Identification of diamonds
Diamonds are the hardest natural substances. A diamond can carve any other gem, but no other gem can carve a diamond. You can also use the "standard hardness tester" to score, and any hardness below 9 degrees is a fake diamond. Diamonds are also lipophilic. If you draw a line on the surface of a diamond with a pen, it will become a continuous straight line, while other gems will break intermittently. The above methods have certain reference value for identifying diamonds. You can also observe it through a magnifying glass with a magnification of 10. Under the magnifying glass of 10 times, you can see that most diamonds have triangular growth lines, and the surface of diamonds has "red, orange and blue" fire light. Radiant. The most accurate and reliable method is to measure the thermal conductivity data with a "thermal conductivity meter" to distinguish between genuine and fake diamonds, but the "thermal conductivity meter" is expensive.
Because diamonds are the first noble and luxurious ornaments, it is not uncommon to replace or pass off diamonds with cheap gems, artificial gem and even glass. Common fake diamonds are as follows:
① Zircon: Very similar to diamond, it is the best substitute for diamond. The identification method is that zircon has polarization and large birefringence. Observing the processed zircon prism surface with a magnifying glass of 10 times, it can be seen that the bottom edge line has obvious ghost, but the diamond has no ghost phenomenon.
(2) Glass: The refractive index of glass is very low, and there is no flickering color light like diamonds; Especially when it sinks into the water, the glass product loses its luster and immediately shows clues.
(3) Soviet diamond: cubic zirconia, first developed by the Soviets, hence the name. Soviet diamond is a synthetic compound, but it is very close to natural diamond in dispersion and refractive index, and it also has the attractive appearance of "fire" light. But its hardness is low (8.5), so it can be distinguished from diamonds. Moreover, the thermal conductivity is much lower than that of diamond, so it can be identified and distinguished accurately by "thermal conductivity meter".
④ Crystal: Although crystal is a transparent crystal of natural minerals, it looks like a diamond after processing, but it lacks the colorful light of diamond.
Identification of ruby
Natural gemstones have "ten Hong Jiu cracks", and natural rubies without any flaws and cracks are extremely rare. Artificial rubies have the same color, few internal defects or crystal inclusions, and are clean and large. As a precious gem, natural rubies over 3 carats are very rare in the market. If you encounter a big ruby, you should pay attention, because the value of natural ruby is thousands of times higher than that of artificial ruby. A little carelessness will "take medicine."
Natural ruby has a strong "dichroism". The so-called dichroism means that there are two colors of red and orange red from different directions. If there is only one color, it may be red spinel, garnet or red glass.
Red spinel and natural ruby are very similar, and they are most easily confused, so be very careful.
Supplementary explanation of ruby
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.
Among the reds of rubies, the most valuable one is the one with the strongest color, called' pigeon blood', which is very valuable. This bright and intense color can almost be called crimson, and you can see the true face of ruby at a glance. Unfortunately, most rubies are light in color and have a pink feeling, so the rubies with pigeon blood tones are more valuable. In addition, because ruby is full of strong vitality and rich colors, people in the past thought it was the incarnation of a dead bird and had ardent illusions about it. Natural rubies are scarce, and high-quality rubies are only produced in Myanmar, and the output is gradually decreasing. Now, it can be said that it has almost declined, and big stones no longer appear.
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 too bright, relatively clean. Ruby is fragile, so be careful when wearing it.
Identification of sapphire
Natural sapphires are often uneven in color, and most of them have a flat growth line. Artificial sapphires are of the same color, and their growth lines are arc-shaped strips, and they are often breadcrumb-shaped or beaded bubbles in the body.
Natural sapphire also has obvious dichroism, one direction is blue, and the other direction is blue-green. Other gemstones are different in color from natural sapphires and can be distinguished.
In addition, the simplest method can be hardness measurement. Natural sapphires can carve traces on topaz, while other sapphires are difficult to carve traces on topaz. Therefore, when buying jewelry, if there is no instrument around, as long as there is a topaz, sometimes some problems can be solved.
Supplementary explanation of sapphire
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.
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.
