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Company standarts - Natural diamonds
Standard of the Organization STO "MGTs"
"Diamonds and natural diamonds cut"
1. Introduction. Scope.
1.1. The standard of the organization "Moscow Gemological Center" (hereinafter STO MGC) is not an industry or national standard. STO MGC defines the methods of testing diamonds and cut diamonds, including those installed in jewelry, and the information content of gemological reports (conclusions and certificates) issued on the basis of an application from an individual or legal entity.
1.2. This standard of the organization applies to loose diamonds and cut diamonds, as well as diamonds and cut diamonds mounted in jewelry, and establishes a set of information reflected in gemological reports (conclusions and certificates) in relation to the quality characteristics of diamonds, their classification and terminology.
1.3. The main provisions of this standard comply with the international standard ISO/TR 11211-1995 "Grading polished diamonds - Terminology and classification" (ISO/TR 11211:1995), the main classification criteria in the sections of competence correspond to or are comparable with those of international standards: ISO/TR 11211:1995, ISO/DIS 24016:2020 "Jewellery and precious metals - Grading polished diamonds - Terminology, classification and test methods" (ISO/DIS 24016:2020 "Jewellery and precious metals - Grading polished diamonds - Terminology, classification and test methods"); the standards of the Russian Federation: GOST R 52913-2008 "Diamonds. Classification. Technical requirements." (hereinafter GOST), STO 45866412-17-2015 "Enhanced diamonds. Classification. Technical requirements." (hereinafter STO) and TU 117-4.2099-2002 "Diamonds. Technical requirements. Classification." of the Association of Russian Diamond Manufacturers (hereinafter TU).
2. Normative references.
This standard uses the recommendations of the following standards and classifiers with references:
- GOST R 51293-99 "Product identification. General provisions.";
- GOST R 1.4-2004 "Standardization in the Russian Federation. Organization standards. General provisions."
- GOST R 1.0-2012 - "Standardization in the Russian Federation. Basic Provisions.";
- GOST R 52913-2008 "Diamonds. Classification. Technical requirements."
- STO 45866412-16-2014 "Precious stones: terms and definitions."
- STO 45866412-17-2015 "Ennobled diamonds. Classification. Technical requirements."
- TU 117-4.2099-2002 "Diamonds. Technical requirements. Classification";
- ISO/TR 11211-1995 "Evaluation of diamonds. Terminology and classification".
- Стандарт ISO 24016-2020 «Jewellery and precious metals – Grading polished diamonds – Terminology, classification and test methods.».
This standard uses the main provisions and conclusions set out in the following literary sources:
- Fantasy colors of diamonds. Bocharov A.M., Nyubin V.V., Mukonin A.A., Slabkovsky D.S. Smolensk, 2011.
- GIA. Colored diamonds. Color Reference Chart. Editor: John M. King. 2006.
- GIA. Diamonds & Diamond Grading. 2008.
3. Terms and definitions.
3.1. Basic definitions .
3.1.1. Diamond is a mineral of natural origin or synthesized in laboratory or industrial conditions, which is native carbon, crystallized in a cubic syngony (hexatetrahedral type of symmetry), not subjected to any external influence associated with a change in its natural properties.
The term “diamond” in the absence of further explanatory definitions always means “natural diamond”. These two terms are equivalent and have the same meaning. (ISO/TR 11211-1995, ISO 24016-2020)
The term "diamond" (as such) shall not be used to describe any other product, including items partially composed of diamond (e.g. doublets). (ISO/TR 11211-1995, ISO 24016-2020)
3.1.2. Enhanced diamond is a diamond (natural or synthetic) that has undergone artificial processing to change its appearance by applying coatings, laser drilling, filling cracks and cavities, irradiation, heating, heating under high (or low) pressure, as well as using other types of physical and/or chemical effects or a combination thereof. (STO 45866412-16-2014 "Precious stones: terms and definitions", ISO/TR 11211-1995, ISO 24016-2020)
Diamonds that have undergone only cleaning (without physical or chemical changes) are not considered to be treated. (STO 45866412-16-2014 "Precious Stones Terms and Definitions.")
3.1.3. Synthetic diamond is a diamond produced in whole or in part in laboratory or industrial conditions by various crystallization and/or recrystallization methods, having essentially the same chemical composition, physical, chemical properties and structure as their natural counterparts. (STO 45866412-16-2014 "Precious stones: terms and definitions", ISO/TR 11211-1995, ISO 24016-2020)
3.1.4. Diamond – for the purposes of compiling gemological reports, the term diamond means the classical definition of a diamond – a natural diamond, cut, round in shape (brilliant cut), as well as cut diamonds of other shapes and types of cuts (including mixed ones).
Exceptions are cut and uncut diamonds:
- Old Rose cut diamonds, which are described (for gemological reporting purposes) as "Old Rose cut diamonds";
- Old Mine cut diamonds;
- Diamonds cut cabochon and including faceted cabochon (Cabochon cut, Faceted cabochon);
- Uncut diamonds in jewelry (rough diamond).
- Modern cut diamonds with chips that have caused the loss of one or more facets (Facetet diamond).
3.1.5. Imitation diamonds are natural minerals or artificially grown compounds similar to diamonds in some physical properties, primarily visually, and differing from diamonds in chemical composition and a number of other properties. (GOST R 52913-2008 "Diamonds. Classification. Technical requirements")
This category also includes composite stones (doublets, triplets), as well as stones coated with diamond or diamond-like films.
The word "diamond" shall not be used to describe or designate such a stone, even in combination with other words. (ISO/TR 11211-1995, ISO 24016-2020)
3.2. Methodological definitions
3.2.1. Identification of diamonds (or cut diamonds) is the process of establishing the identity of the identified characteristics of the sample being examined (here, a diamond or other cut diamond) with the main defining features of the reference sample or their description. (GOST R 51293-99 "Product Identification. General Provisions.")
3.2.2. Classification of diamonds (or cut diamonds) – a system for distributing diamonds according to certain classification criteria. (GOST R 52913-2008 “Diamonds. Classification. Technical requirements.”)
3.2.3. The main classification features of a diamond (or cut diamond) are the main indicators of the quality of a diamond or cut diamond (4C): weight, color, clarity, cut.
- mass (mass of a diamond or cut diamond) – the mass of a diamond (or cut diamond) is determined in metric carats (1 carat is equivalent to 200 mg) and is one of the main classification features.
- color (color of a diamond or cut diamond) – one of the main classification features of a diamond (or cut diamond), characterized by the relative absence (colorless) or presence of natural coloring in a diamond (or coloring in another cut diamond), based on the property of a diamond (or cut diamond) to evoke a certain visual sensation, due to its spectral characteristics in the visible range of the spectrum.
- Clarity is one of the main classification features of diamonds (or cut diamonds), characterized by the absence or degree of manifestation of internal and/or external defects.
- cut (cutting of a diamond or cut diamond) is one of the main classification features of a diamond (or cut diamond), characterized by the type and quality of diamond processing for the purpose of obtaining diamonds (or cut diamonds).
(GOST R 52913-2008 "Diamonds. Classification. Technical requirements", ISO/TR 11211-1995, ISO 24016-2020)
3.2.3.1 Determination and classification of the color of a diamond (or cut diamond) is a sequence of actions in a set of works carried out under specially defined conditions, the purpose of which is to determine the location of the color of a diamond (or cut diamond) on the color scale, in accordance with specially selected reference samples that define the boundaries of color intervals. When classifying the color, the results of instrumental measurements can be taken into account. (GOST R 52913-2008 "Diamonds. Classification. Technical requirements.", ISO/TR 11211-1995, ISO 24016-2020)
3.2.3.1.1. Ordinary color of a diamond (or cut diamond) - the color of a diamond (or cut diamond) that, in terms of its indicators (color shade, tone, saturation), corresponds to the reference samples of diamond color graded from the value "D" to the value "Z" inclusive for diamonds of yellow, brown and gray color shades, as well as for other colors from the value "D" to the value "J" inclusive.
3.2.3.1.1.1. Classification of the color of a diamond (or cut diamond) of ordinary color is a sequence of actions in a set of works carried out under specially defined conditions, the purpose of which is to determine the location of the color of a diamond (or cut diamond) on the color scale of ordinary colors, in accordance with specially selected reference samples that define the boundaries of color intervals. When classifying the color, the results of instrumental measurements can be taken into account. (GOST R 52913-2008 "Diamonds. Classification. Technical requirements", ISO / TR 11211-1995, ISO 24016-2020)
3.2.3.1.2. Extraordinary color of a diamond (or cut diamond) - the color of a diamond (or cut diamond) that differs in its characteristics (color shade) from ordinary diamond colors.
3.2.3.1.2.1. Classification of the color of a diamond (or cut diamond) of extraordinary color – a sequence of actions in a set of works carried out under specially defined conditions, the purpose of which is to determine the location of the color of a diamond (or cut diamond) on the color scale of extraordinary colors, in accordance with specially selected color reference samples or analog samples that determine the boundaries of color intervals. When classifying colors, the results of instrumental measurements may be taken into account.
3.2.3.1.3. Fancy color of a diamond (or cut diamond) - an extraordinary color of a diamond (or cut diamond), in its parameters (tone, saturation) differing from other colors of a diamond by its location in the color field, namely within the blocks of diamonds (or cut diamonds) of fancy color. Note : The definition of fancy does not apply to colors of the monochromatic series such as gray and black. The term "fancy" also does not apply to synthetic diamonds and color-enhanced diamonds.
3.2.3.1.3.1. Classification of fancy color of diamonds (or cut diamonds) is a sequence of actions in a set of works carried out in specially defined conditions, the purpose of which is to determine the location of a fancy-colored diamond (or cut diamond) in the color field within blocks. For the purpose of classifying the color of a diamond (or cut diamond), both instrumental and organoleptic methods of analysis are used.
3.2.3.1.3.2. Basic classification features of the color of a fancy colored diamond (or cut diamond) :
- Hue – A component of the color of a diamond (or cut diamond), characterized by the presence in the diamond (or cut diamond) of a natural color other than white, gray, and black, based on the property of causing a certain visual sensation, caused by its spectral characteristics in the visible range of the spectrum. The color hue is determined by the light of the predominant wavelengths of the visible part of the spectrum.
- Tone – A component of the color of a diamond (or cut diamond) on an achromatic scale (white-gray-black), which determines the conditional amount of “lightness” or “darkness” in the color.
- Saturation – A component of the color of a diamond (or cut diamond) that distinguishes it from achromatic and characterizes the purity of the color shade, which is determined by the intensity of light of the predominant wavelengths of the visible part of the spectrum.
3.2.3.2. Diamond clarity classification is a sequence of actions in a set of works to establish the presence of significant clarity characteristics in a diamond and assign the diamond under study to the corresponding clarity quality group in accordance with the classification of this standard. (GOST R 52913-2008 "Diamonds. Classification. Technical requirements", ISO/TR 11211-1995, ISO 24016-2020). Note : cut diamonds (which are not diamonds by definition) are classified by degree of transparency (transparent, translucent, translucent, opaque) for the purposes of gemological reports.
3.2.3.2.1. Significant clarity characteristics – all detectable (visible or noticeable when viewed through a 10x triplet jeweler’s loupe) clarity characteristics located inside or partially inside a diamond, which include visually apparent diamond defects that affect its transparency.
3.2.3.2.2. Characteristics of purity by origin are divided into:
- inclusions, namely: light, colored and dark volumetric inclusions, dots, clouds, graining (expressed in the color or structure of the diamond) and others;
- cracks and other damage to the integrity of the diamond, such as: feathers, nicks, grooves, pits, chips and others;
- defects that cause poor transparency of the diamond (“haze”), manifested in the overall volume of the diamond;
- laser drilled holes;
(TU 117-4.2099-2002 "Diamonds. Technical requirements. Classification", ISO/TR 11211-1995, ISO 24016-2020)
3.2.3.2.3. Purity characteristics according to the degree of penetration into the volume of the stone can be:
- internal – located entirely inside the diamond, and also partially extending onto its surface;
- external – located on its surface and slightly penetrating into its volume, the elimination of which will not entail a significant loss in mass.
