At present, there are many jade stones similar to nephrite in the jade market. The experts of NGTC have summarized: In recent years, the laboratory has detected some similar jade, the identification features of imitations, and the experts of NGTC, went into the laboratory and recognized The characteristics of the soft jade and its similar jade, imitation.
Now you can try to convert yourself and become a professional gemologist. Today, you walked into the lab, wore a white lab coat and turned on the microscope. What are you going to do?
Step 1: Prepare the sample
The samples requested in the article today are mainly collected from the samples sent by the customers in the market and in the daily tests of NGTC laboratories. It is mainly quartzite, carbonate rock (marble jade) and glass similar to nephrite and jade imitation.
The second step: scientific identification
Gemologists generally conduct routine testing of gemology when conducting laboratory tests. This is mainly to determine the type of jade by testing the gemological properties of jade, that is, identifying features. To identify and determine the variety of jade, first understand the identification characteristics (color, gloss, structure, specific gravity, hardness, refractive index, etc.) of these jade, and observe the color, luster and structure of jade through the naked eye or gem microscope to test its specific gravity. , hardness, refractive index and other properties, the soft jade and its similar jade, imitation products (quartzite, marble jade, glass, etc.) simple and fast distinction.
Conventional identification method
There are actually great differences between nephrite and its similar jade and imitation products. Some of the main identification features are also obviously different, such as color, gloss, structure, specific gravity, hardness, and refractive index. Generally, these kinds of identification features are detected by conventional instruments (gem microscope, refractometer, and electronic equivalent of measurable specific gravity), and the type of jade can be accurately identified.
Main identification features of routine identification
Soft jade mainly has white, blue, green, green, yellow, brown and other colors, grease luster, can achieve glass luster after polishing, refractive index is 1.6-1.61, specific gravity is 2.95, Mohs hardness is 6-7, mainly The felt-like structure (microfiber structure, fiber interlaced structure) is the main one.
2. Quartzite SiO2
The color of the quartzite resembling nephrite is mainly white and yellow, the gloss is glass to grease luster, the refractive index is about 1.54, the specific gravity is 2.64-2.71, the hardness is 7, and the granular structure. The transparency is higher, and the quartzite transparency is generally higher than that of nephrite.
3. Carbonate rock (marble, twirl, marble, etc.)
Marble jade (commonly known as Afghan jade, etc.)
Carbonate rock similar to nephrite is generally the marble of the Afghan jade on the market. Its color mainly consists of white and yellow lights. The gloss is glass luster-grease luster. The refractive index is 1.48-1.66, although the refractive index range is very high. It is wide, but in general, its refractive index is lower than that of nephrite, and its specific gravity is about 2.70. Marble has a very low hardness and a hardness of 3, which is easily scribed with a knife. It is mainly composed of a granular structure, and has a parallel strip-like structure, which is distinct from the waterline of nephrite, and can be separated from the soft jade. Come, with hydrochloric acid will foam. Long-wave and short-wave fluorescence under ultraviolet fluorescent lamps.
Tremolite petrochemical marble
In the laboratory test, I often encounter a kind of jade, which is very similar in appearance to nephrite, but mainly glass luster. It lacks the high-quality luster of nephrite. It has no oily and delicate feeling. The structure is thicker than soft jade. Granular structure, infrared spectrum has both characteristic peaks of oscillating and characteristic peaks of carbonate, which is easy to be misjudged as nephrite. Some experts suggest that it can be named "tunable fossil marble" or "carbon" according to its content. Acid salt fluorite jade. Closed thinking that it can not be simply defined as nephrite or Hetian jade, but there is a certain doubt about the name of the translucent petrochemical marble, which needs further study. This paper first divides this kind of jade into carbonate rock to show its Nephrite is different.
There are several production processes for using glass imitation nephrite: ordinary glass, devitrified glass, and new microcrystalline glass lamps. Glass is the main artificial imitation of nephrite.
Ordinary glass imitation soft jade is the most common, mainly white, green, bluestone and other imitation soft jade color, luster is glass luster, translucent to opaque, often contains a large number of bubbles of varying sizes, some visible to the naked eye, most of the bubbles Spherical, the hemispherical pits left by the bubbles can be seen on the surface of the cut glass. Some glass-like soft jade can also see the flow structure inside, the shell-like fracture, the refractive index is about 1.51, the specific gravity is 2.30-4.50, and the hardness is 5-6. , weak to strong fluorescence.
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