Company standarts - Synthetic cut diamonds

Standard of the Organization STO "MGTs"
"Synthetic cut diamonds"

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 synthetic 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 unmounted synthetic cut diamonds, as well as synthetic cut diamonds mounted in jewelry, and defines a set of information reflected in gemological reports (conclusions and certificates) in relation to their quality characteristics, classification and terminology. The scope of the standard covers synthetic cut diamonds, including those subjected to various types of refinement.

1.3.  The main provisions of this standard correspond to the international standard ISO/TR 11211-1995 "Grading polished diamonds - Terminology and classification" (ISO/TR 11211:1995 "Grading polished diamonds - Terminology and classification") (hereinafter ISO/TR 11211:1995), the main classification criteria in the sections of competence correspond to or are comparable with those of GOST R 52913-2008 "Diamonds. Classification. Technical requirements." (hereinafter GOST), STO 45866412-17-2015 "Enhanced diamonds. Classification. Technical requirements." 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. Synthetic cut diamond – for the purposes of compiling gemological reports on synthetic diamonds, we use this term to mean a cut synthetic diamond of a round shape (brilliant cut), as well as cut diamonds of other shapes and types of cuts (including mixed ones).

Including:

- Old Rose cut diamonds, which are described (for the purposes of gemological reports) as "Old Rose cut";

- Old Mine cut diamonds;

- Diamond 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 more than one facet (“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 a synthetic cut diamond is the process of establishing the identity of the identified characteristics of the sample under study (here, a synthetic 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 synthetic cut diamonds  – a system for distributing synthetic cut diamonds according to certain classification criteria. (in accordance with GOST R 52913-2008 “Diamonds. Classification. Technical requirements.”)

          3.2.3.  The main classification features of a synthetic cut diamond  are the main quality indicators (4C): mass, color, clarity, cut.

• mass (mass of a synthetic cut diamond)  – the mass of a synthetic 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 synthetic cut diamond)  is one of the main classification features of a synthetic cut diamond, characterized by the relative absence (colorless) or presence of natural color in a synthetic cut diamond, based on its property to evoke a certain visual sensation, due to its spectral characteristics in the visible range of the spectrum.
• Clarity (clarity of a synthetic cut diamond)  is one of the main classification features of a synthetic cut diamond, characterized by the absence or degree of manifestation of internal and/or external defects.
• cutting (cutting of a synthetic cut diamond)  is one of the main classification features of a synthetic cut diamond, characterized by the type and quality of diamond processing for the purpose of obtaining cut stones.

(GOST R 52913-2008 "Diamonds. Classification. Technical requirements", ISO/TR 11211-1995, ISO 24016-2020)

          3.2.4. Additional classification features of synthetic cut diamonds – an additional classification feature is fluorescence (luminescence in the long-wave range of the ultraviolet spectrum (315-390 nm) of light [electromagnetic radiation], its color and degree of intensity).

          3.2.5. Classification of the color of a synthetic 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 synthetic 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. (in accordance with GOST R 52913-2008 "Diamonds. Classification. Technical requirements", ISO / TR 11211-1995, ISO 24016-2020)   

               3.2.5.1. Ordinary color of a synthetic cut diamond is the color of a synthetic cut diamond that, in terms of its parameters (color shade, tone, saturation), corresponds to the color standard samples, graded from the value “D” to the value “Z” inclusive for brilliant-cut diamonds of yellow, brown and gray color shades, as well as for other colors from the value “D” to the value “J” inclusive.

               3.2.5.2.  Extraordinary color of a synthetic cut diamond is the color of a synthetic cut diamond that differs in its characteristics (color shade) from ordinary colors of a synthetic cut diamond.

               3.2.5.3. Colored synthetic cut diamond - a cut synthetic diamond of extraordinary color, which in its characteristics (tone, saturation) differs from other colors of synthetic cut diamond by its location in the color field, namely, it is located within the blocks of cut diamonds of fancy color.

