The world's largest diamond-"Millennium Star" (Figure)
This photo taken on June 5438, 2008 shows De Beers' "Millennium Star" diamond. This diamond weighs 203 carats and is one of the largest diamonds in the world. This "Millennium Star" diamond will be displayed to the world in Washington, D.C. at the end of June, along with other precious diamonds.
Tourmaline, the common name of gem-grade tourmaline, comes from the word "Turmali" in ancient Sinhala language, which means "mixed gem". In some historical documents of our country, it is called arsenic, tourmaline, bixia stone, broken evil gold and so on.
There is an interesting story about the origin of tourmaline: it is said that on a warm summer day in 1703, in Amsterdam, the Netherlands, several children were playing with stones brought back by Dutch navigators. Suddenly, a child found that dust and grass clippings near these stones were sucked in. The children were surprised and called their parents to see it. Sure enough, they found that this stone can attract or repel light objects, such as dust and grass clippings. So the Dutch call it a "vacuum stone". It was not until 1768 that the famous Swedish scientist Ringnes discovered tourmaline that people gradually accepted and adopted its current name-tourmaline.
Tourmaline is a common name of China's jewelry industry and belongs to the tourmaline family in mineralogy. The chemical molecular formula is XR3Al6B3Si6O27(OH)4, where X is Na, K and Ca, and R is various metal ions, and the type and content of R directly affect the color of tourmaline. It belongs to the tripartite crystal system. The crystal is a complex triangular column. There are various colors, such as colorless, rose red, pink, red, blue, green, yellow, brown and black, among which blue and fresh rose red are the top grades. Glass luster, transparent to translucent, refractive index is generally 1.624- 1.644, birefringence is 0.0 18-0.040, and dispersion is 0.0 17. It has a strong polychromatic color. The hardness is 7-7.5, and the density is 3.06-3.26 g/cm3. It doesn't make sense. Shell fracture. Tourmaline also has piezoelectricity and pyroelectricity, which is also the origin of its name.
The difference between tourmaline and similar gemstones. Gems similar to red tourmaline include ruby, red spinel, spodumene, red topaz, red beryl, lavender crystal and so on. Gems similar to green tourmaline are diopside, emerald and green beryl. Gems similar to blue tourmaline have blue spinel. The difference between tourmaline and tourmaline is that tourmaline has obvious double shadows at the edges and corners, more gas-liquid inclusions and cracks, strong dichroism, good transparency, large difference in density and refractive index and large birefringence.
Evaluation and purchase of tourmaline. The evaluation and selection of tourmaline is based on color, transparency, number and weight of internal defects. Attention should be paid when purchasing tourmaline: it has good transparency, glass luster on the surface, uneven isomorphic color and few internal defects (inclusions and cracks). Tourmaline is brittle, so be careful to avoid collision when wearing it.
Tourmaline has been loved by people since ancient times because of its bright color, beautiful appearance, various types and high transparency. At present, it is one of the middle-grade gems second only to emeralds and metamorphic rocks. According to records, in the funeral of Empress Dowager Cixi in the Qing Dynasty, there was a lotus carved from tourmaline, which weighed 36.8 yuan and was worth 752,000 silver at that time. People regard tourmaline as "the birthstone of October", which symbolizes happiness and peace.
Tourmaline with gem-grade value is mostly found in the cores of plagioclase pegmatite and lepidolite with strong albitization. 50-70% of the colored tourmaline in the world comes from pegmatite in minas gerais, Brazil. There are also the United States, Russia, Sri Lanka, Myanmar and other countries. Tourmaline, produced in Altay, Xinjiang, China, is crystal clear and colorful, and has the treasure of "watermelon skin" with infrared green inside.
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. 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. 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.
Comparison of carat and diamond size
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.
Ruby's English name is Ruby, which comes from Latin Ruber, meaning red. The mineral name of ruby is corundum.
The chemical composition of ruby is alumina (Al2O3), which is red to pink due to the trace element chromium (Cr3+). It belongs to the tripartite crystal system. The crystal shape is often barrel, short column, plate and so on. Aggregates are mostly granular or dense blocks. Transparent to translucent, glass luster. The refractive index is 1.76- 1.77, and the birefringence is 0.008-0.0 10. Dichroism is obvious, and it is not isotropic. Sometimes it also has a special optical effect-starlight effect, which will reflect charming six-shot starlight under the irradiation of light, commonly known as "six lines". The hardness is 9, and the density is 3.95-4. 10g/cm3. No cleavage, cleavage development. Ruby emits red and dark red fluorescence under long-wave and short-wave ultraviolet irradiation.
