English name: diamond English name: diamond definition: carbon allotrope is the hardest substance known, and there are two kinds: natural and artificial. Discipline: mechanical engineering (first-class discipline); Abrasive abrasives (two disciplines); Abrasive (third-level discipline) This content is approved and published by the National Committee for the Examination and Approval of Scientific and Technical Terminology.

printing block

Diamonds Diamonds are commonly known as "Jin Gangzuan". That is, diamonds, as we often say, are minerals made of pure carbon. Diamonds are the hardest substance in nature. Diamonds are widely used, such as handicrafts and industrial cutting tools. Carbon can form diamond at high temperature and high pressure.

catalogue

Basic introduction

Raw material characteristics

Introduction to chemical properties

physical features

Hardness of diamond

Optical properties of diamond

Classification situation

mineral resources

use

Identification of 1, single refraction of diamond

2. Adsorption of diamonds

3. Characteristics of straight lines

4. Unique diamond luster

history

Place of production

Be distributed

raw material

Diamonds and graphite

artificial

Hardness of mined diamonds

Optical properties of diamond

Basic introduction of writers

Raw material characteristics

Introduction to chemical properties

physical features

Hardness of diamond

Optical properties of diamond

Classification situation

mineral resources

use

Identification of 1, single refraction of diamond

2. Adsorption of diamonds

3. Characteristics of straight lines

4. Unique diamond luster

history

Distribution of producing areas of artificial mining of diamond and graphite raw materials

Hardness of Diamond and Optical Properties of Diamond were edited by the author.

The chemical formula of diamond is N C-NC, diamond is an atomic crystal, a diamond is a macromolecule, and the polymer of NC can only be expressed by its structural formula. Changlin Diamond.

Diamond is what we often say (diamond is its common name), and it is a mineral made of pure carbon. Diamond is the hardest substance in nature, so it has many important industrial uses, such as fine grinding materials, high hardness cutting tools, various drills and wire drawing dies. It is also used as a part of many precision instruments. Diamonds come in various colors, ranging from colorless to black, of which colorless is particularly preferred. They can be transparent, translucent or opaque. Most diamonds are mostly yellow. Diamonds have very high refractive index and strong dispersion, which is also the reason why diamonds reflect colorful flashes. Diamonds emit blue-green fluorescence under X-ray irradiation. Diamonds are found only in kimberlite cones. Kimberlite is their original rock, and diamonds from other places are transported by rivers and glaciers. Diamonds are generally granular. If the diamond is heated to 1000℃, it will gradually become graphite. 1 97765438+February 2 1 day, in Changlin Brigade, Linshu County, Shandong Province, female player Wei discovered a high-quality giant diamond with a weight of 158.786 carats-the largest diamond in China, which is completely transparent and yellowish in color, and can be called "China's". It was named "Chang Lin Diamond" (about the size of an egg yolk, right). The world's largest industrial diamonds and gem-grade diamonds are both produced in Brazil, both exceeding 365,438+000 carats (65,438+0 carats = 200mg). Among them, the gem-grade diamond with the size of 10× 6.5× 5cm was named "Cullinan" and was discovered in Premil Rock Tube in 1905. China Changlin diamond, weighing 158.786 carats, was discovered in Linshu county, Shandong province on 1977 and is listed as a world-famous diamond. The main diamond producing areas in the world are Australia, Zaire, Botswana and Russia. Diamond and graphite belong to the simple substance of carbon. It has excellent physical properties such as superhard, wear resistance, heat sensitivity, heat conductivity, semiconductor and penetration, and is known as the "king of hardness" and the king of gems. The crystal angle of a diamond is 54 degrees 44 minutes and 8 seconds. In 1950s, the United States successfully manufactured synthetic diamonds from graphite at high temperature and high pressure. Now synthetic diamond has been widely used in production and life, but it is still very difficult to manufacture large-particle diamond.

Edit the characteristics of raw materials in this paragraph.

