First, the basic attributes of seasonal jade
(1) mineral composition
Seasonal jade is mainly composed of aphanitic-crystalline seasonal jade, with a small amount of mica minerals, chlorite, limonite, hematite, goethite and clay minerals.
(2) Chemical composition
The chemical composition of seasonal jade is mainly silicon dioxide, and may also contain a small amount of elements such as calcium, magnesium, iron, manganese, nickel, aluminum, titanium and vanadium.
(3) Crystal system
Yingshi is the main component mineral of Yingshi jade, belonging to ternary system.
(4) Structure and construction
Seasonal jade is a microscopic aphanitic crystal aggregate. Granular structure, fibrous structure, cryptocrystalline texture. Block, block, strip, shell, bell structure.
(5) Optical characteristics
1. color
Seasonal jade is rich in colors, such as white, green, gray, yellow, brown, orange and blue. Seasonal jade is colorless when pure. When containing different trace elements (such as iron, nickel, etc.). ) or mixed with other colored minerals, can present different colors (see Figure 3-2-69).
Figure 3-2-69 Various colors of chalcedony
2. Gloss and transparency
The polishing plane can be glass luster, grease luster or silk luster, and the fracture surface is generally grease luster. Slightly transparent-transparent.
3. luminosity
Heterogeneous aggregates without extinction position under cross polarizer.
4. Refractive index
1.544 ~ 1.553, the point measurement method is often 1.53 or 1.54, and individual measurements can reach 1.55.
5. Polychromaticity
There is no multicolor in the aggregate.
6. Absorption spectrum
Generally, there is no characteristic spectrum, and only a few varieties can produce characteristic absorption spectrum because they contain a small amount of chromogenic elements. For example, quartzite containing chromite may have absorption bands of 682 nm and 649 nm.
(VI) Mechanical properties
1. density
Due to the influence of crystallinity and impurities, the density will change to some extent, generally around 2.55 ~ 2.7 1g/cm3.
2. Difficulties
Slightly lower than the single crystal strain, Mohs hardness is 6.5 ~ 7.
Second, the variety of seasonal jade.
Seasonal jade can be divided into the following types according to its structure, mineral assemblage and mineral genetic characteristics.
(A) aphanitic seasonal jade
According to the structure, structural characteristics and the content of secondary minerals, aphanitic British jade can be divided into chalcedony and agate.
1. chalcedony
Ultra-microscopic aphanitic time-dependent aggregates are mostly produced in blocks. The monomers are fibrous, disordered or slightly oriented, and the pores between particles are filled with water and gas. It can contain trace elements such as iron, aluminum, calcium, titanium, manganese and vanadium or other mineral particles. According to the color and other minerals contained, chalcedony can be subdivided into the following varieties.
1) white jade pulp is gray and has a single composition. Slightly transparent-translucent.
2) carnelian red-maroon, colored by trace Fe (the mass fraction of Fe2O3 in some samples is about 1.7%). Slightly transparent-translucent.
3) The green color of chrysotile asbestos with different tones is caused by the uniform distribution of impurity elements such as iron, chromium and nickel or green minerals such as fine chlorite and actinolite. Slightly transparent-translucent (see Figure 3-2-70).
Chlorite produced in Australia, also known as Australian jade or Australian jade. The color is even and green, colored by Ni, often with Huang Tiao and gray tones, and the high quality is bright apple green.
4) The blue chalcedony is gray-blue-blue-green, and the color is produced by the blue minerals contained. Opaque-slightly transparent.
The blue and blue-green chalcedony produced in Taiwan Province Province has a uniform color and is colored by Cu2+. Hardness is close to 7. The density is about 2.58g/cm3. Opaque-translucent. The color of high-quality Taiwan Province blue chalcedony is similar to that of high-quality sky blue turquoise (see Figure 3-2-7 1).
Figure 3-2-70 Chrysotile asbestos
Figure 3-2-7 1 chalcedony in Taiwan Province Province
In addition to the above four kinds of chalcedony, there are some chalcedony with more impurities, mainly iron oxide and clay minerals, the content of which can reach more than 20%, commonly known as "Jasper" in business. They are opaque and dark red and green in color. Merchants are often named after colors, such as green jasper and red jasper (also known as sheep liver stone, see Figure 3-2-72); Sometimes it can also be named after special patterns, such as landscape jasper, blood stone and so on. Among them, landscape jasper is a kind of colorful jasper, and the strips of different colors complement each other, just like a beautiful natural landscape painting, hence the name; Bloodstone (see Figure 3-2-73) is a dark green opaque-slightly transparent jasper with reddish-brown spots scattered on it, which seems to drop blood, hence the name Bloodstone. The most famous origin of bloodstone is India.