The difference between ruby and corresponding ruby. Natural red gems similar to rubies include red spinel, red tourmaline, red beryl, garnet and light red topaz. Similar to artificial gem, there are synthetic rubies and red glass. Its characteristics are as follows: the red spinel is uniform in color, bright red and positive red, and its crystal form is octahedral and isotropic, and it is dark under the polarizer. Red tourmaline is pink, long columnar crystal, and its hardness, density and refractive index are lower than those of ruby. Red beryl is red, hexagonal columnar crystal, anisotropic, and its hardness and density are lower than that of ruby. The synthetic ruby has uniform red color, few internal defects, no defects and few inclusions, and its fluorescence under ultraviolet light is stronger than that of natural ruby.
Evaluation and purchase of rubies. The primary evaluation and purchase factor of ruby is color, followed by weight, transparency and purity. Generally speaking, faceted rubies with pure color, large particles, transparency, no or few inclusions and defects, fine processing and symmetrical parts are excellent products. Burmese rubies are mostly pigeon blood red, with uniform color, large transparency, large particles and few defects and cracks. Ruby in Sri Lanka is light in color, and the main variety is Star Ruby. Thailand pointed bamboo ruby, deep red, not very bright, relatively clean. Ruby is fragile, so be careful when wearing it.
Sapphire's English name is sapphire, which comes from the Latin Spphins, meaning blue. The mineral name of sapphire is corundum, which belongs to corundum family. At present, all kinds of gem-grade corundum except ruby are collectively called sapphire.
The chemical composition of sapphire is alumina (Al2O3), which is blue because it contains trace elements of titanium (Ti4+) or iron (Fe2+). It belongs to the tripartite crystal system. Crystal shape is often cylindrical, short column, plate and so on. The geometric shape is mostly granular or dense block. Transparent to translucent, glass luster. Refractive index 1.76- 1.77, birefringence of 0.008, strong dichroism. Not an isotropic body. Sometimes it has a special optical effect-starlight effect. The hardness is 9 and the density is 3.95-4. 1g/cm3. No cleavage, cleavage development. It can produce beautiful starlight under certain conditions, which is called "starlight sapphire".
Sapphire can be divided into blue sapphire and brilliant (non-blue) sapphire. Indian "cornflower blue" is the best color. It is said that sapphire can protect kings and monarchs from harm, and it is called "the stone of kings". Sapphire has been designated as the "September Birthstone" by the international gem circle, symbolizing kindness, loyalty and loyalty. Sapphire is one of the five precious and high-grade gems in the world.
The difference between sapphire and similar and synthetic sapphire. Similar blue gems include blue spinel, blue tourmaline, blue zircon, blue cone mineral, kyanite and cordierite. Similar synthetic gems include synthetic sapphire, synthetic spinel and cobalt-containing blue glass. Blue spinel: uniform color, slightly gray, octahedral crystal, isotropic body, no dichroism. Blue tourmaline: the color is blue-green, and the crystal is a complex triangular column. Hardness, density and refractive index are lower than those of sapphire, and the dichroism is extremely obvious and the birefringence is large. Blue zircon: zircon that has been heated, with bright color, strong dispersibility and high birefringence. Synthetic sapphire: uniform color, clean, less inclusions and circular bubbles, isotropic.
Evaluation and purchase of sapphire. The evaluation and purchase factors of sapphire are color, weight, transparency and purity. Sapphire is characterized by uneven color, undeveloped polycrystalline twins and strong dichroism. Sapphire produced in Myanmar is bright blue (titanium color) because the inclusion can produce six or twelve starlight. Sapphire from Kashmir, India, is a kind of high-quality sapphire, which is cornflower blue and indigo blue with bright color. Sapphires from Sri Lanka, Thailand, China and Australia also have their own characteristics. Sapphire is fragile, so you should avoid bumping and bumping when wearing it.
Zircon, also known as zircon, is called hyacinthus orientalis in Japan and Zircon in English. Its origin may have evolved on the basis of Arabic "Zarkun", which originally meant "cinnabar and Athena Chu"; On the other hand, it comes from the old Persian word "Zargun", which means "golden yellow". The first official use of "zircon" was in 1783 to describe green zircon crystals from Sri Lanka.
