Classification of the Diamond according to the 4 criteria

The Diamond: The Rule of 4C The diamond is classified according to the rule of 4C: Carat, Clarity, Color, Cut (International Standards).

The color (from D for the best color to M-Z)

Purity (from IF for the best purity to P3 for the least desirable)
Size (from Excellent to Bad), finish, polish and symmetry
The weight: the carat is the unit of measurement of a diamond (1 carat = 0.20 gram) whose currency is in 100 hundredths.

Diamond Carat

The unit of measurement is the metric carat (c. M.), Which is one-fifth of a gram, or 2 decigrams.

So 1 carat = 0.20 gram.

The carat is divided into 100 points (hundredths of a c. M.), In other words, a diamond of 0.25 c. mr. has 25 points. The same applies for other gemstones. Example: a sapphire of 1.15 c. mr. weighs 1 carat and 15 points.

Weight (in carat) and diameter (in millimeters) of round brilliant diamonds

0,03 carat	0,05 carat	0,07 carat	0,10 carat
Ø 2,00 mm	Ø 2,50 mm	Ø 2,70 mm	Ø 3,00 mm
0,15 carat	0,20 carat	0,25 carat	0,33 carat
Ø 3,40 mm	Ø 3,80 mm	Ø 4,10 mm	Ø 4,40 mm
0,40 carat	0,50 carat	0,65 carat	0,75 carat
Ø 4,80 mm	Ø 5,20 mm	Ø 5,60 mm	Ø 5,90 mm
0,85 carat	1,00 carat	1,25 carat	1,50 carat
Ø 6,20 mm	Ø 6,50 mm	Ø 7,00 mm	Ø 7,40 mm
1,75 carat	2,00 carats	2,25 carats	2,50 carats
Ø 7,80 mm	Ø 8,20 mm	Ø 8,60 mm	Ø 9,00 mm

Color

The color classification of the diamond is established according to a color scale which begins at the letter D for the rarest stones as Diamond and ends at the letter Z attributed to the inexpensive stones. The stone is estimated under normalized artificial white light by comparing it to standard stones. The estimation of the color is decisive in the expertise because the price of the diamond depends on it. The color D (invisible color) is the most sought after but also the most expensive. Colors from K to Z (yellowish) are the least popular and also the cheapest.

The often recommended colors oscillate between E and I. The name: “fancy color” is used for colored diamonds (blue, green, canary yellow, light brown, pink, etc.). The price of such stones is often very high. When a stone has undergone an artificial change in its color, the certificate of expertise systematically states “color enhanced” in its comments, it is an inadvisable purchase.

■ Color: D (Exceptional white +, the rarest, formerly called “Jager”) A color diamond of D is completely colorless to the naked eye. It is the most sought after diamond because it does not contain a color atom.

■ Color: E (Exceptional White, formerly called “River”) A colored diamond is colorless to the naked eye. The gemologist uses the reference samples to determine if the diamond is color D or E. Color E diamonds are very good investments.

■ Color: F (Extra White +) Color F denotes a virtually colorless diamond whose color can only be seen by an expert’s naked eye from the reverse side of the diamond table. The color F displays a reasonable cost to purchase and has the advantage of being a very beautiful whiteness at a still affordable cost. It is the color used most often in fine jewelry.

■ Color: G (Extra white, used in jewelry stores and fine jewelry, formerly called “Top Wesselton”) Classification G emphasizes the presence of extremely faint color in the diamond and is only noticed with the naked eye by a experienced gemologist on condition that the diamond is not set and observed from the back of the table. It is sometimes possible to appreciate a mounted G color diamond by comparing the diamond with a mounted diamond of a higher color. Color G is reasonably priced to purchase and has the advantage of being colorless to the naked eye when set.

■ Color: H (White, used in jewelry stores, formerly called “Wesselton”) Classification H offers good value for money in the range considered almost colorless. The extremely faint color presence in the H-colored diamond can only be distinguished with the naked eye by comparison with a higher colored diamond.

■ Color I (Shaded White, formerly called “Top Crystal”) Classification I offers good value for money for people who prefer large stones provided they are cut in ideal or very good proportions. It is better to opt for a faceted cut rather than a straight cut like the barrette or emerald cut. The presence of the faint color can be distinguished with the naked eye by comparison with a higher colored diamond. Diamonds classified as color under I are very rarely certified by international laboratories. Recommended only in brilliant cut and in ideal proportions with slight fluorescence.

■ Color J (Shaded white, formerly called “Crystal”). The color is visible from the front.