(GOST R 52913-2008 "Diamonds. Classification. Technical requirements.", TU 117-4.2099-2002 "Diamonds. Technical requirements. Classification", ISO/TR 11211-1995, ISO 24016-2020)
3.2.3.2.4. The characteristics of cleanliness, according to the degree of visibility by the expert, are divided into:
- Very subtle – Inclusions are usually light in color and very difficult for a trained expert to detect through a 10x triplet magnifier when carefully examining a diamond. They are usually easier to detect when viewing the stone with an arbitration viewing device (binocular), and then found when viewing the diamond through a magnifier.
- Subtle – Inclusions that can be detected by a trained expert through a 10x triplet jeweler's loupe upon careful inspection of the diamond.
- Noticeable - Inclusions that can be easily detected by a trained expert using a 10x triplet jeweler's loupe when examining a diamond.
- Obvious - Inclusions that can be easily detected by a trained expert through a 10x triplet jeweler's loupe during a cursory inspection of the diamond. Sometimes such inclusions, when detected through a loupe, can be seen with the naked eye.
- Visible to the Naked Eye – Inclusions that appear very large when viewed through a 10x triplet jeweler’s loupe. When viewed without a loupe, such inclusions may be noticeable to the naked eye. A distinction is made between : Faintly visible – those that were discovered when viewed through a loupe and that can then be seen with the naked eye; Visible – those that were discovered upon close inspection; Clearly visible – those that can be easily detected with the naked eye; Well visible – those that can be detected upon cursory inspection of the stone.
3.2.3.3. Classification of diamond cutting is a sequence of actions in a set of works to establish the overall quality of the result of work on cutting a diamond into a brilliant, which consists of the qualitative relationships of the proportions of the diamond, the symmetry of the elements of the diamond cut, and the polishing of the diamond. Note : cut diamonds are classified only by the shape of the cut, its type, kind, and variety.
3.2.3.3.1. Diamond proportions are a property of diamond cut, manifested in the ratio of the metric characteristics of diamond cut elements, determining the property of total internal reflection, brilliance and play of the diamond.
3.2.3.3.2. Diamond symmetry is a property of diamond cut that describes the deviation from the norm of the ratio of cut elements and the differences in their metric parameters and location.
3.2.3.3.3. Diamond polishing – a property of diamond cut that describes the processing of the diamond's facets, as well as the presence or absence of processing marks on the facets.
3.2.4 Additional classification features of a diamond (or cut diamond) – an additional classification feature is fluorescence (luminescence in the ultraviolet spectrum [315-390 nm] of light [electromagnetic radiation], its color and degree of intensity).
4. Testing and control methods
Before the start of work on identifying a diamond (or cut diamond) and classifying quality characteristics, for the purposes of producing gemological reports, all diamonds and jewelry are subject to mandatory cleaning.
All work on identifying a diamond (or cut diamond) and classifying quality features for the purposes of producing gemological reports is carried out by at least two experts independently of each other. In case of divergence of opinions, an additional expert is involved.
Testing and control of diamonds and other cut diamonds is carried out in the following order:
1) Carrying out a set of works on diamond diagnostics (determining the origin of the material from which the diamond or cut diamond is made) and identifying signs of diamond enhancement;
2) Carrying out a range of works on classifying diamonds by weight and size-weight characteristics;
3) Carrying out work on classifying a diamond (or cut diamond) by color;
4) Carrying out work on classifying a diamond (or cut diamond) by purity;
5) Carrying out a set of works on classifying a diamond (or cut diamond) according to the quality of its cut;
6) Carrying out a range of works on the classification of luminescence.
4.1. Sequence of work on diagnostics of a diamond (or cut diamond).
The purpose of this set of works is to identify imitations and separate cut diamonds into natural diamonds and synthetic cut diamonds, as well as to establish the fact of the presence of enhancement by color and/or clarity. Determination of the material of diamonds for compliance with a diamond, as well as for compliance with natural unenhanced, enhanced and synthetic diamonds is carried out on a uniform basis.
4.1.1. A preliminary inspection of the insert material (diamond or cut diamond) is carried out visually using a triplet jeweler's loupe with a magnification of 10x in order to identify signs that are not characteristic of a diamond - the presence of optical anisotropy, indirect signs of low (compared to diamond) hardness, and optical effects that are not characteristic of a diamond, or indirectly indicating that the refining process has been carried out.
4.1.2. If the result obtained during the preliminary inspection is satisfactory, a determination is made using hardware diagnostic methods - a tester for determining diamonds (based on determining the thermal conductivity property), a tester for determining the naturalness of a diamond (based on determining the optical absorption property of a natural diamond), and a study of UV luminescence in a viewing UV block in the range of short (250 nm) and long (315-390 nm) waves.
4.1.3. If the hardware diagnostics result is positive, the diamond is examined using a D-Screen type device.
4.1.4. After fulfilling the requirements of paragraphs 4.1.2., 4.1.3., a microscopic examination of the diamond is carried out in an immersion medium, which includes studying the appearance of internal inclusions, the optical properties of the diamond (including in polarized light), color zoning, fluorescence zoning, and determining the presence of substances that are not characteristic of natural diamond (the material of inclusions and/or fillers).
4.1.5. Upon receipt of the inspection results under paragraph 4.1.4., a set of spectral studies is carried out with the aim of confirming the fact of determining the diamond at the spectral level, identifying possible refinement, and confirming the determination of origin (natural or synthetic).
4.1.6. The nature of the diamond's origin must be indicated in the name (Natural diamond, Synthetic diamond), and the fact, type and degree of refinement - in the comments on the footnote. If it is impossible to unambiguously determine the nature of the origin of the diamond in the product, the mineral type (Diamond) and the reason for the lack of an unambiguous result are indicated in the comments (for example: "Determining the nature of the origin of the diamond (cut diamond, insert) is difficult due to the setting").
4.1.7. When examining a group of stones up to 0.25 carats each, fixed in a piece of jewelry in such a way that conditions are created that limit the possibilities of examining diamonds using a full range of methods, a decision on the natural origin of the stones is made on the basis of examination using available methods in the presence of clear signs of natural origin in at least 1/3 of the stones in the batch . At the same time, the remaining 1/3 of the stones must not show clear signs of synthetic origin when examined using available diagnostic methods.
4.2. Procedure for carrying out work on classifying a diamond (or cut diamond).
The determination of the quality characteristics of natural untreated, treated and synthetic diamonds is carried out on a uniform basis, in accordance with the sections of competence - Natural diamonds (ordinary and extraordinary colors), Natural treated diamonds, Synthetic cut diamonds.
The origin of the diamond (or cut diamond) must be indicated in the name, and the fact, type and degree of refinement - in the comments on the footnote.
Carrying out work on classifying a diamond (or cut diamond) involves the following sequence:
- Determination of the mass of a diamond (or cut diamond) and/or size and weight characteristics;
- Definition of color characteristics;
- Determination of purity characteristics;
- Determination of cutting quality characteristics;
- Determination of characteristics of additional evaluation parameters (luminescence).
4.2.1. Classification of diamonds by weight and size-weight parameters.
The weight of a diamond is one of the most important evaluation characteristics of a diamond. In addition, the classification of diamonds by weight is determined by the method of determining other basic quality characteristics, namely the choice of a dimensional scale. In the absence of the possibility of direct weighing based on the measurement of linear parameters, a calculation of the dimensional and weight parameter is made - "estimated weight of a diamond".
4.2.1.1. For the purposes of correctly determining quality characteristics when compiling gemological reports, the following categories of diamonds by weight are distinguished:
- Small ones – weighing up to 0.30 ct (with the standard diameter of a perfectly cut round diamond being up to 4.35 mm).
- Medium – weighing from 0.30 ct inclusive to 1.00 ct (with the standard diameter of a perfectly cut round brilliant diamond from 4.35 mm to 6.45 mm). For the purposes of assessing the quality characteristics of a diamond, the "medium" group of diamonds includes: a size and weight group weighing up to 0.49 ct inclusive (with the standard diameter of a perfectly cut round brilliant diamond up to 5.0 mm), a size and weight group from 0.50 ct to 0.99 ct inclusive (with the standard diameter of a perfectly cut round brilliant diamond from 5.0 mm to 6.45 mm).
- Large – weighing over 1.00 ct inclusive (with a standard diameter of a perfectly cut round diamond of 6.45 mm). Note : when certified according to ISO/TR 11211-1995 or ISO 24016-2020, stones weighing 0.999 carats are rounded up to a weight of 1.00 carats (in accordance with the requirements of the above standards).
4.2.1.2. The mass of an unmounted diamond is determined by weighing the stone on analytical scales of at least class III accuracy.
4.2.1.3. The mass of a diamond set in a product is determined by calculation. In this case, all measurements are made with a micrometer device of the "Leveridge" type, and if the stone is inaccessible for measurement, the linear dimensions are determined using a measuring magnifying glass with a resolution of 10X and a scale division of at least 0.1 mm. The error in determining the mass of a stone accessible for standard measurements and inspection does not exceed 5%. In case of limited access to the stone or the inability to take dimensional indicators, the dimensions of the stone are determined taking into account standard ratios and proportions, and indirect signs indicating the magnitude of such ratios and proportions are also taken into account. In this case, the error in determining the mass of the stone does not exceed 10%.
4.2.1.4. The weight of a diamond is expressed in hundredths of a carat in a gemological report.
4.2.1.5. When reflecting the mass of a stone in a gemological report, when certified according to the rules of ISO/TR 11211-1995 or ISO 24016-2020, the rounding rule of the third nine is used, that is, the weight of a stone of 0.999 carats is rounded to a weight of 1.00 carats (in accordance with the requirements of the above standards).
4.2.1.6. To facilitate the identification of a diamond or a cut diamond, as well as to provide the consumer with the most complete information on the size and weight parameters, the linear dimensions are measured - length, width (maximum and minimum diameter) and height, expressed in hundredths of a millimetre. If it is impossible to use precise instruments to measure the linear characteristics, a measuring magnifying glass with a resolution of 10X and a scale division of at least 0.1 mm is used, and the linear dimensions are not indicated in the report, being replaced by the size and weight characteristic - "estimated weight".
4.2.2. Classification of diamonds by color
The colour of a diamond is determined organoleptically by an experienced appraiser, with the following lighting conditions: the diamond is placed on a neutral white background, under standard artificial light conditions equivalent to northern daylight (at the equinox at 48° north latitude). For these purposes, a D65 light source is used (according to the classification of the International Commission on Illumination - CIE). Additionally, hardware methods for determining colour can be used.
For the purposes of gemological reports, diamond color is described taking into account the distinction between two main groups:
- Ordinary colour diamonds – diamonds with colouring from colourless (exceptional white – in accordance with ISO) to very slightly tinted yellow (tinted colour – in accordance with ISO), namely the colour standard "Z" inclusive (or equivalent in saturation to brown and grey); for colour shades other than yellow, brown and grey – from diamonds with colouring in the form of a slight tint (rare white – in accordance with ISO) to diamonds with a slight tint (slightly tinted white – in accordance with ISO), namely the colour standard "J" inclusive);
- Extraordinary colour diamonds – for diamonds with a primary yellow and brown colour – with a colour more intense and/or darker than tinted colour (according to ISO), namely the colour standard “Z”; all diamonds with other colour shades – with a colour more intense and/or darker than lightly tinted white (according to ISO), namely the colour standard “J”.
4.2.2.1. Classification of diamonds and cut diamonds of ordinary colors:
4.2.2.1.1. The determination of the color parameters of diamonds and cut diamonds of ordinary colors is performed by a qualified specialist with normal vision and color perception by comparison with reference samples of diamond color.
