The first country in the world to discover diamonds is India, one of the four ancient civilizations. The largest diamond in the world is the Cullinan diamond discovered in Pretoria, South Africa on January 21, 1905. It is light sky blue and weighs 3106 carats. It is named after Morgan.
The world's largest diamond - "Millennium Star" (picture)
This photo obtained on the 18th shows the "Millennium Star" diamond of De Beers. The diamond weighs 203 carats and is one of the largest diamonds in the world. The "Millennium Star" diamond will be displayed to the world at the end of June in Washington, the capital of the United States, together with some other precious diamonds.
Tourmaline, the common name for gem-quality tourmaline, its English name is Tourmaline, which is derived from the ancient Sinhala word "Turmali", which means "mixed gemstone". In some historical documents of our country, it is called "arsenic selenium", "tourmaline", "bixiaxi", "broken evil gold", etc.
There is an interesting story about the origin of tourmaline: Legend has it that on a warm summer day in 1703, in Amsterdam, the Netherlands, several children were playing with stones brought back by Dutch voyagers. Suddenly, a child discovered that these stones sucked up dust and grass clippings nearby. The children were very surprised and called their parents to see it. Sure enough, they found that this stone could attract or repel light objects, such as dust and grass clippings. Therefore, the Dutch call it "ash-absorbing stone". It was not until 1768, when the famous Swedish scientist Linnes discovered tourmaline, that people gradually accepted and adopted the current name - tourmaline.
Tourmaline is a commonly used name in my country’s jewelry industry and belongs to the tourmaline group in mineralogy. The chemical molecular formula is XR3Al6B3Si6O27(OH)4, where X is Na, K, Ca, and R is various metal ions. The type and content of R directly affects the color of tourmaline. It belongs to the trigonal crystal system. The crystal is in the shape of a complex trigonal column. There are various colors, including colorless, rose red, pink, red, blue, green, yellow, brown and black, among which azure blue and bright rose red are the top grades. Glass gloss, transparent to translucent, refractive index generally 1.624-1.644, birefringence 0.018-0.040, dispersion 0.017. Extremely polychromatic. Hardness 7-7.5, density 3.06-3.26 g/cubic centimeter. No cleavage, conchoidal fracture. Tourmaline also has piezoelectric and pyroelectric properties, which is where the name tourmaline comes from.
The difference between tourmaline and similar gemstones. Gemstones similar to red tourmaline include ruby, red spinel, spodumene, light red topaz, red beryl, lavender crystal, etc. Gemstones similar to green tourmaline include diopside, emerald, and green beryl. A gem similar to blue tourmaline is blue spinel. The difference between tourmaline is that there are obvious double shadows at the edges and corners of tourmaline, more gas-liquid inclusions and cracks, strong dichroism, good transparency, large differences in density and refractive index, and a large birefringence.
Tourmaline evaluation and purchase. Tourmaline is evaluated and purchased based on color, transparency, number of internal defects and weight. When purchasing, pay attention to: the transparency of tourmaline should be good, the surface should have glass luster, the color of the same crystal should be uneven, and there should be fewer internal defects (inclusions and cracks). Tourmaline is brittle, so care should be taken to avoid impact when wearing it.
Tourmaline has bright, beautiful, changeable colors and high transparency, and has been loved by people since ancient times. At present, it is one of the mid-range gemstones after emerald and alexandrite. According to records, among the burial objects of Empress Dowager Cixi of the Qing Dynasty, there was a lotus carved from tourmaline, which weighed 36.8 qian and was valued at 750,000 taels of silver at the time. People regard tourmaline as the "October birthstone", symbolizing happiness and peace.
Tourmaline with gem-quality value is mostly found in the core of the strongly albite- and lepidolite-based microcline albite pegmatite. 50-70% of the world's colored tourmalines come from pegmatites in Minas Gerais, Brazil. The United States, Russia, Sri Lanka, Myanmar and other countries also have output.
The tourmaline produced in Altay, Xinjiang, my country, is crystal clear and comes in various colors, including the rare "watermelon rind" with reddish green inside.