■ Colors K-L (Slightly tinted, formerly called “Top Cape”) The tint is easily visible. Diamonds in these colors still appear white to the naked eye to a non-professional if they are small in size but above 0.10 carat color saturation is evident.

■ Colors M-Z (Tinted, very pale yellow, formerly called “light cape, cape, dark cape”) The tint is very easily visible. Certain very tinted colors are sought after. Fancy diamonds (Special colored diamonds, see daffodil diamonds …)

Diamond color grading scales

PURITY (Clarity)

The purity of the diamond is assessed in acronyms: FL (for a pure diamond) and decreasingly IF (no internal inclusion visible with a 10X magnifying glass), VVS1 (very very slight inclusions), VVS2, VS1 (very slight inclusions ), VS2, SI1 (slight inclusions), SI2, I1 (inclusions or pits), I2, and finally I3. The quality of diamond purity is assessed by classifying the inclusions by their size, weight, color and nature. Diamond dealers examine diamonds using a microscope and a 10x magnifying glass and can thus determine the nature of the inclusions Definition: Inclusion is an impurity in the internal part of the stone similar to a pitting or an anomaly in its crystal structure, sometimes, it appears in the form of a cloud, a fracture and may also contain liquid. The number of inclusions directly influences the estimate of the degree of purity. The degrees of purity are as follows:

■ Purity: FL (Flawless – pure) Diamonds of FL purity have no internal or external inclusions of any kind visible with a 10x magnifying glass to a trained eye, this is the rarest and most expensive degree of purity

■ Purity: IF (Internally Flawless) Diamonds of IF clarity have a purity without internal flaw and not visible with the most magnifying glasses. Diamonds with such purity are exceptionally rare.

■ Purity: VVS1 (Very Very Small Inclusion 1 – very, very small inclusions 1) Diamonds of purity VVS1 have tiny inclusions that are very difficult to perceive with a magnifying glass magnifying 10 times. Diamonds exhibiting such purity are just like diamonds of extremely rare IF clarity.

■ Purity: VVS2 (Very Very Small Inclusion 2 – very, very small inclusions 2) Diamonds of clarity VVS1 have tiny inclusions that are barely perceptible, with a magnifying glass magnifying 10 times. Diamonds of VVSI purity are extremely rare.

■ Purity: VS1 (Very Small Inclusion 1 – very small inclusions 1) VS1 clarity diamonds have very small inclusions, very difficult to detect with a magnifying glass magnifying 10 times and never visible to the naked eye by the table. Diamonds with VS1 clarity are less expensive than diamonds of higher clarity while having inclusions that are completely invisible to the naked eye.

■ Purity: VS2 (Very Small Inclusion 2 – very small inclusions 2) VS2 clarity diamonds have very small inclusions that are difficult to detect with a magnifying glass magnifying 10 times and never visible to the naked eye by the table. Diamonds with VS2 clarity are less expensive than diamonds of higher clarity while having inclusions that are completely invisible to the naked eye.

■ Purity: SI1 (Small Inclusion 1 – small inclusions 1) Diamonds of SI1 clarity have small inclusions visible with a magnifying glass magnifying 10 times and never visible to the naked eye of an expert. SI1 diamonds are less rare than VS2 clarity diamonds but less expensive and very pleasing to the eye. A nice S “i” is a good choice for a small budget.

■ Purity: SI2 (Small Inclusions 2 – small inclusions 2) Diamonds of SI2 clarity have small inclusions visible with a magnifying glass magnifying 10 times and very rarely visible to the naked eye, this is the “borderline” category. SI2 diamonds are less rare and less expensive than higher purity diamonds while still being pleasing to the eye. An SI2 should be chosen very carefully “eyes wide open”. Choose “off-center” Si2s.

■ Purity: SI3 (Slightly Inclusion 3 – visible inclusions) SI3 clarity diamonds are not certified by international laboratories and are of little interest in terms of quality and purity in French jewelry. The inclusions are visible to the naked eye (by an experienced professional). Always choose “off-center” B3s.

■ Purity: PI1 (Included 1 – inclusions visible to the naked eye) SI3 clarity diamonds are not recognized by international laboratories and are of little interest in the quality of purity in French jewelry. Inclusions are visible to the naked eye (by an experienced professional) and slightly affect the brilliance and beauty of the diamond.
■ Purity: PI2 (Included 2 – inclusions visible to the naked eye) I2 clarity diamonds exhibit very little of interest in purity in French jewelry. Larger and more numerous inclusions compared to SI3 and I1 clarity diamonds. The inclusions are visible to the naked eye and slightly reduce the brilliance of the diamond.

