[Crystal Chemistry]? Theoretical composition (wB%): calculated by Al2[SiO4](OH)2, SiO2? 33.4，Al2O3？ 56.6，H2O？ 10.0; F can replace OH with a theoretical content of 20.65%. F:OH is 3: 1~ 1: 1, which varies with the formation conditions of topaz: pegmatite type, and the F content is close to the theoretical value. In the greisen type, the content of OH increased to 5 ~ 7%; Hydrothermal type, with similar F and OH contents. ?
[Structure and Morphology]? Oblique system, a0=0.465nm, b0=0.880nm, c0 = 0.840nm；; Z=4. The crystal structure consists of O2-, F-, OH-*** and four layers of ABCB, and the stacking layer is ‖(0 10). Al3？ Occupying octahedral gaps and forming [SiO _ 4] tetrahedron connected with [Alo _ 4 (f, OH) _ 2] octahedron. ? Oblique bipyramid, D2h-mmm(3L23PC). Columnar crystal form. Common simplex: rhombic columns M, L, J, rhombic bipyramid N, O, P, Q, parallel double-sided C, B, etc. Cylinders usually have longitudinal stripes. It is usually an irregular granular and massive aggregate. ?
[Physical properties]? Colorless or microstrip blue-green, yellow, milky white, yellow brown or red yellow. Transparent. Glass luster. Cleavage complete. Hardness 8. The relative density is 3.52~3.57. ? Under the polarizer: colorless, biaxial crystal (? )。 2V=44~66？ ，Ng = 1.6 16 ~ 1.644，Nm= 1.609~ 1.637，Np= 1.606~ 1.635。 The interference color is low, usually I-level grayish yellow. ?
[occurrence and combination]? It mainly occurs in granite pegmatite, greisen and high temperature gas hydrothermal veins. ?
[identification features]? Columnar crystal, rhombic cross-section, longitudinal stripes on the cylinder, complete cleavage and high hardness. This can be distinguished from similar synchronizations. ?
[industrial application]? Transparent and beautiful crystals can be used as gems, called topaz, which is a low-grade gem. Crimson is the best quality and expensive; Followed by pink, blue and yellow; Colorless people have the lowest value. It can also be used as grinding materials, bearings of precision instruments, etc. ?
Topaz is formed at high temperature, and its composition is volatile, so it is a typical gas-generated hydrothermal mineral. It occurs in granite pegmatite, acid volcanic caves, greisen and high-temperature hydrothermal tungsten-tin chronological veins. Topaz is transparent and beautiful in color, and it is a high-grade gemstone raw material. Brazil is the origin of high-quality topaz in the world. 1940 A topaz crystal weighing 240.25 kg was found in Brazil. It is clear, transparent and flawless. What are the factors of Katlang production in Urals region of Russia and Pakistan? Chrome and rose topaz. Most topaz in the world is produced in Brazilian granite pegmatite, including varieties of various colors, and the largest crystal weight is 1 17kg. In addition, Sri Lanka, the United States, Myanmar, Urals, Australia and other countries also have gem-grade topaz output. Topaz in China is mainly produced in Inner Mongolia, Jiangxi and Xinjiang. In the17th century, the Braganza diamond (1640 carat) in the crown of the Portuguese king was once considered as the largest diamond, and now it has been proved that it is a colorless topaz.
Topaz is topaz, and its English name is topaz. English names come from two sources: one is Topaz, an island in the Red Sea, and the other is from the Sanskrit TOPUS, which means "fire". This exotic name seems to reveal the mystery represented by this gem. The mineralogical name of topaz is topaz, also known as topaz.
Topaz is an aluminosilicate mineral containing water, and its chemical molecular formula is Al2 [SiO _ 4] (F, OH) _ 2, and the ratio of F to (OH) is different. Crystal belongs to island structure silicate mineral, with rhombic crystal system, mostly rhombic columnar, with longitudinal stripes on the cylindrical surface, and the aggregate shape is columnar, granular and massive. Colors are colorless, light yellow, dark yellow, brown, sky blue, pink, red, light green and brown. Glass luster, transparent to translucent. The refractive index is1.619-1.627, the birefringence is 0.008-0.0 10, and the dispersion is 0.0 14. Polychromaticity is obvious. Hardness 8, density 3.49-3.57 g/cm3. Cleavage develops and is fragile. Under the irradiation of long-wave and short-wave ultraviolet rays, topaz of different colors shows different fluorescence. According to the color, it can be generally divided into wine yellow, colorless, blue, green and red topaz. Among them, the best dark yellow is the most precious, and the better the color of Huang Yue. Followed by blue, green and red.
Topaz is produced all over the world. The most important gem-grade topaz is produced in minas gerais, Brazil, where topaz is yellow, deep Sydney yellow, pink, blue and colorless. Sri Lanka is also an important producing area, and its topaz is mainly blue, green and colorless. California produces blue and yellow topaz.
A large number of colorless topaz produced in Guangdong, Xinjiang, Yunnan and other places in China can be turned into beautiful sky blue by neutron radiation, electron accelerator bombardment, Co60 irradiation and heating. It is worth noting that topaz discolored by neutron radiation is radioactive and needs to be left for a certain period of time (such as more than half a year) before it can be used as a decorative gem, otherwise it will cause certain harm to human body.