In nature, there are many kinds of green transparent gemstones similar to emeralds, such as jadeite, tourmaline, fluorite, olivine, garnet, zircon, etc. Among them, tourmaline, fluorite and jadeite are easily confused because of their similar appearance to emeralds. Visually, green jadeite is generally translucent, often in a patchy structure with interwoven fibers, while high-quality emeralds are transparent and crystal clear. Emerald hardness is 7.5-8, while fluorite hardness is very low, only 4. Emerald accounts for a small proportion, while fluorite, tourmaline and jadeite account for a large proportion. Zircon has strong dispersion and obvious ghost.
In addition, there are artificial emeralds and green glass similar to natural emeralds. The biggest difference between them is that most natural emeralds have defects or inclusions, which shows dichroism. Of course, in order to distinguish strictly and correctly, it is best to use identification instruments such as optometry and polarizer.
Identification of cat's eye
In recent years, there is a kind of glass fiber cat's eye ring on the market, which is embedded in gold or silver rings, making people unable to tell the true from the false. The identification method is that when the torus is rotated, several light bands can appear at the arc top of the fake cat's eye at the same time, while there is only one real cat's eye. The fake cat's eye eyeliner is rigid, while the real cat's eye eyeliner is flexible. True cat's eyes are mostly brownish yellow or light green, while fake cat's eyes are varied in color, such as red, blue and green.
Golden emeralds are second only to diamonds and red sapphires in hardness. Golden emeralds and various changeable stones and opals are not only very beautiful, but also very expensive, because they are extremely rare. Opal is the color-changing effect of emerald with developed vacuum inclusions after Kapson cutting.
Supplementary explanation of opal
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.
Opal is named after its smooth and rotating color like cat's eye, so it is also called' Opal' in English literal translation. Only emerald cat's eyes can be directly called cat's eyes. Opal has the color of honey, especially a light mark, which will reflect to both sides and become' three light marks', so its price is judged to be very high. In terms of color, cream color and lemon color are not as good as honey color, and brown and gray have lower evaluation. Put the cat's eye in the light. You can display a clear light, and when you turn it, the light bar will shake left and right, which is cat's eye discoloration.
In addition to emeralds, there are other kinds of gems that can show the same luster and deformation effect as cat's eyes. Such as calcium carbide, apatite and blue crystal. There is also a mineral [Tiger Eye Stone] which has the same effect because of its fibrous structure of asbestos, but it can't be compared with the golden green cat's eye. The crown of the king of Iran is inlaid with a yellow-green cat's eye, weighing 147.7 carats.
Identification of opal
Opal can be divided into black opal, white opal and yellow opal by color, of which black opal has the highest price. In order to improve the low-priced white or yellow opal, some people change its color artificially and become "black opal" in order to make high profits. The main method is to boil with sugar or inject plastic to make the white opal black. The identification method is that the specific gravity of opal is obviously different after boiling sugar or injection molding, and the specific gravity value becomes lighter when tested in water. The heating needle can also be used to test the injected opal. Natural opal can't be pierced by hot needles, but injected opal can be pierced, and it will produce the smell of plastic melting.
Identification of tourmaline
Tourmaline is a kind of mid-range gem, but because pink and bright blue tourmalines are more expensive, there are also imitations. There are two common imitations, one is artificial coloring with colorless tourmaline; One is made of red glass. The identification method is that the real tourmaline often has obvious dichroism and can be seen as a ghost; Tubular inclusions or cotton wool can be seen in the body, and the crystal cross section is curved triangle. These characteristics are not possessed by imitations. The tourmaline dyed by workers is not difficult to identify because its color is dull and there is no "treasure light" of natural tourmaline.
Identification of crystal
Rock crystals are clear and transparent, often containing cloud, star or flocculent gas-liquid inclusions, and often with microcracks. In addition, the rock crystal is polarized, and you can see the phenomenon of twin crystals, such as a crystal ball. Looking down from the top, there will be a double image. Synthetic crystal or glass products are uniform and pure in the body, without cracks, and often have small bubbles inside. Looking down at the sphere, you can't see the ghost of the line below. Through touch recognition, we can feel that the proportion of synthetic crystals is greater than that of rock crystals; Crystal stone feels cold and glass feels warm.
