Real rubies and sapphires belong to a tripartite system, and their chemical composition is alumina, just like corundum. If it shows other chemical components, it is definitely not corundum. During the growth of natural rubies and sapphires, large and small pits can be formed on their surfaces, while artificial ones will not, but layers of "arc growth lines" can appear. If you see these linear structures on the surface of a gem, you can conclude that it is not a real gem. In addition, in the crystallization process of natural rubies and sapphires, there are some other natural mineral crystals around them, which are often wrapped in rubies and sapphires to become inclusions. These inclusions have two characteristics: one is hornblende; Second, they are often arranged in a certain direction and cross each other at an angle of 60. To the naked eye, it seems that there are many filaments on the surface of red and sapphire. This is just an important symbol of a real gem.
On the contrary, inclusions can also appear in artificial rubies and sapphires, and their inclusions are not all kinds of minerals, but bubbles, which usually appear irregularly, densely or vertically.
Natural and artificial rubies and sapphires can be identified by spectrometer in indoor analysis. Professionals believe that natural rubies and sapphires can see a black line with a wavelength of 450mm in the blue part of the spectrum in the spectroscope. These must be real natural rubies and sapphires. If there is no black absorption line, it must be fake-artificial red and sapphire.
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Ruby is an ancient gem variety. As early as thousands of years ago, people thought that ruby with bright red color had extraordinary "divine power", which could eliminate all diseases and protect personal wealth and status from infringement. In the past hundred years, with the progress of society and the improvement of life, "Wang Xietang flew into the homes of ordinary people in the past", and rubies have become popular and collected gemstones. Ruby is listed as one of the four precious gems by the international jewelry industry, which means "kindness, enthusiasm and nobility". It is the birthday stone in July, and it is also a memorial stone for the 40th and 52nd wedding anniversary.
Due to the low output of natural rubies, synthetic rubies can be confused and disrupt the market to some extent. Therefore, it is necessary to master the preliminary identification knowledge.
I. Physical and chemical properties
The chemical composition of ruby is mainly Al2O3 with a small amount of Cr2O3 (0.5%~3.0%). It belongs to triangular crystal system, the crystal is hexagonal cylinder or column, and oblique twin lines can be seen on the crystal surface. The colors are red, rose and pink. Because it contains chromium, it can emit red fluorescence under strong light, which is particularly gorgeous. Glass to semi-diamond luster. Hardness 9, density 3.9~4. 1g/cm3. The refractive index is 1.762~ 1.770, the birefringence is 0.008, and it has red-orange dichroism. Develop a flat cleavage plane. It often contains inclusions, which vary with different sources and causes.
Second, the naked eye recognition features
Ruby in circulation in the market includes: natural ruby, optimized natural ruby, synthetic ruby, red natural ruby similar to ruby and imitation ruby. Because the physical and chemical characteristics of synthetic rubies and optimized natural rubies are similar to those of natural rubies, it is difficult to accurately distinguish the differences of their physical properties with conventional instruments. The naked eye identification is mainly based on three aspects: the distribution characteristics of colors in gems; Characteristics of inclusions in gems; Possible cleavage and induced surfaces on the surface of gemstones.
(1) Natural Ruby
Natural rubies can be divided into three types according to their genesis and occurrence characteristics: the first type is produced in marble in the gas-hydrothermal contact metamorphic zone, represented by Burmese rubies; The second type is produced in basalt, represented by Thai ruby; The third type occurs in metamorphic plagioclase, represented by Indian ruby. Among them, the first category has the best quality and the greatest value.
1, Burmese ruby
Myanmar is the main producing area of high-quality rubies in the world, which is produced in marble. There are two main varieties: transparent ruby and translucent star ruby.
(1) transparent ruby
The transparent rubies produced in Myanmar are bright red and rose red, with bright, soft and bright colors. Gems are transparent, but not clear. When observed with 10 times magnifying glass, some white filiform inclusions and reflective fractures can be seen, which are mainly identified by color and inclusions:
Color: mostly bright red (pigeon blood red) and rose red, with rich and bright colors but uneven. If you put the ruby into a white porcelain dish filled with clear water, you can see uneven red patches or bands. With fluorescence, the color is brighter and brighter under strong light; If you use a spotlight flashlight in the dark, it looks like a red-hot iron block, and you can't see the small facets and intersecting edges of the pavilion clearly.
Inclusions: There are many inclusions in transparent rubies produced in Myanmar, which is an important basis for identification. There are mainly the following types:
Ruby with filiform rutile inclusions, transparent but unclear, milky white mercerization can be seen under oblique light. Under a 20-fold magnifying glass or a 40-fold microscope, can you see whether it is flat or 60? 、 120? Fine rutile is directionally arranged to form filamentous inclusions with dense intersection angles.