■ Purity: PI3 (Included 3 – inclusions visible to the naked eye) Diamonds of I2, I3 clarity are of no interest in French jewelry. Larger and more numerous inclusions compared to SI3, I1 and I2 clarity diamonds. The inclusions are visible to the naked eye and greatly reduce the shine. The diamond does not present any beauty.

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Size (Cut, proportions)

The physicist and mathematician M. Tolkowsky published in 1919 a study on the optical properties of round brilliant cut and desirable optimal proportions. These values ​​are always updated in the qualifications, in particular the sizes (“cut grade”) noted in the certificates. Thus, it is the variable parameter (proportion) which will allow the fixed data (purity, color, fluorescence) to be expressed. Diamond is a sensor and a reflector of light.

When a diamond is cut according to “good proportions”, listed by the “Cut grade”, the captured light is reflected in the facets, one after the other, making maximum use of the high refraction property of the diamond, to finally emerge. by the top of the stone (by the table). A diamond whose ideal proportions are not respected lets some of the light escape from the sides.The proportions are described in two points:

The table percentage and the depth percentage; both are expressed as a percentage relative to the diameter (or side for princess cut diamonds for example) of the stone representing 100% of the value.

The diamond table represents the flat part of the stone. The ratios correspond to the ratio between the diameter and the size of the table as well as the ratio between the height of the stone and the diameter of the diamond (Depth). These factors, which should not be neglected, condition the brilliance and fire (“light return”) of the diamond.

Note:

It is necessary to consider all the proportions of a stone and not some of them to appreciate the “balance” of a stone. Therefore (except for old cut diamonds), too large or too small a crown angle is stipulated on the certificate.

An open culet or a thick rondiste sanction a diamond of average cut and not very interesting. As a general rule, gemologists refer to the quality of the cut and particularly to the good proportion between the% of depth and the% of table of the stone

Table: flat part of the stone Depth: crown height (crown) + pavilion height + belt height (girdle) = total height The% are all given according to the diameter (100%) The% Depth must be between 58 and 64% The% table between 58 and 66% for very good proportions or a very good cut. The ideal reference for the angle of the crown of a round brilliant is 32 ° 70 ‘to 36 ° 30.

The “Cut Grade (International Standards)” classification:

■ Excellent cut quality: E (Cut Grade Exellent – ideal cut, excellent). The diamond with an excellent cut reflects all the light rays received. The diamond dealer preferred the brilliance of the stone to the weight. For this, the diamond dealer must also consider all the optical properties. The excellent quality size is the prettiest and is frequently referred to as the ideal size. When the proportion is between 59% and 62.50%, we can say that we are in the presence of an ideal proportion.

■ Quality of the cut very good: VG (Cut Grade Very Good – very good). The diamond with a very good cut reflects practically all the light rays received. The cut of very good quality is cheaper than the so-called “ideal” cut while presenting a wise choice.

■ Good cut quality: G (Cut Grade Good). The diamond with a good cut reflects most of the light rays received. The diamond dealer preferred the weight of the stone to the proportions of the stone. Good quality size is cheaper than very good or excellent quality size and may be a good option for many jewelry.

■ Fairly good or medium cut quality F (Cut Grade Fair – medium). A diamond with a fairly good cut sufficiently reflects the light rays received. The stone is of great interest because it will be cheaper than a good quality cut and may present a good option for some jewelry.

■ Poor cut quality P (Cut Grade Poor – bad). The diamond with a mediocre cut should be avoided because it reflects only very moderately most of the light rays received. Note: The proportions of diamonds called “Fancy”, and in particular princess cut diamonds have slightly different criteria from round diamonds.

■ Princess diamond table: “ideal” proportion (Cut Grade Exellent): The light is perfectly reflected. The diamond has a very beautiful shine. (Proportion of the “ideal” table from 60% to 68%).

■ Princess diamond table: “very good” proportion (Cut Grade Very Good): The light is properly reflected. The diamond has a beautiful shine.

■ Princess diamond table: “very good” proportion (Cut Grade Good): The light is properly reflected. The diamond has a good shine.

■ Princess diamond table: “medium” proportion (Cut Grade Fair): The light is moderately reflected. The diamond has a medium shine.

■ Princess diamond table: “bad” proportion (Cut Grade Poor): The light is very poorly reflected. The diamond has little shine. The table is too flattened, the light passes through the diamond which loses all shine.

For information:

In general, the crown height of princess cut diamonds is low, around 10% maximum thickness compared to the total depth of the stone. Also, the roundness of princess-cut diamonds, sometimes thick (up to 5%), offers a guarantee of strength for the angles without modifying the brilliance. The tables of princess diamonds of “excellent” proportions are very popular in the United States. In France, important tables are rather sought after.

