Dushan Jade gets its name because it is produced mainly in Dushan, Nanyang.Dushan is located in the northeast of Nanyang City.Dushan jade is tough and slightly dense, delicate and soft, the color is mottled, warm and moist, there are green, blue, yellow, purple, red, white six kinds of pigments, 77 color types, is the important jade raw materials of arts and crafts carving pieces, become the famous specialty of nanyang, is one of the four famous jade in China.Dushan jade carving has a long history. According to archaeological calculations, the ancestors had known and used Dushan jade as early as 5000 years ago.In old China, jade carving in Nanyang has formed a big industry, with more than 80 workshops in the city.
Dushan jade has been mined for thousands of years, with numerous caves all over the mountain.Ancient jade pit for shaft type, generally more shallow.Using blasting techniques and tools such as rock drills and mining carts, the tunnels have reached hundreds of meters into the mountains and are crisscrossed with intricate branches that are as dense as a web.
The main characteristics of chemical composition :SiO2 is about 41~45%;Al2O3 is about 30~34%;CaO is 18 ~ 20%.This indicates that Dushan jade is composed of calcium aluminum silicate minerals.Dushan jade mine also contains trace copper, chromium, nickel, titanium, vanadium, manganese and so on.
Nanyang jade hardness 6 ~ 6.5.Glassy luster, most opaque, a few micro-transparent.The results of the chemical analysis were:Silica 41 ~ 45%, alumina 30.71 ~ 34.14%, magnesium oxide 0.28 ~ 1.73%, potassium oxide 0.02 ~ 2.64%, ferric oxide 0 ~ 0.8%, ferrous oxide 0.27 ~ 0.88%, manganese oxide 0.02 ~ 0.1%, chromium trioxide 0.01 ~ 0.34%,Crystalline water 0.23 ~ 0.74%, carbon dioxide 0.06 ~ 0.52%.The results of trace element analysis of Nanyang jade are: chromium 0.01 ~ 0.5%, nickel less than 0.1%, vanadium 0.001 ~ 0.1%, manganese 0.01 ~ 0.05%, titanium 0.001 ~ 0.5%.
Nanyang jade is a kind of altered plagioclase, which is composed of several minerals, such as tehatite, epidote, tremolite, sericite, biotite and sphene.Through the microscope identification, the jade contains a variety of alteration minerals, and the alteration is dominated by zoetritism, epidritism and tropholite.Because jade contains a variety of metal impurities electroelement ions, so the color of jade has a variety of tones, mainly green, white, variegated color, also see purple, blue, yellow and other colors.
The cause of formation
It is found in Dushan rock mass and can be divided into gabbro mylonite belt, mylonite gabbro belt and gabbro cataclastic belt according to dynamic metamorphism.Research shows that the dushan jade is inclined long period after high, in the warm liquid deposits, forming temperature is 355 ~ 430 ℃, jade is the product of the number of multi-stage, along with the hot fluid from early to late, Ca, Cr, Fe and Ti ion content increased gradually, jade color from colorless to white to purple, sky blue to green, late feldspar brand also gradually increase.
Dushan jade is a unique variety of jade in China, mainly produced in Dushan, Nanyang, Henan Province, Xinjiang, Sichuan and other places.
① Dushan jade from Henan Province
Produced in Dushan, Nanyang City, Henan Province, so named Dushan jade (Nanyang jade), is an ancient jade species.
② Xinjiang Dushan jade
Xinjiang Dushan jade is a kind of altered anorthosite, due to the weathering of the rock protruding, higher than the surrounding rock, Yuanwang also like "Dushan" named Xinjiang Dushan jade.
Geological characteristics: located in the west junggar region, produced in the ultrabasic tropicolige rock is vein, beadlike penetration, contact boundary is clear, a few meters wide vein dozens of meters long.
Color: white with green spots, milky white, green, blue.
Rock characteristics: Alterated anorthosite, olivine anorthosite, semi-idiomorphic columnar granular structure, local radiate structure, scale amorphous structure.
Mineral composition: plagioclase, olivine, zoisite, serpentine, hydrocalgarite, grapevine, chlorite.
