The English name of the diamond is "Diamond", which is derived from the Greek word "Adamas", which means "hard and incomparable". The saying goes "no diamonds, no porcelain." Diamonds have always been the treasures of nature that people have always dreamed of. It is common to refer to unrefined mineral rough as diamond and the finished finished diamond as diamond.
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Diamonds are often granular crystals. Common crystal forms are octahedrons, rhombohedral dodecahedrons, cubes, and tetragonal, tetragonal, octahedron and hexahedron and their polymorphism. And the size of the particles is one, the general particle size is 2~10mm, and the maximum is up to several thousand carats, such as "Cullinan" drill, "Star of Hope", "Changlin Diamond" and so on.
Diamonds are typical diamonds. The colors can be divided into two categories, one is colorless to yellow, brown series, which is the Cape of Good Hope series, and the other is color diamonds, including yellow, brown, pink and reddish purple, black, Blue, the series of colored diamonds. Diamonds have good transparency. Generally, the density of transparent diamonds is relatively stable. The hardness is the highest among the known natural gemstones. It has good stability and is insoluble in strong acids and alkalis. When the temperature of the diamond reaches 650 ° C under oxidizing conditions, It begins to slowly oxidize, producing carbon dioxide, a property used for laser drilling and cutting, and since the diamond is composed of carbon, no traces are left on the film by X-rays. Diamonds have a very low coefficient of thermal expansion. A sudden change in temperature has little effect on the diamond. Diamonds without inclusions and cracks can be cooled quickly after heating to 1800 ° C in a vacuum without any damage to the diamond. Diamond is the best thermal conductivity of all materials, using this property to create an instrument specifically for the detection of diamonds - diamond thermal conductivity meter. Diamonds are generally non-conductive. Type IIb diamonds are semiconductors due to the inclusion of element B. They are used in thermistors and have high sensitivity. Synthetic diamonds may be conductive due to the inclusion of catalysts (Fe, Ni).
The quality level of diamonds directly affects the price of diamonds. Now there is a unified evaluation standard in the world, and the price of diamonds has a uniform price. The quality evaluation of diamonds can be carried out in four aspects: Carat, Color, Clarity, and Cut, which is commonly referred to as the "4C" evaluation standard.
(1) The international common weight unit for weight diamonds is carat. The conversion relationship between carat and gram is: 1.00 ct = 0.200 g, 1.000 g = 500 ct. And the accuracy of the balance is higher than 0.001g, and it can also be weighed by carat. When the diamond is set on the jewellery or the condition is limited and the balance cannot be directly used, the military method of the diamond measurement can be used to estimate the weight. Different cut style diamonds have different calculation formulas. The weight of the standard round multi-face cut diamond = the average diameter of the waist 2 × full depth × 0.0061, where the length unit is in millimeters, the weight unit is in carats, and 0.0061 is the conversion factor. In the diamond trade, the price of a diamond is generally expressed in terms of “how much per caratâ€. The price of a diamond is related to the weight of the diamond. The greater the weight of the diamond, the more rare it is and the higher the price.
(2) The color of color diamonds can be divided into two categories, one is the color series (described in detail above), the color of these diamonds is generally evaluated separately; the other is the Cape series, which is colorless to In the yellow series, most diamonds fall into this category. For the color grading of such diamonds, various countries or organizations in the world have corresponding evaluation criteria. The luminosity of diamonds under UV and X-rays is quite different, and the fluorescence of diamonds has a great influence on the color grading. This is because the color of strong fluorescent diamonds is different from that of UV-free sunlight. The color of the light conditions. Diamonds with blue-white fluorescence will have improved color levels in the presence of UV-rich light, while yellow fluorescent diamonds will have lower color levels. Therefore, in the color grading of diamonds, the fluorescence test should be carried out first, and the adjustment of the diamond color grade should be considered in the classification, and the diamond grading should be carried out under the standard light source as much as possible.
(3) Clarity refers to the degree of ambiguity in the interior and surface of the diamond. The presence of these mites reduces the light transmitted through the diamond, reduces the brightness and fire of the diamond, and affects the aesthetics of the diamond. Diamonds can be divided into two categories: one for internal features and the other for external features. Their type, quantity, size, location, shading and proportion determine the clarity of the diamond. The evaluation should be based on the factors involved in the five aspects of the inclusion as a whole and should not be determined separately. The American College of Jewelry (GIA) has developed guidelines for the graded evaluation of diamond clarity, and China has also issued guidelines for the classification of diamond clarity.
(4) Cut due to the unique nature of diamonds, the cutting of diamonds is very important to diamonds, directly affecting the brightness and fire of diamonds. The cutting is also more careful, and the weight of diamonds is kept as much as possible. Therefore, the cut of diamonds is to evaluate diamonds. One of the four major standards of quality. The cut evaluation of diamonds mainly refers to the proportion of diamond cutting, polishing and post-treatment, and is mainly for the diamond cutting process of standard round multi-face cutting. Specific evaluation of diamond cutting indicators have ratios and degrees of modification, including ratios of table width, crown angle, pavilion depth, waist-thickness ratio, cusp ratio, and full depth ratio. According to the quality of the ratio, the quality is divided into four levels: good, good, average and poor. Since the discovery of diamonds in India more than 2,000 years ago, more than 30 countries have discovered diamonds, and more than 20 of them have become commercial producers. These countries are South Africa, Australia, Angola, Namibia, Zaire, Russia, Botswana, China, etc. The amount of production and the value of diamond production in each country are changing.
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