Diamond, also known as diamond, the mineral name is diamond. The English name Diamond comes from the ancient Greek word Adamant, which means hard and inviolable substance.
The chemical composition of diamonds is carbon, the only single element among gemstones. Belongs to the equiaxed crystal system. The crystal forms are mostly octahedron, rhombohedral dodecahedron, tetrahedron and their polymorphs. Pure diamonds are colorless and transparent, showing different colors due to the mixing of trace elements. Strong diamond luster. The refractive index is 2.417 and the dispersion is medium, 0.044. Homogeneous body. The thermal conductivity is 0.35 cal/cm·second·degree. Tested with a thermal conductivity meter, the response is the most sensitive. With a hardness of 10, it is the hardest mineral known so far. Its absolute hardness is 1,000 times that of quartz and 150 times that of corundum. It is afraid of heavy blows and will cleave and break after a heavy blow. A set of cleavages is complete. Density 3.52 g/cm3. Diamonds are luminescent and can emit light cyan phosphorescence at night after being illuminated by sunlight. X-ray irradiation emits sky blue fluorescence. The chemical properties of diamond are very stable and are not easily soluble in acids and alkali at room temperature, and acids and alkali will not affect it.
The difference between diamonds and similar gemstones and synthetic diamonds. Common substitutes or fakes in the gem market include colorless gemstones, colorless spinel, cubic zirconia, strontium titanate, yttrium almandine garnet, yttrium gallium garnet, and artificial rutile. Synthetic diamonds were first successfully developed in Japan in 1955, but were not mass produced. Because synthetic diamonds are more expensive than natural diamonds, synthetic diamonds are rare on the market. Diamonds can be distinguished from similar gemstones by their unique hardness, density, dispersion, and refractive index. For example: imitation diamond cubic zirconia is mostly colorless, has strong dispersion (0.060), strong gloss, and high density of 5.8 g/cubic centimeter, and it feels heavy when weighed by the hand. Yttrium almandine has a soft dispersion and is difficult to distinguish from diamonds with the naked eye. Therefore, you should keep the identification characteristics of diamonds in mind when purchasing to avoid unnecessary losses.
Moissanite: Very similar to diamond, it is the latest diamond imitation - synthetic silicon carbide. It is a world-patented product that was developed and researched by the American C3 Company with an investment of US$45 million and launched in June 1998. Its chemical composition is SiC, which is nearly colorless, has a refractive index of 2.56-2.69, a dispersion of 0.104, a birefringence of 0.043, a hardness of 9.25, and a density of 3.22 g/cm3. Detection method: The thermal conductivity meter cannot distinguish between diamonds and moissanite, and must be identified with the American C3 Company’s 590 Colorless Silicon Carbide/Diamond Detector. When measured with diiodomethane (density 3.32 g/cm3) liquid, moissanite floats and diamonds sink. You can also use a magnifying glass to observe inclusions and use fire methods to assist identification.
Approximate comparison between carat and diamond size
When evaluating and purchasing diamonds, the following four aspects should be considered:
(1) Color: Colorless For best, the darker the tone, the worse the quality. Diamonds with colored colors, such as red, pink, green, blue, etc., are treasures among diamonds and are expensive.
(2) Defects: The cleanliness of the diamond should be carefully observed under a ten-fold microscope. The more defects and the more obvious the location, the worse the quality and the price will be reduced accordingly.
(3) Weight: The price of a diamond is proportional to the square of its weight. The greater the weight, the higher the value.
(4) Cut: It should be cut according to standard proportions to form a standard round diamond shape. If the proportion is inappropriate, the diamond will not "fire" and the price will drop. If the surface has fine lines and artificial damage, its price will also drop.
Diamonds rank first among the five most precious and high-end gemstones in the world, and are known as the "King of Gems" and "Priceless Treasures". International gemstones define diamonds as the "birthstone of April". The first country in the world to discover diamonds was India, one of the four ancient civilizations. The largest diamond in the world is the Cullinan Diamond discovered in Pretoria, South Africa on January 21, 1905. It is light sky blue and weighs 3106 carats, which is approximately the size of a man's fist.
