For a long time, it is generally believed that jadeite is always green and expensive. Jet is also called "Cui Mo". Although many books have mentioned the color of jade, there are not many people in the industry who have really seen pure black jade. When people talk about the black color of jadeite, they always think that it is the dirty color and flaw in jadeite, and call it "flying excrement" or "black pimple". Some researchers even think that dark green jade is the cheapest jade. It was not until a string of "Cui Mo" in Hong Kong fetched a high price of HK$ 6.5438+0.3 million that people noticed that this unknown black pimple was worth millions, so the jade industry was blown up. The black jade originally abandoned by jade manufacturers in the corner is also worth a hundred times, and for a time, "Luoyang paper is expensive". Some jade collectors are also proud of collecting ink (jade).

So what exactly is jet? At present, the black jadeite on the market can be divided into two categories.

The first kind is black jade. The research samples are several cut stone chips and some finished products in the market. This jet is grayish black in appearance and translucent black in light transmission observation. Jade has a columnar and variegated metamorphic interwoven structure. The finished product can see obvious flash (emerald). The refractive index is 1.655 ~ 1.658, and the density is about 3.36 ~ 3.32 g/cm3. The absorption spectrum shows that the purple region is strongly absorbed, and there is no absorption line at 437nm. X-ray diffraction analysis shows that the main mineral is jadeite. So this kind of jet is the undisputed black "jade".

However, there are some problems in detailed microscopic observation. The problem is that black is not the primary color, which means that jadeite minerals are not black. Emerald is displayed because there are a lot of filiform and sharp black substances distributed among jadeite minerals. Further enlargement shows that these blacks can even be used as secondary inclusions in jadeite, which exist in the microstructure defects of jadeite. Therefore, it can be confirmed that this black jade is not the original black jade, that is to say, its color was formed in the later stage. Due to the uneven distribution of black, this jadeite is usually not completely black, and white patches and stone flowers are often seen in some places. Therefore, its value is actually not high, and it is also very common in jade stalls.

The second kind is black pyroxene jade.

The appearance of this jet is black on wool or thick jade, dark green when transmitted by strong light, and light dark green-dark green when observed on finished products or thin jade. Its structure is more delicate and dense, except for some flocculent stone flowers, it is not easy to observe obvious Cui Hua or flying wing flash, and some samples can only be seen when magnified 10 times. But it is very important that this kind of jade, after being well polished, often presents a black and shiny appearance and good glass luster, thus giving people a solemn and mysterious feeling.

Common gemological tests show that the refractive index of this kind of jade is between 1.670 ~ 1.688, and the density is about 3.34 g/cm3, and typical absorption spectra are rarely seen. However, the thin section observation shows that its structure is fine, the minerals have no obvious crystal form and polychromatic, the interference color is grade I yellow and white, and the electron probe chemical composition analysis shows that it is yellow and white. X-ray diffraction analysis shows that diopside is the main mineral. Therefore, from its physical constants, chemical composition and structural analysis data, it can be confirmed that this kind of jet is different from the omphacite-type dark green jade mentioned in the general literature. Because its mineral composition and chemical composition are different from the typical varieties known at present, and its physical constants are similar to those of ordinary jadeite, the author thinks that this black jade is called jet jade.

But at present, there are more than two kinds of black jadeite or black jadeite on the market, one of which belongs to amphibole jade in both color and structure, so it is similar to the second kind of black jadeite mentioned by the author, which is composed of amphibole minerals. For the latter, it cannot be called black jade, nor can it be called black jade. Its identification can be based on the difference of refractive index. The refractive index of black jadeite is 1.76 ~ 1.78, while that of black jadeite composed of amphibole is1.610 ~1.626. Other black materials commonly used as warning surfaces in the market are black cubic zirconia and black agate.

The value of black jadeite is mainly evaluated from the aspects of texture, color and defects. Those with dense and delicate texture, it is difficult to see the crystal structure of minerals under the microscope of 10 times, but they are green-blue-green under light transmission, uniform black under white light, strong glass luster, no cracks or flocculent stone flowers inside, and high value; On the other hand, if the texture is rough and green, or the light-transmitting color is light dark green, the color is not deep enough under reflection, or there are micro-cracks or flocs in it, the value is low.

Of course, for the finished product, whether the proportion of jewelry is harmonious, whether the shape is full, whether the carving is fine and whether the polishing is perfect will also have a great impact on the value of jet.

Therefore, if you buy high-value jet, collectors should carefully identify it.

At present, rings and small carvings made of high-quality black jadeite are deeply loved by collectors and merchants in Singapore and Taiwan Province, with good prices and rare fine products.