The evaluation system developed by the GIA, takes into account four main parameters of a diamond:
- Carat weight
- Cut grade
All of these, and even some additional parameters must be indicated in the passport (certificate) diamonds, the GIA issued.
SYSTEM EXPERT EVALUATION
In world practice, use different grading systems. The most common is the system of assessment developed by the Gemological Institute of America (GIA), and are familiar with this system, experts all over the world. Other known evaluation systems are the system of Higher Diamond Council in Belgium (IDC and HRD), CIBJO system Scandinavian nomenclature (Scan D.N.), are sometimes used old terms, especially to describe the color.
1. ASSESSMENT mass (weight) of diamonds
Weight loose diamonds is determined by weighing on the carat weights. Weighing is accurate to at least three decimal places, the weight is recorded to the second digit, the third digit is discarded if it is not equal to 9. allowed simultaneous batch weighing diamonds. Small diamonds are often scattered through a set of screens into size groups, in which case the sizes are sold. By combining and splitting batches of diamonds may be some change in mass, referred to in the documents.
2. ASSESSMENT OF COLOR DIAMOND
A particular value are the diamonds that have no color, completely colorless. Most gem diamonds are shades of varying intensity. It is conditionally possible to divide all the diamonds in the two groups with a more numerous yellow or tint of varying intensity (a series of "cape") and of fancy colors diamonds group. To accurately determine the color of diamonds series "cape" There is a set of color standards, for example, the most well-known standards of GIA scale (from D to Z).
The color scale is divided into groups, it begins with a completely colorless diamonds, followed by a smooth transition with an increase in yellow color saturation and ends the last group, which has a clear yellow color. According to GIA system, usually denoted by the color of each letter of the alphabet from D - colorless to Z - yellow. On the same scale, you can evaluate the color brown in a number of stones, taking into consideration not hue and color saturation of only stone. Yellow and brown rocks, with characteristic colors below the Z, are considered fancy.
Estimation of color by GIA system
|Color designation||Color equivalent||Determination of the color category of medium-trained eye|
|D||Bluish-white||When viewed through the area, these stones appear colorless|
|F||Slightly bluish, leading-transparent, white|
|I||White color with a subtle shade||When viewed through the area
Diamonds seem to be at least 0.2 ct colorless
Diamonds are more than 0.2 ct are barely noticeable yellowish tint
|J||White with slight color tint|
|K||Pale yellowish tint|
|M||Yellow shade||When viewed through the area increased yellow hue
Diamonds seem to be painted
Assessment of purity of diamonds GIA system
|Designation||Purity group||Feature cleanliness groups|
|IF||Internally flawless||Clean under a microscope at 10x magnification unnoticeable inner imperfections detected only minor surface imperfections, which can easily be eliminated by re-polishing.|
|Very, very small inclusions||Very, very small inclusions under 10x magnification the smallest point in the class vvs1 rocks seen through the site is extremely difficult, they can only be detected when viewed through a stone pavilion. this class also includes diamonds with very small and shallow inclusions that are eliminated by re-polishing. in class vvs2 tiny inclusions with a hard stones can be detected when viewed through a stone platform.|
|Very small inclusions||Very small, small, switching at 10x magnification slight inclusions in the form of very small feathers and clouds are found in hard rocks and class vs1 somewhat easier to grade diamonds vs2.|
|Small inclusions||Small inclusions visible under 10x magnification notable inclusion in Class si1 stones are found quickly and easily in a class si2 stones; sometimes small inclusions in the rock class si2 visible to the naked eye.|
|Imperfect||Notable inclusions in the rocks of these classes obvious inclusions are visible under 10x magnification and even with the naked eye through the area. these inclusions affect the durability of stone or so numerous that seriously affect the transparency and brilliance of a diamond.|
3. ASSESSMENT CUT DIAMONDS
Impact of the cut quality at high cost, because the diamonds with different quality cut look completely different. However, the effect on the value of certain proportions, or deviations in symmetry, or polishing defects, the question is always difficult. Therefore, the price lists (price lists) are no tables that clearly pointed to the discount or premium for quality of cut. Stone may have such a proportion that will please one customer and repel the other. Therefore we can say that the quality of the cut is speculative option that allows professionals to market to buy cheaper and sell dearer.
|The proportions and finishing||Proportions class|
|Excellent||Very good and good||Fair||Poor|
|The size of the site||53-60%||61-64%||65-70%||70%|
|Rundist||Medium - slightly thick
(medium - slightly)
Thin - thick
Very thin - very thick
|Extremely thin - extremely thick|
|The depth of the pavilion||43%||42-44%||41-46%||41-46%|
|Caletta||none - small||Medium||Large||Very large|
|Polish||very good - excellent||Good||Fair||Poor|