The chemical formula of diamond is C, and its crystal forms are mostly octahedron, rhombic dodecahedron, tetrahedron and their aggregates. Without impurities, it is colorless and transparent. When it reacts with oxygen, it will also produce carbon dioxide, which belongs to the simple substance of carbon with graphite. The bond angle of diamond crystal is109 28', which is a kind of crystal with excellent physical properties such as superhard, wear resistance, heat sensitivity, heat conductivity, semiconductor and penetration. Known as the "king of hardness", the king of gems. The angle of the diamond crystal is 54 degrees, 44 minutes and 8 seconds. Traditionally, people often call processed products diamonds, while unprocessed products are called diamonds. In China, the name of diamond was first found in Buddhist scriptures. Diamonds are the hardest substance in nature. The best color is colorless, but there are also special colors, such as blue, purple and golden yellow. Diamonds of these colors are rare and precious among diamonds. India is the most famous diamond producer in history. Now many famous diamonds in the world, such as "Mountain of Light", "Regent" and "orlov", all come from India. The output of diamonds is very scarce, and the finished diamonds are usually one billion times the amount mined, so the price is very expensive. Polished diamonds are usually round, rectangular, square, oval, heart-shaped, pear-shaped and olive-pointed. The heaviest diamond in the world is Cullinan, 1905 produced in South Africa, weighing 3 106.3 carats. It was divided into nine small diamonds, one of which, Cullinan 1, known as the "Star of Africa", still ranks first in the world.
Crystal structure: the unit cell is face-centered cubic structure, and each unit cell contains 2 groups of 8 C atoms.
Diamonds Diamonds usually come in yellow, brown, blue, green and pink, but colorless ones are more popular. There are 10 extra-large gem-grade diamonds weighing more than 620 carats (124 grams) in the world, among which the largest Cullinan weighs 3 106 carats (62 1.35 grams) and has a size of 5×6.5×65438. 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, the former Soviet Union, South Africa, Brazil, Namibia, Ghana, Central Africa, Sierra Leone and China.
It is the tenth hardness grade of Mohs mineral.
Attachment: giant diamonds and big diamonds produced in China;
In the twenty years since 197 1, several diamonds over 50 carats and over 100 carats have been discovered in China. The order of discovery time is as follows:
[1]1971On September 25th, a diamond weighing 52.7 1 carat was found beside Suqian Highway in Jiangsu Province.
[2] 1 97765438+February 2 1 day, in Changlin Brigade, Linshu County, Shandong Province, female player Wei found a high-quality giant diamond of1weight 158.786 carats, all transparent and yellowish in color, which can be called "the best in China". It was named "Chang Lin Diamond"
[3]1981August 5, 2005 124.27 carat giant diamond was found in Chenbu, Tancheng, Shandong. It was named "Chenbu 1".
[4] 1982 In September, a 96.94-carat diamond was found in Chenbu, Tancheng, Shandong Province.
[5] 1983 In May, a 92.86-carat diamond was discovered in Chenbu, Tancheng, Shandong Province.
[6]1983165438+1October 14 A giant diamond named "Mengshan No.1" was found in Mengyin, Shandong Province.
According to the data of 1987, the main diamond metallogenic areas in China are: ① Liaodong-Jinan metallogenic area, with kimberlite in Mesozoic and Mesozoic. (2) Western Shandong, northern Jiangsu and northern Anhui are metallogenic areas, and there may be multi-stage kimberlites in the Lower Paleozoic. ③ Kimberlite is found in Taihang Mountain, Songshan Mountain and Wutai Mountain in Shanxi, Henan and Hebei mining areas. ④ Hunan, Guizhou, Hubei and Sichuan metallogenic areas, and four diamond placers with industrial value were found in Shui Yuan Valley, Hunan Province.
Hunan diamonds are produced in Dingjiagang, Taoyuan and Qianyang in Changde, Hunan. Hunan diamonds are mainly placers, mainly distributed in Yuanshui River Basin, with scattered distribution and low grade, but good quality, with gem-grade diamonds accounting for about 40%. According to legend, during the Ming Dynasty, sporadic diamond discoveries were made in Yuanjiang Valley, Hunan Province, and large-scale prospecting began in the 1950s. Diamonds are distributed in all waters of Yuanjiang River, but only Dingjiagang in Changde, Chexichong in Taoyuan County, Xinzhuanglong in Xupu County (Qianyang) and Yaotou in Yuanling County are of mining value.
Diamonds in Hunan have different shades, with obvious differences inside and outside, and are distributed in strips and spots. Its brown series diamond crystals are yellow-brown, with clean interior and a large number of brown spots on the surface. Brown spots are yellow, tan, brown, black and so on. , mainly distributed on the corroded surface of diamond. Brown is mainly caused by the radiation of radioactive particles in nature. The overall particle size of diamond is small, but the texture is good, mainly single crystal, accounting for about 98% of the total output; The crystals are relatively complete, mainly octahedron, dodecahedron and hexahedron; Most crystals are light transparent or yellow, brown, etc. The grain weight is less than 28mg, generally10.9 ~15 mg; 22% crystals contain inclusions; There are cracks on the surface of 60% crystals, and the surface dissolution is not heavy.
history
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.
Place of production
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, it is more likely to find diamond mines in places where garnet and olivine are produced. 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 this, that is, in the 1950s, geologists of De Beers Company had searched for diamond mines all over the world according to the indicated 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.
