Diamond Four C's
The expert value is the procedure of the value of the diamond by comparison it with other brilliants according to several criteria. The totality of criteria forms the system of expert value. . Usually expert value is put into effect according to four parameters (Four CS):
-
The first “C” - Carat Weight. On this stage the exact determination of weight take place by weighing on balances or by calculation according formulas if the brilliant is fixed in the ring. The weight of the brilliant is measured in carats (1 ct = 0,2 grammes).
-
The second “C” - Color. Absolutely colorless diamonds are met rarely. Practically all diamonds has tinges of different colors and intensity. The task of the expert is to determine the exact intensity and color of the brilliant in standard lighting with the use of color's standards. Then the value is appropriated according to the color.
-
The third “C” - Clarity. On this stage all intern defects of the stone are revealed. The value approached according to the clarity.
-
The fourth “C” - Cut (The Quality of Cutting). On this stage the characteristic of the diamond shape, the quality of cutting and the final cutting are given.
On the basis of these parameters it's possible to decide how this brilliant stands out against a background of other brilliants. According to this it can be more expensive or cheaper.
Different systems of expert's value of the diamonds are used in the world practice. The most spread is the system of value worked out by Hematological Institute of America. All experts are acquainted with this system. Other famous systems of value are the system of High Diamond Council of Belgium, system of CIBJO, Scandinavian nomenclature, sometimes old terms are used for describing colors. (Russian system of value is used in Russia.)
The value of the weight of the brilliants
First the comparison with the weight of corns of some cereals was put in the basis of the definition of the weight in different parts of the planet. In Europe the smallest unit of weight was barely corn. Because of in ancient times the diamonds came to Europe from Asia then the plant the seeds of which were used as the measure of weight of gemstones is necessary to search in Asia. Probably the ancient unit of the weight of gemstones is connected with the seeds of acacia Ceratonia siliqua which is spread in the countries of the Mediaterranean. The middle weight of the seed of acacia is approximately equal to carat. Besides the is word “carat” is formed from the Greek name of plant which sound similar to carat.
Some sources suggest that the origin of the word “carat” goes from the word kuara – the name of the coral tree Erythrina corallodendron, which middle seed weight is approximately equal to the weight of acacia seed.
The mass of the brilliant is determined by weighing on the carat's balance. Up to the end of XIX century different standards of carat in grammes are used. The weight of carat varied from 0,1885 to 0,2135 grammes. But in 1907 it was suggested to stand the weight on the basis of determined standard – the metric carat equal to 200 mg. The metric carat was officially taken in the following countries:
1908 – Spain
1909 – Japan, Swiss
1910 – Bulgaria, Denmark, Italy, Norway
1911 – Holland, Portugal, Sweden
1912 – France
1913 - Belgium, USA
1914 – Great Britain
1922 – Austria, Ireland, Mexico, USSR, Thailand
1923 – South Africa
The weighing is carried out with the exactness up to the third sign after comer. The mass is written up to the second sign and the third sign is thrown if it's not equal to 9. It's possible to weigh the batch of diamonds. Small brilliants are often dissipate through the number of sieves on the size groups and in this case are sold according to the size. During the uniting and splitting of the diamonds the change of mass can take place.
If the diamond is fixed in the jewelery good then his mas can be exactly determined only after refixing. So it is recommended to weigh the gemstones before fixing. The mass of the fixed diamond can be calculated with the help of the formulas. For example, the formula of calculating of the weight of the diamond with standard round cutting is:
{M=D2 x H x 0,0061}
Where: M – Mass in carats (ct.); D – Diameter (mm); H -High (mm);
In the case of thick girdle the coefficient is increased from 0,0061 to 0,0067 according to the thickness.
The mistake of calculating according to formulas is over 10%for rightly cutting diamonds and can be higher for gemstones with distorted geometry, with old and nontraditional cuttings.
In determination of the weight of brilliants by formulas it's necessary to mention the fact that weight is determined by calculating method.
