round, diamond cutting also includes heart shape, square column shape (emerald shape), olive pointed shape (horse eye shape), pear shape, square shape (princess shape), ellipse shape and water drop shape.
Don't judge by the shape of the diamond, usually determine the cutting shape of the diamond according to the given stone.
Characteristics of diamonds
Diamonds, also known as Jin Gangzuan, are called diamonds. English is Diamond, which comes from agonist in ancient Greece, meaning hard and inviolable substance.
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. Thermal conductivity 0.35 calories/cm? Second degree. 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. Therefore, the identification characteristics of diamonds should be kept in mind when purchasing, so as to avoid unnecessary losses.
Mosan diamond: very similar to diamond, it is the latest diamond imitation-synthetic silicon carbide. It is a world patent product developed by C3 Company of the United States with an investment of US$ 45 million. It was listed on1June, 998. Its chemical composition is SiC, almost colorless, with refractive index of 2.56-2.69, dispersion of 0. 104, birefringence of 0.043, hardness of 9.25 and density of 3.22g/cm3. Detection method: The thermal conductivity meter can't distinguish diamond from Mosan diamond, so it must be identified by the 590 colorless silicon carbide/diamond detector of C3 company in the United States. Using diiodomethane (density: 3.32g/cm3) liquid, it was found that mosan stone floated and diamond sank. You can also use a magnifying glass to observe inclusions and fire method for auxiliary identification.
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.
Diamonds rank first among the five precious and high-grade gems in the world, and are known as "the king of gems" and "priceless treasures". International Gems defines diamonds as "the birthstone of April". The first country to discover diamonds in the world is India, one of the four ancient civilizations. The largest diamond in the world is the Cullinan diamond found in Pretoria, South Africa on June1905+1October 2/KLOC-0. It is light sky blue and weighs 3 106 carats, which is similar to a man's fist. Polished into 105 diamonds of different sizes, the largest of which, the "Star of Africa", weighs 530.2 carats and is embedded in the scepter of King Edward VII of England. The most famous big diamond in China is called "Chang Lin Diamond", which weighs 158.78 carats,1977 65438+February 2 1. Wei, a female member of Changlin Village, Jishan Town, Linshu County, Shandong Province, found it while farming.
Gemstone diamonds are mostly concentrated in placer or kimberlite and lamprophyre cones. The most famous diamond producing areas in the world are Australia, South Africa, Zaire, Botswana, Russia and other countries. China's Liaoning, Shandong, Hunan and other provinces have output