A summary of some knowledge about jadeite ABC goods

In the jade trade, there is a consensus on the definitions of A, B, and C jade: natural jade pieces that have not been filled or colored are called A grade. Jadeite that has been filled (such as filled with high molecular polymers, etc.) is called B-grade jade; the mineral composition of B-grade jade is the same as that of natural jade, and the color is natural, but the filling glue will affect the brightness of the color, as well as the transparency and gloss after aging. If the jade is treated with color, it is called C-grade jade; the mineral composition of C-grade jade is the same as that of natural jade. If filling and coloring are performed at the same time, it is called B+C goods. The name of B-grade jadeite may come from the prefix "Bleached & polymer- impregnated jadeite". The name of C-grade jade may come from the prefix of "Colored jadeite" (Ouyang Qiumei has another explanation). A, B, and C goods do not mean the "grades" of A, B, and C (A grade, B grade, C grade in English). They are generally called A jadeite, B jadeite, and C jadeite in English. Since Jadeite (hard jade) or Jadeite (hard jade rock) is not equal to jadeite (Feicui) (see my other article), it is now recommended to call them A feicui, B feicui, and C feicui (A jadeite, B jadeite, and C jadeite).

It is generally believed that reliable identification of A, B, and C grade jade requires comprehensive consideration, and a single method is prone to errors. There are many articles and monographs on the identification of A, B and C grade jadeite. This article only proposes some issues encountered in the identification research and asks for your advice and discussion.

1. Minerals that make up jadeite

The constituent minerals of jade are mainly jadeite in monoclinic pyroxene clusters, or other pyroxene minerals (such as chrome jadeite, omphacite, etc.) containing high content of jadeite molecules (NaAlSi2O6); the mineral composition of jade is considered to be the product of high pressure and low temperature metamorphism, and this has been confirmed by jade synthesis experiments. If NaAl in jadeite is replaced in large quantities by Ca, Mg, Fe, Cr, etc., it will exceed the range of jadeite composition and turn into other pyroxenes (such as chrome jadeite, omphacite, diopside, aegirine, etc.). Jade composed of diopside, nepheline, etc. can also be called "pyroxene jade", but it is not jadeite. The article "Black Jade" published in the March 2000 issue of "Jewelry Technology" calls black diopside jade jade, which the author believes is inappropriate. The national standard "GB/T 16553-1966 Jewelry and Jade Identification" has made relatively accurate regulations for the identification of jadeite. However, the range of jadeite in trade is wider than that of jadeite (see my other article). Since jade is a polycrystalline aggregate, the more accurate method to determine whether it is jade and the mineral composition of jade category is electron probe image composition analysis, but it is limited by instrumentation and high cost. A faster and more convenient method is the micro-powder oil immersion method, which only requires an ordinary polarizing microscope and a few bottles of refractive index immersion oil. The sample taken for test is very small, so even high-end ring faces will not affect their beauty and value.

2. Color of Emerald

Emerald green jade is considered a treasure, and there is a saying that "a point higher in color means ten times higher price." Therefore, the technology of adding color to jade is constantly innovating. In addition to red and purple, there are at least four varieties on the market that only add green. The value of colored jadeite that appears to be natural emerald green is only one percent to one thousandth of that of grade A jadeite, or even lower than grade B jadeite. Colorless jade is dyed into bright green jade and sold as high-end jade, causing some consumers to suffer great losses and mental burden. Jadeite that was colored with chromium salts in the early days appeared red when observed through a Charpy filter (natural green grossular garnet also appears red). Batches of chromium-dyed jadeite ring faces were discovered by the Gemological Institute of America as early as 1956 (Zhou Guoping, 1989). Nowadays, many dyed jades no longer use chromium salts. Their characteristics under a Charpy microscope are similar to those of natural jade, and their stability is also better (one such dyed emerald green jade in my collection has been stored for three years and is still as bright as new), so observation under a Charpy filter can only be used for reference. In the past, colorant could be seen deposited in the network of cracks in dyed jadeite. However, this phenomenon is no longer seen in some of today’s dyed green jadeite (including some B+C jewelry or sheets). So if you can’t see colorant deposits in the cracks, it is not necessarily a genuine A-grade jadeite. In recent years, jadeite bracelets and pendants that are dyed unevenly light green have become common on the market and are sold as natural jadeite. This type of jewelry has soft colors, a certain degree of transparency (water), no glue injection, a clear 437 nm absorption line under a spectroscope, and the knocking sound, ultraviolet fluorescence characteristics, and Charles filter observation are all basically consistent with natural jade. The retail price of this kind of bracelet is generally between 500 and 1,500 yuan each, and it is more popular among the general working class and tourists. According to data from multiple tests, a dye (not polished chromium powder) is filled in the micropores. Due to the reflection of light, the dyed part of the jadeite has a light green color as a whole. Some are dyed the entire bracelet, some are dyed only partly, and some are also dyed purple (also known as "spring color"), making a bracelet appear a special variety with several sections of light green and several sections of light purple. Most of the dye can be washed away by soaking in a solvent such as detergent (with ultrasonic cleaning if necessary), but generally a lighter green color will remain after cleaning. Using a 10x magnifying glass (even obvious with the naked eye), you can see the dark green silk impregnated in the micropores. Jadeite that has been dyed and then washed is lighter in color, but more natural and can be more deceptive. - 1 - It is not only difficult for ordinary consumers to identify, but some business owners with certain business experience also fail to see the suspicious points and buy such accessories in large quantities. Even jewelry testing professionals may mistake dyed jadeite as natural jadeite in the test report if they are a little careless.