Dushan Jade Color
Because it contains color minerals and a variety of pigment ions, so that the color of Dushan jade complex and varied.Among them, more than 50% is variegated jade, 30% is green jade, 10% is white jade.The jade is green or emerald green when it contains chromium.Yellow when containing vanadium;At the same time containing iron, manganese, copper, is pale red;At the same time containing titanium, iron, manganese, nickel, cobalt, zinc, tin, etc., mostly purple.Dushan jade is a kind of multicolor jade, according to the color can be divided into eight varieties.
Dushan jade green
Green comes emerald green, include green, greyish green, turquoise, yellow-green, often accompany with white jade alone, color distributes uneven, show irregular ribbon, filament shape or group block shape distributes more.The texture is exquisite, approximate jadeite, has vitreous luster, transparent to translucent performance is different, among them translucent blue-green jade alone is the best variety of dushan jade, in the business also someone calls "sky blue jade", or "nanyang jade".In mining, the yield of this high-quality variety is gradually reduced.The opaque green jade is mostly grey green.
Red dushan jade
Also known as "lotus red".Often behave for pink or hibiscus color, depth is different, it is micro transparent to opaque commonly, quality of a material is exquisite, burnish is good, with white jade shows transition concern alone.The content of such jade is less than 5%.
Hibiscus red (and dry white red, permeable red).
White dushan jade
Overall white, milky white, fine texture, with grease like luster, often translucent to micro transparent or opaque, according to the transparency and texture of the different and permeable white, oil white, dry white three kinds of appellations, which to permeable white is the best, white jade accounted for about 10% of the whole dushan jade.
White Dushan Jade is mainly milky white, some with grey and pink.
According to the difference of color and transparency, it is divided into:
Water white jade (also divided into white, water white),
White jade (also divided into fine white, waxy white, white and ripe white),
Black white jade (also divided into a gray tone of bird white and part of the more gray so-called blue) and so on.Among them, the quality of water white jade is the best and black white jade is the worst.In the classification of rocks, Baidushan jade mainly belongs to fine grained zoisite plagioclase or amphibolic zoisite plagioclase.
Purple dushan jade
Color shows dark purple, texture is exquisite, hard and dense, vitreous luster, diaphaneity is poorer.Commonly known as bright brown jade, soy purple jade, brown jade, purple spot jade, brown jade.
Huang Dushan jade
For different depths of yellow or brown yellow, often translucent distribution, which often have white or brown mass, and with the transition color.
Dushan jade in brown
Dark brown, grayish brown, tan, uneven depth of performance, such jade is often translucent, often with gray and green Dushan jade was a transition state.The light colored ones are better.
Black dushan jade
Color such as ink color, so it is also called "Mo jade".Black, dark green, opaque, granules are bulky, often lumpy, lumpy or punctate, accompanied by white jade, the variety is the worst variety of Dushan jade.
Green dushan jade
Cyan, gray-green, blue-green color, often manifested as a block, ribbon, opaque, for the common variety of Dushan jade.
Variegated Dushan jade
In the same specimen or finished product is often shown as the above two or more colors, especially in some larger Dushan jade raw materials or carving pieces often appear four to five or more color varieties, such as green, white, brown, green, ink and other colors are each other disseminated or gradual transition in the same body,Even on the ring surface of less than 1cm, brown, green and white color coexist. This complex color combination and distribution feature has important guiding significance for the identification of Dushan jade.Variegated jade is the most common variety of Dushan jade, accounting for more than 50% of the entire reserves.
The color is good or bad in turn for pure green, emerald green, blue green, light blue green, blue permeable white, green white, dry white and miscellaneous.Dushan jade with positive color, high transparency, fine texture and no impurities crack for the best.Among them to hibiscus stone, permeable white jade, jade value is higher.In addition, the use of jade blocks of different colors to imitate the natural production of beautiful color jade carvings received praise.
Because dushan jade is mainly used for raw materials of jade, the larger the block, the better. The general requirements should be greater than 1 kg or more. The special products of individual jewelry can be lowered.