Diamond shapes – (cutting)

We distinguish the cut of the round brilliant from the so-called “fancy” cuts, such as the princess cut, emerald, oval … and many others.

■ Brilliant cut: The shape of the round brilliant (57 facets) is certainly the most successful, the one for which the study of the optimal proportions has been the most extensive. It is also the most classic.

■ The “fancy” sizes are generally less expensive than the round sizes, more difficult to evaluate, the quality of the proportions and the size will influence the price a lot. Some examples of common shapes:

■ The Princess cut: suitable for architectural jewelery with clean lines. It is a square or rectangular cut, usually with 76 facets that ensure a strong sparkle. A princess cut is smaller and cheaper than a round brilliant of equal weight. The width of the table requires good purity.

■ The Emerald cut: the Emerald cut highlights the ‘transparent’ beauty of the diamond. It is a distinguished size, sober but very “class”. Requires good purity diamonds: the table must be pure or VVS, any inclusions on the side.

■ The Oval cut: resolutely modern shape that combines the classicism of the round shine and the elegant femininity of more elongated shapes such as those of the marquise and the drop. The finish, polish and symmetry The term “finish” defines the polished quality of the stone as well as its symmetry. The symmetry of a diamond is judged by the alignment of the facets with respect to each other. It is very easy for an expert to highlight its properties with a magnifying glass.

Fluorescence

This characteristic relates to the diamond’s ability to fluoresce when exposed to ultraviolet (UV) light. As a general rule, the more fluorescence there is, the less valuable the diamond is, but this is not always true, especially for so-called “low” colors such as K and L where fluorescence makes the stone appear whiter in color. masking the yellow or brown tint with a shade of blue.

The assessments indicated on the certificates are as follows:

■ None: signifying a total absence of fluorescence
■ Slight: signifying a slight fluorescence
■ Medium: signifying an average fluorescence
■ Strong: meaning strong fluorescence

Polished (finish)

Note: Poli corresponds to the exterior finish of a stone, it is essential for the diamond to diffuse maximum shine. The classification varies from poor to excellent. An excellent polish is rated “Excellent” etc.… Estimate of the polish and expert opinion of the diamond: Excellent (excellent) Very good (very good); Good; to avoid: Fair (quite good); medium; Poor (bad).

How the expert value of diamonds?

D (exceptional white +); E (exceptional white); F (extra white +); G (extra white); H (white); I (shade white); J (shade white); K (slightly tinted); L (slightly tinted); M to Z (tinted).

Diamond appraisal annotation: Fancy color: fancy light, fancy, fancy intense, fancy vivid and fancy deep.

Diamond appraisal annotation: Color enhanced, the artificially modified color, is mentioned on the certificate: mention; to avoid, discount up to 70%. This is a strongly advised against purchase.

Diamond expert commentary

Proportion of stone in percentage …..%

Diamond appraisal annotation: Crown angle (Observation indicated on the certificate only if the angle is too large or too small), Ideal from 32 ° 70 “to 36 ° 30: …%

Regarding stones in general except diamonds, the ratio between the thickness of the crown and the depth of the pavilion is 1 to 3. Example: 2 mm for the crown (for the top) and 6 mm for the pavilion (for the bottom).

Proportions of the table. The beauty of the table of a diamond is considered optimal when the proportion (height of the diamond divided by the diameter of the table is between 55% and 58%:……%.

The same appreciation values ​​apply for the other stones. As a rule of thumb for other stones other than diamond, the area of ​​the table should be half the area of ​​the stone. It is through the table that your stone is illuminated.

Refractive index

Diamonds refractive index is a measurement of 2.417. This means that light travels through a diamond 2.417 slower than it travels through air.

The ability of diamonds to reflect light is confirmed by the refractive index. The refractive index of the stones is approved using a refractometer. Diamond appraisal comment: the index varies between 2.417 to 2.419 for diamonds:…… The dispersion of the diamond, ID (dispersion index) : 0.044: Note: The dispersion favors the shimmering of the colors of the rainbow and gives the diamond all these “lights”.

Technical characteristics of the diamond

Diamond is the hardest of the minerals (10 on the Molhs scale).
Chemical composition of diamond Pure carbon (C.);
Crystallization: cubic system;
Density: between 3.4 and 3.9;
Moth’s scale hardness: 10; Refractive index 2.42; Dispersion: 0.044;
Very high thermal conductivity (600 to 1600 Watt / m Kelvin);
Very low coefficient of thermal expansion (0.000001 / °).

Sources: PinterPandai, Mining, The International Diamond Council (IDC), CIBJO

Photo credit: Pixabay

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