Hetian jade, one of "China's four famous jade" .In the traditional narrow sense, it refers to the jade produced in Hotan, Xinjiang Province, which is famous in the world on behalf of "Ziliao".In the broad sense, hetian jade refers to nephrite.Although Hetian jade is named after Xinjiang Hetian, it is not a regional concept, not specifically referring to the jade produced in Xinjiang Hetian area, but the name of a kind of product.China to the transblende composition of more than 98% of the stones are named Hetian jade, are in the range of national standards.
Crystal system
The main minerals of Hetian jade are tremolite and anthracite, which belong to monoclinic crystal system.The common crystal shape of these two minerals is long columnar, fibrous and leaf. Hetian jade is an aggregate of these fibrous minerals.
Structure
The main structure of hetian jade is metamorphic structure, including felt metamorphic structure, fiber-metamorphic structure, fiber-metamorphic structure, lamellar metamorphic structure, lamellar metamorphic structure and radiating (broom-like) metamorphic structure.The second is the rare remnant structure and the metasomatic coronal structure.
Although the mineral particles of Hetian jade have certain orientations, they are not strong, and occasionally the particles have wavy extinction phenomenon and plastic deformation.All these indicate that the metamorphic stress intensity is within the elastic limit of the mineral.
The main structures of Hetian jade include block structure and sheet structure, the block structure is more common.
Texture
Texture is the comprehensive performance of the quality of jade, including shape, moisture, cracks, impurities and so on.The mineral composition of Hetian jade determines its fine texture:
(1) Because its particle size is very fine, so the texture is very delicate, the ancients called "meticulous and chestnut", for other jade.
(2) warm and nourishing.Have grease luster, give a person with moist and soft feeling, the ancients so-called "warm and smooth and ze", suet jade is to jade moist as suet general and famous.
(3) Moderate transparency.That is, "water head is good", which is slightly transparent.The jade pieces cut into are vivid and lively.
(4) Few impurities.Some of them are flawless and consistent inside and outside, which is what the ancients called "flaws do not hide flaws in flaws", or "gills can be known from outside".
Hardness
Hardness is one of the important signs of identification of hetian jade, refers to the mineral resistance to external mechanical forces (such as characterization, pressing, grinding, etc.) invasion of the ability, in the gem jade science usually used in the Mohr hardness is one of the marking hardness.In the jewelry industry, hardness is generally regarded as an important mark to distinguish gemstones from jade.The hardness of gems is generally above 7 degrees of Mohs, and the hardness of jade is generally 4-7 degrees of Mohs, and the following 4 degrees of Mohs is usually called colored stone or carving stone.High hardness, good polishing, can make the jade shiny, but also easy to long-term preservation.
Hetian jade by the determination of Mohs hardness of 6.5-6.9, hardness is relatively large, different varieties slightly different.Generally speaking, the hardness of sapphire is slightly greater than white jade.
Toughness
Toughness is usually the intrinsic bonding ability of jade, that is, its ability to resist external pressures or breaking forces.Toughness is not easy to break, wear - resistant.Nephrite toughness is very big, this characteristic is other jade does not have, can make fine workmanship.
Among the common gems, the toughness of black diamond is 10, tremolite is 9, emerald, ruby, sapphire is 8, diamond, crystal, aquamarine is 7-7.5, olivine is 6, emerald is 5.5, topaz, moonstone is 5, opal is 3, fluorite is 2.For example, the toughness of tremolite jade is 1000, and the relative toughness of other jade or minerals is: 500 jade, 250 serpentine (such as xiu jade), 10 -- 20 quartz, 5 quartz, 2 -- 3 corundum, 2 mica.It can be seen that the toughness of tremolite jade is the largest in jade, and its compressive strength can exceed that of steel.According to scientific tests, the compressive strength of medium carbon steel is 1600 kg/square centimeter, while the compressive strength of Hetian jade can reach up to 6541 kg/square centimeter.