The value of the diamond color
Diamond's color is one of the most characteristic features. At the same time color is the most important feature of the diamond because of color effect on the human eye. It's well-known that visible white color is the mixture of rainbow colors from red to orange, yellow, yellow-green, green, blue-green and to blue. Separate components of visible light are absorbed in the brilliant – it is caused by the presence of different micro elements or by particularity in the diamond structure. Not absorbed parts of the light form the visible color of the diamond. And if the components of light are absorbed evenly then the brilliant seems colorless.
The important feature of the diamond's color is pale intensity of the color. Most of diamonds which are used in jewelery goods has pale color tinges and tones. Non trained human eye can't distinguish neighboring colors in scale. And colored diamonds usually impress everyone.
The diamonds which has no any color, simply colorless are of particular value. The most of jewel diamonds has the tinges of different intensity. Conditionally all diamonds can be divided into two groups: the larger one with yellow color or with colors tinge of different intensity (series “kape”) and the group of brilliants with fantasy colors. There are the set of standard for determination of the diamond's color from series “kape”, for example, the scale of standards of Hematological Institute of America(GIA) (from D to Z).
The color scale is divided into groups. It begins from colorless diamonds the smooth transfers with increasing of intensity of yellow color goes and finishes with the last group which has exactly yellow color. According to GIA system every color is determined by the letter of Latin alphabet from D-colorless to Z-yellow. It's possible to value diamonds with brown color according to this value. In this case only the intensity of color is concerned. Yellow and brown diamonds lower then Z is concerned fantasy ones.
The procedure of color value requires the presence of standard white light, standard white background, the set of color's standards and skills of the expert. In the case of diamonds with fantasy colors it's necessary to confirm the origin of the color by gemological way.
The white paper formed in special way, standard brilliants and the source of the day light of the north sky (north light) are necessary for the most simple way of color value of the diamond. Brilliants are put on the paper near the central flexion, there shouldn't be any shadows. The light should be absent-minded in order to take away the colors of refraction and the shining of the diamonds which can prevent the value. In such conditions it's possible to distinguish light color tinges of every diamond with the help of short concentrated view. During the process of color value of the diamond it is necessary to change the position of the paper relatively to the source of light. Also it's necessary to breath on the diamond in order to value the color of the diamond.
Some diamonds can fluorescent with pale blue, even pale green, yellow or red light. The fluorescence of the diamond is caused by the intensive radiation with ultraviolet rays.
The value of diamond clarity
The diamond was formed in the depth of Earth during several time phases. During all these periods the temperature, pressure and surrounding were different. As a result the features of natural origin appeared. These features are often called internal defects of the brilliant. Because of the diamond is the creature not only of nature but of a man too then it can has the external defects which revealed or formed during the process of diamond producing.
The clarity can be understood as the free of the diamond from inclusions and internal defects or as the comparative site of the diamond in the scale “brilliant without defects – brilliant with defects”. The characteristics of clarity are classified as inclusions (internal defects) or surfaced defects. Defect is considered to be internal even in the case of its going out on the surface if it's impossible to take it away during polyshing without loss of the weight. In other cases brilliants are considered to be the most valuable.
The value of clarity is carried out under the increase in 10 times or with common eye. Defects seen in the larger increase and which are not seen in 10-times increase are not taken into account. While value the influence of the defects on the clarity size, nature, quantity, location, bright/color of internal features and sometimes external features are concerned.
The rareness of the diamond, its attractiveness and solidity are depends on the clarity of the diamond.
The degree of revealing and visibility of external and internal defects are described by following terms:
Very hard visible defects are very difficult to find out during long and attentive studying of the brilliant from all sides with the use of 10-times increase.
Hardly seen defects are difficult to find out during long and attentive studying of the brilliant from all sides with the use of 10-times increase.
Visible defects can be found out in attentive view of the diamond from all sides with the use of 10-times increase.
Slightly visible defects can be easily found out in attentive view of the diamond from all sides with the use of 10-times increase and hardly seen with common eye.
Well visible defects can be found out in 10-times increase and also can be noticed by common eye.
Very well visible defects have the view of volume objects, they are seen very well.
For symbol of internal and external defects the following terms are used.:
Point is the smallest defect without volume.