Zircon is mainly composed of zirconium silicate, and its chemical molecular formula is Zr[SiO4]. Besides zirconium, it also contains hafnium, rare earth elements, niobium, tantalum and thorium. Zircons are divided into high-type zircon and low-type zircon according to their genesis. In gemmology, zircon can be divided into three types according to the influence of radioactive elements in zircon on refractive index, hardness and density: high type, medium type and low type. Zircon belongs to tetragonal system. The crystal morphology is a short columnar crystal composed of a square column and a square bipyramid, and the aggregate is granular. Pure colorless, impurities are red, yellow, blue, purple, brown and so on. The best colors are colorless and transparent red and blue. It has diamond luster, transparent to translucent, and white stripes. The refractive index of "high type" is 1.925- 1.984, and that of "low type" is1.780-1.815. The birefringence "high type" is 0.059 and the birefringence "low type" is 0.005. The "high type" has a large deviation of 0.04. The hardness is "high type" 7-7.5 and "low type" 6. The high density is 4.6-4.8g/cm3, and the low density is 3.9-4. 1g/cm3. It is very brittle. Under ultraviolet irradiation, "high-type" zircon shows red fluorescence.
According to the color, high-type zircon can be further divided into colorless, blue, red, brown, yellow, green zircon and so on. Zircon is often used as a substitute for diamonds because of its strong luster, high dispersibility and high hardness. Has become a leader in low-grade gems.
The difference between zircon and similar gems. Zircon is easily mixed with diamond, sphene and artificial rutile. The difference between the two is that diamond is isotropic, dark and hard in polarizer; The birefringence and dispersion of sphene and synthetic rutile are higher than those of zircon, and "fire color" often appears.
Evaluation and selection of zircon. The main factors are color, cleanliness, cutting style and weight. The most popular colors of zircon are colorless and blue, and blue is more valuable. Colorless zircon: It is the highest quality variety among gem-grade zircon. Because of its high dispersion and transparency, it is often used as a substitute for diamonds. Blue zircon: It is a high-quality variety with the highest value among zircons, and it is loved by people for its bright blue, flawless transparency and high dispersion. Zircon is brittle and its hardness is much lower than that of diamond, so you must be careful when wearing it as an ornament.
In the eyes of westerners, wearing red zircon can play a hypnotic role, drive away the plague and defeat evil. Nowadays, some countries regard zircon and turquoise as "birthstones in December", symbolizing success and victory. High-type zircon is a mineral crystallized in the early stage of magma, which contains no or a small amount of radioactive elements and is harmless to human body. The world's most famous blue zircon, weighing 208 carats, is now in the new york Museum of Natural History.
Gem-grade zircon is mostly found in metamorphic rocks and basalts. Gemstone zircon is mainly produced in Sri Lanka, Myanmar, Cambodia, Australia and other countries. South China, North China and East China of China also have output.
Emerald, the English name of emerald, originated from ancient Persian, and later evolved into Latin Smaragdus, which became today's English name around16th century. Emerald is also called "green" and "emerald". The ancient Greeks called emeralds "shining gems".
Emerald is a silicate containing beryllium and aluminum, and its molecular formula is Be3Al2[Si6O 18], which belongs to the noblest member of beryl family. It belongs to hexagonal system. Crystal simplex is hexagonal column and hexagonal bipyramid, mostly rectangular column. Aggregates are granular, blocky, etc. Emerald green, glass luster, transparent to translucent. The refractive index is 1.564- 1.602, the birefringence is 0.005-0.009, and the polychromatic property is not obvious. Not an isotropic body. The hardness is 7.5 and the density is 2.63-2.90g/cm3. The cleavage is incomplete, and the shell breaks. Fragile. Under the irradiation of X-rays, emeralds emit very weak pure red fluorescence.
The difference between emeralds and similar natural green gems, synthetic emeralds and fakes. Similar natural green gems include fluorite, green tourmaline, apatite, jadeite, green sapphire and garnet containing chromium, vanadium, calcium and aluminum; Artificial emeralds and imitations include synthetic emeralds, beryl, foil-lined emeralds and oiled emeralds. The differences are as follows: fluorite, blue-green, isotropic, low hardness 4, density 3. 18 g/cm3, larger than emerald, light blue fluorescence. Green tourmaline and dark blue green tourmaline become pure green after treatment, with obvious dichroism, high birefringence, 0. 18 and high density. Apatite, light green apatite, with blue hue, small hardness of 5, large refractive index of 1.632- 1.667, and phosphorescence under ultraviolet light. Emeralds, high-quality translucent emeralds are more like emeralds, but emeralds have a fiber interwoven structure with finer fibers, which emeralds do not have. Eclogite contains chromium, vanadium, calcium and aluminum, emerald green, isotropic, and has a strong diamond luster. Emerald is synthesized artificially by flux growth method and hydrothermal method, with rich colors, strong red fluorescence under ultraviolet light and bright red under color filter. There are also beryl three-layer stones, foil-lined emeralds, oil-colored emeralds, etc., which can be distinguished from emeralds after careful observation and identification.