                    3.2.5.3.1.  Color classification of colored synthetic cut diamonds  –  Color classification of colored synthetic cut diamonds 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 a synthetic cut diamond in a color field within blocks of fancy colored cut diamonds. For the purpose of color classification of synthetic cut diamonds, both organoleptic and instrumental methods of analysis are used.  

                    3.2.5.3.2. Main classification features of color of colored synthetic cut diamond : 

 -   Hue – A component of the color of a synthetic cut diamond, characterized by the presence of a natural color in it, different from white, gray and black colors, 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 synthetic cut diamond on an achromatic scale (white-gray-black), which determines the conditional amount of “lightness” or “darkness” in the color of the stone.

-   Saturation – A component of the color of a synthetic cut diamond that distinguishes it from an achromatic diamond 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.

          3.2.6.  Clarity classification of synthetic cut diamonds – 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. (in accordance with GOST R 52913-2008 “Diamonds. Classification. Technical requirements”, ISO/TR 11211-1995)

(GOST R 52913-2008 "Diamonds. Classification. Technical requirements", ISO/TR 11211-1995, ISO 24016-2020)

               3.2.6.1. Significant clarity characteristics  of a synthetic cut diamond are all detectable (visible or noticeable when viewed through a 10x triplet jeweler's loupe) clarity characteristics located inside or partially inside a synthetic cut diamond, which include visually apparent defects that affect its transparency.

               3.2.6.2. Characteristics of purity  by origin  are divided into:

• inclusions, namely: light, colored and dark volumetric inclusions, dots, clouds, graining (expressed in color or in the structure of synthetic 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)

               3.2.6.3. Characteristics of purity according to the degree of penetration into the volume of the stone  can be:

• internal - located entirely inside the stone, and also partially extending onto its surface;
• external – located on the surface of the stone 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)

               3.2.6.4.  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 a cut diamond through a magnifier.
• Subtle – Inclusions that can be detected by a trained expert through a 10x triplet jeweler's loupe during careful inspection of a cut diamond.
• Noticeable - Inclusions that can be easily detected by a trained expert using a 10x triplet jeweler's loupe when examining a cut diamond.
• Obvious - Inclusions that can be easily detected by a trained expert through a 10x triplet jeweler's loupe during a cursory inspection of a cut 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 visible to the naked eye.
  

A distinction is made between :Faintly visible – those that were discovered when viewed with a magnifying glass and which can then be seen with the naked eye; Visible – those that were discovered when viewed carefully; Clearly visible – those that can be easily detected with the naked eye; Well visible – those that can be detected when looking at the stone at a glance.

          3.2.7. Determining the quality of the cut of a synthetic  diamond  is a sequence of actions in a set of works to establish the overall quality of the result of the work on cutting a synthetic diamond, which consists of the qualitative relationships of proportions, symmetry of the cutting and polishing elements.

               3.2.7.1. Proportions of a synthetic  cut diamond  – a property of the cut of a synthetic cut diamond, manifested in the ratio of the metric characteristics of the cutting elements, determining the property of total internal reflection, brilliance and play of the synthetic diamond.

               3.2.3.3.2. Symmetry of a synthetic  cut diamond  is a property of the cut of a synthetic cut diamond that describes the deviation from the norm of the ratio of the cut elements and the differences in their metric parameters and location.

               3.2.7.3. Polishing of a synthetic  cut diamond  is a property of the cut of a synthetic cut diamond that describes the processing of the edges, as well as the presence or absence of traces of processing on the edges.

     

4. Testing and control methods

Before starting work on identifying a cut synthetic diamond and classifying its quality characteristics, for the purposes of producing gemological reports, all cut synthetic diamonds and jewelry items are subject to mandatory cleaning.