It was polished into 105 diamonds of various sizes, the largest of which, the "Star of Africa", weighed 530.2 carats and was set on the scepter of King Edward VII of England. The most famous large diamond in my country is called the "Changlin Diamond", weighing 158.78 carats. It was discovered on December 21, 1977 by Wei Zhenfang, a female commune member of Changlin Village, Qishan Town, Linshu County, Shandong Province, while plowing the land.
Gem-quality diamonds are mostly concentrated in placers or kimberlite and potash lamprophyre rock tubes. The most famous diamond producing areas in the world include Australia, South Africa, Zaire, Botswana, Russia and other countries. China's Liaoning, Shandong, Hunan and other provinces have output.
The English name of ruby ??is Ruby, which comes from the Latin Ruber, which means red. The mineral name of ruby ??is corundum.
The chemical composition of ruby ??is aluminum oxide (Al2O3), which is red to pink due to the trace element chromium (Cr3). It belongs to the trigonal crystal system. The crystal shape is often barrel-shaped, short columnar, plate-shaped, etc. The aggregates are mostly granular or dense blocks. Transparent to translucent, glassy luster. The refractive index is 1.76-1.77, and the birefringence index is 0.008-0.010. Obvious dichroism, heterogeneous body. Sometimes it has a special optical effect - starlight effect, which reflects charming six-ray starlight when illuminated by light, commonly known as "six lines". The hardness is 9 and the density is 3.95-4.10 g/cubic centimeter. No cleavage, cleavage development. Ruby fluoresces red and dark red under long-wave and short-wave ultraviolet irradiation.
The difference between rubies and corresponding red gemstones. Natural red gemstones similar to rubies include red spinel, red tourmaline, red beryl, pyrope, and light red topaz. Similar artificial gemstones include synthetic ruby ??and red glass. Its characteristics are as follows: the color of red spinel is uniform, bright red, true red, the crystal shape is octahedral, homogeneous, and dark under a polarizer. Red tourmaline is pink in color, has a long columnar crystal shape, and has lower hardness, density, and refractive index than ruby. Red beryl is red, has a hexagonal columnar crystal shape, is heterogeneous, and has lower hardness and density than ruby. Synthetic rubies have a uniform red color, few internal defects, flawless, and few inclusions, and their fluorescence under ultraviolet rays is stronger than that of natural rubies.
Ruby evaluation and purchase. The primary evaluation and purchase factor for rubies is color, followed by weight, transparency and clarity. Generally speaking, faceted rubies with pure color, large particles, transparency, no or few inclusions and defects, fine processing, and well-proportioned parts are considered top-grade. Burmese rubies are mostly pigeon blood red, with uniform color, high transparency, large grains, and few flaws and cracks. Sri Lankan rubies are light in color and the main variety is star ruby. Thai sharp bamboo pattern ruby, deep red, not too bright in color, relatively clean. Ruby is brittle and is afraid of being knocked or beaten, so you should be careful when wearing it.
The English name of sapphire is Sapphire, which comes from the Latin Spphins, which means blue. The mineral name of sapphire is corundum, which belongs to the corundum family of minerals. At present, in the gem industry, besides rubies, all other gem-grade corundums are collectively called sapphires.
The chemical composition of sapphire is aluminum oxide (Al2O3), which is blue due to the trace elements titanium (Ti4) or iron (Fe2). It belongs to the trigonal crystal system. The crystal shape is often cylindrical, short columnar, plate-shaped, etc., and the geometry is mostly granular or dense block. Transparent to translucent, glassy luster. The refractive index is 1.76-1.77, the birefringence is 0.008, and the dichroism is strong. Heterogeneous body. Sometimes there is a special optical effect - starlight effect. The hardness is 9 and the density is 3.95-4.1 g/cubic centimeter. No cleavage, cleavage development. Under certain conditions, beautiful six-ray starlight can be produced, which is called "star sapphire".
