We can confirm that the testing organization that issued the certificate has passed these special qualifications through the signs on the certificate. The mark on a general certificate is "CMA".
"CMA" is the English abbreviation of China Metrology Certification. It is a comprehensive certification and evaluation of the testing ability and reliability of testing institutions by the metrological administrative department of the people's government at or above the provincial level according to the provisions of the People's Republic of China (PRC) Metrology Law and the National Metrology Law. This symbol only indicates that the organization is a unit that has passed the measurement certification review and is a necessary qualification for any unit that issues a jewelry appraisal certificate. The inspection report marked "CMA" can be used for product quality evaluation, results and judicial appraisal, and has legal effect.
Step 2: Appearance description (look at the model and observe the sample)
The next step is to confirm whether the purchased jewelry and jade are consistent with the samples described in the certificate, including the photos of the samples, the weight on the label and the weight on the certificate, and whether the appearance and description of the jewelry correspond.
Photos are the direct evidence to distinguish different jewels and jade, and the identification certificate photos are clear and accurate, which will greatly increase the difficulty of forgery. However, in some cases, because the jewelry styles are similar and the photo features are similar, it is difficult to distinguish them. In this case, the accurate weight is another valid data that can be verified. In addition to photos and weight, the appraisal certificate will also provide some distinctive appearance features, such as the sugar color of jade, the size of bracelet and so on.
Step 3: Test the content (the most important content).
This step should be the content of the exam that we are most concerned about, and we should know which content on the certificate is the most important.
Grading certificate of inlaid diamonds: the most important thing to pay attention to is the color grade and clarity grade of diamonds, and some certificates also have the cut ratio of diamonds.
Purity inspection certificate of precious metal ornaments: the most important thing is of course the type and content of precious metals.
Jewelry and jade appraisal certificate: the inspection conclusion is the most important. According to the national standard, natural jewelry and jade are no longer marked with the word "natural", but must be marked with artificial processed or synthetic gems, such as: the conclusion is "ruby", which means that this ruby is pure natural; "Ruby (treatment)" means the specific treatment method, which means that this ruby is a natural gem, but its appearance has been improved by some artificial treatment; "Synthetic ruby" means that ruby is not naturally produced, but is purely synthesized by artificial laboratory.
"Remarks" column: Generally, some relatively special samples will be encountered in the testing process, which will be explained in the remarks. For example, in the appraisal certificate of Hetian jade, once the surface treatment is involved, the specific treatment method will be indicated in the remarks.
Step 4: Official seal or inspection mark
In order to prevent the certificate of appraisal institution from being forged, the appraisal certificate must be stamped with the official seal of the unit, and the red official seal as the inspection mark is often not printed with the certificate, but stamped after inspection.
Now some large authentication machines are carrying out heavy anti-counterfeiting. For example, Xinjiang Rock and Mineral Gem Quality Inspection Station added the function of online inquiry in the new certificate issued in 2007. When inquiring, you need to enter the batch verification code and enterprise verification code, which is convenient for consumers to verify and understand the relevant information of jewelry and jade purchased online.
Step 5: Understand the standards.
The general appraisal certificate will also indicate the appraisal and identification standards of jewelry and jade. The current national standards specifically include:
GB/T 16552 name of jewelry and jade; GB/T 16553 jewelry and jade identification; GB/T 16554 diamond classification; GB/T 18043 nondestructive testing method of precious metal jewelry content: x-ray fluorescence spectrometry; GB 1 1887 Rules and naming methods for the purity of precious metals in jewelry.
If you see one or two of these standards on the certificate, you can know what standards jewelry and jade are tested according to. In addition, the certificate should also have the signatures of more than two appraisers and the date of identification of the certificate. Knowing these five parts, you will find out whether your favorite baby is true or not, and if the certificate doesn't match.
Step 6: Understand the basics.
The following is the noun explanation of the inspection items that are often seen on the jewelry appraisal certificate:
Color color
Color is the feeling produced in the brain by the response of the optic nerve of the fundus to light waves (visible light from 390nm to 780nm). After visible light is selectively absorbed by an object, the color produced by the mixing of its remaining light waves is the color of the object.
optical characteristics
It refers to various phenomena caused by substances acting on the direction and propagation direction of incident light, including homogeneity, heterogeneity, anisotropic body axis, positive and negative light and other characteristics.