Gold natural diamond

The chemical composition of diamond is carbon, which, like graphite, is a homogeneous polymorph of carbon. In the chemical composition of minerals, there are always elements such as silicon, magnesium, aluminum, calcium, manganese and nickel. And common impurity elements such as sodium, boron, copper, iron, cobalt, chromium, titanium, nitrogen and carbohydrates. The crystal structure of diamond minerals belongs to equiaxed tetrahedron structure and has the same polar bond. Carbon atoms are located at the top and center of tetrahedron and have high symmetry. The carbon atoms in the unit cell are connected by homopolar bonds with a distance of 1.54? (10-10m). The common crystal forms are octahedron, rhombic dodecahedron, cube, tetrahedron and hexahedron. The Mohs hardness of diamond is 10, the microhardness is 98 654.9MPa( 100060kg/mm2), and the absolute hardness is 1000 times higher than that of corundum. Minerals are brittle, shell-like or hackly fracture, and will crack along the crystal cleavage plane under small impact, with medium or perfect cleavage parallel to octahedron and perfect cleavage parallel to dodecahedron. The minerals are relatively pure, and the density is generally 3 470-3 560kg/m3. The color of diamond depends on the purity, the type and content of impurity elements. Ultra-pure diamonds are colorless and usually have different degrees of yellow, brown, gray, green, blue, ivory and purple. Pure people are transparent, translucent or opaque, with impurities; Under cathode ray, X ray and ultraviolet ray, it will emit different colors of fluorescence such as green, sky blue, purple and yellow-green. Light blue phosphorescence is emitted in the darkroom after the sunlight is irradiated; Diamond luster, a little greasy or metallic luster, high refractive index, generally 2.40-2.48. The thermal conductivity of diamond is generally136.16w/(m k), in which the thermal conductivity of Ⅱ A diamond is extremely high, which is 25 times that of copper at the temperature of liquid nitrogen, and drops sharply with the increase of temperature, such as 5 times that of copper at room temperature; The specific heat capacity increases with the increase of temperature, such as 399.84 J/(kg k) at-106℃ and 472.27 J/(kg k) at 107℃. The coefficient of thermal expansion is very small, which increases with the increase of temperature, such as 0 at -38.8℃ and 5.6× 10-7 at 0℃. The ignition point is 720 ~ 800℃ in pure oxygen, 850 ~ 65438 0000℃ in air and 2000 ~ 3000℃ in absolute oxygen. Diamond is chemically stable, acid-resistant and alkali-resistant, and does not react with concentrated HF, HCl and HNO3 at high temperature. The surface of diamond will be slightly oxidized only when it is boiled in the melt of Na2CO3, NaNO3 and KNO3 or in the mixture of K2Cr2O7 and H2SO4. Corrosion in high temperature gases of O, Co, CO2, H, Cl, H2O and CH4. Diamond also has non-magnetism, poor conductivity, oleophilic hydrophobicity and triboelectricity. Only Ⅱ B diamond has good semiconductor properties. According to the difference of nitrogen impurity content and thermal, electrical and optical properties of diamonds, diamonds can be divided into two categories: type I and type II, and further subdivided into four subcategories: 1a, 1b, 2a and 2b. Type Ⅰ diamond, especially subtype Ⅰ A, is a common common diamond, accounting for about 98% of the total natural diamonds. Type I diamonds contain a certain amount of nitrogen, which has good thermal conductivity, poor electrical conductivity and good crystal shape. Type ⅱ diamond is extremely rare, with little or no nitrogen content, and has the characteristics of good thermal conductivity and crystal bending. Diamonds of type Ⅱ b are semiconductors. Second-class diamonds are mostly used in aerospace technology and cutting-edge industries because of their excellent properties.

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chemical property

In diamond crystal, carbon atoms are interconnected by tetrahedral bonds, forming an infinite three-dimensional skeleton, which is a typical atomic crystal. Every carbon

All [1] atoms form * * * valence bonds with four other carbon atoms through SP3 hybrid orbitals, forming a regular tetrahedron. Because the C-C bond in diamond is very strong, all valence electrons participate in the formation of valence bond, and there are no free electrons, so diamond is not only hard, but also has a very high melting point and is not conductive. In industry, diamonds are mainly used to make probes and abrasives for drilling, and also used to make high-grade decorations such as hand ornaments with complete shapes, which are very expensive.

physical features

The Mohs hardness of diamond is10; Because of the highest hardness, diamond powder must be used in diamond cutting. The density of diamond is 3.52g/cm3, the refractive index is 2.4 17, and the dispersion rate is 0.044.