4.2.2.1.2. The distance from the light source to the sorting tray should be maintained within 20-25 cm. A decrease in the distance is allowed to confirm color characteristics 1 and 2.
4.2.2.1.3. Samples of reference colours and the sample to be determined are placed on the viewing surface with the pavilion facing up. Inspection is carried out in positions perpendicular to the main face of the pavilion from bottom to top and from top to bottom, then parallel to the plane of the girdle.
4.2.2.1.4. When determining and classifying color, after conducting a visual (organoleptic) comparison with a reference sample, the results of instrumental measurements may be taken into account.
4.2.2.1.5. For stones with an ordinary color that have completely lost their transparency, the corresponding verbal index is indicated in the color definition parameter:
- “white” for stones with color characteristics “1”-“3” (with a weight of less than 0.30 ct.) and “1”-“5” (with a weight of 0.3 ct.) – “D”-“H” (in accordance with ISO);
- “lightly tinted white” for stones with color characteristic “4” (with a weight of less than 0.30 ct.) – “I”-“J” (in accordance with ISO), and “6”-“7” (with a weight of 0.3 ct.) – “I”-“J” (in accordance with ISO);
- “faint” (yellow, brown, gray and other)” for stones with a color characteristic of “5” (with a weight of less than 0.30 ct.) – “K”-“M” (in accordance with ISO), and “8”-“8 faint” (with a weight of 0.3 ct.) – “K”-“M” (in accordance with ISO);
- "slightly color" (yellow, brown, gray and other)" for stones with color characteristics "5" - "6" (with a weight of less than 0.30 ct.) - "N" - "P" (in accordance with ISO), and "8 slightly" (with a weight of 0.3 ct.) - "M" - "P" (in accordance with ISO);
- “slightly color” (yellow, brown, gray and other)” for stones with a color characteristic below “6” (with a weight of less than 0.30 ct.) and “8 light color” (with a weight of 0.3 ct.) – “Q”-“Z” (in accordance with ISO).
4.2.2.1.6. For uncut diamonds in products, for diamonds that have lost a significant part of the surface (with an area greater than one main facet of the crown), as well as for cabochon-cut diamonds and old rose-cut diamonds, the color parameters are not determined.
4.2.2.1.7. When determining the color of a diamond and a cut diamond in a product, the comparison is made with a standard installed in a holder made of metal of the corresponding color, simulating the cast of the product. In this case, the standard is viewed in accordance with the position of the diamond in the product.
4.2.2.1.8. For stones of 0.3 carats and more in size with the color characteristics "8lt" ("8 light [color]") (according to color standard samples "Y" - "Z" in accordance with ISO), fixed in jewelry (if it is impossible to accurately assign to the corresponding group (ordinary or fancy colors - "Fancy light color") without removing from the frame - the color characteristic "Light [color]" ("Light Yellow", "Light Brown", "Light Gray" and others, relative to the main color shade) is indicated).
4.2.2.1.9. Table. Classification of ordinary-color diamonds weighing up to 0.3 ct by color groups in accordance with the STO IGC and the relationship with other grading systems.
ISO/TR 11211:1995 |
MGC-2016 |
GOST R 52913-2008 | ||||||
---|---|---|---|---|---|---|---|---|
Conventional color |
Color Description |
Conventional color |
Color Description |
Conventional color |
Color Description |
|||
D |
Exeptional white + (exclusively white +) |
1 |
Colorless |
1 |
Colorless higher, colorless |
|||
AND |
Exceptional white (exclusively white) |
|||||||
2 |
With a slight tint |
2 |
With a slight tint |
|||||
F |
Rare white + (rare white +) |
|||||||
G |
Rare white (rare white) |
|||||||
3 |
With a slight tint |
3 |
With a slight yellowish, lilac, gray and barely perceptible brown tint |
|||||
H |
White (white) |
|||||||
I |
Slightly tinted white + (with a slight white tint +) |
|||||||
4 |
With a clearly visible shade |
4 |
With clearly visible yellow, lemon, grey and a subtle brown tint |
|||||
J |
Slightly tinted white (with a slight white tint) |
|||||||
5 |
6 |
Yellow – with yellow… color throughout the diamond, as well as a slight brown tint. With visible brown tint and gray |
||||||
K |
Tinted white + (with a white + tint) |
5 5 b, g (brown, grey) |
With a pronounced color shade (yellow, brown, gray and other colors) (yellow, brown, grey) |
|||||
L |
Tinted white (with a white tint) |
|||||||
M |
Tinted color (with a color tint) |
|||||||
7 |
Yellow – with yellow… color throughout the diamond, as well as a slight brown tint. Brown, yellowish-brown, black |
|||||||
N |
|
|||||||
O – P |
Tinted color (with a color tint) |
Very light and lightly colored (yellow, brown, gray and other colors) (yellow, brown, grey) |
||||||
slC b, g Slightly color (brown, grey & other) |
||||||||
Q – X |
||||||||
Y – Z |
Tinted color (with a color tint) |
|||||||
Fancy color |
Fantasy colors Fancy color |
Fantasy yellows |
Notes :
*1) The color range designation using the color index is indicated in reports for color shades other than yellow. The color range designation without the color shade index is used for stones fixed in products, in cases where the color shade of the fixed stone cannot be determined with complete certainty.
*2) In stones with a large number of inclusions that determine the overall perception of color, the color is determined by the overall perception (gray or brown).
*3) Stones of brown and grey colour shades, darker than the colour standard “Z”, not related to fancy colours, as well as stones of black colour, are assigned a descriptive colour characteristic (for example: Light Brown, Brown, Dark Brown)
*4) When determining the color of a diamond in a product depending on the type of setting and its possible influence on the color of the stone, the color characteristics are not placed higher than the gradation “2” (“ F ” according to ISO).
4.2.2.1.10. Table. Classification of ordinary-color diamonds weighing over 0.3 ct inclusive by color groups in accordance with STO IGC-2016 and the relationship with other grading systems.
ISO/TR 11211:1995 |
MGC-2016 |
GOST R 52913-2008 | ||||||
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Conventional color |
Color Description |
Conventional color |
Color Description |
Conventional color |
Color Description |
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D |
Exeptional white + (exclusively white +) |
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1C |
Colorless higher (and also with a shade of blue), without luminescence |
1 |
Colorless higher ones, as well as those with a blue tint |
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1 |
Colorless, luminescence not higher than average |
2 |
Colorless |
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AND |
Exceptional white (exclusively white) |
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2 |
With a subtle hint |
3 |
With a subtle hint |
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F |
Rare white + (rare white +) |
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3 |
With a slight tint of yellowness |
4 |
With a slight tint |
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G |
Rare white (rare white) |
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4 |
With a slight yellowish tint |
5 |
With a slight yellowish tint, and also with a slight brown tint |
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H |
White (white) |
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5 5 b, g |
With visible tint (yellow, brown, gray) (yellow, brown, grey) |
6-0 |
6-1 |
With visible yellow and grey tint With visible brown tint |
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I |
Slightly tinted white + (with a slight white tint +) |
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6 6 b, g |
With a clearly visible shade (yellow, brown, gray) (yellow, brown, grey) |
7 |
With a clearly visible yellow… tint Lightly colored brown |
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J |
Slightly tinted white (with a slight white tint) |
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9-1 |
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7 7 b, g |
With a pronounced color shade |
8-1 |
Very faintly colored yellow
Lightly colored brown |
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K |
Tinted white + (with a white + tint) |
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L |
Tinted white (with a white tint) |
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8 8 y, b, g |
Very lightly colored (yellow, brown, gray and other colors) (yellow, brown, grey & other) |
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8-2 |
9-2 |
Faintly colored yellow Lightly dyed brown |
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M |
Tinted colour (with a color tint)
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9 9 y, b, g |
Lightly colored (yellow, brown, gray and other colors) (yellow, brown, grey & other) |
8-3 |
Lightly colored yellow Lightly dyed brown |
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N |
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8-4 |
9-3 |
Light yellow
Brown |
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O – P |
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slC y, b, g
Slightly color(yellow, brown, grey & other) |
Very light and easy to paint (yellow, brown, gray and other colors)
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8-5 |
Yellow Brown (9-3)
Dark brown (9-4)
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Q – X |
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9-4 |
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Y – Z |
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Fancy Yellow |
Fantasy colors Fancy color |
Fantasy yellows |
Notes:
*1) The color range designation using the color index is indicated in reports for color shades other than yellow. The color range designation without the color shade index is used for stones fixed in products, in cases where the color shade of the fixed stone cannot be determined with complete certainty.
*2) In stones with a large number of inclusions that determine the overall perception of color, the color is determined by the overall visual perception (gray or brown).
*3) Stones of brown and grey colour shades, darker than the colour standard “Z”, not related to fancy colours, as well as black stones, are assigned a descriptive colour characteristic (for example: Light Brown, Brown, Dark Brown).
*4) When determining the color of a diamond in a product, depending on the type of setting and its possible influence on the color of the stone, the color characteristics are not placed higher than the gradation “3” (“ F ” according to ISO).
Comments:
- For stones of 0.3 carats or more in size with a color characteristic of “1” MHC that do not have luminescence or have luminescence that does not exceed the intensity of the characteristic “faint”, an additional group “1C” is introduced, indicating an exceptionally high degree of lack of coloration.
- The color characteristic “Light [colore]” (“Light Yellow”, “Light Brown”, “Light Gray” and others, relative to the main color shade) for stones fixed in jewelry is indicated subject to the fulfillment of points “ 4.2.2.1.8. ”
4.2.2.2. Classification of diamonds and cut diamonds of extraordinary colours.
4.2.2.2.1. The determination of the main classification features and parameters of the colour of extraordinarily coloured diamonds and cut diamonds is carried out by a qualified specialist with normal vision and colour perception by determining the main colour based on the general sensation of colour, taking into account the effects of reflection, absorption, “window”, and cut shape.
4.2.2.2.2. The distance from the light source to the sorting tray should be maintained within 20-25 cm. A decrease in the distance is allowed to identify subtle differences in the sample being determined and the reference sample.
4.2.2.2.3. The diamond sample to be assessed is placed on a V-shaped field with a white matte background, first with the pavilion facing upwards, and the inspection is carried out perpendicular to the main facets of the pavilion. Then the stone is additionally inspected with the crown facing upwards, the stone is inspected perpendicular to the table and additionally perpendicular to the main facets of the crown.
4.2.2.2.4. The color shade of a diamond and cut diamonds is determined on the basis of the Munsell color atlas in accordance with the scale of color shades of diamonds recommended by the GIA ( Table 4.2.2.2.5 ).
4.2.2.2.5. Table. Description of the color shade (Hue) component used in describing the color parameters of extraordinary colored diamonds and cut diamonds.