Optical isotropic body isotropic material
An isotropic body refers to a substance whose optical properties are the same in all aspects. Equiaxed and amorphous materials are optically isotropic.
Optical anisotropic bulk anisotropic material
Refers to substances with different optical properties in all directions, which is called anisotropic body for short. Except for equiaxed and amorphous materials, they are all optically anisotropic.
Refers to the crystal has two special directions (two optical axes), when light is incident parallel to these two directions, birefringence does not occur. The crystals of orthorhombic system, monoclinic system and triclinic system are all biaxial crystals.
Refractive index
The ratio of the propagation speed of light in air (or vacuum) to that in gem materials is the refractive index, also called refractive index.
The biggest difference between two or three principal refractive indexes in an anisotropic body is birefringence, also called refractive index (or refractive index).
absorption spectrum
Refers to the spectrum produced by selective absorption when continuous spectrum light irradiates jewelry and jade materials. In a narrow sense, it refers to the phenomenon that the spectrum produced by selective absorption in visible light (700-400nm) appears as black bands or black lines.
shine
The ability and characteristics of material surface to reflect light. According to the strength of luster, it can be divided into sub-metallic luster, semi-metallic luster, diamond luster and glass luster. The special luster caused by aggregate or surface features are: greasy luster, waxy luster, pearl luster, silky luster and so on.
Transparency transparency
Refers to the transparency of jewelry and jade materials. Can be divided into: transparent, translucent, translucent, translucent, opaque.
Ultraviolet fluorescence
Refers to the visible light waves produced when ultraviolet rays irradiate jewelry and jade. According to the intensity of light, it is divided into: strong, medium, weak and none.
Flame color dispersion value flame
When white light shines on a transparent faceted gem, the phenomenon that the gemstone shows spectral color flicker due to dispersion is called fire color.
The dispersion value is the physical quantity of the dispersion intensity (that is, the fire color intensity) of the reflective material. Theoretically, it is expressed by the difference of refractive index between red light (B=686.7nm) and violet light (G=430.8nm). The greater the difference, the greater the dispersion intensity (the stronger the fire color).
density
The density of a gem refers to the mass of a substance in a unit volume. The unit is grams per cubic centimeter.
difficulty
Hardness refers to the ability of gem materials to resist external mechanical effects such as scratches, squeezing or grinding. The hardness of gemstones is expressed by Mohs hardness in mineralogy.
Split, fracture, separation
Cleavage refers to the property that a crystal splits into a smooth plane along a certain crystallization direction under the action of external force. Cleavage is divided into extremely complete, complete, medium and incomplete.
Fracture refers to the nature of irregular fracture surface of crystal under external force. Common fracture types are: uneven, serrated, shell-like and so on.
Cleavage is the property that a crystal breaks along a certain crystallization direction (such as the junction of twins) under the action of external force.
Internal characteristics
It refers to the solid, liquid and gas inclusions contained in gem materials, special types of inclusions (such as negative crystals) and phenomena related to the crystal structure of gems. Such as: growth line, ribbon, winding, cleavage, cleavage, etc.
External character
The external characteristics are divided into the external characteristics of crystals and the external characteristics of cut stones.
The external characteristics of crystals refer to special phenomena related to crystal structure, such as transverse crystals, longitudinal crystals, twins, growth pits, erosion and hillock dissolution, in addition to the shape, color, transparency and luster of crystals.
The external features of cut gemstones refer to the phenomena left in the process of cutting and polishing, such as scratches, polishing lines (marks), micro-notches, holes, damage, burn marks, impact marks, whiskers, extra facets, sharp or smooth edges, etc.
Optimization processing enhancement
All methods used to improve the appearance (color, clarity or special optical effects), durability or usability of jewelry and jade except cutting and polishing. It is divided into two categories: optimization and processing.
Optimization enhancement
Traditional, widely accepted and optimized treatment methods show the potential beauty of jewelry and jade.
Treatment treatment
Non-traditional and not yet accepted optimization treatment method.
Common optimization methods
Optimization methods: heat treatment, bleaching, wax dipping, colorless oil dipping and dyeing (chalcedony, agate).
Treatment methods: immersion in colored oil, filling (glass filling, plastic filling or other hard materials such as polymers), immersion in wax (turquoise), dyeing, irradiation, laser drilling, film covering, diffusion and high temperature and high pressure treatment.