In the past 20 years of reform and opening up, China's jewelry industry has made great progress and achievements. Experts predict that the jewelry industry in the 21st century may become a pillar industry supporting the steady development of the national economy. At present, the development of China's jewelry industry is in the stage of transition from extensive to intensive, that is, from the growth of the quantity (production, sales), to the gem identification work to promote scientific and technological progress, update the varieties and improve economic benefits. Can be divided into three aspects:
1 Name the jewel and determine what it is.
2 material classification, clear material properties.
3 gem quality classification.
(1) Name the gemstone. For gem identification, the density and refractive index data of the gemstone are mainly determined, and the name can be determined. For example, the measured gem density is 3.52 (±0.01) g/cm"3, the refractive index is 2.417, and the dispersion is O.O44. Combined with its high thermal conductivity, it can be named diamond (diamond). If you also have data on the chemical composition and crystal structure of gemstone minerals, the name of the gemstone will be more precise. Based on the name of the gemstone mineral, it will be divided according to color or special light (cat's eye, starlight, discoloration and color change). Variants. For example, the variant name of beryl gem minerals by color is green beryl (also known as emerald), blue beryl is called aquamarine, and colorless beryl is called beryl. Special light beryl variant There are beryl cat eyes, star beryl, etc. Corundum gemstone minerals are classified according to color. The corundum with special lightness can be used to draw star ruby, star sapphire, sapphire cat eyes and so on.
(2) Material classification. Material classification and identification is one of the most difficult tasks for gemologists. Before you can name a gemstone, you must first answer the following questions:
1 Is the gem natural or synthetic or artificial?
2 Is the gem dyed and surface coated? Have you been oiled or chemically treated?
3 Is the gem treated by heat treatment or color diffusion?
4 Is the gemstone treated with radiation?
5 Is the surface crack and hole of the gemstone manually filled?
According to the material properties, we divide the materials into two categories: gems and artifacts.
The gems are:
1 Natural gemstone: A substance completely formed by nature, which refers to natural mineral crystals that have not been artificially affected, and is synonymous with "pure" and "natural". Includes a variety of natural materials.
2 Optimize gemstones (manually treated gemstones): The stone is a natural substance. Through various new methods and new methods such as chemical, thermal, optical, high-energy ray radiation, the quality of gemstones is improved to improve the value of gemstones. The boundary between natural gemstones and treated gems is often difficult to draw a line because of the different means of treatment and the strength of the treatment.
The artifacts are:
1 Synthetic gemstone: The product formed by crystallizing it under artificially controlled crystallization conditions by an artificial method, whose physical properties or chemical properties and crystal structure are basically consistent with the corresponding natural gemstones. Such as synthetic diamonds, synthetic rubies, synthetic sapphires, etc.
2 artificial stone: refers to various crystals of artificial growth, its chemical composition, physical properties and crystal structure, no natural control. This artificial stone is a replica of a gemstone, such as artificial cubic alumina (ZrO2), which has a higher hardness (8.5) and a similar optical effect to diamonds, but its chemical composition, physical properties and crystal structure. Unlike natural diamonds, there is no natural control. It can only be called artificial stone, not "synthetic gems."
3 piece stone (also called combination stone): piece stone refers to two or more kinds of crystal or amorphous, by adhesive or other means, unnaturally combined into a product, the components can be divided into Gems, other minerals, chemicals. The combination stone entering the market: emerald mosaic stone, ruby ​​mosaic stone and so on.
4 Imitations: using a variety of materials: chemical, plastic, glass, artificial crystals and other materials, mimicking the effects of natural gemstones, synthetic gemstones, appearance or color, without their chemical, physical and crystal structure. There are both gemstone imitations and synthetic gemstone imitations.
5 Remanufactured products: The artificial materials that are condensed into a whole by processing the gem materials by melting, bonding or fusing.
At present, various man-made products have flocked to the market to identify various man-made products to ensure the acquisition of real gemstones. The task of gem mineralogy workers is quite heavy.
(3) Quality classification of gemstones. The quality of gemstones is graded according to three major categories: diamonds, colored stones and jade. At present, the principles and methods of grading are relatively complete with the quality grading standards of diamonds, and the quality grading standards for colored gems and jade have not yet obtained a universally recognized unified standard like the diamond 4C standard at home or abroad. The quality classification of diamonds is generally adopted in the international 4C classification standard, namely weight, color, clarity and cut. China has formulated the National Standard for Diamond Grading, and in principle adopts the 4C standard. However, it should be noted that for the 4C standard, people's understanding and mastery have different tendencies in different periods, that is, the focus of 4C will be different. At first, people emphasized weight, and the bigger the diamond, the more valuable. Later, it was discovered that not all the quality of the big diamonds was good, so the development to the pursuit of high color grade, and even high clarity, crystal clear, dazzling, more precious and versatile. What is the next focus? People will wait and see! It has now been suggested that the most perfect diamond comes from superb cutting. The status of the cut is likely to rise.
The jewellery industry in various countries is studying the establishment of a quality grading system for colored gemstones and jade. It is proposed that the quality grading standards for colored gems and jade will be gradually established and improved based on the 4C standard of diamond quality grading. This is a current concern.
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