Certificates fall into three categories: 1. The first category is national inspection. Namely NGTC, which belongs to the Jewelry and Jade Jewelry Management Center of the Ministry of Land and Resources. It is the maker of China's jewelry industry standards and the most authoritative testing institution.
2. The second category is provincial inspection. That is, various provincial jewelry and jade appraisal centers. For example, a provincial gem and precious metal testing center and a provincial gem and jade appraisal center, among which Yunnan Jewelry Research Institute is the most authoritative in jade testing ability.
How to identify the authenticity of a certificate 1 Look at the signs: On a genuine jade certificate, the most conspicuous signs are several English abbreviations. Common signs are "CMA", "CAL" or "CNAL". CMA is a sign that the measurement certification of testing institutions is qualified, and the institutions with this sign are legal testing institutions. CNAL is the symbol of the national laboratory. CAL refers to the standards of inspection institutions recognized by AQSIQ. Among them, "CMA" is necessary. If there is no "CMA" on a certificate, it means that the institution that issued this certificate has no appraisal qualification at all, and such a jade appraisal certificate is a false certificate.
2. Look at the number: a valid certificate will have a number on it, which is an important sign to check the authenticity of the certificate. Many false certificates deliberately don't write the number, just to prevent us from finding the authenticity of the certificate after checking the number. A certificate without a serial number is equivalent to a blank sheet of paper.
3. Look at the steel seal: the seal stamped on the jade appraisal certificate must be steel seal, and the handwriting on the steel seal must be clear and legible.
4. Look at the inspector's signature: If a formal quality inspection certificate of jewelry and jade is issued, two people need to sign it, and one of them must have the signature of China people and the national quality inspector of jewelry and jade (registered), and the registration is within the validity period. Only the signature can not be stamped (can be printed), so the inspection certificate will have legal effect.
5. Look at the specific items and * * * features: the appraisal result is the most intuitive, but if you want to know more about the jadeite, you need to look at the specific jadeite items, such as various physical, chemical and optical features. Every piece of jade must have a certificate of conformity, and the same certificate cannot be used just because it is similar or the same batch of materials. Everyone should carefully identify and prevent the appearance of Zhang Guan Dai Li.
Regarding the basic properties of jadeite, we must understand: refractive index: 1.66 (this is unique to jadeite itself and different from other gems);
Density: 3.33 (which is also the feature that distinguishes jadeite from other gems);
Magnification detection: fiber interwoven structure (this is the unique structure of jadeite), or flaky flash structure;
Absorption spectrum: 437nm absorption line (unique absorption spectrum of jadeite);
Color filter inspection: no response (some dyed jadeite will turn red under the color filter);
Luminance: aggregate (jadeite is a kind of micro-mineral aggregate);
Fluorescence: None (some B goods will have fluorescence reaction after injecting glue);
Appearance characteristics: glass luster (some B goods will show waxy luster).
Note: All inspection columns in the inspection certificate must be filled in by computer, not by hand.