All work on identification of synthetic diamond cut and classification of 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 cut synthetic diamonds is carried out in the following order:

1) Carrying out a set of diagnostic works (determining the material and the nature of the origin of the material from which the cut diamond is made (natural or synthetic) and identifying signs of refinement;

2) Carrying out a range of works on the classification of cut synthetic diamonds:

2-1) Carrying out a range of works on the classification of synthetic diamonds cut by weight and size-weight characteristics;

2-2) Carrying out a range of works on classifying synthetic diamonds cut by color;

2-3) Carrying out a range of works on classifying synthetic diamonds cut by purity;

2-4) Conducting a set of works on the classification of synthetic diamonds cut by cutting quality;

2-5) Carrying out a set of works on classification of luminescence of cut synthetic diamonds.

     4.1. Sequence of work on diagnostics of cut synthetic diamonds.

 The purpose of this set of works is to identify imitations and separate cut diamonds into natural diamonds and cut synthetic 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 cut synthetic diamonds is carried out on a uniform basis.

           4.1.1.  A preliminary inspection of the insert material 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 diamond - the presence of optical anisotropy, indirect signs of low (compared to diamond) hardness, and optical effects that are not characteristic of diamond, or indirectly indicate 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 diamond tester (based on determining the thermal conductivity property), 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 or another appropriate detector.

           4.1.4.  After fulfilling the requirements of paragraphs 4.1.2., 4.1.3., a microscopic examination of the diamond is carried out (if necessary, in an immersion medium), which includes studying the appearance of internal inclusions, the optical properties of the diamond, color zoning, fluorescence zoning, and determining the presence of substances that are not characteristic of natural diamonds (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 level of spectral methods, identifying possible refinement, and confirming the determination of origin (natural or synthetic).

          4.1.6.  The nature of the origin of a loose diamond and/or a cut diamond must be indicated in the name (Natural diamond, Synthetic diamond), and the fact, type and degree of refinement - in the comments. If it is impossible to unambiguously determine the nature of the origin of a diamond in a 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 a 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 based on 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. The procedure for carrying out a set of works on the classification of cut synthetic diamonds.

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 - "Synthetic cut diamonds (ordinary and extraordinary colors)", "Synthetic cut diamonds that have undergone treatment".

The origin of the 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 the qualification of a cut synthetic diamond involves the following sequence:

- Determination of the mass of a cut diamond and/or its 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 synthetic diamonds cut by mass and size-weight parameters.

          The mass of a cut synthetic diamond is one of its most important evaluation characteristics. In the absence of the possibility of direct weighing based on the measurement of linear parameters, a calculation of the size-weight parameter is made - "estimated weight of the diamond".

               4.2.1.1.   For the purposes of compiling gemological reports, the following categories of cut synthetic diamonds by weight are distinguished:

                - Small – 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 – with a weight of over 1.00 ct inclusive (with a standard diameter of a perfectly cut round diamond of 6.45 mm).

                4.2.1.2.  The mass of an unmounted synthetic cut diamond is determined by weighing the stone on an analytical scale with an accuracy class of at least III.

                4.2.1.3.  The mass of a cut synthetic diamond installed in a product is determined by calculation. In this case, all measurements are made using a micrometer device of the "Leveridge" type, and if the stone is unavailable for measurement, the linear dimensions are determined using a measuring magnifying glass with a resolution of 10 ^X and a scale division of at least 0.1 mm. The error in determining the mass of a stone available for standard measurements and inspection does not exceed 5%. If access to the stone is limited or there is no possibility of taking 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 mass of a synthetic cut diamond is expressed in hundredths of a carat in a gemological report.

                4.2.1.5.  When reflecting the mass in the gemological report, the rule of rounding the third nine is used (for example, if the weight of the stone is 0.999 ct, then the size of 1.00 ct will be indicated in the gemological report).

                4.2.1.6.  To facilitate the identification of a synthetic 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 10 ^X 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 synthetic diamonds cut according to color characteristics.

          The colour of a cut synthetic diamond is determined by an organoleptic method by an experienced appraiser, while the following lighting conditions are met: 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 (according to the classification of the International Commission on Illumination - CIE) is used.

          Additionally, hardware methods for color determination can be used.