Inclusion – defect which has the view of the volume object of different size, shape and color. It is situated inside the diamond.
Stripe – defect of the brilliant looked like as the thin line.
Crack – the split in the diamond. It can be internal or go on the surface.
Cloud – the misty site formed by accumulation of the smallest defects.
The value of diamond cutting
The influence of the quality of cutting on the price is high because of diamonds with different quality of cutting look like in different ways. But how different proportions or deviations in symmetry or defects of polyshing influence on the diamond price is not a simple question. The diamond can have such proportions which can be enjoyed by one buyer and can push away another. So we can say that the quality of cutting is the speculative parameter which allows professionals to buy cheaper and to sell at higher price.
Here is the information according to every cut shape of the diamond.
Round |
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|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
59.5 - 61.9 |
59.1 - 62.3 |
58.5 - 63 |
57.5 - 63.5 |
57 - 64 |
56 - 67 |
<56 >67 |
|
Table % |
55 - 57 |
53 - 58 |
52 - 60 |
51.5 - 63 |
51 - 65 |
50 - 70 |
<50 >70 |
|
Symmetry |
VG - EX |
G - EX |
G - EX |
G-EX |
All |
All |
All |
|
Culet |
None |
None - Med |
None - Sl. Large |
None - Large |
None - Large |
None - Very Large |
None - Extr. Large |
|
Girdle |
Thin, Med, Sl Thk |
Thin, Med, Sl Thk, Thk |
Thin, Med, Sl Thk, Thk |
Very Thn - Thick |
Very Thn - Very Thick |
Ext Thn - Ext Thick |
Ext Thn - Ext Thick |
|
Polish |
VG - EX |
G - EX |
G - EX |
All |
All |
All |
All |
|
Clarity |
SI1 - FL |
SI1 - FL |
All |
All |
All |
All |
All |
|
Princess
|
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|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
65 - 70 |
63 - 70 |
62 - 73 |
62 - 75 |
56 - 82 |
55 - 86 |
<55 >86 |
|
Table % |
65 - 72 |
65 - 72 |
62 - 74 |
57 - 78 |
55 - 85 |
57 - 89 |
<57 >89 |
|
Ratio L:W |
1:1 - 1.05:1 |
1:1 - 1.10:1 |
1:1 - 1.75:1 |
1:1 - 1.75:1 |
1:1 - 2:1 |
1:1 - 2:1 |
1:1 - 2:1 |
|
Radiant
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
63 - 70 |
63 - 70 |
63 - 72 |
62 - 74 |
56 - 78 |
55 - 83 |
<55 >83 |
|
Table % |
68 - 72 |
68 - 72 |
67 - 74 |
65 - 78 |
63 - 80 |
53 - 83 |
<53 >83 |
|
Ratio L:W |
1:1 - 1.05:1 |
1:1 - 1.15:1 |
1:1 - 1.75:1 |
1:1 - 1.75:1 |
1:1 - 2:1 |
1:1 - 2:1 |
1:1 - 2:1 |
|
Emerald
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
61 - 67.5 |
61 - 67.5 |
61 - 69 |
60 - 70 |
58 - 75.5 |
54.5 - 81 |
<54.5 >81 |
|
Table % |
62 - 69 |
62 - 69 |
62 - 71 |
61 - 72 |