Diamond mining
Primary diamond is located deep underground (130- 180 km), at high temperature (900- 1300℃) and high pressure (45-60)&; 2 15; The crystallization age is 65438±008 pa, which occurs in kimberlite or eclogite and has a long formation age. South Africa's Kimberley mine, peridotite diamonds were formed about 3.3 billion years ago, almost the same age as the earth; The ages of Australian argyle mine, Botswana Olab mine and eclogite diamond are 65.438 0.58 billion years and 990 million years respectively. The diamond crystal hidden in such a large underground depth for hundreds of millions of years will have to help the volcano erupt, and the lava flow will bring the magma containing diamonds to the earth's near surface or migrate to the river sand for a long time. The former forms primary tubular ore and lover ring, while the latter forms alluvial ore. After hard mining, these ore bodies need multiple treatments to get strange original stones from them. Only about 20% of rough diamonds can be used as rough diamonds for jewelry, and most of them can only be used for industrial purposes such as cutting, grinding and polishing. It is roughly estimated that at least 250 tons of ore must be mined and processed to obtain diamonds weighing 1ct, and the recovery rate is quite low. If you want to choose beautiful diamonds from finished diamonds, the ratio between them is even more disparity.
Characteristics of diamonds
If any two different minerals are carved into each other, one of them will be damaged. 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) Gloss, as hard, flat and bright as a diamond, has a particularly strong reflection on white light. This very characteristic reflection is called diamond luster.
Diamond raw materials
The raw material of diamonds is ancient plankton! ?
Carbon is a common element. Animals and plants contain a lot of carbon, even in the air. Our body is no exception, which also contains a lot of carbon atoms. The human body contains about 18% carbon.
However, although carbon is a common element on the ground, it is very rare on the earth. According to the analysis of the solar spectrum and meteorites falling to the earth, it is speculated that oxygen is the most chemical element constituting the earth, followed by silicon, aluminum and iron. These four elements account for 87% of the total mass of the earth; If calcium, sodium and potassium are added, the total * * * accounts for 96%. The remaining 4% is all other elements including carbon.
In addition, the greater the mass of the elements that make up the earth, the more inclined they are to gather toward the center of the earth. Carbon is a relatively light element, concentrated near the surface of the earth, so there is basically no carbon in the depths of the earth. Professor Yasuhiko Yagi, who specializes in the deep structure of the earth at the Institute of Physical Properties of the University of Tokyo, Japan, said: "Since the birth of the earth 4.6 billion years ago, carbon in it has been extremely scarce. Therefore, there will not be many raw materials for forming diamonds inside the earth. "
On the other hand, scientists also know through isotope analysis that at least some of the substances that make up diamonds belong to carbon left by organic matter. This means that with the movement of tectonic plates, the remains of plankton (animals and plants) deposited on the seabed hundreds of millions to billions of years ago are brought from the sedimentary layers to the interior of the earth, where diamonds may form.
Professor Yagi said: "In short, carbon is a trace element in the earth, so it is not surprising that diamonds are extremely rare."
[Edit this paragraph] logo
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.
5, according to the specific gravity (density) detection of diamonds.
The density of diamonds is about 3.5 grams per cubic centimeter, while the density of other "suspected diamonds" is generally about 3.25 grams per cubic centimeter. If the "suspected diamond" is soaked in the diiodomethane solution (density is 3.35g), it will float due to other things and sink due to the diamond.
[Edit this paragraph] The difference between diamond and graphite.
Both graphite and diamond belong to elemental carbon and have the same chemical properties, but diamond and graphite are not the same substance, they are allotropes composed of the same elements. The difference is the physical structure characteristics.
The chemical formula of both is C.
The regular hexagon formed between graphite atoms is a plane structure and is flaky.
Diamond atoms have three-dimensional regular tetrahedron structure and pyramid structure.
[Edit this paragraph] High hardness synthetic diamond
The R&D Center of General Electric Company of the United States has synthesized synthetic diamonds with atomic density per unit volume higher than that of any existing solid substance, and the hardness is higher than that of natural diamonds, which is the hardest material in the world. It contains 99% carbon 13 isotope and natural diamonds. According to scientists' observation, with the increase of carbon isotope density 13, the distance between atoms will be slightly reduced, which makes the hardness of artificial diamonds exceed that of natural diamonds with slightly loose atomic arrangement. In the process of synthesizing synthetic diamonds, scientists first precipitate carbon in methane gas rich in carbon isotope 13 into small diamond fragments by chemical evaporation, and then use very high pressure to decompose and recrystallize these small fragments into massive diamonds with a maximum weight of 3 carats.
synthetic diamond
Artificial diamond micropowder
[Edit this paragraph] Other
Usage: 1: When people take diamond powder, it 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. In medieval Europe, it was popular among princes and nobles.
Usage 2: Diamond abrasive for diamond wire drawing dies of geological drills and petroleum drills, and diamond for diamond dressers.
Diamond hardness tester for glass cutting tools, diamond for handicrafts.
Usage 3: The sound quality will be greatly improved if the speaker is coated on the audio paper basin.
[Edit this paragraph] Hardness of diamonds
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 5 apatite
Grade 6 orthoclase
Seventh grade timely
Grade 8 topaz
Grade 9 corundum
Grade 10 diamond
Diamond mineral resources
diamond
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.
China is relatively poor in diamond 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.