          The color of a synthetic diamond cut for the purposes of gemological reports is described taking into account the distinction of two main groups: 

          - Ordinary colour diamonds – diamonds with a colour ranging from colourless (exceptional white – in accordance with ISO) to lightly tinted (tinted colour – in accordance with ISO, namely the colour equivalent standard “Z” inclusive);

          - Colored diamonds are diamonds with a coloration more intense and/or darker than lightly colored ones (tinted color – in accordance with ISO, namely the color equivalent standard “Z” inclusive).

               4.2.2.1.  Classification of synthetic diamonds of cut ordinary colors:

                    4.2.2.1.1.  Determination of color parameters for synthetic diamonds of cut ordinary colors is performed by a qualified specialist with normal vision and color perception by comparison with reference color equivalent samples. 

                    4.2.2.1.2.  The distance from the light source to the sorting tray must be maintained within 20-25 cm. A reduction in the distance is allowed to confirm the color characteristics of 1C, 1 and 2 that do not have luminescence or have weak luminescence (faint).

                    4.2.2.1.3.  Samples of standard colours of cut diamonds and the sample to be determined are installed on the viewing surface with the pavilion facing up. The 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 from bottom to top and from top to bottom.

                    4.2.2.1.4.  When determining the color, after conducting a visual (organoleptic) comparison with the reference sample, the results of instrumental measurements may be taken into account.

                    4.2.2.1.5.  For uncut synthetic diamonds in products, for cut synthetic 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 synthetic diamonds of cabochon cut and old rose cut (“Old Rose cut”), the color parameters are not determined.

                    4.2.2.1.6.  When determining the color of cut synthetic diamonds in a product, the comparison is made with a standard of equivalent color 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 cut synthetic diamond in the product.

                    4.2.2.1.7. The color of ordinary colored synthetic cut diamonds is classified using descriptive terms (Table 4.2.2.1.8 ):

•  Colorless
• Near colorless
• With a slight tint (Faint)
• Very light tint
• With a light tint (Light)

                     4.2.2.1.8. Table.  Classification of cut diamonds from synthetic raw materials by color groups in accordance with STO MGC.

Note :  When determining the color of a synthetic cut 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 “ NC ” (“ Near colorless ” according to ISO).

               4.2.2.2. Classification of synthetic diamonds cut extraordinarily colored (including colored):

                    4.2.2.2.1.  The determination of the main classification features and color parameters of cut extraordinary colored, including colored synthetic diamonds is performed by a qualified specialist with normal vision and color perception by determining the main color of the cut diamond, based on the general sensation of the color of the cut synthetic diamond, 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 assessed sample of cut colored synthetic diamond is placed on a V-shaped field with a white matte background, crown up, the stone is examined perpendicular to the field and additionally perpendicular to the main facets of the crown.

                    4.2.2.2.4.  The assessed sample of a cut, extraordinarily colored synthetic diamond (excluding colored diamonds) is placed on a V-shaped field with a white matte background, pavilion facing upwards; the stone is inspected perpendicularly to the main facets of the crown from bottom to top and from top to bottom, and then parallel to the plane of the girdle.

                    4.2.2.2.5.  The color shade of a cut synthetic diamond 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 4.2.2.2.6 ).

                    4.2.2.2.6.  Table. Description of the color shade (Hue) component used to describe the color parameters of synthetic cut diamonds of extraordinary color, including colored ones.

Notes:

*1) 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.

*2) The term for the primary color "Brown" is used for "warm" colors in the range of primary spectral colors from "Orange" to "Yellow": "reddish Orange", "Orange", "yellowish"  Orange », «orangy Yellow», «Yellow» tone/saturation – 1-8/1-3;

                     4.2.2.2.7.  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.

                     4.2.2.2.8.  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 parameters of color gradation, 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.  The colour of cut extraordinary coloured (excluding coloured) synthetic diamonds is classified using descriptive terms followed by the addition of a colour description (Table 4.2.2.2.11 ):

                     - With a slight tint (Faint);

                     - With a very light tint (Very light)

                     - With a light tint (Light)

                     4.2.2.2.11. Table. Classification of extraordinarily colored cut diamonds from synthetic raw materials by color groups in accordance with STO MGTS.

