Diamond evaluation criteria?
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Diamond’s 4C classification
For a finished diamond, the international 4C standard is used to classify. These 4C include: color, cactid, clarity, and cut (CAT). The 4C standard has a direct impact on the quality of the finished diamond.
It color: In color evaluation, we mainly classify the colorlessness of the Kaipu series -light yellow series diamonds. The hierarchical standards currently used are mainly participating in politics for CIBJO (International Jewelry Jewelry Federation) and CTIA (American Gem Institute). There is a little difference between them: the color stone in the CTBJO laboratory is called “standard -bonus stone”, each of which is the lower limit of each color level; It represents the upper limit of each color level from e -day.
In the case of a set of standard ratio stones, we have a suitable light source (comparison lamp), the appropriate classification environment (using standard optical originals in dark rooms) and abundant With experience, we can classify the color of the diamond.
Weight: General Carati internationally indicates the weight of the gem and the weight of the diamond on the price of diamonds. If all other factors of the finished diamond are the same, the higher the price of diamonds, the higher the price. In the diamond industry, the price of diamonds is represented by how much per carat. For diamonds that weigh within a certain range, each carat can listen to the quotation at the same price. Diamonds exceeding this range are different per carat. For unsolved diamonds, the weight is generally used in carats or balance; for the inlaid diamonds, the weight is generally measured by measured its diameter and the weight is calculated by the standard.
The preparations before grading:
a. Clean diamond: Use alcohol and wipe the diamonds that are not easy to get rid of hair. Do not use the diamonds after cleaning, and you should use the tweezers to clamp it.
b. Use 10 times large mirror or 10 times stereo binocular microscope to observe.
c. Lighting conditions: Usually the color comparison lamp or eye light when color grading is selected.
(2) Division of Diamond Clear level: Diamond’s clarity is divided into LC (mirror flawless); VVS level (extremely micro flaw), it separates two sub -level VVS , And VVS2 (depending on the size of the flaw); VS (micro -flawr level) and two sub -grade VS, and VS2; SI (small flaws) and two sub -level SIs, and SI2; P -level (unclear clearly (unclear clearly ) And three sub -grade P1, P2 and P3 levels (visible to the naked eye, divided by position and different sizes).
(3) Factors affecting diamond clarity:
a. c. Position of the parcel;
d. The brightness of the package;
e. In grading, we must not only observe the internal characteristics of diamonds, but also pay attention to certain natural and artificial external characteristics. For example, the original crystal surface, growth pattern, grinding line and damage. These also affect the clarity of diamonds.
The cutting classification: In the cutting level, we mainly classify the rigorous proportion of the diamonds of the round multi -faceted type. Because of the reason, it is only estimated.
The standards for cutting diamonds are slightly different from different countries, which are mainly related to people’s aesthetic views. In our country, the cutting ratio of diamonds is: 56? 66%is moderate, and the pavilion is 41? 45%is moderate.
It three cases in the cutting of diamonds are diamonds that are obviously cut. They are:
a. “Fish Eye” Diamond Caused the leak from the pavilion, and cannot produce
b. “Block” diamond: Because the diamond’s pavilion is too deep, the light cannot reflect to the table, and the diamond looks dark and bright.
c. “Thin” diamonds: There are two reasons, one is the correct ratio of the countertop, but the crown angle is too small; This diamond looks very thin, it is not easy to inlay, and the fire is poor.
In observing work cutting, we must observe the following points:
(1) Terminal width, (2) pavilion depth ratio, (3) crown corner and pavilion corner, (4) The original degree of waist edge, (5) polishing, (6) extra face and so on. A cut diamond, the fire color is very strong, and the light is shining a little.
In here, the grading of natural diamonds has been completed. But we must not only accurately grades natural diamonds, but also identify imitation products and optimized processing products mixed in natural diamonds.
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