Abbreviation |
Description |
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English language |
Russian language |
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P |
Purple |
Purple |
rP |
Reddish Purple |
Reddish Purple |
Pink* Brown-purple* |
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RP |
Red-Purple |
Red-Purple |
Pink* Brown-Purple* |
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PR |
Purple-Red |
Purple-Red |
Pink* Brown-Purple* |
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pR |
Purplish Red |
Purple Red |
Pink * Brown-Pink* |
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R |
Red |
Red |
Pink* Brown-Pink* |
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oR |
Orange-Red |
Orange-Red |
Brown-Pink* Brownish Pink* |
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rO |
Reddish-Orange |
Reddish Orange |
Pink-Brown* Pinkish Brown* |
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THE |
Orange |
Orange |
Brown* Brown-orange* |
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yO |
Yellowish Orange |
Yellowish-Orange |
Brown* Brown-orange* |
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THEY |
Yellow Orange |
Yellow-Orange |
Brown* Yellow-Brown* |
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LTD |
Orange-Yellow |
Orange-Yellow |
Brown* Yellow-Brown* |
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Ltd |
Orangу Yellow |
Orangey Yellow |
Brown* Yellow-Brown* |
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AND |
Yellow |
Yellow |
Yellow-Brown* |
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gY |
Greenish Yellow |
Greenish-Yellow |
Brown-Greenish-Yellow* |
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GY |
Green-Yellow |
Green-Yellow |
Brown-Greenish-Yellow* |
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YG |
Yellow-Green or |
Yellow-Green |
Gray-Greenish-Yellow* |
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yG |
Yellowish Green |
Yellowish Green |
Gray-Greenish-Yellow* |
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G |
Green |
Green |
Grey-Green* |
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bG |
Bluish Green |
Bluish Green |
Grey-Green* |
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BG |
Blue-Green |
Blue-Green |
Grey-Green* |
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GB |
Green-Blue |
Green-Blue |
Grey-Blue* |
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gB |
Greenish Blue |
Greenish Blue |
Grey-Blue* |
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B |
Blue |
Blue |
Grey-Blue* |
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vB |
Violetish Blue |
Violet Blue |
Grey-Blue* |
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bV |
Bluish Violet |
Bluish-Violet |
Grey-Violet* |
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V |
Violet |
Violet |
Grey-Violet* |
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Highlighted colors |
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Pk |
Pink* |
Pink* |
Br |
Brown* |
Brown* |
Note:
* The term "Pink" is used for colors with a predominance of the primary spectral color "Red": "Red" tone/saturation – 1-4/1-4, 5/1-2, 3/5; "reddish Purple" tone/saturation – 1-4/1-5; "Red-Purple or Purple-Red" tone/saturation – 1-5/1-6; "strongly purplish Red" tone/saturation – 1-5/1-3, 3-4/3-4; "slightly purplish Red" tone/saturation – 1-4/1-4, 3/5; "orangy Red tone/saturation – 1-3/1-3; "Red-Orange or Orange-Red tone/saturation – 1-5/1-2, 1-3/3.
The term "Brown" is used for colors in the range of primary spectral colors from "Orange" to "Yellow": "Orange"; "yellowish Orange"; "orangy Yellow": "Yellow" tone/saturation – 1-8/1-3.
4.2.2.2.6. If it is necessary to emphasize the influence of the additional color on the main color, additional definitions “slightly, very slightly, strongly, very strongly” can be introduced before the definition of the additional color.
4.2.2.2.7. After determining the “color shade (Hue)” parameter of an extraordinarily colored diamond with a “Tone (Tone)” – “Saturation (Saturation)” ratio not exceeding such ratios in the scale of equivalent colors for ordinary colored diamonds, the color of the diamond is determined based on a comparison with samples of equivalent colors.
4.2.2.2.8. When determining the parameters of color gradation, the sample being determined is placed between two reference samples. Moreover, if the sample being determined is identical to the boundary sample of the reference, the color is determined to be decreasing.
4.2.2.2.9. When determining the color parameters, after conducting a visual (organoleptic) comparison with a reference sample, the results of hardware measurements may be taken into account.
4.2.2.2.10. When determining the parameters of an extraordinary diamond color in a product, additional lateral viewing is required.
4.2.2.2.11. When characterizing the color of extraordinary colored diamonds of natural origin without signs of enhancement, when describing the equivalent color, the following verbal index is indicated:
- “Faint [Colore Hue]” in the range, according to the color standard sample, “K”-“M” (upper part of the range) – in accordance with ISO;
- “Slightly [Colore Hue]” in the range, according to the color standard sample, “M” (lower part of the range) - “X” – in accordance with ISO;
- “Light [Colore Hue]” in the range, according to the color standard sample, “Y”-“Z” – in accordance with ISO;
4.2.2.2.12. For stones with the color characteristics "Light color" (according to the color standard sample "Y" - "Z" in accordance with ISO), fixed in jewelry (if it is impossible to accurately assign to the corresponding group (ordinary or fancy colors - "Fancy light color") without fixing from the frame - the color characteristic is indicated ("Light Yellow", "Light Brown", "Light Gray" and others, respectively, of the main color shade).
4.2.2.2.13. For unmounted diamonds of extraordinary colour of natural origin without signs of enhancement, when describing a colour more saturated or darker than the equivalent colour "Z" (tinted colour - in accordance with ISO), the term "Fancy" is used. The term "Fancy" is not used when describing diamonds whose colour was determined without being removed from the setting.
4.2.2.2.14. When determining the color parameters, the sample being determined is placed between two reference samples. Moreover, if the sample being determined is identical to the boundary sample of the reference, the color is determined downwards. In this case, the diamond sample being evaluated is placed on a V-shaped field with a white matte background with the crown facing up, the stone is examined perpendicular to the table and additionally perpendicular to the main facets of the crown. When classifying the color of the test sample, the results of viewing in the pavilion facing up position may be taken into account.
4.2.2.2.15. The classification of natural fancy-colored diamonds is based on the definition of the main classification features:
- Color shade (Hue);
- Tone;
- Saturation.
4.2.2.2.16. Classification of fancy diamond colors is based on the ratio of the parameters "Tone" - "Saturation" in accordance with the colors of the album of fancy diamond colors of the Gemological Institute of America ("GIA. Colored diamonds. Color Reference Chart."). Additionally used: the Munsell color atlas and standard samples.
4.2.2.2.17. For diamonds without signs of enhancement, the color of which is defined as fancy when describing the color depending on the degree of saturation and tone (in accordance with the position on the color field of the shade), the following evaluation characteristics of fancy color for color shades (Color Hue) are distinguished:
- Fancy Light [Colore Hue];
- Fancy [Colore Hue];
- Fancy Intense [Colore Hue];
- Fancy Vivid [Color Hue];
- Fancy Deep [Colore Hue];
- Fancy Dark [Colore Hue].
4.2.2.2.18. For diamonds that have signs of color enhancement or for which the natural origin of the color cannot be confirmed, when describing the color depending on the degree of saturation and tone (in accordance with the position on the color field of the shade), the following color evaluation characteristics for color shades (Color Hue) are distinguished:
- Light [Colore Hue];
- [Color Hue];
- Intense [Color Hue];
- Vivid [Color Hue];
- Deep [Color Hue];
- Dark [Color Hue].
4.2.2.2.19. When reflecting information about the color of stones with fancy colors, the gemological reports of the IGC separately provide the color hue characteristic (Color Hue) and separately the color evaluation characteristic (Color Grade), based on the “tone/saturation” ratio.
4.2.2.2.20. The term “Fancy” is not used for diamonds that have undergone color enhancement.
4.2.2.2.21. For achromatic diamonds, when classifying the color, the name of the color is indicated, expressed by the verbal definition “black”, “gray” with an indication of the degree of color manifestation, “white”; without using the term “Fancy”.
4.2.3. Classification of diamonds by clarity.
4.2.3.1. The clarity of a diamond for the purposes of compiling a gemological report is determined using a standard triplet jeweler's loupe (with 10x magnification) on a neutral white background, under standard artificial light conditions equivalent to northern daylight (at the equinox at 48° north latitude). For these purposes, the D65 light source (according to the classification of the International Commission on Illumination - CIE) is used.
4.2.3.2. The identification of diamond clarity factors and their classification as significant clarity characteristics is made on the basis of an initial inspection using a standard triplet jeweler's loupe (with 10x magnification), but the final decision is made after a mandatory inspection of the identified inclusions and "clean" areas using a binocular microscope, including in conditions other than standard lighting, based on a secondary study of the clarity characteristics under standard lighting when viewing using a standard triplet loupe.
4.2.3.3. To perform a set of works to determine the purity of a diamond, the following sequence of determining purity factors is provided:
- quantity;
- size;
- contrast;
- view;
- location.
4.2.3.4. The clarity characteristics of a diamond are revealed by examining the stone in the following order:
- playground;
- middle zone (upper wedges and main edge of the crown);
- peripheral zone (lower wedges of the crown)
- round player;
- pavilion.
4.2.3.5. After the clarity factors have been identified, their overall impact on the clarity of the diamond is assessed. When assessing diamonds of boundary clarity groups, it is recommended to compare them with a reference sample that sets the lower limit for the given group.
4.2.3.6. For the purposes of classifying natural diamonds up to 0.30 ct. in size by clarity, the following procedure for determining the quality group* by clarity is adopted (see Table 4.2.3.1.1):
4.2.3.6.1. Clarity group "1" MHC ("LC" - in accordance with ISO/TR 11211:1995, ISO 24016-2020) - Free from defects or having single, very faintly noticeable surface or point defects (not visible at 10x magnification) (clarity quality factors) in the middle zone (visible only when viewing the diamond from its lower part or detected using an arbitration viewing device) and in the peripheral zone (visible only when viewing the diamond from its lower part or detected using an arbitration viewing device).
Significant characteristics of purity: dots, stripes.
4.2.3.6.2. Clarity group "2" MHC ("VVS" - in accordance with ISO/TR 11211:1995) - Diamonds with very slight defects (clarity quality factors) in the middle and peripheral zones. Single, slight defects in the central zone are allowed. Stones belonging to group "c" may have minor natural facets on the side of the pavilion crown and in the girdle plane, noticeable from the side of the crown.
Significant purity characteristics: dots, stripes, cracks (“cleavage”) in the peripheral zone.
4.2.3.6.3. Clarity group "3" MHC ("VS" - in accordance with ISO/TR 11211:1995) - Diamonds with slightly noticeable defects (clarity quality factors) in the middle and peripheral zones, single slightly noticeable defects in the central zone are allowed. For non-round cut stones, a single tiny natural facet (knife) on the surface of the crown in its peripheral part is allowed.
Significant characteristics of purity: dots, stripes, cracks, clouds.
4.2.3.6.4. Clarity group " 4 " MHC ("SI1" - in accordance with ISO/TR 11211:1995) - Diamonds with noticeable defects (clarity quality factors) in any zone, single defects are allowed in the central zone. For stones of this group, single minor natural facets (naifs) on the surface of the crown in its peripheral part or a single one in the middle are allowed.
Significant characteristics of purity: dots, stripes, cracks, clouds.
For the purity group code “4” for unfixed stones, an additional division of the group into two subgroups is adopted:
Without index – for stones with single defects that are barely noticeable to the naked eye. Stones belonging to this subgroup may contain single colored or dark spots in the girdle area that do not affect the appearance and general perception of the stone.
Index "c" ("cloudy") - for stones with a diffuse transparent light cloud of very weakly noticeable few light inclusions and single very weakly noticeable tiny cracks ("cleavage", "crack", "feather"), some of which may be very weakly noticeable under a magnifying glass. Stones belonging to subgroup "c" have inclusions that can form clusters that do not worsen the appearance and general perception of the diamond.
4.2.3.6.5. Clarity group " 5 " MHZ ("SI2" - in accordance with ISO/TR 11211:1995) - Diamonds with defects (clarity quality factors) visible defects, including those slightly visible to the naked eye. For stones of this group, single minor natural facets (naifs) are allowed on the surface of the crown in its middle and peripheral parts, as well as on the pavilion side, visible from the crown side, the total size of which does not exceed 1/5 of the cut facet.
For the purity group code “5” for loose stones, the group is divided into two subgroups:
Without index – for stones with noticeable few light inclusions and single cracks (“cleavage”, “crack”, “feather”), some of which may be very slightly noticeable to the naked eye. Stones belonging to this subgroup may contain a small amount of colored or dark inclusions that do not affect the appearance and general perception of the stone.
Index "c" ("cloudy") - for stones with noticeable few light inclusions and single tiny cracks ("cleavage", "crack", "feather"), some of which may be very slightly noticeable to the naked eye. Stones belonging to subgroup "c" have inclusions that can form clusters that do not worsen the appearance and overall perception of the diamond.
