1.CMA logo, namely English China Metrology Certification, which means "China Compulsory Quality Certification". It means that the agency has passed the national evaluation, and any unit that issues a jewelry appraisal certificate must have this mark. The data provided by such quality inspection institutions can be used as notarized data and have legal effect.
2.CNAL logo, namely China National Accreditation Committee for Laboratories. It means that the jewelry and jade testing laboratory has been recognized by the national laboratory accreditation criteria in terms of technical strength and equipment capacity. This standard is the same as the international standard ISO/IEC 17025 "General requirements for testing and calibration laboratories".
3.CAL mark refers to China certified laboratory. According to "People's Republic of China (PRC) Product Quality Law", product quality inspection institutions must pass the examination by the quality supervision and management departments at or above the provincial level or their authorized departments before undertaking the task of product quality inspection. The inspection report printed with the inspection mark has legal effect and can be used as the basis for judging the quality of products. In fact, this qualification is the most important and the most difficult to obtain. Because the first two recognize the hardware conditions, it is not difficult to obtain, but the CAL qualification takes into account the comprehensive level and credibility of the organization. The symbol indicates that the inspection organization has certain strength and inspection ability, and is authorized by the state to undertake supervision and spot check inspection tasks. The appraisal certificate with this logo has authority and legal effect.
Generally, diamond inlay certificates are issued in China, which is different from the standard of rough diamond certificates abroad. According to the international practice, the diamond clarity of mosaic certificate is divided into five grades: LC, VVS, VS, SI and P, while the diamond clarity over 47 is still 10.
The color of diamond is an important index to evaluate diamond. It should be unscientific and inaccurate to divide them into extremely white, white, light yellow and yellow in the old national standard issued by 1996. It has been cancelled now, and it is in line with international standards. In the ISO international standard, D-F is colorless and G-J is near GOLORLESS, which should be colorless and near colorless in translation. According to the new national standard implemented on June 1 65438+1October12003, the colors of diamonds are divided into seven grades, namely, D-E, F-G, H, I-J, K-L, M-N and < N. The standards for diamonds are as follows. There are at least 12 kinds of internal defects (features) and as many as 8 kinds of external defects. Despite the help of colorimetric stones and other means, there will still be errors in people's visual inspection, so small differences are wholeheartedly. The conclusions drawn by different appraisal institutions are allowed to have a level of error.
For the color of platinum bracket, the latest national standard stipulates that the total content of platinum and palladium in platinum alloy jewelry should not be less than 950‰, usually 950‰ or 990 ‰; 18K gold consists of 75% gold and 25% copper, silver and nickel (the ratio of the three can be adjusted).
For the most difficult identification in cutting work, the new national standard has been further clarified than in the past. First of all, the identification of cutting work will not be done if the score is less than 20 points. Secondly, the ratio of platform width to pavilion depth is defined as the ratio description index of certificate. The so-called "eight arrows and eight hearts" or even "nine hearts and one flower" respected by some consumers and businesses cannot be used as a standard to measure the quality of diamond cutting.
Diamond cutting is a comprehensive index, and it is difficult to make a detailed and complete evaluation in places with limited certificates. We learned from the communication that foreign countries are also studying new evaluation methods of cutting, such as replacing the decorative degree of cutting with symmetry. For cut diamonds, that is, diamonds that have reached the ratio index, symmetry can simply and intuitively reflect the cut quality of diamonds. However, it is more difficult to use symmetry to represent poorly cut diamonds. The latest comprehensive evaluation method of optical symmetry diamond cutting is still in the initial stage of exploration, and we will closely follow it.