The great toughness of hetian jade is inseparable from its unique felt structure.Toughness is not easy to break, and wear-resistant, for the artistic modeling and fine carving of jade has great benefits, which is an important factor of Hetian jade as the group of jade.
Color
Color is not only an important criterion for evaluating the quality of Hetian jade, but also the main basis for classifying Hetian jade.
The color of hetian jade and other areas of nephrite compared, more tones, its own series.World through flash Shi Yu basically for white, blue, yellow, black, green (green) 5 kinds of color, there are some intermediate transition color, because the iron content is very low, hetian jade is basic for the first four kinds of color, while the magnesium iron rock in flash Shi Yu iron is higher, basically for the green, jade, according to the color, jade, hetian jade white jade, topaz, mo 4 major categories, which can be further divided,For example, white jade includes suet jade, white jade, green white jade, etc. Jasper is also produced in the rivers of Kunlun Mountains, but the primary ore belongs to ultramafic rock type, so it should not be included in Hetian jade. In Hetian jade, white jade and topaz are the most valuable.In particular, the suet white jade in Hetian jade is rare, only produced in Xinjiang. In ancient times, people thought that "Khotan jade has five colors, and the white jade is the most expensive, such as crisp."
Another characteristic of Hetian jade is that it has uncut jade. Ancient people attached great importance to uncut jade. Song Yingxing, a scientist in the Ming Dynasty, said:"Every brand to hide the jade, their skin jade skin, take it as inkstone, such as value, brand of the jade, there are more than vertical and horizontal feet no blemishes, the ancient emperors thought seal, the so-called choi liancheng, also not easy to get, no blemishes, the vertical and horizontal five or six inches to cup, this is when the weight of the treasure, also" hetian jade jade skin, according to the characteristics can be divided into the color of skin, skin, Shi Pi three kinds of sugar,Color skin may be the husk of the jade has a brown or brown very thin layer of skin (about 1 mm thick), is caused by oxidation, as you can see though the quality of the jade, such as autumn pears, tiger, deer, often for the fine jade, jade sugar skin thicker, such as red camel, JuMo ore often have this kind of jade, jade with jade, white jade or Shi Pi rocky surrounding rock is outer, surrounding rock will be taken to the jade,Such as and Shi Bi is "the reason for its skin and treasure."
Transparency
Transparency is the degree of visible light transmissibility of jade, which is mainly related to the intensity of light absorption of jade. In mineralogy, it is generally divided into transparent, translucent and opaque three kinds.Identification of transparency to the jade polished, in a certain thickness to see perspective of other objects, transparent body, translucent body, micro-transparent body, non-transparent body and other 4 levels.Hetian jade belongs to the micro transparent body, in the general degree of aggressiveness, can pass through the light, but can not see through the image.
Generally speaking, the high transparency is also called water head foot, although water head foot can foil the texture and color of jade, but not all the high transparency is good jade.Hetian jade in the general thickness is a translucent - micro-transparent body, although it can pass through the light, but can not see the object.This transparency enhances the warm and moist luster of Hetian jade, so Hetian jade carving should not be cut too thin.
Luster
Gloss is the ability of jade to reflect light.Hetian jade luster belongs to oil luster, this luster is very soft, not strong is not weak, that is, there is no strong light crystal inspiration, there is no weak light wax texture.The ancients called hetian jade "warm and smooth and ze", that is, its luster with a very basic oil, give a person with moist feeling, especially in hetian jade suet jade is famous for having the same moist luster as the fat of sheep.
Gloss is an important basis for evaluating the texture of Hetian jade. Generally, the value of gloss oil is higher, and the value of gloss dryness will be reduced.
Voice
The sound made by jade after being hit was an important property for ancient people to identify jade.
Hetian jade made of jade qing, percussion issued by the sound of the Qingyue long, such as the ringing of the qing, absolutely and resume, residual sound Shen Yuan, slowly do, this is the jade said: "knock, the sound of the Qingyue to long, its end."This characteristic, other non - amphibolite jade.