Fingerprint inclusions are colorless gas-liquid inclusions and colorless solid inclusions in ruby, which are arranged intermittently in the form of fingerprints. The gas-liquid inclusions are mostly gas-liquid inclusions, and the solid inclusions are mostly angular short columns.
Flat crack rings are developed around pyrrhotite, apatite and other mineral crystals wrapped in the solid inclusion ruby in an omelette shape, which reflect bright white light under the irradiation of light and combine with the mineral crystals to form an omelette shape.
The healing crack surface in ruby often shows white reflection under illumination. The fracture is generally colorless, but sometimes it can be filled with some yellow-brown iron.
Usually, it is impossible to see all the above types of inclusions in a particle, but you should see filamentous rutile inclusions, which can be used as an important identification basis for Burmese rubies.
(2) Star ruby
Mostly dark red or dark pink, translucent-slightly transparent, with six stars. Three components can be clearly seen in the gem. 、 120? Crossed filiform inclusions, or ribbons and twins of different shades. In the center of the six-shot starlight, there is a bright spot that spreads outward, and each star line extends from the center to the edge and gradually becomes thinner.
Ruby of similar origin is also produced in Sri Lanka, Pakistan, Afghanistan, northern Vietnam and Yunnan, China. The main differences are as follows: the ruby produced in Sri Lanka is light in color and the rutile inclusion is columnar and slender; Ruby produced in Pakistan and Afghanistan is red in color, small in particle size and has many defects. Ruby produced in northern Vietnam is mostly pink, with large particles and poor transparency, and three groups of cleavage develop. However, the ruby produced in Yunnan, China has large particles, bright colors and poor transparency.
2. Ruby made in Thailand
Ruby produced in basalt in Thailand contains a small amount of iron, so the color of ruby is dark, mostly dark red. The main identification features include:
Color: the color is even, but not bright, with brown or purple tones. Sometimes the visible intersection angle is 60? 、 120? Ribbon.
Inclusions: Gemstones are transparent and the inside is clear. Filamentous rutile inclusions are not seen, but omelette-like solid inclusions, fingerprint-like gas-liquid inclusions and parallel bands formed due to the difference of twin reflection are occasionally seen.
3. Ruby produced in India
Ruby produced in metamorphic plagioclase in India is mostly rose-red, with large particle size and poor transparency, with an intersection angle of 60? 、 120? Twin lines are developed, and four sets of step-like reflection cleavage planes are clearly visible.
(2) Optimize the treatment of ruby
1, ruby optimized by thermal diffusion
Thermal diffusion optimization of ruby is to put polished colorless sapphire into baking material containing chromium, and make chromium diffuse to the surface of colorless sapphire at high temperature to make it appear red.
The rubies optimized by thermal diffusion are mostly orange-red and dark-red, with dark and uneven colors. Under the sunlight, you can see many small grid marks with a magnifying glass of 20 times. If put into water, the natural ruby can be seen with naked eyes on the surface of the gem without nodular little red dot, and the color is darker at the waist and corners. Dichroism is more yellow and orange-brown than natural ruby.
2. Glass filled with rubies
In order to make up for the natural surface of rubies (pits formed by symbiosis with other minerals), jewelers often fill them with red glass. If you put this gem in a porcelain dish filled with water and carefully observe it with a magnifying glass of 10 times, you will find that the color of the glass is somewhat different, and bubbles may be seen inside the glass.
Step 3 dye and glue the ruby
Many rubies produced in India have developed four sets of double crystal lines (cleavage planes), forming criss-crossing white reflective bands, which seriously affect the appearance of gems. Some jewelers fill the cracks with red dye and glue to cover up the defects. Most of the optimized rubies are dark red with purple and slightly transparent. White stripes arranged in parallel can be seen under the reflected light, and red grids filled in the bimorph cleavage can be seen under the transmitted light.
(3) Artificial ruby
The synthetic ruby with commercial significance mainly includes flame melting method and flux method.
Synthesis of Ruby by 1 and Flame Melting Method
(1) Synthesis of Transparent Ruby
The transparent ruby synthesized by flame melting method is red, deep rose and pink, with bright and uniform color and looks dull and dazzling. The interior of the gem is clean, and no flaws can be seen with the naked eye. Put it on a plate filled with water and observe it with a magnifying glass of 20 times. Occasionally, you can see arc growth lines and circular bubbles.
(2) Synthesis of star ruby.
Synthetic star rubies are mostly translucent and purplish pink. There are three main differences from natural six-shot starlight gem: first, the starlight effect is more obvious than natural ruby, which can be clearly seen even in weak light; Second, there is no bright spot in the center where the star intersects the line, and the star extends from the center to the edge with equal thickness; Third, after polishing the bottom of the gem, the naked eye can see a relatively clear arc growth line, which is 60? 、 120? The straight growth line is obviously different from the small cleavage plane with reflection.