Sapphires can be divided into blue sapphires and vivid (non-blue) sapphires. The best color is "cornflower blue" produced in India. It is said that sapphire can protect kings and monarchs from harm, and is known as the "Emperor Stone". The international gem industry defines sapphire as the "birthstone of September", symbolizing love, loyalty and perseverance. Sapphire is one of the world's five most precious high-end gemstones.
The difference between sapphire and similar blue gemstones and synthetic blue gemstones.
Similar blue gemstones include blue spinel, blue tourmaline, blue zircon, benitonite, kyanite, cordierite, etc. Similar synthetic gemstones include synthetic sapphire, synthetic spinel, and cobalt-containing blue glass. Blue spinel: uniform color, slightly gray, octahedral crystal, homogeneous, no dichroism. Blue Tourmaline: The color is greenish blue, the crystal is a complex triangular columnar, the hardness, density, and refractive index are lower than those of sapphire, the dichroism is extremely obvious, and the birefringence is high. Blue zircon: Heat-treated zircon with bright color, strong dispersion and high birefringence. Synthetic sapphire: uniform color, clean, few inclusions, round bubbles, homogeneous.
Sapphire evaluation and purchase. Factors for evaluating and purchasing sapphires are color, weight, transparency and clarity. The biggest characteristics of sapphire are uneven color, lack of development of polycrystalline twins, and strong dichroism. Sapphires produced in Myanmar are bright blue (colored by titanium). Due to inclusions, they can produce six-ray or twelve-ray starlight. Indian Kashmir sapphire is cornflower blue, slightly purple indigo, bright in color, and is a high-quality sapphire. Sapphires produced in Sri Lanka, Thailand, China, and Australia also have their own characteristics. Sapphire is brittle and should be avoided from being dropped or bumped when wearing it.
Zircon, also known as "zircon stone", is called "hyacinth stone" in Japan, and its English name is Zircon. One theory is that its origin may have evolved on the basis of the Arabic "Zarkun", which originally meant "cinnabar and cinnabar"; another theory is that it originated from the ancient Persian "Zargun", which means "golden". The first official use of "Zircon" was in 1783 to describe green zircon crystals from Sri Lanka.
The main component of zircon is zirconium silicate, with the chemical formula Zr[SiO4]. In addition to mainly containing zirconium, it often also contains hafnium, rare earth elements, niobium, tantalum, thorium, etc. Zircon is divided into high-type zircon and low-type zircon according to its origin. In gemology, zircon is divided into three types: "high type", "intermediate type" and "low type" based on the degree to which the radioactive elements in zircon affect the refractive index, hardness and density. Zircon belongs to the tetragonal crystal system. The crystal shape is a short columnar crystal composed of tetragonal prisms and tetragonal bipyramids, and the aggregates are granular. Those that are pure are colorless, while those that contain impurities are colored red, yellow, blue, purple, brown, etc. The best colors are colorless and transparent red and blue. It has diamond luster, transparent to translucent, and has white streaks. The refractive index "high type" is 1.925-1.984, and the "low type" is 1.780-1.815. The birefringence is 0.059 for "high type" and 0.005 for "low type". The "high type" dispersion is stronger, 0.04. Hardness "high type" 7-7.5, "low type" 6. The density of "high type" is 4.6-4.8 grams/cubic centimeter, and the "low type" is 3.9-4.1 grams/cubic centimeter. Has strong brittleness. Under ultraviolet irradiation, "high-type" zircon fluoresces red.
High-type zircon can be further divided according to color: colorless, blue, red, brown, yellow, green zircon, etc. Due to its strong luster, high dispersion and high hardness, zircon is often used as a substitute for diamonds. It has become the leader in mid- to low-end gemstones.
The difference between zircon and similar gemstones. Zircon is easily mixed with diamonds, sphene, and artificial rutile. The difference between them is: diamond is a homogeneous body, dark in polarizer and has high hardness; sphene and artificial rutile have higher birefringence and dispersion than zircon, and often appear "fire".
