Step one: logo (the certificate also depends on the logo)
We can use the logo on the certificate to confirm that the testing agency that issued the certificate is approved for those special qualification certifications and general certificates The logo that will appear on it is: "CMA".
“CMA” is the English abbreviation of China Metrology Accreditation. It is a comprehensive certification and evaluation of the testing capabilities and reliability of testing institutions conducted by the measurement administrative departments of the people's governments at or above the provincial level in accordance with the provisions of the People's Republic of China and the National Metrology Law. This mark only means that the organization is a unit that has passed the measurement certification review, and is a qualification that any unit that issues a jewelry appraisal certificate must possess. Inspection reports marked with "CMA" can be used for product quality evaluation, results and judicial appraisal, and have legal effect.
Step 2: Appearance description (check the model and sample)
The next step is to confirm whether the purchased jewelry and jade are consistent with the sample described in the certificate, including: photos of the sample, Whether the weight on the label corresponds to the weight on the certificate, the appearance and description of the jewelry.
Photos are direct evidence to distinguish different jewelry and jade. The photos of the identification certificate are clear and accurate, which will greatly increase the difficulty of forgery. However, in some cases, it is difficult to distinguish due to the same jewelry styles and similar photo features. 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 candy color of the jade, the hand size of the bracelet, etc.
Step 3: Testing content (the most important content)
This step should be the testing content we are most concerned about, and we must know which content on the certificate is the most important.
Inlaid diamond grading certificate: The most important thing to pay attention to is the color grade and clarity grade of the diamond. Some certificates also have diamond cut proportions.
Precious metal jewelry purity inspection certificate: 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 national standards, natural jewelry and jade are no longer marked with the word "natural", but artificially processed or synthetic gemstones must be clearly marked. For example: the conclusion is "ruby", indicating that the ruby ??is purely natural; "ruby" (Treatment)" indicates the specific treatment method, indicating that the ruby ??is a natural gem, but has been artificially processed in some way to improve its appearance; "synthetic ruby" indicates that the ruby ??is not naturally produced, but pure An artificial laboratory compound.
"Remarks" column: Generally, if some samples with relatively special conditions are encountered during the testing process, they will be explained and noted in the remarks. For example, in the appraisal certificate of Hetian jade, once it involves surface treatment, the specific treatment method will be noted in the remarks.
Step 4: Official seal or inspection mark
In order to prevent the appraisal agency certificate from being counterfeited, the appraisal certificate must be stamped with the official seal of the unit. The red official seal, as the inspection mark, is often not integrated with the certificate. What is printed is the seal affixed after inspection.
Nowadays, some large identification machines are heavily guarded against counterfeiting. For example, the new version of the certificate launched by the Xinjiang Rock Mine Gem and Jade Quality Inspection Station in 2007 also has a new online query function. When making inquiries, you need to enter the batch verification code and enterprise verification code, so that consumers can verify in a convenient way and inquire online about the relevant information of the jewelry and jade they purchased.
Step 5: Understand the standards
General identification certificates will also indicate the standards for jewelry and jade identification. The current national standards are:
GB/ T 16552 Name of jewelry and jade; GB/T 16553 Identification of jewelry and jade; GB/T 16554 Diamond grading; GB/T 18043 Non-destructive testing method for the content of precious metal jewelry X-ray fluorescence spectrometry; GB 11887 Regulations 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 the jewelry and jade were tested according to. In addition, the certificate should also have the signatures of more than two appraisers and the appraisal date of the certificate. After understanding these five parts, it will be clear whether your favorite baby is real or fake, and whether the certificate matches.
Step 6: Understand the basic knowledge
The following are noun explanations of inspection items commonly seen on jewelry appraisal certificates:
Color
Color is the feeling produced in the brain by the optic nerve in the fundus of the eye sensing light waves (visible light 390nm to 780nm). After visible light is selectively absorbed by an object, the color produced by the mixing of the remaining light waves is the color of the object.
Optical character
Refers to the various phenomena caused by the material's effect on the direction and propagation direction of incident light, including the homogeneity and heterogeneity of the material. , the axiality and positive and negative optical properties of heterogeneous bodies.
Optical homogeneous body isotropic material
Refers to a substance whose optical properties are the same in all aspects, referred to as homogeneous material. Equiaxed crystal system and amorphous materials are optically homogeneous bodies.