4.2.3.6.6. Clarity group " 6 " MGC ("I1" - in accordance with ISO/TR 11211:1995) - Diamonds with defects (clarity quality factors) that have a moderate negative effect on the appearance of the stone, from slightly noticeable to noticeable to the naked eye, the stones look transparent. For stones of this group, single small natural facets (naifs) on the surface of the crown in its middle and peripheral parts, as well as on the pavilion side, noticeable from the crown side, the total size of which does not exceed the size of 1/3 of the cut facet are allowed.
For the purity group code “6” for loose stones, the group is divided into three subgroups:
Without index – for stones with numerous light inclusions and cracks (“cleavage”, “crack”, “feather”), barely noticeable and/or noticeable to the naked eye. Stones belonging to this subgroup may contain a small number of dark inclusions that do not affect the appearance and general perception of the stone.
Index "c" ("cloudy") - for stones with numerous light inclusions and single cracks ("cleavage", "crack", "feather"), including those that are barely noticeable and/or noticeable to the naked eye. Stones belonging to subgroup "c" have inclusions that form haze-like clusters, moderately worsening the appearance and overall perception of the diamond.
Index "d" ("dark") - for stones with numerous dark inclusions and cracks ("cleavage", "crack", "feather"), including those that are barely noticeable and/or noticeable to the naked eye. Stones belonging to subgroup "d" have a significant number (more than 35% of the total) of dark inclusions that do not affect the appearance and general perception of the stone. Stones belonging to subgroup "d" may have cracks ("cleavage", "crack", "feather") that do not affect the appearance of the stone.
4.2.3.6.7. Clarity group " 7 " MGC ("I2" - in accordance with ISO/TR 11211:1995) - Diamonds with defects (clarity quality factors) that have a strong negative effect on the appearance of the stone or its integrity (including potential), some inclusions are very clearly visible to the naked eye, stones may have significant opaque areas. For stones of this group, significant natural facets (naifs) on the surface of the crown in its middle and peripheral parts, as well as on the pavilion side, visible from the crown side, are allowed.
For the purity group code "7" for loose stones, the group is divided into three subgroups:
Without index – for stones with numerous light inclusions and cracks (“cleavage”, “crack”, “feather”), including those visible to the naked eye. Stones belonging to this subgroup may contain a small number of dark inclusions that do not affect the appearance and general perception of the stone.
Index "c" ("cloudy") - for stones with numerous light inclusions and single cracks ("cleavage", "crack", "feather"), including those visible to the naked eye. Stones belonging to subgroup "c" have inclusions that form clusters in the form of a thick haze, significantly worsening the appearance and overall perception of the diamond.
Index "d" ("dark") - for stones with numerous dark inclusions and cracks ("cleavage", "crack", "feather"), including those visible to the naked eye. Stones belonging to the subgroup "d" have a significant number (more than 35% of the total) of dark inclusions, which significantly worsen the appearance and overall perception of the stone.
4.2.3.6.8. Clarity group " 8 " MGC ("I3" - in accordance with ISO/TR 11211:1995) - Diamonds with defects (clarity quality factors) that have a very strong negative impact on the appearance of the stone and its integrity (including potential). Stones of this clarity group may have natural facets (with a total size greater than the size of the 1st facet of the cut).
4.2.3.6.9. Outside the assessment of quality characteristics of clarity is the group of picked diamonds - " Rej" (" Rejection ") MGC (Not classified - "Rejection" - in accordance with ISO / TR 11211: 1995) - Diamonds with defects (quality factors of clarity), making the stone completely opaque for viewing the facets of the pavilion. Such stones can have multiple natural facets and losses in the form of significant chips (including on the crown). *
Note: * Stones with significant surface chips – greater than the size of one crown facet or with no integrity – are classified as “Faceted diamonds” for the purposes of gemological reporting, with no clarity quality specifications.
4.2.3.6.10. Table. Classification of diamonds weighing up to 0.3 ct by clarity groups in accordance with STO MGTS-2016 and the relationship with other grading systems.
ISO/TR 11211:1995 |
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MGC-2016 |
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GOST R 52913-2008 |
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Conventional designation of purity |
Description of purity |
Conventional designation of purity |
Description of purity |
Conventional designation of purity |
Description of purity |
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LC (FL) |
Loupe Clean ( Flawless ): No internal inclusions or graining visible at 10x magnification. |
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1
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Without defects. Having single, very barely noticeable superficial or point (not visible at 10x magnification) defects (quality factors of cleanliness) in the middle and peripheral zone. |
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1 |
No defects |
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LC (IF) |
Loupe Clean ( Internally Flawless ): No internal inclusions visible at 10x magnification. Surface graining or minor surface defects (blemish) are acceptable. |
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2 |
Having defects: - in the central zone, one light point, visible only when viewing the diamond from its lower part; - or in the middle and peripheral zones no more than two barely perceptible light points, - or one barely perceptible strip |
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Plumbing |
Very , Very Slightly Included : Inclusions are very difficult for an experienced appraiser to detect under 10x magnification. Pinpoint single inclusions are visible from the pavilion side or slightly visible from the crown side and are usually localized in the middle and peripheral zones. |
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2 |
Having very slight defects (quality factors of cleanliness) in the middle and peripheral zones. (Single point slight defects in the central zone are allowed) |
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3 |
Having defects: - in the central zone no more than two minor dark dots; - or in any area no more than four small light spots, - or no more than two stripes, - or one strip and three small light dots; - or one minor crack in the peripheral zone |
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VS |
Very Slightly Included : Inclusions are small and detectable by a trained appraiser under 10x magnification. Typical inclusions include: included crystal, group of pinpoint inclusions, "cloud", "feather". |
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3 |
Having noticeable defects (quality factors of cleanliness) in the middle and peripheral zones, single slightly noticeable defects in the central zone are allowed. |
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4 |
Having defects: - in the central zone there is one small light cloud, - or one small crack, - or no more than three small dark dots; - or in any zone no more than six defects in the form of small light dots and stripes; - or in the middle and peripheral zones no more than three minor cracks |
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5 |
Having defects: - no more than two small graphite inclusions in any zones - or no more than two small cracks; - or one small cloud in combination with a graphite inclusion; - or several small cracks in combination with a graphite inclusion |
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SI1 |
Slightly Included : Inclusions are slight, noticeable for SI1 and very easily visible for SI2 under 10x magnification. Inclusions of the SI group can usually be seen with the naked eye. |
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4
4s («cloudy») |
Having a few obvious defects (quality factors of purity) in any zone (in the central zone, single defects are allowed). Defects are mainly not contrasting. |
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SI2 |
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5
5 c («cloudy»)
5 d («dark») |
Having defects (quality factors of purity) obvious or slightly visible to the naked eye |
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6 |
Having multiple defects: - in any areas in the form of various inclusions and cracks, including those poorly visible to the naked eye |
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I1 |
Included 1: Inclusions visible to the naked eye and having a negative impact on the appearance of the stone. |
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6
6 c («cloudy»)
6 d («dark») |
Having defects (quality factors of clarity) that are barely visible and visible to the naked eye and slightly worsen the appearance of the stone. |
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7 |
Having defects: - in any zones of various types, visible to the naked eye and transparent for viewing at least 60% of the bottom facets of the diamond |
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I2 |
Included 2: Inclusions that are visible to the naked eye and that significantly affect the appearance of the stone or its integrity. |
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7
7 c («cloudy»)
7 d («dark») |
Having defects (quality factors of clarity) visible and visible to the naked eye and noticeably worsening the appearance of the stone or affecting (including potentially) its integrity. |
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8 |
Having defects: - in any zones of various types, visible to the naked eye and transparent for viewing from 60% to 30% of the bottom facets of the diamond |
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9 |
Having defects: - in any zones of various types, visible to the naked eye and transparent for viewing less than 30% of the bottom facets of the diamond |
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I3 |
Included 3: Inclusions visible to the naked eye and having a significant effect on both factors. |
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8
8 c («cloudy»)
8 d («dark») |
Having defects (quality factors of purity) visible and visible to the naked eye and significantly worsening the appearance of the stone, as well as affecting (including potentially) its integrity. |
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Rejection |
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Rej
(Rejection) |
Rich in inclusions
Having defects (quality factors of purity) filling the entire volume of the stone, significantly worsening the appearance of the stone and affecting (including potentially) its integrity.
Diamonds are predominantly transparent to view less than 10% of the pavilion facets or have completely lost transparency - translucent, translucent, opaque. |
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Notes:
*1) When determining the clarity characteristics of a diamond in a product depending on the type of setting and its possible impact on the visibility of potential clarity factors, clarity gradation ratings higher than the ISO gradation of “ 3 ” (“ VS ”) are not given.
4.2.3.7. For the purposes of classifying diamonds of 0.3 ct. inclusive in size by clarity, the following procedure for determining the quality group* by clarity is adopted (see Table 4.2.3.7.13. ):
4.2.3.7.1. Cleanliness group " 1( FL) "* МГЦ ("LC" - in accordance with ISO/TR 11211:1995) - Without defects;
4.2.3.7.2. Clarity group " 1( IF) "* МГЦ ("LC" - in accordance with ISO/TR 11211:1995) - Diamonds with single, very slightly noticeable surface defects (clarity quality factors) in the form of surface graining, light defects indistinguishable under 10x magnification from the pavilion side are allowed. Single light defects localized in the peripheral zone, distinguishable only when viewing the diamond from its lower part and detected using an arbitration viewing device are typical.
Significant characteristics of purity: dots, stripes.
4.2.3.7.3. Clarity group " 2 " MHZ ("VVS1" - in accordance with ISO/TR 11211:1995) - Diamonds with single, very slight internal and surface defects (clarity quality factors) in the form of dots and stripes. Characterized by single, slightly noticeable defects in the peripheral zone, visible from the crown side; or single, pinpoint, very slight defects in the central zone, detectable from the pavilion side or with the help of an arbitration viewing device.
Significant characteristics of purity: dots, stripes.
4.2.3.7.4. Clarity group " 3 " MHC ("VVS2" - in accordance with ISO/TR 11211:1995) - Diamonds with very slight internal and surface defects (clarity quality factors) in the form of dots, very small included crystals, grains, stripes, cracks ("cleavage"). Several slight defects in the volume of the stone are typical, single slight defects in the central zone are allowed, including colored ones. A single crack in the peripheral zone is a determining factor of clarity quality.
Significant clarity characteristics: dots, streaks, included crystal and/or grain, cleavage.
4.2.3.7.5. Clarity group " 4 " MHZ ("VS1" - in accordance with ISO/TR 11211:1995) - Diamonds with single, barely noticeable internal and surface defects (clarity quality factors) in the form of dots, small included crystals, stripes, cracks ("cleavage", "cracks"). Several very barely noticeable defects in the volume of the stone, including colored ones, are typical. Single, very barely noticeable defects in the central zone are allowed. A single, light, barely noticeable cloud in the middle or peripheral zone is a determining factor in the clarity quality.
Significant clarity characteristics: dots, stripes, included crystal and/or grain, cleavage, cracks, cloudiness.
For the purity group code “4”, the group is divided into two subgroups:
- Without index – for stones with single, barely noticeable internal and/or external defects (clarity quality factors) in any zone in the form of tiny dots, stripes, cracks and fissures, microseams and growth lines. Single, very barely noticeable light defects are allowed. Single, very barely noticeable contrasting inclusions or a light, barely noticeable cloud in the middle or peripheral zone are the determining factor of clarity.
- Index "c" (cloudy) - for stones that have a cloud in the volume of the stone that is very faintly visible under a magnifying glass, but somewhat easily detectable when viewed under a microscope at magnification up to 20X . Stones of this category may additionally have defects that are characteristic of the group.
4.2.3.7.6. Clarity group " 5 " MHZ ("VS2" - in accordance with ISO/TR 11211:1995) - Diamonds with a few, barely noticeable internal and surface defects (clarity quality factors) in the form of dots, stripes, cracks ("cleavage", "cracks"), clouds, included crystals and grains, as well as their aggregates, microseams and growth lines. Noticeable scattered defects in the volume of the diamond are typical. Several barely noticeable defects (including colored ones) or single noticeable light defects in the central zone are allowed. The smallest single flat natural facet (knife) in the peripheral zone is allowed.