Hardness of diamond

Mohs hardness 10, new Mohs hardness 15, microhardness 10000kg/mm2, which is 1000 times higher than that in time and 150 times higher than that in corundum. The hardness of diamond is directional. The hardness of octahedral crystal face is greater than that of rhombohedral crystal face, and the hardness of rhombohedral crystal face is greater than that of hexahedral crystal face. According to Mohs hardness scale, it is divided into 10 grade, with diamond as the highest grade and 10 grade. For example, the hardness of knives is about 5.5, copper coins are about 3.5 to 4, nails are about 2 to 3, and the hardness of glass is 6. 1 grade talc, grade 2 gypsum, grade 3 calcite, grade 4 fluorite, grade 6 apatite, grade 7 orthoclase, grade 8 topaz, grade 9 corundum and grade kloc-0/0 diamond mark any two different minerals with each other, and one of them will be destroyed. One mineral can scratch all other minerals, but no mineral can scratch it. This is a diamond. Why are diamonds so hard? It was not until the second half of the18th century that scientists figured out the "materials" that make up diamonds. As mentioned above, as early as 1 century, there were records about diamonds. However, in the following 1600 years, people never knew what the composition of diamonds was. Until11970s and 1990s, French chemist lavoisier (1743 ~ 1794) and others carried out the experiment of burning diamonds in oxygen, and found that carbon dioxide gas was obtained, that is, substances combining oxygen and carbon. The carbon here comes from diamonds. Finally, these experiments prove that the material of diamond is carbon. Knowing that the composition of diamonds is carbon still cannot explain why diamonds have such great hardness. For example, pencil lead is made of graphite and carbon. However, graphite is a mineral softer than human nails. Why are diamonds so different from graphite? This question was answered by the British physicist william bragg and his son in 19 13. Bragg and his son observed diamonds with X-rays and studied the arrangement of atoms in diamond crystals. They found that in the diamond crystal, each carbon atom is closely combined with the surrounding four carbon atoms to form a compact three-dimensional structure. This is a special structure that has never been seen in other minerals. Moreover, this dense structure makes the density of diamond about 3.5 grams per cubic centimeter, which is about 1.5 times that of graphite. It is this dense structure that makes diamond have the greatest hardness. In other words, diamonds are minerals formed by the extrusion of carbon atoms.

Optical properties of diamond

(1) The brightness of optical recognition diamond has very high reflectivity, its critical angle of reflection is small, its total reflection range is wide, light is prone to total reflection, and the amount of reflected light is large, thus producing very high brightness. (2) The flashing of the flashing diamond is flashing, that is, when the diamond or light source moves relative to the observer, the surface reflects and flashes white light. Colorless, transparent and well-crystallized octahedral or curved diamonds can show good scintillation even without cutting and grinding. (3) The crystal faces of dispersion or fire diamonds are like a prism, which can decompose the white light entering the crystal through refraction, reflection and total reflection into the constituent colors of white light-red, orange, yellow, green, blue, indigo and purple. (4) The crystal plane or cleavage plane with luster as hard, flat and bright as a diamond has a particularly strong reflection effect on white light, which is called diamond luster.

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Diamond is the crystallization of carbon under high temperature and high pressure, and it is the hardest mineral in nature. Its name comes from the Greek word "Adamas", which means hard and invincible. Diamond is a rare and precious nonmetallic mineral, which plays an important role in the national economy. Diamonds can be divided into two types according to their uses: gem-grade diamonds with high-quality particles that can be used as decorations, and industrial diamonds with low-quality particles that can be used in industry. Gem-grade diamonds, also known as diamonds, are brilliant and crystal clear, known as the "king of gems" and recognized as the first high-value commodity in the world. Its ownership and consumption level are often regarded as a sign to measure the economic prosperity of individuals and countries. Diamond (industrial diamond), which is not up to gem level, is widely used in electromechanical, optical, construction, transportation, metallurgy, geological exploration, national defense and other industrial fields and modern high-tech fields because of its superhardness. Diamonds can be divided into two types according to the trace elements they contain: type I diamonds and type II diamonds. Type I diamonds are mostly common ordinary diamonds. Type ⅱ diamonds are rare, accounting for only 1% ~ 2% of the total diamonds. Type ⅱ diamond is often used in space technology and cutting-edge industry because of its good thermal conductivity, cleavage and semiconductor characteristics. High-quality large-grained type II diamonds with bluish color are regarded as treasures among diamonds, such as the world-famous "Cullinan" diamond weighing 3 106 carats.

Edit mineral resources in this section.