Evaluation and purchase of jadeite. The evaluation and purchase of emeralds are based on color, transparency, cleanliness and weight. Natural emeralds mainly include Colombian emeralds, Urals emeralds, Brazilian emeralds and Zimbabwean emeralds. The colors are mostly transparent and bright emeralds, yellow-green and so on. The appearance is soft and fluffy, and the inclusions are common. It is bright in the polarizer, and there are four light and shade changes in 360-degree rotation, which is an anisotropic body. Polychromaticity is not obvious under dichroic mirror. Pink under the color filter. Emerald is fragile, afraid of high temperature, will fade in case of fire, and will burst easily in case of high temperature. Pay great attention when wearing and storing.
Cat's eye, namely "cat's eye", "cat's eye" and "cat essence". Opal, also known as oriental cat's eye, is a rare and precious variety in jewelry. Opal is named because it is as flexible and bright as a cat's eye and can change with the intensity of light. This optical effect is called "cat's eye effect".
There are many gems with cat's eye effect. Gemmologists call the chrysoberyl with cat's eye effect opal. Generally speaking, opal refers to emerald-green cat-eye gemstone, while other gemstones with cat-eye effect must be preceded by the word "cat's eye", such as aquamarine cat's eye and tourmaline cat's eye.
Opal is a kind of gold emerald in mineralogy and belongs to spinel mineral. Gold emerald is an alumina containing beryllium, and its chemical molecular formula is BeAl2O4. It belongs to orthorhombic system. Crystal morphology is often short columnar or plate-shaped. Opal has many colors, such as honey yellow, brownish yellow, wine yellow, brownish yellow, yellowish green, yellowish brown, grayish green and so on, among which honey yellow is the most precious. Transparent to translucent. The glass is greasy and shiny. The refractive index is 1.746- 1.755, and the birefringence is 0.008-0.0 10. Dichroism is obvious, the dispersion is 0.0 15, and it is not isotropic. The hardness is 8.5, and the density is 3.71-3.75g/cm3. Shell fracture.
The difference between cat's eyes like opal and artificial cat's eyes. In nature, tourmaline, beryl, apatite and kyanite can produce cat's eye effect, but they are not as precious as gold-green cat's eye. Tourmaline cat's eye: hardness 7-7.5, density 3.06g/cm3, refractive index 1.624- 1.644. Quartz cat's eye: low hardness, about 6.5, low density, 2.78 g/cm3, low refractive index, 1.44. Artificial cat's eye: opal made of artificial glass fiber, with brown, blue and red colors. The artificial opal has 2-3 bright bands at the arc top, while the natural opal has only one bright band. Observing with a magnifying glass, we can see that the artificial opal has a hexagonal honeycomb structure, with a low hardness of about 5, a low density of 2.46 g/cm3 and a refractive index of 1.44.
Evaluation and purchase of opal. The evaluation of opal is based on the color, the position of eyeliner, the shape and weight of the gem. High-quality cat-eye gemstone, the cat-eye line should be thin and narrow, and the boundary should be clear; Eyes should be flexible to open and close, showing vivid light; The color of the cat's eye should be in sharp contrast with the background; And the cat's eye line should be located in the center of the cambered surface. When purchasing, we should distinguish opal from other precious cat eyes and artificial cat eyes according to the identification characteristics, and purchase genuine opal.
In Southeast Asia, opal is often regarded as a symbol of good luck, and it is believed that it will protect the owner's health and longevity and stay away from poverty. Opals are often called "noble gems". It belongs to one of the five precious and high-grade gems in the world together with the variable stone. Hope, a British gem collector, collects a famous opal, which is carved into the shape of an altar with a torch at the top. The whole gem is spherical with a diameter of about 1- 1.5 inches. Opals are mainly produced in hydrothermal deposits and pegmatite veins. The most famous opal producing areas in the world are Trana Bula and Goyle in the southwest of Sri Lanka. Opals are also found in Brazil and Russia, but they are very rare.