Significant clarity characteristics: dots, stripes, cleavage, cracks, included crystals and grains, cloud, microseams and growth lines.
For the purity group code “5”, the group is divided into two subgroups:
- Without index – for stones with a few, barely noticeable internal and/or external defects (clarity quality factors) in any zone in the form of small dots, stripes, cracks, clouds, included crystals and grains (as well as their aggregates), microseams and growth lines. Typical are noticeable scattered defects in the volume of the diamond, including single small dark and colored defects, single flat natural facets (knifes) in the peripheral zone.
- Index "c" (cloudy) - for stones that have a very faint "haze" or cloud in the entire volume of the stone under a magnifying glass. Stones of this category may additionally have defects characteristic of the group.
4.2.3.7.7. Clarity group " 6 " MHZ ("SI1" - in accordance with ISO/TR 11211:1995) - Diamonds with a few noticeable and/or one to several obvious internal and/or surface defects (clarity quality factors) in any zone in the form of small dots, stripes, cracks and feathers, included crystals, grains, as well as their aggregates, clouds, microseams and growth lines. Typically, noticeable defects are present in the volume of the diamond or obvious ones in the peripheral zone. Small single flat natural facets (knifes) in the peripheral zone or a single natural facet (knife) in the middle zone are allowed.
Significant clarity characteristics: dots, stripes, cracks and cleavage, included crystals and grains (as well as their aggregates), clouds, microseams and growth lines.
For the purity group code “6”, the group is divided into two subgroups:
- Without index – for stones with few noticeable and/or from single to several obvious internal and/or external defects (clarity quality factors) in any zone in the form of small dots, stripes, cracks and fissures, included crystals and granular grains (as well as their aggregates), clouds, microseams and growth lines. Typical are noticeable and obvious defects in the volume of the diamond, including an insignificant number of dark and colored defects, and single flat natural facets (naifs) in the peripheral zone. Single defects that are barely visible to the naked eye are allowed. Single obvious contrasting inclusions in the central zone are the determining factor of clarity.
- Index "c" (cloudy) - for stones that have a slightly noticeable "haze" throughout the entire volume of the stone. Stones of this category may additionally have defects characteristic of the group.
4.2.3.7.8. Clarity group " 7 " MHZ ("SI2" - in accordance with ISO/TR 11211:1995) - Diamonds with a few noticeable and/or one to several obvious internal and/or surface defects (clarity quality factors) in any zone in the form of small dots, stripes, cracks ("cleavage", "cracks") and single cracks ("feather"), included crystals, grains, as well as their aggregates, clouds, microseams and growth lines. Noticeable defects in the volume of the diamond are characteristic. Single defects, slightly noticeable to the naked eye, in the peripheral zone are allowed. Small single flat natural facets (knifes) in the middle and peripheral zones are allowed.
Significant clarity characteristics: dots, stripes, cleavage, cracks and feathers, included crystals and grains (as well as their aggregates), clouds, haze, microseams and growth lines.
For the purity group code “7”, the group is divided into two subgroups:
- Without index – for stones with few noticeable and/or from single to several obvious internal and/or external defects (clarity quality factors) in any zone in the form of small dots, stripes, cracks and fissures, included crystals and granular grains (as well as their aggregates), clouds, microseams and growth lines. Typical are noticeable and obvious defects in the volume of the diamond, including an insignificant number of dark and colored defects, and single flat natural facets (naifs) in the peripheral zone. Single defects that are barely visible to the naked eye are allowed. Single obvious contrasting inclusions in the central zone are the determining factor of clarity.
- Index "c" (cloudy) - for stones that have a slightly noticeable "haze" throughout the entire volume of the stone. Stones of this category may additionally have defects characteristic of the group.
4.2.3.7.9. Clarity group " 8 " MHC ("I1" - in accordance with ISO/TR 11211:1995) - Diamonds with numerous noticeable and obvious internal and surface defects (clarity quality factors) that have a moderate negative effect on the appearance of the stone. Characterized by a few internal inclusions and cracks ("cleavage", "cracks", "feather"). For stones of this group, noticeable flat natural facets (knifes) in the middle and obvious ones in the peripheral and crown areas are allowed; weakly visible and single defects clearly visible to the naked eye are also allowed. Stones of this group may have chips on the pavilion, not exceeding the size of one facet and visible through the crown.
Significant clarity characteristics: cleavage, cracks and feathers, included crystals and grains (as well as their aggregates), clouds, haze, turbidity, microseams and growth lines.
For the purity group code “8”, the group is divided into three subgroups:
- Without index – for stones with numerous visible and/or several obvious internal and/or external defects (clarity quality factors) in any zone in the form of small dots, stripes, cracks and fissures, included crystals and grains (as well as their aggregates), clouds, microseams and growth lines. Characterized by numerous visible and obvious defects in the volume of the diamond, including dark and colored defects. Several obvious inclusions in the central zone are the determining factor of clarity. Weakly visible and single defects visible to the naked eye are allowed, as well as noticeable flat natural facets (naifs) in the middle and obvious ones in the peripheral and crown zones.
- Index "c" ("cloudy") - for stones with a slightly noticeable "haze" throughout the entire volume of the stone or a slightly noticeable turbidity that cannot be considered a cloud (local, up to 20% of the stone's volume). Stones of this category may additionally have defects characteristic of the group and generally retain a diamond shine.
- Index "d" ("dark") - for stones corresponding to the description of the group "without index", but having a significant number (more than 35%) of dark and color defects (quality factors of clarity), affecting the appearance and general perception of the stone. Stones of this category have defects characteristic of the group.
4.2.3.7.10. Clarity group " 9 " MHC ("I2" - in accordance with ISO/TR 11211:1995) - Diamonds with numerous internal and surface defects (clarity quality factors) visible to the naked eye and negatively affecting the appearance or integrity of the stone (including potential). A characteristic feature is a partial loss of transparency for viewing (at least 50% of the pavilion facets are visible). Stones of this group may have chips on the pavilion and crown that do not exceed the size of one facet and are visible through the crown.
Significant clarity characteristics: dots, stripes, cleavage, cracks and feathers, included crystals and grains (as well as their aggregates), clouds, turbidity, microseams and growth lines.
For the purity group code “9”, the group is divided into three subgroups:
- Without index – for stones with numerous light inclusions and cracks (cleavage, cracks, feather), visible to the naked eye, negatively affecting its appearance, possibly moderate impact on potential integrity. In a diamond, as a rule, there is a loss of transparency, not exceeding 50%. Stones of this category may contain a small number of dark inclusions and retain a diamond shine.
- Index "c" ("cloudy") - for stones with noticeable turbidity in the volume of the stone. Stones of this category may have defects characteristic of the group and may partially lose their diamond shine throughout the entire volume.
- Index "d" ("dark") - for stones corresponding to the description of the subgroup without an index, but having a significant number (more than 35% of the total) of dark and color defects (quality factors of clarity), affecting the appearance and general perception of the stone. The stone may partially lose its diamond shine and play.
4.2.3.7.11. Clarity group " 10 " MHZ ("I3" - in accordance with ISO/TR 11211:1995) - Diamonds with multiple internal and surface defects (clarity quality factors), including those clearly visible and well visible to the naked eye and negatively affecting the appearance, possibly significantly affecting the potential integrity of the stone. A characteristic feature is partial transparency for viewing (from 10 to 50% of the pavilion facets are available for viewing). The stone may partially lose its diamond shine. Stones of this group may have chips on the pavilion and crown (on the crown, not exceeding the size of one facet) and clearly visible through the crown.
Significant clarity characteristics: dots, stripes, cleavage, cracks and feathers, included crystals and grains (as well as their aggregates), clouds, turbidity, microseams and growth lines.
For the purity group code “10”, the group is divided into three subgroups:
- Without index – for stones with numerous light inclusions and cracks (cleavage, cracks, feather), visible to the naked eye, having a negative impact on the appearance of the stone and transparent for viewing from 20 to 50% of the pavilion facets. Defects can also have a negative impact on the potential integrity of the stone. Stones belonging to the subgroup may contain a small number of dark inclusions and partially lose their diamond shine.
- Index "c" ("cloudy") - for stones with significant turbidity in the volume of the stone. Stones of this subgroup may have defects characteristic of the group and significantly lose their diamond shine.
- Index "d" ("dark") - for stones corresponding to the description of the subgroup without an index, but having a significant number (more than 35% of the total) of dark and color defects (quality factors of clarity), affecting the appearance and general perception of the stone. The stone partially or completely loses its diamond shine.
4.2.3.7.12. Outside the assessment of quality characteristics of clarity is the group of picked diamonds - " Rej" (" Rejection ") MHC (Not classified - "Rejection" - in accordance with ISO / TR 11211: 1995) - Diamonds that, in terms of clarity characteristics, do not meet the description for stones of the clarity group " 10 " MHC ("I3" - in accordance with ISO / TR 11211: 1995). These include stones that have completely lost transparency, diamond shine, as a rule, semi-translucent or not translucent. Stones of this clarity group may have multiple natural facets and losses in the form of significant chips (including on the crown) exceeding the size of one facet of the crown or have lost integrity. **
Note:
*For the clarity group code " 1 ", the interval corresponding to the clarity "LC" (in accordance with ISO) is adopted; the division into clarity groups " 1 FL " and " 1 IF " is carried out in accordance with the need for a more detailed distinction between clarity groups for premium-class stones ("1" and "2" - in accordance with GOST, as well as "FL" and "IF" in accordance with the GIA graduation rules)
** Stones with significant surface chips – exceeding the size of one crown facet or having lost integrity – are classified as “Faceted diamonds” for the purposes of compiling gemological reports without specifying quality clarity characteristics.
4.2.3.7.13. Table. Classification of diamonds weighing over 0.3 ct inclusive by clarity groups in accordance with STO MGTS-2016 and the relationship with other grading systems.
ISO/TR 11211:1995 |
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MGC-2018 |
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GOST R 52913-2008 |
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Conventional designation of purity |
Description of purity |
Conventional designation of purity |
Description of purity |
Conventional designation of purity |
Description of purity |
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LC (FL) |
Loupe Clean ( Flawless ): No internal inclusions or graining visible at 10x magnification. |
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1 (FL) |
No defects |
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1 |
No defects |
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LC (IF) |
Loupe Clean ( Internally Flawless ): No internal inclusions visible at 10x magnification. Surface graining or minor surface defects (blemish) are acceptable.
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1 (IF) |
Having very slight, single internal and surface defects (quality factors of purity) in the form of dots or stripes. (Light defects are barely noticeable from the pavilion side, or isolated light defects localized in the peripheral zone) |
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2 |
Having defects: - in the central zone, one light point, visible only when viewing the diamond from its lower part; - or in the middle and peripheral zones no more than two barely perceptible light points, - or one barely perceptible strip |
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VVS1 |
Very , Very Slightly Included 1: Inclusions are very difficult for an experienced appraiser to detect at 10x magnification. Point-like single inclusions are visible from the pavilion side and are usually localized in the middle and peripheral zones.
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2 |
Having single, barely noticeable and very barely noticeable internal and surface defects (quality factors of purity) in the form of dots or stripes. (Light single defects visible from the crown side, including very weakly visible ones in the central zone, or colored single defects in the middle and/or peripheral zones) |
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3 |
Having defects: - in any zone no more than three minor light spots; - or in the middle and peripheral zones no more than two defects in the form of minor dark dots or stripes |
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VVS2 |
Very , Very Slightly Included 2: Inclusions are very difficult for an experienced appraiser to detect under 10x magnification. Pinpoint single inclusions are barely noticeable from the crown side.