                    4.2.2.2. 12.  When determining the color gradation parameters of cut colored synthetic diamonds in a product, additional lateral viewing is used.

                    4.2.2.2.13.  The classification of the color of synthetic extraordinarily colored (including colored) colored cut diamonds is based on the definition of the main classification features:

• Color shade (Hue);
• Tone;
• Saturation.

                    4.2.2.2.14.  The classification of the color of cut colored synthetic diamonds is based on the ratio of the parameters "Tone" - "Saturation" in accordance with the colors of the album of fancy colors of diamonds of the Gemological Institute of America ("GIA. Colored diamonds. Color Reference Chart."). Additionally used: the Munsell color atlas and standard samples. 

                    4.2.2.2.15.  For colored synthetic cut diamonds, 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 characteristics are distinguished:

• Light [Color];
• [Color];
• Intense [Color];
• Vivid [Color];
• Deep [Color];
• Dark [Color];

                    4.2.2.2.16.  For synthetic cut diamonds of achromatic colors, 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”.

               4.2.3. Classification of synthetic diamonds cut by purity.

                    For the purposes of classifying cut diamonds from synthetic raw materials by purity, the following procedure for determining the quality group by purity* is adopted (see Table 4.2.3.7):

                    4.2.3.1.  Purity group " FI " MHC – Without defects;

                    4.2.3.2.  Clarity group " VVL I " MGC - Cut diamonds with very slight point or surface defects (clarity quality factors) in the middle zone (distinguishable only when viewing the cut diamond from its lower part) and in the peripheral zone. Single point, very slight defects in the central zone are allowed.

Significant characteristics of purity: dots, stripes.

                    4.2.3.3.  Clarity group " VL I " MGC - Cut diamonds with slightly noticeable defects (clarity quality factors) in the middle and peripheral zones. Single, slightly noticeable point defects in the central zone are allowed.

Significant clarity characteristics: dots, stripes, cleavage.

                    4.2.3.4.  Clarity group " L I " MGC - Cut diamonds with noticeable defects (clarity quality factors) in the middle and peripheral zones; single noticeable defects in the central zone are allowed.

Significant characteristics of purity: dots, stripes, cracks, clouds.

                    4.2.3.5.  Clarity group " I " MGC - Cut diamonds with obvious defects (clarity quality factors) in any zone, single defects are allowed in the central zone. Inclusions may be slightly visible to the naked eye. 

                    4.2.3.6.  Clarity group " HI " MGC - Cut diamonds that have outstanding defects (clarity quality factors) noticeable or visible to the naked eye.

                    4.2.3.7.  Table. Classification of cut diamonds from synthetic raw materials by purity groups in accordance with STO MGTS.

 Note:  When determining the clarity characteristics of a cut diamond in a product depending on the type of setting and its possible influence on the visibility of potential clarity factors, clarity gradation ratings higher than the “ VLI ” gradation (“ VL ” according to ISO/TR 11211-1995) are not given.

 

               4.2.4. Classification of cut diamonds from synthetic raw materials by cutting quality.

                    4.2.4.1.  The quality of cut of synthetic diamonds 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 cutting of synthetic diamonds cut in the “standard” format report, the following are assessed:

                   - For round brilliant-cut synthetic diamonds – three parameters: 

                        - Proportions – the relationship between the main elements of cutting, which determine the appearance, degree of total internal reflection, brilliance and “play” of a cut synthetic 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 cut synthetic diamond;

                        - Polishing is the quality of surface treatment of the facets (and girdle), which affects the appearance, shine and “play” of a cut synthetic diamond.

                  - For cut synthetic diamonds of other shapes – 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 cut synthetic diamond;

                       - Polishing is the quality of surface treatment of the facets (and girdle), which affects the appearance, shine and “play” of a cut synthetic diamond.

