How to distinguish between ABC grade jadeite? The most direct method

★ A-grade

It refers to pure natural jadeite, which has only been carved and polished without any artificial falsification such as high heat or high pressure. It is jadeite with natural color and has not been "manufactured" by means of dyeing, electroplating, coating, etc. Mainly look at the following points:

1. Luster: The luster of jade is oily to glassy, ​​with bright spots and sediment.

2. Color: The color of natural jade is positive, true and soft, with clear color transitions and strong contrast between color and texture. The color root and texture are closely connected, and a beautiful halo like a moon is formed around the edge of the color. The appraisal certificate should indicate "jade" or "natural jade".

3. Structure: When observed under magnification, it shows a fiber interwoven structure and does not fluoresce under ultraviolet light.

4. Appearance: fine texture and obvious stone patterns.

5. Sound: slight impact, the sound is crisp and pleasant.

6. Feel: It feels heavy and cool to the touch, and smooth and delicate.

7. Density and refractive index: The density is about 3.33g/cm3, and the refractive index point measurement method is 1.66.

8. Fluorescence: There is no fluorescence under ultraviolet light, but sometimes some fluorescence can be seen, which is caused by some impurities.

9. Among the large-scale instrument identification methods, the infrared spectrometer is the most common and the most effective large-scale instrument: A-grade products have good transmittance in the range of 2600~3200cm-1, and usually have no absorption peaks. There are also less common methods such as laser Raman spectrometer and cathodoluminescence microscopy, which are not described in detail.

Through bleaching or glue injection, natural jade with black spots or lack of transparency is soaked in strong acid or alkali to destroy the internal molecular structure, remove the "dirt" and "cotton", increase transparency, and then use high pressure to inject epoxy resin or alternative fillers into the micro cracks caused by strong acid corrosion, which plays the role of filling, forming cracks and increasing transparency.

Similarly, let's look at the points for judging A-grade goods one by one:

1. Luster: B-grade jadeite has been acid-washed, bleached, and filled with glue. It has good water head and a clean texture, but its luster is darker and gluey. Due to the damage of strong acid, diffuse reflection occurs and the surface gloss weakens. After adding organic fillers, it often has resin gloss, waxy gloss, or a mixture of glass gloss with resin gloss and waxy gloss.

2. Color: The color of B is still the original color of jadeite, which looks good at first glance, but upon closer inspection, the color is dull, evil, and not moisturized. Under the light, the color transparency is weakened, the color distribution is more floating, and there is no color root. The color edge does not have a transition zone like A-grade jadeite. The appraisal certificate is marked with "Jadeite (processed)".

3. Structure: Under magnification, the internal fiber interwoven structure is destroyed, dissolution occurs on the surface and inside along the mineral crystals, and internal interconnected cracks are generated. Under transmitted light, the internal structure is loose, the boundaries of the grain edges are blurred, the grains are broken to produce cracks, and the cleavage is discontinuous. Dissolution concave shells or bead-like reticular patterns can be seen under reflected light.

4. Surface characteristics: Due to the large difference in hardness between the filling material and the jade itself, there are obvious pits at the original cracks. The filling material is obviously lower than the two sides, and many cracks organize criss-crossing "ditches" (be careful to distinguish it from the pockmarked surface caused by poor polishing). Cementing materials or residual bubbles can be seen in the larger "ditches". The edges of the surface cracks are relatively smooth, and the "emerald nature" is not obvious, but small cracks are relatively concentrated in some parts. This is a manifestation of the extremely small gaps between the damaged jade particles that have not been completely filled. The surface of B-grade jade with better technology is very smooth, without the above phenomenon, but many bright spots similar to the "emerald nature" reflective spots appear on the surface or internal overlapping distribution of coarser particles. Many small bright spots can be seen under a high-power microscope. These are small bubbles, which are retained due to the failure to evacuate all the air in the gaps during the filling process.

Comparison of the "orange peel effect" of A-grade jade and the "acid-etched mesh" and "dissolution pits" on the surface of B-grade jade

5. Sound: The sound of a slight impact is dull, which is significantly different from the crisp sound of A-grade products (this method is mainly applicable to the identification of bracelets).

6. Feel: B-grade jade is slightly lighter than A-grade jade, and the cool feeling is reduced because it is filled with resin.

7. Density and refractive index: Most bleached jadeites have slightly lower density and refractive index, with a density of 3.00~3.43g/cm3 and a refractive index of about 1.65. However, due to the complex mineral composition of jadeite, the density and refractive index values ​​of some natural jadeite may also be low. Therefore, these two data can only be used as a reference and cannot be used as a basis for determining whether jadeite has been filled.

8. Fluorescence: No or weak to strong ultraviolet fluorescence under ultraviolet light. The fluorescence is evenly distributed or mottled. Most of the early "B-grade" jadeite has fluorescence, yellow-green, bluish-green, or blue-white. However, jadeite processed by this method recently usually has weak fluorescence or no fluorescence.

9. Thermal reaction: The colloid will carbonize after heating at 200~300 degrees Celsius.

10. Infrared spectrometer: B-goods contain organic matter, and different fillers have different structures, showing different absorption bands in the range of 2600~3200cm-1. The transmittance is good, and there is usually no absorption peak.

This is jade that has been optimized through weak acid and weak alkali cleaning (without strong acid corrosion, bleaching, or glue filling), or refers to jade that has been filled with the latest developed organic glue. It can be used to identify the difference between A+B goods, as there are acid etching marks. Look at the distribution of flocs and cracks inside the jade. Natural jade has obvious flocs and cracks, while processed jade is more perfect in all aspects. Here you need to look at more goods to increase your practical experience.

Sound: The sound is still crisp and the structure has not been seriously damaged. Many merchants will sell it as A-grade products.

Refers to dyed jadeite, which is completely artificially colored and has a weird color. It is suitable for those with coarser particles and has poor durability. The original bright color will fade due to long-term exposure to sunlight, erosion by acid and alkali solutions, and oxidation by air.

1. Gloss: Similar to B-grade products.

C grade jadeite

2. Color: Artificial dyeing is mostly done by directly immersing the jade in dye and heating it for a long time. Sometimes it needs to be heated repeatedly, so the color is not correct and looks evil. The color does not exist naturally inside the jade, but is filled in the mineral cracks, distributed in a network pattern, with no color roots. Precipitation or aggregation of dye can be seen in larger cracks; clear cracks can be seen in the brown jade.

When observed through a Charles filter, green turns into red or colorless (different colorants react differently under the Charles filter). If wiped with a strong fader, the surface color can be removed or faded. Due to the injection of dyes, long-term wearing is not good for health. The appraisal certificate indicates "Jade (processed)".

3.Structure: Similar to B goods.

4. Sound: It sounds more muffled than the B-grade products.

5. Feel: No cold feeling at all.

6. Fluorescence: When exposed to ultraviolet light, it will emit yellow-green or orange-red (dyed red jadeite) fluorescence.

★ B+C goods

Refers to jadeite that has been filled and colored.

Color: It has been acid-washed, bleached, glue-filled and artificially dyed. The appearance looks beautiful in both color and water head, but it also looks dull and evil.

★ D-goods

It refers to the green film coated on colorless jade, or other imitation jade. The durability of the coated jade is poor, and the film is easy to fall off. The refractive index is about 1.56. Under magnified observation, it can be seen that the surface gloss is weak (mostly resin gloss), there is no granularity, bubbles are visible in some parts, and the film can be seen falling off, mostly at the edge. It feels soft to the touch and astringent.

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