Identification of olivine
Olivine is a kind of low-grade gem with yellow in green and similar to olive color. The most common counterfeit olivine on the market is made of stained glass. The main difference between the two is that olivine has obvious "double shadow", while glass does not; Crystal inclusions are often seen in olivine, and only bubbles are contained in glass. Olivine has a specific gravity of 3.5 and a hardness of 7, which is greater than that of glass (2.6) and hardness (6).
Identification of pearls
Pearls are divided into natural pearls and cultured pearls, and cultured pearls are divided into seawater pearls and freshwater pearls. Natural pearls are low in output and expensive; Moreover, cultured pearls can be produced in large quantities, so the price is much lower. The main difference between them is that natural pearls and cultured pearls have no nuclei. The inner core of natural pearls is often just some sand or parasites, or even no inner core. However, the inner core of cultured pearls is artificially made large round beads, so the outer coating is thin. On the body surface, natural pearls rarely roll because of their random growth environment and poor roundness. The inner core of cultured pearls is round, so the roundness of pearls is better. Natural pearls are transparent because of their long growth time, delicate texture, thick nacre, smooth skin and few "convex bubbles". The cultured pearls are thin in layer, rough in texture, "waxy" in luster, and have some uneven "bubbles" on the surface, so the transparency is poor. If it is a perforated pearl, observe the hole carefully with a magnifying glass. If it is a cultured pearl, you can generally see a brown boundary inside the pearl, which is the boundary between the inner core and the pearl layer that grows later.
At present, imitation pearls often appear in the market, which are generally made of glass beads coated with fish scale powder or silver powder. Their luster is obviously different from that of real pearls, and their weight is also different, so people with a little experience can identify them. If you scrape off a nail or a knife, the true face of Lushan Mountain will be revealed immediately.
The jewelry industry has some experiences in identifying pearls, which are introduced as follows:
(a) the color, size, shape and luster of the beads. They are all identical, that is, artificial pearls. Because real pearls can't be consistent anyway.
The luster of real pearls is like a rainbow, colorful and very beautiful. Fake pearls are dull and have no colorful rainbow tones because of the coating on their surfaces.
③ Real pearls have good transparency, while fake pearls have poor transparency.
④ Real pearls have a smooth and cool feeling through hand feel, while fake pearls are often warm and greasy.
⑤ With a magnifying glass of 10 times, the growth texture can be seen on the surface of real pearls, while the fake pearls have no growth texture, only the coating can be seen.
Different identification methods of fake crystals with different materials
When crystal became popular, many counterfeit products appeared in the market, which not only troubled consumers, but also puzzled many stores themselves because they were not professional enough.
There are counterfeit products, such as:
1. Acrylic and plastic products can be distinguished from the touch, temperature and hardness of hands. In addition, acrylic and plastic are easy to cause light distortion and refraction, which is generally not difficult to distinguish, so such counterfeit products are becoming scarce.
2. Glass products, clear as water at first glance, have no texture, low hardness (5), single refractive index, mixed with bubbles and easy to distinguish.
3. Melted crystal refers to the crystal synthesized from domestic crystal slag, just like glass, but most of them have been made into spheres with the size of seven or eight centimeters to ten centimeters, which are very beautiful, but the refractive index is single and the hardness is low (5), which can be distinguished by polarizer.
4. Crystal glass is actually "lead glass". The most popular glass products in the market are those with lead metal. Because of its good refractive index and dispersion rate, it is dazzling and dazzling. It is most suitable for decoration and decoration, but not for spiritual use. Generally, it can be distinguished by vision.
5. Artificial crystal, also called "crystal cultivation", the original stone has no hexagonal crystal system, which is the easiest place to judge; But if it is ground into a finished product, it is not easy to distinguish it by the above method, and it is necessary to use an "ultraviolet spectrometer" to distinguish between true and false. The most common products on the market are colorless and transparent white crystal, amethyst, topaz and aquamarine crystal fakes. I suggest that friends, when encountering controversial crystal ore, it is best to send it to an impartial third party, such as an appraisal office, for identification. It doesn't cost much, but it has professional guarantee. If necessary, even send it to more than two appraisal institutes for appraisal. It's best to choose "original stone" and look at its crystal shape, growth line and primary minerals. It can't be wrong. In addition, buying crystal ore containing "inclusions" is the best proof of "growing in nature", which is wrongly called impurities and defects by ordinary people. /xlgw/list.asp？ ProdId=00 16