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3 |
Having barely noticeable internal and surface defects (quality factors of cleanliness) in the form of dots, stripes, cracks (“cleavage”). (Several light, barely noticeable defects in the volume of the stone. Single color defects in the central zone are allowed. A single crack in the peripheral zone is a determining factor in the quality of purity) |
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4 |
Having defects: - in the central zone no more than two minor dark dots; - or in any area no more than four small light spots, - or no more than two stripes, - or one strip and three small light dots; - or one minor crack in the peripheral zone |
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VS1 |
Very Slightly Included: Inclusions are small and detectable by a trained appraiser under 10x magnification. Typical inclusions include: included crystal, group of pinpoint inclusions, "cloud", "feather".
For the VS1 group, inclusions are less noticeable than for the VS2 class. |
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4 |
Having barely noticeable internal and surface defects (quality factors of cleanliness) in the form of dots, stripes, cracks (“cleavage”, “cracks”), clouds. (Several light, barely noticeable defects in any zone. Several barely noticeable defects in the central zone are allowed, including single color defects. A single crack or cloud in the central zone is a determining factor in the quality of cleanliness) |
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5 |
Having defects: - in the central zone there is one small light cloud, - or one small crack, or no more than three small dark dots; - or in any zone no more than six defects in the form of small light dots and stripes; - or in the middle and peripheral zones no more than three minor cracks |
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VS2 |
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5 |
Having noticeable internal and surface defects (quality factors of purity) in the form of dots, stripes, cracks, included crystals, clouds, micro seams and growth lines. (Light, noticeable, scattered defects in any zone. Several color defects in the central zone are allowed.) |
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6 |
Having defects: - in any areas no more than eight small scattered light defects in the form of dots, stripes, small cracks, bubbles, microseams and growth lines; - or up to five small dark dots; - or one minor graphite inclusion |
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SI1 |
Slightly Included : Inclusions are minor, noticeable for SI1 and very easily noticeable for SI2 at 10x magnification.
SI inclusions can usually be seen with the naked eye. |
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6
6 c («cloudy») |
Having obvious internal and surface defects (quality factors of purity) in the form of small dots, stripes, cracks and fissures (feather), included crystals, clouds, micro seams and growth lines. (Light, noticeable, scattered defects in any area. Defects that are barely noticeable to the naked eye are allowed. A single, obvious contrasting inclusion is the determining factor in the quality of purity). |
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7 |
Having defects: - in any zones no more than eight small scattered defects (including those barely visible to the naked eye) in the form of dots, stripes, small cracks, clouds - or one small graphite inclusion |
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SI2 |
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7
7s («cloudy»)
7 d («dark») |
Having numerous noticeable, obvious internal and surface defects (quality factors of purity), including those that are barely noticeable to the naked eye. |
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7 a |
Having defects: - no more than two small graphite inclusions in any zones - or no more than two small cracks; - or one small cloud in combination with a graphite inclusion; - or several small cracks in combination with a graphite inclusion |
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8 |
Having multiple defects: - in any areas in the form of various inclusions and cracks, including those poorly visible to the naked eye |
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I1 |
Included 1: Inclusions visible to the naked eye and having a negative impact on the appearance of the stone. |
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8
8 c («cloudy»)
8 d («dark») |
Having numerous noticeable, obvious and visible to the naked eye internal and surface defects (clarity quality factors), leaving the diamond transparent to view. |
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9 |
Having multiple defects: - in any zones in the form of various inclusions, cracks or various inclusions in combination with cracks, including those visible to the naked eye |
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10 |
Having defects: - in any zones of various types, visible to the naked eye and transparent for viewing at least 60% of the bottom facets of the diamond |
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I2 |
Included 2: Inclusions that are visible to the naked eye and that significantly affect the appearance of the stone or its integrity. |
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9
9 c («cloudy»)
9 d («dark») |
Having numerous visible internal and surface defects (quality factors of purity), including those visible to the naked eye. Partially opaque (at least 50% of the pavilion faces are visible). |
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11 |
Having defects: - in any zones of various types, visible to the naked eye and transparent for viewing from 60% to 30% of the bottom facets of the diamond |
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12 |
Having defects: - in any zones of various types, visible to the naked eye and transparent for viewing less than 30% of the bottom facets of the diamond |
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I3 |
Included 3: Inclusions visible to the naked eye that have a significant effect on both factors. |
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10
10 c («cloudy»)
10 d («dark») |
Having numerous internal and surface defects (quality factors of clarity), including those clearly visible and well visible to the naked eye and negatively affecting the appearance, possibly significantly affecting the potential integrity of the stone. Partial transparency for viewing is typical (from 10 to 50% of the pavilion facets are available for viewing). The stone may partially lose its diamond shine and/or have chips on the pavilion and crown that do not exceed the size of one facet. |
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Rej
(Rejection) |
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Rej
(Rejection) |
Having numerous internal and surface defects (quality factors of clarity), including those clearly visible and well visible to the naked eye and negatively affecting the appearance and potential integrity of the stone. Partial transparency for viewing is typical (less than 20% of the pavilion facets). The stone may lose its diamond shine and/or have chips on the pavilion and crown that do not exceed the size of one facet. |
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Notes:
*1) When determining the clarity characteristics of a diamond in a product depending on the type of setting and its possible impact on the visibility of potential clarity factors, no grades higher than “ 3 ” (“ VS 1 ” according to ISO) are given.
*2) The designation of the clarity group code using the subgroup index is indicated in reports on loose diamonds.
4.2.3.8. To determine the purity of a loose stone with purity characteristics of " 2 " and higher for diamonds up to 0.3 ct. in size and with purity characteristics of " 3 " and higher for diamonds over 0.3 ct. inclusive ("VVS" and higher in accordance with ISO), a binocular microscope (with a magnification of up to 40x) is used as an arbitration control means. To determine the purity of a loose stone with purity characteristics of " 4 " and higher for diamonds up to 0.3 ct. in size and less than 1.5 mm in diameter, a binocular microscope (with a magnification of up to 40x) is also used as an arbitration control means.
4.2.3.9. To determine the purity of a stone set in a frame with a purity rating of " 4 " and higher for diamonds up to 0.3 ct. in size and with a purity rating of " 5 " and higher for diamonds over 0.3 ct. inclusive ("VS" and higher in accordance with ISO), a binocular microscope (with a magnification of up to 40 times) is used as an arbitration control tool.
4.2.3.10. For black, grey, brown and colourless stones that have completely lost their transparency, purity determination is not performed.
4.2.3.11. For uncut diamonds in products, as well as for cabochon-cut diamonds, old rose-cut diamonds, and diamonds of any cut with chips in the form of loss of 1 or more crown facets (“Facetet diamond”), the purity parameters are not determined.
4.2.4. Classification of diamonds by cut quality.
4.2.4.1. The quality of diamond and cut diamond cuts is determined only for stones provided for examination in loose form with a weight of at least 0.10 ct. For diamonds mounted in jewelry, the quality characteristics of the cut are not determined.
4.2.4.2. When determining the quality of a diamond’s cut, the following are assessed in the gemological report:
- For round diamonds – three parameters:
- Proportions are the relationship between the main elements of cutting that determine the appearance, degree of total internal reflection, brilliance and “play” of a diamond.
- Symmetry is a property that describes the deviation from the norm of various cutting elements and their placement, which affects the appearance, features of brilliance and “play” of a diamond.
- Polishing is the quality of surface treatment of the facets (and girdle) of a diamond, which affects the appearance, shine and “play” of the diamond.
- For diamonds of other shapes and cut diamonds – two parameters:
- Symmetry is a property that describes the deviation from the norm of various cutting elements and their placement, which affects the appearance, features of brilliance and “play” of a diamond.
- Polishing is the quality of surface treatment of the facets (and girdle) of a diamond, which affects the appearance, shine and “play” of the diamond.
4.2.4.3. When determining the quality characteristics of a diamond's cut, the main tool for determining and monitoring the angles of inclination and linear dimensions is the proportionoscope "Megascope. Ogi Sistem Ltd."
4.2.4.4. When checking linear dimensions and proportions, a measuring magnifying glass with 10x magnification and a calibrated ruler with a division value of 0.1 mm, and a measuring electronic micrometer device "Leveridge" are used as additional means of control.
4.2.4.5. When assessing low symmetry and polishing quality, a 10x triplet jeweler's loupe and a measuring loupe with 10x magnification and a calibrated ruler with a division value of 0.1 mm are used.
4.2.4.6. The four-character quality grading is used only for round brilliant diamonds with 57 facets.
4.2.4.7. For round brilliant diamonds with 17 and 33 facets, standardized by the National Standard, in the report of the “extended” format for stones not set in a frame, the “proportions” parameter is assessed, with the recommended proportions accepted as “Excellent”, and the cut that differs from the recommended proportions is assessed in accordance with the assessments of low symmetry and polish as “Very good”, “Good”, “Fair”.
4.2.4.8. When assessing the proportions of round brilliant diamonds with 57 or more facets, depending on the size and weight group, the parameters of the elements of the cutting shapes are taken into account, namely:
For diamonds up to and including 0.99 ct:
- Size of the site;
- Crown angle;
- Pavilion inclination angle;
- Girdle thickness;
- Culet size;
- The sum of the angles of inclination of the root and the pavilion.
For diamonds of 1.00 ct. inclusive and larger:
- Size of the site;
- Crown angle;
- Pavilion inclination angle;
- Crown height;
- Depth of the pavilion;
- Girdle thickness;
- Culet size;
- Overall height;
- The sum of the angles of inclination of the root and the pavilion;
- Height of the upper crown wedges;
- Height of pavilion wedges;
4.2.4.9. The assessment of the proportions of round brilliant diamonds with 57 or more facets is made depending on the size and weight group of the diamond in accordance with the parameters given in tables 4.2.4.10. and 4.2.4.11.
4.2.4.10. Table. Evaluation of the proportions of round brilliant diamonds with 57 facets (Kr-57) and more, up to and including 0.99 ct.
Gradation of quality characteristics |
Weight in carats, inclusive |
Site size, %. |
Crown tilt angle, °. |
Pavilion inclination angle, °. |
Girdle thickness, %. |
Culet size, %. |
Sum of the angles of the corne and the pavilion |
---|---|---|---|---|---|---|---|
Excellent |
to 0.49 |
55-65 |
30-35 |
40-42 |
1,5-3,0 |
≤ 2 |
70-77 |
from 0.49 to 0.99 |
55-65 |
30-35 |
40-42 |
1,5-3,0 |
≤ 1 |
70-77 |
|
Very Good |
to 0.99 |
50-65 |
30-40 |
38-43 |
1,0-5,0 |
≤ 2 |
69-79 |
Good |
to 0.99 |
50-70 |
30-40 |
38-44 |
0,5-6,0 |
< 4 |
68-80 |
Fair |
to 0.99 |
other |
other |
other |
other |
other |
other |
4.2.4.11. Table. Evaluation of the proportions of round brilliant diamonds with 57 facets (Kr-57) and more, with a size of 1.00 ct.