Figure 3-2-72 "Sheep Liver Stone"
Figure 3-2-73 Blood stone
2.agate
Hidden jade with banded structure. According to the characteristics of color, band, impurity or inclusion, it can be divided into the following varieties.
(1) classified by color
Agate can be divided into white agate, red agate, green agate and black agate according to color (see Figure 3-2-74).
White agate is gray-grayish white, and pure white is rare (see Figure 3-2-75). The banded structure in white agate is caused by subtle differences in color or transparency. White agate can only be used after dyeing, except for large pieces and even colors used for carving.
Natural red agate is rarely very dark in color, but it is mostly light reddish brown and orange. Red stripes and white stripes with different shades and transparency are alternately distributed in the block (see Figure 3-2-76). Red is caused by tiny iron oxide particles. Most of the red agates on the market are made by heat treatment or artificial dyeing.
The natural color of green agate is rarely particularly bright, mostly light gray-green, and its color is produced by tiny minerals such as chlorite. Most of the green agates appearing on the market are artificially dyed.
Figure 3-2-74 Various agates
Figure 3-2-75 White agate
Figure 3-2-76 Red Agate
(2) Classification by strip
Onyx, also known as striped agate, is a kind of agate with single color and clear stripes. Common onyx can have black and white stripes or red and white stripes. When the strip of onyx becomes very narrow, it can also be called silk-wrapped agate (see Figure 3-2-77). A more expensive agate wrapped in silk is composed of red and white strips wrapped in silk.
(3) Classification by impurities or inclusions
Moss agate is a kind of agate with impurities, with moss and dendritic patterns. Generally speaking, green is formed by gathering tiny scales of chlorite; Black is composed of oxides of iron and manganese. The craft value of moss agate is very high, and those blue-black patterns give people rich imagination space, so moss agate has become a valuable variety in agate.
Agate contains thin liquid or mineral inclusions, such as red flaky hematite between agate fine bedding. Interference and diffraction effects can be produced under the irradiation of light. If cut correctly, agate will appear colorful halo (see Figure 3-2-78).
The enclosed agate crystal cave in water bile agate is covered with natural liquid (usually water), which is called water bile agate. When the liquid is blocked by the four walls of agate (usually an opaque thin shell composed of timely particles), the whole agate is noisy when shaking, but it has no technical value; When the liquid is in a transparent-translucent cavity, this agate has great technological value (see Figure 3-2-79).
Figure 3-2-77 Silk-wrapped Agate
Figure 3-2-78 Agate
Figure 3-2-79 Water bile agate crafts
(4) Other commodity varieties.
In addition to the above classification, the main components of Yuhuashi produced in Nanjing and Tianzhu produced in Tibet are also aphanitic silica.
Rain flower stones are divided into two categories: generalized rain flower stones and narrow rain flower stones. Shi Yuhua in a broad sense refers to all kinds of oval gravels, including agate, flint, siliceous rock, quartzite, gangue, silicified limestone, volcanic rock, opal, crystal and amethyst in various colors (see Figure 3-2-80). Shi Yuhua in a narrow sense refers to agate produced in the gravel layer of Yuhuatai in Nanjing. In ancient times, rain flower stone was called "aragonite" or "granular stone" because of its obvious banded pattern characteristics.
Figure 3-2-80 Rain Flower Stone
Rain flower stones are red, yellow, blue, green, brown, gray, purple, white, black and other colors. And the patterns are varied, so it is known as the "first stone in the world" among the ornamental stones.
Tianzhu is a token of Tibetan religion. According to the circular pattern on the surface of dzi beads, it can be divided into: one-eye dzi beads, two-eye dzi beads and nine-eye dzi beads. Its main mineral composition is chalcedony. Most of the common dzi beads on the market are optimized. There are also imitations of resin, glass and other materials.