Human beings have a long history of understanding and developing diamonds. As early as the 3rd century BC, diamonds were discovered in ancient India. Since A.D., diamonds have always been a symbol of wealth, power and status of the country, nobles and dignitaries in the palace. The world's diamond mineral resources are not rich, and the world's proven diamond reserve base is only 1996 ct, which is far from meeting the needs of gemstones and industrial consumption. Since the 1960s, the technology of synthetic diamond has risen, and it has been perfected in the 1990s. Synthetic diamonds almost completely replaced industrial natural diamonds, accounting for more than 90% of the world's industrial diamond consumption (more than 99% in China). The main diamond producers are Australia, Russia, South Africa, Botswana and Zaire. The global distribution of diamonds is mainly controlled by the central sales organization of De Beers. China discovered diamonds about 200-300 years ago. During the Ming and Qing Dynasties (about17th century), farmers in Hunan Province searched for diamonds in river sand. Geological exploration of diamonds began in 1950s. Up to now, six famous diamonds weighing more than 90 ct have been found in China, such as "Chang Lin Diamond" weighing about 158 ct, while other China diamonds are relatively poor in mineral resources. Through nearly 50 years of geological work, the reserves have been proved only in Liaoning, Shandong, Hunan and Jiangsu provinces. By the end of 1996, China's diamond reserves were 20,897,800 ct, which did not occupy an important position in the world. In terms of quality, the diamonds produced in Liaoning Province, China are of high quality, and the output of gem-grade diamonds accounts for about 70% of the total output. Since 1990s, the annual output of diamonds in China is about10 ~150,000 ct, which is far from meeting the needs of domestic consumption. More than 99% of industrial diamonds in China rely on domestic synthetic diamonds, and the output of synthetic diamonds in China reached 440 million ct in 1997, and the proportion of natural industrial diamonds in consumption is extremely limited. There are two types of diamond mines: magmatic rocks and placer mines. There are three kinds of magmatic rocks containing diamond: kimberlite, lamprophyre and peridotite, among which kimberlite and lamprophyre are of industrial significance.

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People who eat diamond powder will stick to the stomach wall. In the long-term friction, it will cause gastric ulcer, and if it is not treated in time, it will die of gastric bleeding. It is a chronic poison that is difficult to prevent. During the Renaissance, chronic poison made of diamond powder was popular among Italian giants. In addition, there are diamonds used in geology and oil drilling, diamonds used in wire drawing dies, diamonds used in abrasives, diamonds used in trimmers, diamonds used in glass cutting machines, diamonds used in hardness testers and diamonds used in handicrafts. If coated on the audio paper basin, the sound quality of the speaker will be greatly improved. Ornamental diamonds, because of their high refractive index, shine under the light and become ladies' favorite gems. Huge beautiful diamonds may be priceless. Diamonds with dark colors are more expensive. At present, the most expensive colored diamond is aquamarine diamond with a slight blue color. Diamonds are divided into type I and type II, mainly depending on whether they contain N elements: type I contains N elements; Type II does not include. The blue diamond is type B, which is a semiconductor.

Edit this paragraph to identify

With the increasing demand for jewelry and diamonds, the market for fake diamonds such as artificial diamonds is expanding, and even some jewelry operators can't tell the difference. Here are some simple ways to identify the authenticity of diamonds.

1, single refraction of diamond

The single refraction of diamond is determined by its essential characteristics. While other natural gemstones or artificial gem are mostly birefringent. When the fake diamond is observed with a magnifying glass of 10 times, it is easy to see that the edges and corners overlap, and two bottom lights are exposed at the same time from the slightly inclined front. If the difference in birefringence is small, such as zircon, you can also see the image of overlapping background light.

2. Adsorption of diamonds

Diamonds have a certain affinity for grease and dirt, that is, oil stains are easily adsorbed by diamonds. So touching the diamond with your fingers will feel sticky, and your fingers seem to feel sticky. This is not found in any gem. This method needs training to master the nuances.

3. Characteristics of straight lines

The surface of the diamond is polished very smoothly. Dip the pen in ink and cross the diamond. If it is a real diamond, the surface will leave a smooth and continuous line, which is characterized by a straight line. Forgery will leave dots and lines. Observation in this way should be made with the help of a magnifying glass.

4. Unique diamond luster

Under the incandescent light of 100 degree, it is easy to see which diamond has diamond luster by comparing with the counterfeit. This method should not be carried out in too dark or too strong light.