Zircon evaluation and purchase. The main factors are color, clarity, cut style and weight. The most popular colors of zircon are colorless and blue, with blue ones being more valuable. Colorless zircon: It is the highest quality variety of gem-grade zircon. Because of its high dispersion, transparent and colorless, it is often used as a substitute for diamonds. Blue zircon: It is a high-quality variety of zircon with the highest value. It is loved by people for its bright blue, flawless transparency and high dispersion. Zircon is brittle and has much lower hardness than diamond. You must be careful when wearing it as jewelry.
In the eyes of Westerners, wearing red zircon can have a hypnotic effect, drive away plagues, and defeat evil. Nowadays, some countries use zircon and turquoise together as the "December birthstone", symbolizing success and victory.
High-type zircon is a mineral that crystallized in the early stages of magma. It contains no or little radioactive elements and is harmless to the human body. The most famous blue zircon in the world, weighing 208 carats, is now collected in the Museum of Natural History in New York, USA.
Gem-quality zircons are mostly found in metamorphic rocks and basalts. Gem-grade zircons in the world are mainly produced in Sri Lanka, Myanmar, Cambodia, Australia and other countries. There is also output in South China, North China, and East China in our country.
The English name of emerald is Emerald, which originated from ancient Persian and later evolved into Latin Smaragdus. It became the English name today around the 16th century AD. Emerald is also called "Luzon Green" and "Emerald". The ancient Greeks called emerald a "glowing" gem.
Emerald is a silicate containing beryllium aluminum, its molecular formula is Be3Al2[Si6O18], and it is the most "noble" member of the beryl family. It belongs to the hexagonal crystal system. The simple crystal shapes are hexagonal prisms, hexagonal bipyramids, and mostly rectangular prisms. The aggregates are in the form of granules, blocks, etc. Emerald green, glassy luster, transparent to translucent. The refractive index is 1.564-1.602, the birefringence is 0.005-0.009, and the pleochroism is not obvious. Heterogeneous body. Hardness 7.5, density 2.63-2.90 g/cubic centimeter. Incomplete cleavage, conchoidal fracture. Very brittle. Under X-ray irradiation, emerald emits very weak pure red fluorescence.
The difference between emeralds and similar natural green gemstones, synthetic emeralds, and fakes. Similar natural green gemstones include fluorite, green tourmaline, apatite, jade, green sapphire, and chrome-containing vanadium grossular garnet; artificial emeralds and imitations include synthetic emerald, beryl three-layer stone, and foil-lined emerald. Green, oil-infused emerald, etc. The difference is as follows: fluorite, slightly bluish green, homogeneous, with a small hardness of 4, a density of 3.18 g/cubic centimeter, larger than emerald, and a light blue fluorescence. Green tourmaline, dark blue green tourmaline is changed to pure green after treatment, with obvious dichroism, high birefringence of 0.18, and high density. Apatite is a bluish light green apatite with a blue hue, a small hardness of 5, a large refractive index of 1.632-1.667, and phosphorescence under ultraviolet light. Jade, high-quality translucent emerald green jade is more similar to emerald, but jade has a fiber interwoven structure with finer fibers, while emerald does not have this structure. Chromium-containing vanadium grossular garnet, emerald green, homogeneous, strong sub-adamantine luster. Synthetic emerald, synthesized by flux growth method and hydrothermal method, has rich color, strong red fluorescence under ultraviolet light, and bright red under color filter. There are also beryl three-layer stones, foil-lined emeralds, oil-infused emeralds, etc., which can be distinguished from emeralds after careful observation and identification.