3. Optical characteristics of jadeite

The natural emerald green color of jadeite is due to the small amount of chromium. To identify whether the color of jadeite is natural or added, a simpler and more reliable method is to use a spectroscope. However, some jade pieces have weak light transmittance or light color, and the absorption lines are not easy to observe. For those with fluorescent reaction, ultraviolet fluorescence instrument can be used for inspection. Furthermore, the coloring elements in the color body can be detected by using an electron probe instrument, but the detection cost is high and the content of light-colored coloring elements is often below the detection limit. Jadeite feicui generally has a strong absorption line of 437 nm under a spectroscope. For chrome-jadeite feicui, the 437 nm absorption line is more difficult to see. Some literature suggests that the 437 nm line is caused by iron; however, in completely colorless glassy jadeite, this line is also very strong; so the formation mechanism of the 437 nm line needs further study. Jadeite with true green color generally has chromium absorption lines of 690 (strong), 660 (medium), and 630 nm (weak). It often forms stepped absorption bands at -690, 690-660, and 660-630 nm, which are strong, medium, and weak respectively; the light green -630 band or line is so weak that it cannot be seen clearly. Green dyed with chromium salts has a wide absorption band at 660 nm±; some green, purple, red, etc. dyed with organic dyes have no absorption in the 700-630 nm region. The ultraviolet fluorescence effect of jadeite is an important reference for identifying A, B, and C grade jadeite:

(1) Natural jadeite generally has no fluorescence, but some of the "white cotton" jadeite has a light yellow fluorescence.

(2) B-grade jadeite is mostly filled with organic glue and generally has a blue-white fluorescence (filled with wax also has a blue-white fluorescence). Currently, many "83 jade" bracelets and pendants (B-grade jadeite) on the market have a uniform, medium-strong blue-white fluorescence. Some B-grade products have no fluorescence, they may be filled with silicone (? ) or other substances.

(3) Most dyed jadeite on the market today has no fluorescence (same as natural jadeite); but some have obvious fluorescence. Certain fluorescence characteristics are very meaningful for identification, such as a jadeite dyed green that emits a strong yellow-green fluorescence (jadeite dyed this green has a short shelf life and turns yellow after the green fades), and a jadeite dyed red that has a strong straw yellow fluorescence.

4. About "Cui Xing"

Some experts believe in their monographs that the important feature that distinguishes natural jade from other jades (including B-grade jade) is that natural jade has "jade quality" (commonly known as "fly wings"), which is the luster of the crystal surface of the jadeite mineral (011). Phantom crystalline diopside (such as the diopside in Qinghai jadeite) (Qu Yihua, 1994) and amphibole (such as the amphibole jade in some "Black Wusha" of Myanmar) also have developed (011) cleavage and can also have "jade quality". The "jade quality" is generally not visible in microcrystalline jadeite, so the "jade quality" cannot be used as a characteristic mark of natural jadeite.

5. Knocking sound

The knocking sound cannot be used as a basis for determining whether jade is A or B grade. Some jade sellers often use lightly knocking two bracelets together to produce a crisp "steel" sound to indicate that they are natural jade. The knocking sound of B-grade jade with obvious fillings is slightly duller. However, the jade that makes the "steel" sound is not necessarily natural jade. Diopside (such as Qinghai jade), amphibole albite (such as Burmese "Shuimozi" jade), etc. also have a "steel sound". Some of the B-grade products currently on the market can also produce a crisp "steel" sound.

6. Reticulated

Jade washed with strong acid generally has obvious pores and reticular structures. Stress and weathering can produce obvious pores and reticular structures in natural jade, which are often difficult to distinguish from the reticular cracks caused by acid corrosion. The opinion that "those with cracks, pitting and pits are definitely B-grade goods" may be inappropriate. Therefore, the author suggests removing the concept of "glue-free B goods". The natural pores of jade can be filled with zeolite, clay minerals, etc. in the later stage; during the cutting, grinding and polishing process, it can also be filled with mineral powder or polishing powder. Products with these fillers are not B-grade products and are easy to identify.