Optical anisotropic material anisotropic material
Refers to substances whose optical properties are different in various directions, referred to as anisotropic material. Except for equiaxed crystal system and amorphous materials, they are all optically heterogeneous bodies.
Refers to a crystal that has two special directions (two optical axes) and does not undergo birefringence when light is incident parallel to these two directions. Orthrhombic, monoclinic, and triclinic crystals are biaxial crystals.
Refractive index, birefringence refractive index, birefringence
The ratio of the propagation speed of light in air (or vacuum) to that in gem material is the refractive index, also called the refractive index.
The maximum difference between two or three principal refractive indexes in a heterogeneous body is the birefringence, also known as the refractive index (or refractive index).
Absorption spectrum
Absorption spectrum refers to the spectrum produced by selective absorption when a continuous spectrum of light irradiates jewelry and jade materials. In a narrow sense, it refers to the spectrum produced due to selective absorption in the visible light (700-400nm) range, which appears as a black band or black line on the spectrum.
Gloss luster
The ability and characteristics of a material surface to reflect light. According to the intensity of luster, it is divided into: metallic luster, semi-metallic luster, adamantine and vitreous luster; special luster caused by aggregates or surface features include: grease Luster (greasy luster), waxy luster (waxy luster), pearly luster (pearly luster), silky luster (silky luster), etc.
Transparency
Refers to the degree of light transmission of jewelry and jade materials. It can be divided into: transparent, semitransparent, translucent, semitranslucent and opaque.
Ultraviolet fluorescence
refers to the visible light waves produced when jewelry and jade are irradiated with ultraviolet light. According to the intensity of luminescence, it is divided into: strong, medium, weak, and none.
Fire, dispersion value
When white light irradiates a transparent faceted gem, the gem will flash with spectral colors due to dispersion, which is called fire.
The dispersion value is the physical quantity of the dispersion intensity of the reflective material (that is, the intensity of the fire). Theoretically, it is represented by the difference in the refractive index of the material relative to red light (B=686.7nm) and violet light (G=430.8nm). The greater the difference, the greater the dispersion intensity (the stronger the fire). .
Density density
The density of gemstones refers to the mass of material per unit volume. The unit is g/cm3.
Hardness
Hardness refers to the ability of a gem material to resist mechanical effects such as external scratching, pressing or grinding. Gemstone hardness is expressed on the Mohs scale of mineralogy.
cleavage, fracture, parting
Cleavage refers to the property that a crystal splits along a certain crystallographic direction to form a smooth plane under the action of external force. Cleavage is divided into extremely complete, complete, moderate and incomplete.
Fracture refers to the property of crystals producing irregular fracture surfaces under the action of external forces. Common fracture types include: uneven, jagged, shell-shaped, etc.
Cracking is the property of crystals cracking along a certain crystallographic direction (such as the junction of twin crystals) under the action of external forces.
Internal character
Refers to the solid phase, liquid phase and gas phase inclusions contained in gem materials, special types of inclusions (such as negative crystals) and gemstones. phenomena related to the crystal structure. Such as: growth lines, ribbons, twin grains, cleavage, cracking, etc.
External characteristics external character
External characteristics are divided into external characteristics of crystals and external characteristics of cut gemstones.
The external characteristics of crystals refer to special phenomena related to the crystal structure in addition to crystal shape, color, transparency and gloss, such as horizontal lines, vertical lines, twin grains, growth pits and etching images. , melting hills and other phenomena.
The external characteristics of cut gems refer to the phenomena left during the cutting and polishing process, such as: scratches, polishing lines (marks), micro-nicks, cavities, damage, burn marks, impact marks, Bearded girdle, extra facets, sharp or rounded edges, etc.
Enhancement
All methods other than cutting and polishing used to improve the appearance (color, clarity or special optical effects), durability or usability of gemstones for jewelry. Divided into two categories: optimization and processing.
Optimization enhancing
A traditional and widely accepted optimization treatment method that brings out the potential beauty of jewelry and jade.
Treating
Non-traditional optimization methods that are not yet accepted.
Common optimization treatment methods
Optimization methods: heat treatment, bleaching, wax dipping, colorless oil dipping, dyeing (chalcedony, agate).
Treatment methods: Dip in colored oil, filling (glass filling, plastic filling or other polymer and other hard material filling), wax dipping (turquoise), dyeing, irradiation, laser drilling, coating , diffusion, high temperature and high pressure treatment.