Emerald evaluation and purchase. Emeralds are evaluated and purchased based on color, transparency, clarity and weight. Natural emeralds mainly include Colombian emeralds, Ural emeralds, Brazilian emeralds and Zimbabwean emeralds. The colors are mostly transparent, bright emerald green, light yellow green, etc. The appearance is soft and velvety, and inclusions are common. It is bright in the polarizer and has four light and dark changes when rotated 360 degrees, making it a non-homogeneous body. The pleochroism is not obvious under a dichroic microscope. It appears pink under the color filter. Emerald is relatively brittle and is afraid of high temperatures. It will fade when exposed to fire and is prone to bursting at high temperatures. Be very careful when wearing and storing it.
Cat’s eye, namely “cat’s eye”, “cat’s eye” and “cat’s spirit”. Cat’s Eye, also known as Oriental Cat’s Eye, is a rare and valuable species in jewelry. Because the light phenomenon exhibited by cat's eye stone is the same as that of a cat's eyes, it is flexible and bright and can change with the intensity of light, hence its name. This optical effect is called the "cat's eye effect".
There are many gems with cat-eye effect. In the gemological community, chrysoberyl with cat's eye effect is called cat's eye. Generally speaking, cat's eye refers to chrysoberyl, while other gems with cat's eye effect must be preceded by the word "cat's eye". Names, such as aquamarine cat's eye, tourmaline cat's eye, etc.
In mineralogy, cat's eye is a kind of chrysoberyl and belongs to the spinel group minerals. Chrysoberyl is a beryllium-containing aluminum oxide with the chemical formula BeAl2O4. It belongs to the orthorhombic crystal system.
The crystal morphology is often short columnar or plate-shaped. Cat's eye stones come in various colors, such as honey yellow, brown yellow, wine yellow, brown yellow, yellow green, yellow brown, gray green, etc. Among them, honey yellow is the most valuable. Transparent to translucent. Glass to grease luster. The refractive index is 1.746-1.755, and the birefringence is 0.008-0.010. The dichroism is obvious, the dispersion is 0.015, and it is a heterogeneous body. Hardness 8.5, density 3.71-3.75 g/cubic centimeter. Shell-shaped fracture.
The difference between cat’s eye stone and other similar gemstone cat’s eyes and artificial cat’s eyes. Gemstones that can produce cat's eye effect in nature include tourmaline, beryl, apatite, quartz kyanite, etc., but they are not as precious as gold-green cat's eye. Tourmaline cat's eye: hardness is small, 7-7.5, density 3.06 g/cubic centimeter, refractive index 1.624-1.644. Quartz cat's eye: low hardness, about 6.5, low density, 2.78 g/cubic centimeter, and low refractive index, 1.44. Artificial cat's eye: Cat's eye stone made of artificial fiberglass, available in brown, blue and red. However, artificial cat's eye stone appears with 2-3 bright bands at the top of the arc, while natural cat's eye stone only appears with one bright band. Observing with a magnifying glass, you can see that the artificial cat's eye stone has a hexagonal honeycomb structure, a low hardness of about 5, a low density of 2.46 g/cubic centimeter, and a refractive index of 1.44.
Cat’s eye stone evaluation and purchase. The evaluation of cat's eye is based on factors such as color, position of the eyeliner, shape of the gemstone, and weight. For a high-quality cat's eye gemstone, the cat's eye line should be thin and narrow with clear boundaries; the eyes should be flexible in opening and closing to show vitality; 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 arc. When purchasing, you should distinguish cat's eye stone from other gemstone cat's eyes and artificial cat's eyes based on identification characteristics to buy genuine cat's eye stone.
In Southeast Asia, cat's eye is often considered a symbol of good luck. People believe that it will protect its owner's health and longevity and avoid poverty. Cat's eye stone is often called the "noble gemstone". Together with alexandrite, it is one of the five most precious and high-end gemstones in the world. Hope, a British gem collector, collects a famous cat's eye stone. This gemstone is carved into the shape of an altar, with a torch on the top. The entire gemstone is spherical, with a diameter of about 1-1.5 inches. Cat's eye is mainly produced in gas-generated hydrothermal deposits and pegmatite veins. The most famous opal producing areas in the world are Tranabra and Gol in southwest Sri Lanka. Cat's eye is also found in countries such as Brazil and Russia, but it is very rare.