Topaz is a typical gas-generated hydrothermal mineral, which occurs in granite pegmatite, acid volcanic caves, greisen and high-temperature hydrothermal tungsten-tin chronological veins. The world-famous producing areas are Brazil, Urals of Russia and Katlang of Pakistan. Topaz can be used as bearings and grinding materials, and good quality can be used as gems. Topaz is produced in China, Inner Mongolia and Jiangxi.
In the eyes of westerners, topaz can be worn as a talisman, which can ward off evil spirits, eliminate sadness and enhance confidence. Soaking wine with topaz powder can cure asthma, insomnia, burns and bleeding. China has a long history of understanding and utilizing topaz. Topaz is an attractive, beautiful and cheap intermediate gem, which is deeply loved by people. Many countries in the world have designated topaz as the "November birthstone", which symbolizes friendship, fraternity and fraternity.
Topaz is a common gem, which is composed of fluorosilicate with hardness of 8. The common colors are colorless, pink, yellow and blue. Common gemstones that are easily mixed with topaz mainly include crystal, aquamarine, tourmaline and glass imitation, among which topaz is the easiest to mix together. In fact, except for the soft and fluffy appearance of topaz, it is extremely difficult for the naked eye to distinguish the two, which is also the fundamental reason why yellow crystals can cause people to doubt the value of topaz in the market.
It is easier to distinguish the raw materials of topaz and crystal. Topaz's columnar crystal surface has vertical stripes, while the crystal has horizontal stripes. For non-inlaid ornaments, the specific gravity (feel) can also be used as a basis for differentiation. The specific gravity of topaz is above 3.49, while that of topaz is only about 2.65. When you weigh it with your hand, topaz feels like a "falling" hand, while the crystal is lighter. Of course, the luster of topaz gem is soft, while the luster of crystal is "cold" and sharp, which can also be distinguished.
Topaz and tourmaline can be distinguished by the naked eye. The most important thing is that tourmaline is very dichromatic, while topaz is weak except pink. In addition, tourmaline has strong birefringence, and double images are often seen.
What is the difference between blue topaz and aquamarine? The general situation is more difficult, and the characteristics that can be used as a reference are: blue aquamarine often has some yellow-green tones and a little dichroism. Light specific gravity. Accurate identification should be determined by refractometer.
Glass and topaz have different luster and polarization. Topaz is rock crystal, which has good heat transfer, so it feels very cold, while the glass is "warm". When magnified, topaz can sometimes see gas-liquid inclusions composed of immiscible liquids, and glass often contains spherical bubbles, which can be used as auxiliary evidence.
Tips for buying topaz jewelry
(1) First of all, pay attention to the color when buying topaz. Bright and pure wine yellow and orange topaz are good products.
(2) Gemstone processing should be standardized and bright, and there should be no cracks, defects and edge collapse.
(3) Ask whether the color is natural or radiant. ?
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Also called? Topaz?
Topaz is a fluorosilicate with the chemical formula Al2(F, OH)2? SiO4 _ 4, orthorhombic crystal system, the original stone crystal is mainly columnar, sometimes produced as water-eroded pebbles. Topaz has a complete cleavage parallel to the bottom surface, with a hardness of 8, a density of 3.5-3.6g/cm3, a colorless, brown and blue refractive index of 1.6 1.62 and a birefringence of 0.010. The refractive index of red, orange, yellow and pink topaz is 1.63- 1.64, the birefringence is 0.008, the biaxial crystal is positive, the glass luster is low, and the dispersion is 0.0 14. Whether polychromatic color is obvious depends on body color, which varies greatly. ?
The varieties of topaz are mainly divided according to color. Topaz can be divided into the following varieties according to different colors:
Yellow topaz, including yellow to yellowish brown and thick yellow, is also called sherry topaz in business, because its color is similar to sherry (a pale yellow or dark brown wine produced in Spain and other places), and it is characterized by velvet-like soft texture and soft luster. ?
Topaz from light orange to golden yellow also belongs to this category. Golden topaz is often called "Brazilian topaz". Wine yellow and golden yellow topaz are the best varieties of topaz. ?
Blue topaz: This is a popular topaz variety in the international market, because it is cheaper than aquamarine, but its appearance quality is similar. Its color is mainly sky blue, and it often has a little gray or green tone including blue, sky blue and light blue, and light blue is common. Generally, the particles are small, and occasionally large particles can be seen. Mainly produced in Brazil. In addition, it is common in the market to irradiate blue topaz. ?
Powder-to-red topaz: At present, most of the powder-to-red topaz sold in the international market is obtained by heating yellowish-brown topaz. The color of this processed product is relatively stable and will not be reversed. ?
Colorless topaz: A variety can be called a forgotten gem. Because colorless topaz has low refractive index and small dispersion, it is relatively flat and inconspicuous after being polished into small faces, and it is not liked by people. ?
Other colors of topaz, in addition to the above, there are light purple, green, yellow-green topaz and so on. , but they are rare.