56 - 75 |
55 - 82 |
<55 >82 |
|
Ratio L:W |
1.3:1 - 1.4:1 |
1.2:1 - 1.75:1 |
1.05:1 - 2:1 |
1.05:1 - 2:1 |
1.05:1 - 2:1 |
1.05:1 - 2:1 |
1.05:1 - 2:1 |
|
Oval
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
59 - 62 |
59 - 62 |
59 - 63 |
57.5 - 65.5 |
55 - 69 |
46 - 76 |
<46 >76 |
|
Table % |
57 - 60 |
57 - 60 |
54 - 61.5 |
52 - 64 |
51 - 66 |
50 - 71 |
<50 >71 |
|
Ratio L:W |
1.4:1 - 1.6:1 |
1.35:1 - 1.65:1 |
1.3:1 - 1.7:1 |
1.1:1 -1.90:1 |
1.1:1 -1.90:1 |
1.1:1 -1.90:1 |
1.1:1 -1.90:1 |
|
Pear
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
59 - 63 |
59 - 63 |
59 - 64 |
58 - 65 |
54 - 69 |
51 - 73 |
<51 >73 |
|
Table % |
57 - 60 |
57 - 60 |
54 - 62 |
53 - 64 |
51 - 66 |
48 - 70 |
<48 >70 |
|
Ratio L:W |
1.6:1 - 1.7:1 |
1.5:1 - 1.75:1 |
1.25:1 - 1.85:1 |
1.2:1 - 1.9:1 |
1.1:1 - 2.0:1 |
1.1:1 - 2.0:1 |
1.1:1 - 2.0:1 |
|
Marquise
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
59 - 63 |
59 - 63 |
58 - 64 |
57.5 - 65 |
54.5 - 69 |
50.5 - 75 |
<50.5 >75 |
|
Table % |
57 - 60 |
57 - 60 |
55 - 62 |
53 - 64 |
51 - 66 |
50 - 70 |
<50 >70 |
|
Ratio L:W |
1.9:1 - 2.1:1 |
1.75:1 - 2.25:1 |
1.70:1 - 2.3:1 |
1.60:1 - 2.4:1 |
1.50:1 - 2.5:1 |
1.50:1 - 2.5:1 |
1.50:1 - 2.5:1 |
|
Heart
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
57 - 59 |
57 - 59 |
56 - 60 |
54 - 60 |
51 - 62 |
46 - 67 |
<46 >67 |
|
Table % |
57 - 60 |
57 - 60 |
54 - 62 |
53 - 64 |
51 - 66 |
48 - 70 |
<48 >70 |
|
Ratio L:W |
0.98:1 - 1.02:1 |
0.90:1 - 1.10:1 |
0.85:1 - 1.15:1 |
0.82:1 - 1.18:1 |
0.80:1 - 1.20:1 |
0.80:1 - 1.20:1 |
0.80:1 - 1.20:1 |
|
Cushion
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
59 - 62 |
59 - 62 |
58 - 64 |
57 - 69 |
55 - 73 |
50 - 80 |
<50 >80 |
|
Table % |
57 - 60 |
57 - 60 |
54 - 62 |
52 - 70 |
51 - 75 |
50 - 80 |
<50 >80 |
|
Ratio L:W |
1:1 - 1.05:1 |
1:1 - 1.10:1 |
1:1 - 1.12:1 |
1:1 - 1.15:1 |
1:1 - 1.20:1 |
1:1 - 1.20:1 |
1:1 - 1.20:1 |
|
Trilliant
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
40 - 42 |
40 - 42 |
38 - 44 |
37 - 45 |
35 - 48 |
30 - 54 |
<30 >54 |
|
Table % |
58 - 60 |
57 - 60 |
54 - 62 |
52 - 65 |
51 - 67 |
48 - 72 |
<48 >72 |
|
Ratio L:W |
0.98:1 - 1.02:1 |
0.95:1 - 1.05:1 |
0.92:1 - 1.08:1 |
0.90:1 - 1.10:1 |
0.88:1 - 1.12:1 |
0.88:1 - 1.12:1 |
0.88:1 - 1.12:1 |
|
Asscher
|
|||||||
|
|
Premium Ideal |
Ideal |
Excellent |
Very Good |
Good |
Fair |
Poor |
|
Total Depth % |
59 - 67 |
59 - 67 |
59 - 69 |
57 - 72 |
55 - 75 |
50 - 78 |
<50 >78 |
|
Table % |
57 - 60 |
57 - 60 |
53 - 62 |
52 - 72 |
51 - 75 |
50 - 78 |
<50 >78 |
|
Ratio L:W |
1:1 - 1.02:1 |
1:1 - 1.05:1 |
1:1 - 1.05:1 |
1:1 - 1.08:1 |
1:1 - 1.08:1 |
1:1 - 1.08:1 |
1:1 - 1.08:1 |