7. density

The density of natural jade is generally 3.25-3.45 g/cm3. The density of B-grade jadeite is generally lower than 3.25 g/cm3. The density of natural jade with obvious porosity can be as low as 3.15 g/cm3±. The glue-injected "Bai San Yu" jewelry currently appearing in large quantities on the market is made of primary jade ore. Due to the natural cracks, pores and impurities, it is acid-cleaned and glue-injected during the processing. It has certain primary porosity, but generally has no obvious reticular structure. It is similar to B-grade jadeite. There is a jade chicken heart (point measured refractive index 1.66, density 3.313 g/cm3). The infrared absorption spectrum measured by Ouyang Qiumei from Hong Kong and the author respectively obtained the same absorption peak of B-grade jade with typical resin filling. However, only a small amount of pores was shown in the microscope and electron microscope photos magnified 500~2000 times, and there was no obvious filling in the pores. This type is called "invisible filling" (this is because the newly formed surface cracks in the jewelry processed using injection molding sheets are not filled). Therefore, items that do not show obvious resin filling under a magnifying glass or microscope are not necessarily A-grade items. The view that "to identify B-grade jadeite, specific gravity and fluorescence are indicators, structure is the key, and infrared spectrum is the conclusion" should be treated with caution.

8. B goods

Some articles believe that the filler of B-grade products is epoxy resin. Wu Shuntian et al. (1995) pointed out that the filling materials commonly seen in B-grade jadeite on the market are resins similar to opticon. Other filling materials include phthalate type compounds, polystyrene, etc. Organic polymers are a relatively complex system; the author searched the infrared absorption curve data of a glue-injected jadeite and came up with the names of 25 organic substances with similar characteristics by searching the memory data of the infrared spectrometer. Traditional wax filling treatment is generally not considered to be B-grade jade and is still considered A-grade jade. However, Wu Shuntian and others believe that most of the wax fillings should be B-grade products. This opinion should be taken into consideration because for some porous jadeite, the visual effects of filling with glue and filling with wax are similar and are equally deceptive. - 2 - Microscopes (including transmission and reflection microscopes) are generally simple and effective for observing structures and fillings. To distinguish whether the filling is wax or organic glue, Su Wenning et al. (1995) proposed the hot needle reaction morphology and picking out for oil immersion observation (or using an embroidery needle to pierce the filling glue to reveal small convex holes, and piercing the filling wax to reveal white skin particles on the edge). This method is feasible for parts with larger fillings. Infrared absorption spectroscopy and Raman spectroscopy (the latter is more superior) basically solve the problem of identifying whether it is filled with organic matter (including the difference between wax and glue). Infrared and Raman spectroscopy can also determine mineral composition, but the pyroxene minerals related to jadeite are a complex isomorphic series, and the database provided by the manufacturer lacks necessary comparative data. Some fillings do not have characteristic spectral lines (Raman spectroscopy cannot be used for amorphous materials).

9. Artificial Jade

The introduction of artificial jade into the market was reported six or seven years ago (Liao Yonghe, 1994; etc.). According to the data (Zhao Yanhe et al., 1993; Shen Caiqing, 1995), the mineralogy, chemical composition, structure, color, density, refractive index, ultraviolet fluorescence, infrared absorption spectrum, X-ray powder diffraction analysis and other data of synthetic jade are the same as those of natural jade. However, there has been no report on the detection of synthetic jade jewelry on the market so far. This should attract the attention of the testing department.

10. Identification issues

In accordance with the national standard "GB/T 16552-1966 Names of Jewelry and Jadeite", jade B and C grades must be marked with "(processed)" after the name in the test report and product label, such as "jade bracelet (processed)". Considering that the value of colored jadeite is much lower than that of A-grade and B-grade jadeite, it is more deceptive; through investigations on market transactions, some operators interpret the word "processing" on product labels or inspection certificates as "optimization processing" or "backlog processing", "price reduction processing", etc. Jewelers at home and abroad feel that B and C grade jadeite have a huge impact on the jadeite market. The majority of merchants dealing in natural jadeite jewelry hope that B and C grade jadeite will be clearly labeled. From the perspective of consumers' right to know, and to make it easier for consumers to understand, it is suggested that when the national standard is revised, consideration should be given to directly labeling injected and dyed jadeite jewelry as "injected jadeite XX", "dyed jadeite XX", "injected and dyed jadeite XX", such as "injected jadeite bracelet", "dyed jadeite Guanyin", "injected and dyed jadeite Buddha", etc.

11. Classification of Jadeite Grades

On the premise that the jade pieces being appraised are natural jade, they are divided into grades and price levels according to the 5C2T standard [Composition), color, clarity, cut, carat, transparency, and texture] (B and C goods generally do not need to be divided into work-level grades). The specific classification criteria are discussed in another article. In today's world, any noble and popular product will have its counterfeit products. The use of high technology to manufacture counterfeit products can almost reach the level of "flawless". Jade is the crown of jades. High-end jade continues to create astonishing sky-high prices at various auctions. As a result, B-grade, C-grade and other counterfeits of natural jade emerge in an endless stream, causing genuine merchants, consumers and inspectors a lot of headaches. When one counterfeit product is just discovered, another new counterfeit appears, making the original identification method ineffective. In all cases, the counterfeit comes first, and the identification technology comes later. Those who make counterfeit goods make huge profits and have the funds to introduce high-tech, while general testing departments and staff do not have such conditions. It can be said that "the devil is always one step ahead of the saint." As an ordinary member of the jewelry research and testing industry, we should work seriously and steadily, learn humbly from colleagues and friends in the business community, and strive to explore in order to adapt to the needs of the development of jewelry trade.

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