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Good things are hard to find, just as diamonds are always born with poisonous snakes. Listen to the story of the diamond valley brought to you by Pliny, a famous ancient Roman philosopher. According to legend, in 350 BC, Alexander the Great, king of Macedonia, marched eastward to India and found diamonds in a deep pit, but there were many poisonous snakes guarding them. These poisonous snakes can kill people a few feet away. Alexander ordered the soldiers to refract the light with a mirror, burn the poisonous snake to death, and then throw the mutton into the pit. The diamonds in the pit stuck to the mutton, which attracted vultures. After the vulture flew away with mutton and diamonds, the soldiers followed the vulture and got the diamonds. Since then, it is said that poisonous snakes are the patron saint of diamonds. Are poisonous snakes really sent by God to guard diamonds? Dancing with snakes actually depends on the unique charm of diamonds, which is the unique fluorescence phenomenon of diamonds. When the diamond is irradiated by X-rays or ultraviolet rays, it will glow, especially in dark places or at night, and it will glow in blue, green, yellow and other colors. In ancient China, diamonds with this property were called "night pearls". Diamonds in a deep valley near Muftiri, India, emit light blue fluorescence at night after being irradiated by ultraviolet rays from the sun during the day. These fluorescent lamps attract many phototropic insects, insects attract a large number of frogs, and frogs attract many poisonous snakes. Interlocking, this is the reason why there are many poisonous snakes in the deep valley of diamonds. Until the middle of19th century, people still regarded diamonds as magical stones. Of all the 4,200 known minerals, why is diamond the hardest? Where and how are diamonds produced? All this was completely unknown to people at that time. Human beings have a long history of dealing with diamonds. As early as 1 century, there were records about diamonds in Roman literature. At that time, the Romans did not regard diamonds as decorative gems, but only used them as carving tools because of their unparalleled hardness. Later, with the development of technology, diamonds became more and more expensive as jewels. By the15th century, some European cities, such as Paris, London and Antwerp (a city in northern Belgium), have seen some craftsmen polishing large diamonds with diamond powder and processing diamonds. As a gem, diamonds are becoming more and more expensive. However, the scientific research on diamond is relatively slow. An important reason is that no "mine" with diamonds has been found for a long time. The diamonds that have been found are collected by luck in river sand and gravel in India and Brazil, and the quantity is very small and very rare. Especially high-quality diamonds are extremely expensive, and only princes and nobles can afford them. In that case, it is almost impossible to study such an expensive diamond. Things changed in the19th century. 1866, a boy named erasmus Jacobi lived on a farm in South Africa. He was playing on the beach of the Orange River and came across a diamond weighing 2 1.25 carats (4.25 grams). Carat, the weight unit of gemstones, 1 carat = 0.2g). This diamond was immediately sent to the Paris International Fair by the British colonial governor (1867 ~ 1868) and was named "Eureka" (Greek, meaning "I found it"). Hearing the news of the discovery of diamonds in South Africa, thousands of prospectors flocked to the Orange River, forming a frenzy of searching for diamonds. One of the brothers named bernat soon discovered a diamond mine near Kimberly. The discovery of diamond mines is of great significance. By studying the geological structure of mines, it is possible to know where diamonds may form.

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As mentioned earlier, the bernat brothers discovered the Kimberly diamond mine at 1870. It is this discovery that makes people know what kind of rocks may contain diamonds. It turned out to be a volcanic rock formed after magma cooled in ancient times. Then, the researchers found that in addition to diamonds, this volcanic rock also contains two minerals called garnet and olivine. Therefore, in those places where garnet and olivine are produced, it is relatively possible to find diamond mines. Therefore, garnet and olivine have become "indicator minerals" for finding diamonds. The method of finding diamond mines according to indicator minerals was not suddenly discovered one day. In 1970s, John Gianni, a geochemist of Smithsonian Institution, published his research results after carefully studying the relationship between garnet and diamond. However, before that, that is, in the 1950s, geologists of De Beers Company had been searching for diamond mines all over the world according to indicator minerals. At present, there are diamond mines all over the world. Among them, Australia, Congo, Russia, Botswana and South Africa are five famous diamond producing areas. Dr Steven Hagarty, a geophysicist at the University of Massachusetts in the United States, studied the age of 1999 lava containing diamonds around the world and found that these lava containing diamonds were formed by magma ejected from various places in at least seven different periods in the past. The oldest lava was formed about 10 billion years ago. In these seven magmatic eruptions, Africa and Brazil ejected the most diamonds from 654.38+0.2 billion years ago to 80 million years ago. It was the Mesozoic Cretaceous in the heyday of the dinosaur era. Lava containing diamonds was formed by magma ejected 22 million years ago at the latest. As for whether the lava formed later contains diamonds, it is still uncertain.