What is the method of jadeite appreciation? Anyone who knows, tell me.

The quality of jadeite is generally judged from five aspects: texture, hardness, transparency, specific gravity and color. The texture of jade refers to the delicate and moist degree of jade. One of the differences between jade and stone is that jade is delicate, moist and hard, translucent and glossy as fat; Stone, on the other hand, is rough and dry, lacking luster and opaque. Hardness refers to the ability of jade to resist external forces (such as pressing, engraving and grinding). The higher the hardness, the more difficult it is to process and the better the quality of jade.

Although the hardness index of jade can be known by detecting its internal crystal structure with instruments, the method of scraping hardness is generally used in operation. The hardness of common jade in China is between 4 and 6 degrees, which is higher than copper and lower than glass. In other words, jade can be carved on copper and glass.

People often distinguish gems, jade and colored stones according to their hardness. Generally speaking, the Mohs hardness of gemstones is above 7, such as diamonds, rubies, sapphires and jadeites, but Opal gemstones are an exception, with Mohs hardness of 5.5; The Mohs hardness of high hardness jade is between 6 and 7.5, such as Hetian jade, Nanyang jade and jadeite. The hardness of low-hardness jade is 4-6, such as turquoise and jadeite (the hardness of some serpentine jade is lower, as low as 2.5). The minerals below 4 are generally not called jade, but called colored stones.

In addition to describing hardness, there is also a hardness standard called compressive hardness, or indentation hardness, that is, absolute hardness, which refers to the ability to resist external impact, and is also called toughness in the jade industry. The highest compressive hardness in nature is black diamond, marked as 10 degree, followed by Hetian jade, with compressive hardness of 9 degrees, jadeite, ruby and sapphire of 8 degrees, diamond, crystal and aquamarine of 7-7.5 degrees and so on. On the other hand, the compressive hardness of Hetian jade is 1000, that of jadeite jade is 500, that of Xiuyu jade is 250, and that of agate is only 5. Hetian jade has such high toughness because its crystal distribution is woven like a blanket, and the intermolecular force is very large.

In practice, a jade craftsman usually looks at jade by observing craters. Generally, he cuts a small piece, breaks it with a small hammer, and observes the fracture, which is glassy compared with strength and toughness. Jade with strong toughness is not easy to break, even if it does, the fracture is uneven; The fracture of glassy jade is called "bright slag" through bright section, which is similar to shell shape. Jade, which is between toughness and glassy, is usually called "bad" and "meat", and its slag mouth is granular, parallel bundle, needle and so on. Through this observation, we can also observe whether jade has cleavage characteristics. If there is cleavage or crack, the jade will break in the direction of cleavage or crack when knocking.

It can be seen that Hetian jade, a kind of jade with excellent toughness, has very strong plasticity during processing. Among the gems with the same Mohs hardness or higher, Hetian jade will never crack when carving, so its texture is delicate, moist and shiny. Of course, toughness and hardness will also be affected by jade impurities, and impurities can also be understood by measuring toughness and hardness. This is a major factor that determines the use of a piece of jade. For example, jade magazine is not strict in making jade mountain seeds and utensils, but it requires pure and uniform jade materials when making jewelry.

The hardness of jade is one of the important criteria for identifying jade, and the luster of gem is also the basic criterion for identifying the authenticity and grade of gem.

Generally speaking, the luster of gems can be simply divided into "strong light", "burning light", "flash" and "weak light". But light is the strongest brightness, and people must squint. For example, the polished diamond total reflection surface has such brightness; Burning brightness is also very high, dazzling and high-hardness gems generally have burning brightness after polishing; Flash is the brightness of ordinary glass, which is divided into strong flash and weak flash. Jade with high hardness is generally strong flash, while jade with low hardness is weak flash. However, the light intensity of the stone surface with lower hardness is weak after polishing.

In addition to brightness, luster is also one of the identification characteristics of gems.

It is also divided into four categories: semi-metallic luster with refractive index between 2.6 and 3, such as goethite; Diamond luster, with refractive index between 1.9-2.6, such as diamond; The refractive index of glass luster is between 1.3- 1.9, such as jadeite; Grease luster, like animal fat, the most famous is the sheep fat white jade in Hetian jade. Every specific gem has a specific refractive index, and it is difficult to keep consistent with it under various conditions such as hardness, density, refractive index and brightness. Therefore, through the identification of these standards, the identity and initial value of gems can be confirmed.