Gradation of quality characteristics Quality parameter |
Excellent |
Very Good |
Good |
Fair |
---|---|---|---|---|
Site size, %. |
55< … <63 |
54≤ … ≤66 |
50< … <70 |
other |
Crown tilt angle, °. |
32≤ … ≤36 |
28≤ … ≤37,7 |
26≤ … ≤40 |
other |
Pavilion inclination angle, °. |
40,5< … ≤41,8 |
39,5< … ≤42,1 |
38,5≤ … ≤43,1 |
other |
Crown height, % |
12,0 – 16,0 |
11,0≤ … ≤18,0 |
9,0≤ … ≤19,5 |
other |
Pavilion depth, % |
43,0 – 44,5 |
41,5≤ … ≤45,0 |
40,0≤ … ≤46,0 |
other |
Girdle thickness, %. |
1,5 – 3,0 |
1,0 – 4,5 |
0,5 – 6,0 |
other |
Culet size, %. |
≤1,0 |
≤2,0 |
2,0≤ ≤4,0 |
other |
Total height, %. |
58,5≤ … ≤62,5 |
55,5≤ … <64 |
53≤ … <67 |
other |
Sum of the angles of the root and pavilion, ° |
72,5≤ … ≤77 |
70≤ … <79 |
68≤ … ≤80 |
other |
Height of the upper crown wedges in profile, % of crown height |
40 – 50 |
40 – 50 |
< 40 и 50 < |
< 40 и 50 < |
Height of pavilion wedges in profile, % of pavilion depth |
75 – 90 |
75 – 90 |
< 75 и 90 < |
< 75 и 90 < |
4.2.4.12. When assessing the symmetry of diamonds, the parameters of the symmetry of the elements of the cutting shapes are taken into account, namely:
- Deviation of the girdle contour in roundness;
- Crown height deviation;
- Deviation in pavilion depth;
- Displacement of the center of the table from the axis of symmetry of the cut;
- Displacement of the culet from the axis of symmetry of the cut;
- Deviation (unevenness) of the site in width;
- Deviation (unevenness) in the thickness of the girdle;
- Deviation (unevenness) in the size of the angles of the crown edges;
- Deviation (unevenness) in the size of the angles of the pavilion faces;
- Violation of rib convergence (visual assessment);
- Violation of the convergence of the edges of the top and bottom (visual assessment);
- Deviation of the shape of the site from the shape of a regular octagon (distortion of the shape of the site);
- Differences in shape and size of symmetrically located edges (visual assessment);
- Curvature (waviness) of the girdle (visual assessment);
- Uneven processing of the girdle (visual assessment);
- Conical girdle (visual assessment);
- Uneven processing of edges and girdle (visual assessment);
- The number of nibs and additional facets (extra facets) and their visibility.
4.2.4.13. The assessment of diamond symmetry is carried out in accordance with the parameters given in Table 4.2.4.14.
4.2.4.14. Table. Evaluation of diamond symmetry.
Gradation of quality characteristics Quality parameter |
Excellent |
Very Good |
Good |
Fair |
---|---|---|---|---|
Deviation of the girdle contour in roundness |
< 1.0%, but not more than 0.1 mm Absent or barely visible |
≤ 1.3%, but not more than 0.1 mm Visible |
≤1,5 % Well visible |
other |
Crown height deviation |
< 1,0 % |
< 2,0 % |
< 5,0 % |
other |
Deviation in pavilion depth |
< 2,0 % |
< 3,0 % |
< 6,0 % |
other |
Offset of the center of the platform from the axis of symmetry of the faceted insert |
≤ 0,5 % |
≤ 1,5 % |
≤ 2,0 % |
other |
Displacement of the culet from the axis of symmetry of the faceted insert |
≤ 0,5 % |
≤ 1,5 % |
≤ 2,0 % |
other |
Total displacement of the culet and platform from the axis of symmetry |
≤ 1 % |
≤ 2 % |
≤ 3 % |
other |
Deviation (unevenness) of the site in width |
< 2,0 % |
< 4,0 % |
< 8,0 % |
other |
Deviation (unevenness) in girdle thickness (in % of diameter)* |
< 1,0 % Absent or barely visible |
< 2,0 % Visible |
< 5,0 % Well visible |
other |
Deviation (unevenness) in the magnitude of the angles of the crown edges |
≤ 1,0 ° |
≤ 2,0 ° |
≤ 4,0 ° |
other |
Deviation (unevenness) in the size of the angles of the pavilion faces |
≤ 1,0 ° |
≤ 2,0 ° |
≤ 4,0 ° |
other |
Failure to bring edges and wedges into a knot (Violation of edge convergence) |
Absent or barely visible (1-2 edges are not brought into a knot) |
Visible (more than 2 edges are not connected into a knot) |
Well visible (more than 2 edges are not connected into a knot) |
other |
Displacement of the ribs and nodes of the crown relative to the ribs and nodes of the pavilion (Violation of the convergence of the edges of the top and bottom), % of the width of the lower wedge of the crown |
Absent or barely visible (1-2 ribs or nodes are displaced up to 10% inclusive.) |
Visible (1-2 ribs or nodes are displaced up to 20 inclusive.) |
Well visible (ribs or nodes are shifted up to 20 inclusive) |
other |
Deviation of the shape of the site from the shape of a regular octagon (distortion of the shape of the site) |
Absent or barely visible |
Visible |
Well visible |
other |
Differences in shape and size of symmetrically located edges and wedges |
Absent or barely visible (1-2 edges or wedges are slightly distorted) |
Visible (more than 2 edges or wedges are distorted) |
Well visible (edges are noticeably distorted) |
other |
Curvature (waviness) of the girdle |
Absent or barely visible |
Visible |
Well visible |
other |
Uneven processing of the girdle |
Absent or barely visible |
Visible |
Well visible |
other |
Conical girdle |
Absent or barely noticeable |
Visible |
Well visible |
other |
Uneven processing of edges and girdle |
Absent or barely visible |
Visible |
Clearly visible |
other |
The number of nibs and extra facets (extra facets) and their visibility |
No more than 4 naifs or extra facets are allowed on the pavilion edges, invisible from the crown side. |
Naifs or extra facets on the pavilion edges visible through the crown are allowed. |
Naifs or extra facets on the crown or clearly visible through the crown are allowed. |
other |
* In percentage terms, the difference between the maximum and minimum values of the girdle thickness deviation for the “Excellent” and “Very Good” quality groups should not exceed 25% and 30%, respectively.
4.2.4.15. When assessing the polishing of round brilliant diamonds with 57 or more facets, the polishing parameters manifested in the characteristics of the external defects of the surface of the cutting elements are taken into account, namely:
- Minor scratches;
- A strike mark (easily visible from the crown side) can be taken into account when assessing clarity;
- "Jagged edges" (easily visible from the crown side can be taken into account when assessing clarity);
- Polishing lines;
- Rib abrasion;
- Grooves and small chips (easily visible from the crown side may be taken into account when assessing clarity);
- Traces of scorch on the surface;
- Traces of laser treatment (easily visible from the crown side can be taken into account when assessing cleanliness);
- Uneven processing of edges and girdle (taken into account when assessing symmetry);
- Additional edges (taken into account when assessing symmetry);
- Naturally occurring characteristics (e.g. surface graining) that are easily visible from the crown may be taken into account when assessing clarity.
4.2.4.13. The polishing of a diamond is assessed based on the external defects identified that can be taken into account when assessing the polishing, and their visibility when viewed through a triplet magnifying glass with 10x magnification in accordance with the parameters given in Table 4.2.4.17.
4.2.4.17. Table. Evaluation of diamond polishing.
Gradation of quality characteristics Quality parameter |
Excellent |
Very Good |
Good |
Fair |
---|---|---|---|---|
Visibility of external defects when viewing the stone through a magnifying glass with 10x magnification |
Defects are absent or are difficult to detect |
Defects are difficult to detect |
Defects are visible under a magnifying glass |
The defects are obvious and easy to detect. |
4.2.4.18. The overall assessment of the cut quality of round brilliant diamonds with 57 or more facets is based on the resulting value reflecting the complex influence of the assessments of the proportions, symmetry and polish quality of the diamond in accordance with the parameters given in Table 4.3.4.19. The resulting complex assessment of the cut quality of diamonds for recording in short form is given as: “Excellent”, “Very Good”, “Good”, “Fair”.
4.2.4.19. Table. Comprehensive assessment of the cutting quality of round brilliant diamonds with 57 facets (Kr-57) and more.
Gradation of quality characteristics Quality parameter |
Polishing and Symmetry | ||||
---|---|---|---|---|---|
Excellent |
Very Good |
Good |
Fair | ||
Proportions |
Excellent |
Excellent |
Excellent |
Very Good |
Good |
Very Good |
Very Good |
Very Good |
Very Good |
Good |
|
Good |
Good |
Good |
Good |
Good |
|
Fair |
Fair |
Fair |
Fair |
Fair |
4.2.4.20. The quality of the cut of stones fixed in a frame is not assessed.
4.2.5. Additional classification features of a diamond.
4.2.5.1. An additional classification feature for the purposes of producing gemological reports in accordance with this standard is fluorescence - luminescence in the ultraviolet spectrum of light (electromagnetic radiation), its color and degree of intensity.
4.2.5.2. Determination of fluorescence parameters for diamonds is performed by a qualified specialist with normal vision and color perception by comparison with reference fluorescence samples.
4.2.5.3. Determination of fluorescence parameters is carried out under ultraviolet illumination with a wavelength of 365 nm using a standard gemological light source with a power of 9-12 watts.
4.2.5.4. Determination of fluorescence intensity is performed in a black box for observing ultraviolet luminescence with the diamond positioned with the platform facing the observer.
4.2.5.5. The classification of the intensity (degree of manifestation) of fluorescence is carried out in accordance with the following gradation based on comparison with reference samples:
- None. Under standard long-wave ultraviolet light conditions, no signs of luminescence are observed when viewed from the site; subtle fluorescence may be observed from the pavilion.
- Faint. Under standard conditions of illumination with a long-wave ultraviolet radiation source, when observed from the site side, a faint fluorescence is observed; from the pavilion side, the fluorescence is clearly visible.
- Medium. Under standard conditions of long-wave ultraviolet light, when viewed from the platform, a distinct fluorescence is observed; from the pavilion, a very distinct glow is observed, partially preventing a through view of the stone.
- Strong. Under standard conditions of illumination with a long-wave ultraviolet radiation source, when observed from the site, a very distinct fluorescence is observed, partially preventing a through view of the stone.
4.2.5.6. The determination of the color shade of fluorescence is carried out in a black box for observing ultraviolet luminescence with the faceted synthetic diamond positioned with the platform towards the luminescence source when viewed through the main faces of the pavilion.
4.2.5.7. In the gemological report for the intensity "Faint" the luminescence color is indicated only if it differs from blue. For the luminescence intensity above "Medium" inclusive - the color shade of the luminescence is indicated in the gemological reports.
4.2.5.8. In the gemological report, luminescence parameters are indicated only for single stones not fixed in a frame, as well as for single central inserts in jewelry weighing from 0.3 ct. inclusive. If there are multiple inserts in the product, luminescence parameters are indicated only for the central insert, which significantly exceeds the side inserts in terms of its size and weight characteristics.
Note to the Standard of the Moscow Gemological Center Organization STO MGC "Diamonds and natural cut diamonds".
Types of diamond enhancement (processing to improve its quality characteristics) and their abbreviated designations for the purposes of compiling gemological reports.
Types of diamond enhancement |
The purpose of beautification |
Conventional designation |
---|---|---|
Laser drilling |
Removal of unwanted inclusions by burning (drilling) with a laser beam in order to improve external perception. |
LD |
Glass Filling |
Filling open cracks and pores with highly refractive amorphous mixtures (glass) in order to mask the cracks. |
GF |
Dyeing of cracks and pores |
Colouring of diamonds with various dyes along cracks and pores in order to change the colour characteristics. |
D |
Colore Glass Filling |
Filling open cracks and pores with highly refractive amorphous mixtures (glass) with an admixture of dye in order to mask cracks and change color characteristics. |
SD |
Surface painting (Coating) |
Surface coloring by applying coloring compounds, building up mineral films and other methods of changing the color of a diamond with foreign dyes in order to change the color characteristics. |
Co |
High temperature treatment (Heating) |
High-temperature treatment of a diamond to change its color characteristics or to fix the effect of other enhancement methods. |
HT |
Irradiation treatment |
Radiation treatment of a diamond to change its color characteristics |
R |
High temperature processing in a high pressure environment (Heating & Pressure) |
High temperature treatment of diamonds in a high pressure environment to change the color characteristics of diamonds |
HPHT |
Color change without specifying the method of action (Treated Color) |
Changing the colour of a diamond or cut diamond by any of the above methods, a combination of them or any other methods not mentioned in this list |
Treated Color |