(2) Crystallize timely jade (quartzite, Dongling stone)
Crystalline seasonal jade is composed of granular seasonal particles. The particle size is generally 0.0 1 ~ 0.6 mm, and the aggregate is massive and slightly transparent to translucent. The density is similar to that of single crystal, ranging from 2.64 to 2.71g/cm3. Pure people are colorless, and if they contain tiny other colored minerals, they can show different colors. Merchants are often named after their places of origin, such as Beijing (produced in the suburbs of Beijing), Guicui (produced in Guizhou) and Shetaicui (produced in Dashetai Town, Urad Qianqi, Inner Mongolia). The common variety of crystal seasonal jade is Dongling stone.
Dongling stone is a kind of seasonal jade with placer gold effect, which often contains minerals of other colors and presents different colors. Chromite is green, which is called ludongling stone (and ludongling stone produced in Xinjiang contains green fibrous actinolite); Monazite is blue, called blue Dongling stone; Lepidolite is purple, which is called zidonglingshi. Generally speaking, the timely particles of Dongling stone are relatively coarse, and the flaky minerals contained in it are also relatively large, so flaky minerals can present a sparkling sand effect in the sun.
The green Dongling stone is the most common one in the domestic market (see Figure 3-2-8 1). Under the magnifying glass, you can see the thick chromite phosphate, which is roughly oriented and slightly reddish brown under the color filter.
Figure 3-2-8 1 Dongling Stone
(3) Jade (wood and stone) is replaced by silica
Wood stone is also called silicified asbestos. Its primary mineral is blue sodium amphibole asbestos, which was later replaced by silica, but it still retains the appearance of fibrous crystals and presents a fibrous structure. Observed under a high-power microscope, the "fibers" are as thin as hair and arranged in a directional way. Frankly, silica has crystallized, showing very fine timely particles. Due to the different substitution degree, the physical properties of wood-changed stone are slightly different. When the substitution degree of SiO2 _ 2 is high, the hardness is close to 7 and the density is relatively low. Generally speaking, the density varies from 2.64 to 2.7 1g/cm3. Slightly transparent to opaque. Silk luster. According to the color, wood stone can be divided into tiger eye stone, eagle eye stone and other varieties.
1. Tiger Eye Stone
It is brown, brown to reddish brown, brown and brown wooden stone. Tan and brown are caused by limonite, which is an iron-containing oxide. The surface of the finished product can have silk luster. When the fibers that make up the tiger's eye stone are arranged in fine order, the cat's eye effect can appear on the surface of the arc gem (see Figure 3-2-82).
Figure 3-2-82 Tiger Eye Stone
The cat's eye effect of tiger's eye stone is generally wide, and it is rare to see the eyeliner opening and closing phenomenon like the golden emerald cat's eye when swinging left and right.
2. Hawkeye stone
It is a gray-blue, dark gray-blue and blue-green wooden stone. Blue is the color of residual blue sodium amphibole asbestos. It can also have a cat's eye effect.
3. Zebra Tiger Eye Stone
It is a yellow-brown and blue mottled wooden stone.
Thirdly, the optimization and identification of timely jade.
The optimization treatment of seasonal jade mainly adopts two methods: heat treatment and dyeing, and water injection treatment in water bile agate.
(1) heat treatment
The main varieties used for heat treatment are agate and tiger eye stone.
Uneven light maroon agate can be directly heated in the air to become more uniform and bright red. This is because agate contains a little limonite. Under the condition of high temperature oxidation, Fe2+ in limonite is transformed into Fe3+, and the water is removed, and limonite is transformed into hematite, so agate becomes bright red.
The heat treatment principle of tiger's eye stone is the same as agate. Yellow-brown tiger's eye stone can be turned into brown-red when heated under oxidizing conditions. Tiger's eye stone can be transformed into grayish yellow and grayish white by heating under reducing conditions, which can be used to imitate the golden emerald cat's eye.
(2) Dyeing
At present, most chalcedony (agate) products on the market are dyed. Among them, it can be divided into direct impregnation coloring with organic dyes, infiltration coloring with inorganic dyes, reactive precipitation coloring and so on. The dyed chalcedony (agate) shows extremely bright and uniform red, green and blue colors (see Figure 3-2-83). The dyeing of chalcedony (agate) belongs to optimization.