                 4.2.4.3.  When determining the characteristics of cutting quality, the main means 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 grading system for assessing the quality of cut is used only for round brilliant-cut synthetic diamonds with 57 facets.

                 4.2.4.7.  For round brilliant diamonds with 17 and 33 facets, in reports for loose stones, the parameter "proportions" is assessed, with the recommended proportions accepted as "Excellent", and a cut that differs from the recommended proportions may be assessed in accordance with the symmetry and polish assessments as "Very good", "Good", "Fair". 

                 4.2.4.8.  When assessing the proportions of a round brilliant-cut synthetic diamond with 57 or more facets, depending on the size and weight group, the parameters of the cutting shape elements are taken into account, namely:

                 - For stones up to and including 0.99 ct:

                      - Size of the site;

                      - Crown inclination angle;

                      - Pavilion tilt angle;

                      - Thickness of the girdle;

                      - Culet size;

                      - The sum of the angles of inclination of the root and the pavilion.

                 - For stones of 1.00 ct. inclusive and larger:

                      - Size of the site;

                      - Crown inclination angle;

                      - Pavilion tilt angle;

                      - Crown height;

                      - Depth of the pavilion;

                      - Thickness of the girdle;

                      - 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 the pavilion wedges;

               4.2.4.9.  The assessment of the proportions of round brilliant-cut synthetic diamonds with 57 or more facets is made depending on the size-weight group 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 a faceted synthetic diamond of round brilliant cut with 57 facets (Kr-57) and more, up to and including 0.99 ct.

                4.2.4.11.  Table. Evaluation of the proportions of a faceted synthetic diamond of round brilliant cut with the number of facets – 57 (Kr-57) and more, of size from 1.00 ct.

 

               4.2.4.12.  When assessing the symmetry of a cut synthetic diamond, the parameters of the symmetry of the elements of the cutting shapes are taken into account, namely:

               - Deviation of the girdle contour in roundness;

               - Deviation in crown height;

               - Deviation in the depth of the pavilion;

               - Displacement of the center of the platform 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 edges (extra facets) and their visibility.

               4.2.4.13.  The symmetry of a cut synthetic diamond is assessed in accordance with the parameters given in Table 4.2.4.14.

               4.2.4.14. Table. Evaluation of symmetry of cut synthetic diamond.

                             Note: * In percentage terms, the difference between the maximum and minimum values ​​of 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 a cut synthetic diamond, 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;

                - Impact marks (easily visible from the crown side can be taken into account when assessing purity);

                - "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 can be taken into account when assessing purity);

                - Traces of burning on the surface;

                - Traces of laser treatment (easily visible from the crown side can be taken into account when assessing purity);

                - Uneven processing of edges and girdle (taken into account when assessing symmetry);

                - Additional faces (taken into account when assessing symmetry);

                - Characteristics of natural origin (for example, surface graining - easily visible from the crown side - can be taken into account when assessing clarity); 

               4.2.4.16.  The polishing of a cut synthetic 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 polishing of cut synthetic diamond.

               4.2.4.18.  The overall assessment of the cutting quality of a round brilliant-cut synthetic diamond with 57 or more facets is based on the resulting value reflecting the complex influence of the assessments of the proportions, symmetry and polishing quality of the diamond in accordance with the parameters given in Table 4.2.4.19. The resulting complex assessment of the cutting 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 quality of a round brilliant-cut synthetic diamond with 57 facets (Kr-57) or more.

                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 cut synthetic 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 shade and degree of intensity).

                4.2.5.2.  Determination of fluorescence parameters for cut synthetic 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 faceted synthetic 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 lighting conditions with a long-wave ultraviolet radiation source, no signs of luminescence are observed when viewed from the site; subtle fluorescence may be observed from the pavilion.

                - weak (Faint); Under standard lighting conditions 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 lighting conditions with a long-wave ultraviolet radiation source, 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 lighting conditions 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.  The gemological report for a cut synthetic diamond indicates the intensity of luminescence and its color shade.

               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.