2. Synthesis of Ruby by Flux Method
Ruby synthesized by flux method is somewhat similar to natural ruby in appearance, showing uneven red and rose red, transparent but not clear, milky white feathery or smoky inclusions can be clearly seen by naked eyes, and orange yellow under transmitted light. The "naked eye recognition" features of this artificial ruby mainly include:
Ruby synthesized by color flux method has uneven color. When placed in a white porcelain dish filled with water and observed with a magnifying glass of 20 times, it can be seen that due to the incomplete melting of part of chromium oxide, dense little red dot or plaque is formed in the deep red. In addition, the ribbon similar to natural ruby is fuzzy, not as straight and slender as natural ruby.
The inclusion flux method is characterized by a large number of inclusions, mainly including grid-like, fingerprint-like brown or black flux droplet inclusions, black flux patches, clustered needle-like inclusions, triangular, hexagonal silvery white or black platinum flake inclusions.
To sum up, it can be seen that the ruby synthesized by the two methods has few inclusions and rich and uniform colors. However, the ruby synthesized by flux method has many inclusions and uneven color, and dense little red dot or patches formed by residual flux can be seen under a magnifying glass.
(4) The difference between ruby and similar red natural gemstones and imitations.
Red natural gemstones and imitations similar to rubies in the market mainly include red spinel, garnet, pink and red tourmaline, red glass and so on. Its main physical properties are shown in table 1, and its specific identification features are as follows:
Table 1 Summary of Main Physical Properties of Ruby and Similar Red Natural Gems and Imitations
Gem Name Hardness Density (g/cm3) Refractive Index Birefringence Polychromaticity
Ruby 93.991.76 ~1.770.008 has strong dichroism.
The synthetic ruby 93.991.76 ~1.770.008 has strong dichroism.
Zircon 7.54.701.92 ~1.980.059 is medium.
Spinel 83.60 1.720 None
Mg-Al Garnet 7.53.7 ~ 3.91.74 ~1.760 None.
Tourmaline 73.061.62 ~1.640.0438+08 is medium.
Glass 5~62.3 1.470 None.
1, red spinel
The color of red spinel is very similar to ruby, but the red color of red spinel is relatively uniform, and no red spots or color groups can be seen. Seen from different directions, it has no dichroism. Fluorescence is weaker than ruby. When illuminated from the top with a flashlight in the dark, it becomes bright, but the edge or facet of the pavilion can be seen. The interior is clean and clear, except for a small amount of octahedral spinel, magnetite inclusions and shell-like healing cracks filled with brown iron, there is no filamentous rutile inclusions or 60 angle in ruby. 、 120? Ribbon.
2. Mg-Al garnet
Garnet is uniform red, clean inside, and few inclusions can be seen by naked eyes. In strong light, the earthy tones in the color increases, which is not as good as in dark light. Mg-Al garnet has no fluorescence. When the crown is illuminated by a flashlight in the dark, the facets of the pavilion are clearly visible, and the reflective color contrast between two adjacent facets is remarkable.
3, pink, red tourmaline
Pink tourmaline, with uniform color and no fluorescence phenomenon, is illuminated by a strong flashlight in the dark, and many people reflect red light on the pavilion facet, showing the shape of the facet. The birefringence is large, and there is obvious ghost at the bottom of faceted tourmaline. The interior of the gem is relatively clean, and inclusions are rarely seen. It has pyroelectricity, can generate charge after friction, and can absorb small pieces of paper near it.
4. Red glass
Red glass has uniform color and clean interior, and sometimes circular bubbles and vortex structures can be seen. Glass luster. Warm feel, high specific gravity, no fluorescence phenomenon.
Third, the economic evaluation index and purchase instructions
(A) economic evaluation indicators
The economic evaluation of ruby mainly includes four indexes: color, weight, clarity and cut. For details, please contact: 1, Liu, Liu Kai. International color grading standards and recent prices of rubies and sapphires. The gem is in China. 1994 (3): 34-35.
2. Diamond Encyclopedia Ruby Classification Standard (2) Purchase Instructions
1. There are many kinds of rubies on the market. When you plan to buy rubies, you must pay attention to many distinguishing features that natural rubies should have.
2. Pay attention to the name ruby. According to international jewelry practice, the name of ruby cannot be preceded by the place of origin. Ruby is produced in many places, and the largest natural ruby producing area is Myanmar. In addition, Thailand, Sri Lanka, Zambia, Pakistan, India, China and Viet Nam also produce rubies.
3. Pay attention to the identification according to the important identification characteristics of synthetic rubies, so as to prevent unscrupulous traders from confusing the fish with the pearls;
4. Pay attention to the ruby two-layer stone with natural ruby as the crown and synthetic ruby as the pavilion, and carefully observe the waist of the gem from the aspects of luster, color and presence of adhesive.