Fig. 3-2-83 Agate with various colors after dyeing.
The dyeing method of quartzite is to heat quartzite first and then dye it after quenching. Mainly dyed green, commonly known as "Malaysian jade" in the market. The diameter of the timely particles is 0.03 ~ 0.3mm, the Mohs hardness is 6.5 ~ 7, and the density is 2.63 ~ 2.65g/cm3. Magnification test showed that the dye was distributed among the particles in the shape of silk screen. There is a broad absorption band of 650nm under the spectroscope (see Figure 3-2-84). It can have dark green fluorescence under short-wave fluorescence, which is mainly used to imitate jadeite.
Figure 3-2-84 Absorption Spectrum of Dyed Quartzite
(3) water injection treatment in water bile agate.
When there are many cracks in water bile agate or during processing, the water in the water bag will overflow slowly until it dries up, and the whole water bile agate will lose its technological value. The solution is to immerse water bile agate in water and use capillary action to backfill water, or use injection method to backfill water, and finally use glue to plug tiny cracks. The identification method is whether there are traces of manual treatment on the wall of the water sac. Gently draw a line in a suspicious place with the tip of a needle. If holes or cracks filled with gum or wax are found, they can be treated with water injection.
Fourthly, the identification of seasonal jade and its imitation.
The imitation of seasonal jade is mainly glass. These glass products are completely glassy or semi-crystallized. There can be red, green and other colors, and some can also have a ring structure. Compared with agate and other jade, these glass imitations have lower density and refractive index, and can contain bubbles, and most of them are completely or abnormally extinguished under the cross polarizer.
Five, timely quality evaluation of jade.
Seasonal jade can be used to make various ornaments, such as small pendants, bracelets, necklaces, sculptures, rings and so on. Its quality requirements and evaluation can be measured from the following aspects:
1. color
The raw materials of seasonal jade should have a certain color, or can be dyed into a certain color, such as green, yellow, red and so on. Quartzite jade with gray and brown variegated colors is difficult to be directly used for dyeing. The color should be relatively uniform, and the purer and brighter the finished product, the better.
2. Special patterns and inclusions
When the color of jade raw materials can form certain patterns and patterns, such as red and white stripes in agate are regularly arranged to form silk-wrapped agate, and uneven colors in jasper can form landscape patterns, so the value of materials will be improved.
In addition, when the colored mineral inclusions in jade can form certain patterns, the value of aquatic agate formed by the arrangement of chlorite phosphate and moss agate accumulated by iron and manganese impurities is higher than that of gray agate. The more beautiful the finished pattern, the more artistic it is, the better.
The bigger the "water bag" in water bile agate, the more "water", the higher the transparency and the higher its value.
3. Texture
Timely jade requires uniform and delicate structure and tight combination, and the fewer cracks, impurities and "sand cores", the better.
4. Transparency
Seasonal jade should have certain transparency, and completely opaque materials are difficult to design and apply.
Step 5 split
Need a certain degree of fragmentation.
6. Processing technology
The raw materials of seasonal jade are generally of low value, but they can be valuable if they are cleverly conceived, beautifully colored and finely processed. For example, the "shrimp plate", "dragon plate" and "water bile agate ornaments" of traditional jade carvings in China are all known as national treasures.
6. A brief introduction to the origin of seasonal jade.
Seasonal jade has many producing areas and different occurrences. Chalcedony (agate) deposit includes primary ore and secondary ore. Primary ore is mainly produced in the pores and cracks of basic and intermediate acid volcanic intrusions and tuffs, and is filled and condensed by colloidal solution rich in silica. Secondary deposits are formed by weathering, leaching and transportation of primary deposits. Such as the rain flower stone in Nanjing and the agate "lake" in Inner Mongolia. Chalcedony (agate) deposits have been discovered in more than 20 provinces and cities in China. Quartzite is mainly produced in quartzite formed by regional metamorphism and hydrothermal contact metamorphism (such as Shetaicui produced in Inner Mongolia). Henan Dense Jade occurs in the fracture of metamorphic quartzite, which belongs to the late hydrothermal metasomatic deposit. Wood metamorphic rocks are mainly produced in metamorphic asbestos deposits, such as Neixiang-Xichuan area in Henan and Luodian in Guizhou. There are many high-quality jade mines in time, almost all over the world.