Certificates explanation
In this section we provide a detailed explanation of the different fields that make up our IGE diamond and coloured stone certificates.
Diamond certificate
1. IGE report number / date
By providing this number you will be able to request the details of any certificate that has been issued by this laboratory. At the IGE we keep copies of all the documents issued over more than 50 years of operation of our Laboratory. This number can also be used to access the certificate data through our section Report check if it has been issued since 2015.
2. Nature
The nature is indicated: natural diamond or synthetic diamond.
3. Shape / cut
Shape refers to the appearance of the outline of the gemstone (round, oval, rectangular, square, triangular, etc.) in the girdle plane.
The cut reflects standards followed in the stoning process, in terms of the number and arrangement of the facets (brilliant, emerald, princess, radiant, barion, etc.).
4. Measurements
Measurements are determined in millimetres with a Leveridge precision gauge to two decimal places.
In the most common case, the round brilliant cut, several measurements are made of the diameter of the diamond and the maximum and minimum values obtained are considered. The height is then measured.
For the other sizes, the three main measurements are given: length, width and height.
5. Weight
The unit of weight used for gemstones is the carat, which is equivalent to 0.2 grams.
For the indication of the weight on the certificate, no arithmetical rounding is carried out, the third decimal place is only rounded up to the upper hundredth if it is a nine (this is a general rule for all international laboratories). For example:
1.498 ct are 1.49 ct on the certificate
1.499 ct are 1.50 ct on the certificate
6. Color
Colour is one of the most important characteristics that affects the quality of the gemstone. Under this aspect, the diamond is classified into two groups: colourless diamonds and fancy coloured diamonds. The quality is evaluated completely differently in each group.
The vast majority of cut diamonds belong to the group of colourless diamonds. Of these, most belong to the well-known Cape series. Diamonds in this group have a characteristic straw yellow hue. The best quality is considered to be those with the least saturation of this characteristic hue.
In the IGE laboratory, as in other recognised laboratories, the determination of the colour grade is carried out by visual comparison with a standard diamond scale, under conditions adopted under international criteria.
The IGE laboratory's standard scale consists of nine round brilliant-cut standards. All of them are contrasted with CIBJO and HRD scales.
Some diamonds have the property of displaying colour with sufficient saturation and purity to be referred to as fancy coloured diamonds.
The certificates for these specimens indicate next to the colour: the secondary shade, if applicable; an adjective indicating the intensity; the term 'fancy' and the adjective 'natural' or 'treated', depending on the determination of the origin of the colour. For example: "Fancy intense blue, natural".
7. Clarity
One of the most important quality characteristics of a diamond is its purity. This term defines the degree of transparency and internal cleanliness of the gemstone. The degree of purity is primarily determined by the presence, more or less overt, of "inclusions". It has been adopted by international convention that a diamond is 'pure' when it shows no inclusions when viewed at ten times magnification by an expert, using a loupe corrected for chromatic aberration and sphericity.
Purity classification is done by applying the CIBJO and ISO nomenclature.
8. Fluorescence
Fluorescence is observed with ultraviolet light of 365nm wavelength.
The fluorescence intensity is determined by comparison with a contrasted diamond standard scale, consisting of three blue fluorescence diamonds, using the following graduation: none, slight, medium, strong.
Examples: “fluorescence: none”, “fluorescence: slight, bluish”
9. Cut grade
In this section the cut grades assessed on the basis of its proportions.
The cut parameters are assessed with the grades: excellent, very good, good, fair y poor.
10 y 12. Proportions
The cut reflects standards followed in the stoning process. In relation to the diamond, these standards are extraordinarily severe in the brilliant (round) cut. The proximity of the proportions of the diamond to the optimal cut dimensions has a great influence on the appearance of the stone, which is why the data on the proportions of the stone are included in the certificate, being an important parameter of quality.
11. Symmetry / polish
This term contains characteristics that reflect, on the one hand, the skill and experience of the cutter and, on the other hand, the care received by the gemstone afterwards.
13. Inclusions
The types of inclusions (impurities) found in the analysed diamond are listed.
14. Comments
This section of the certificate reflects those data that, due to their special objectivity, deserve to be indicated, as well as any other aspect that needs to be highlighted, such as treatments, inscriptions on the girdle, etc.
15. Photograph
A photograph of the gemstone is included in this section. You can find it in higher resolution by accessing, with the certificate number, at Report check.
16. QR code
By scanning the QR code you can verify the authenticity of the certificate and find more information about the quality references.
17. Signature
Signature of the responsible Chief Gemologist.
18. Diagram
In the purity grading process, visibility is the only determining criterion, the most important factors being: appearance, size, number and relative location. Calibration devices are not used to measure inclusions.
The certificate shows the drawings of the gemstone, one seen from the crown and the other from the pavilion. This is indispensable for the objective grading of the purity. It is also a great help to identify the gemstones in a second examination.
In the drawings, internal inclusions are shown in red and external defects in green. All inclusions which are on the upper side are drawn on the crown diagram, as well as those which, being on the lower side, are clearly visible through the crown. All inclusions that reach the surface of the cylinder head or those that are only visible through the surface of the cylinder head are drawn on the cylinder head diagram.
The certificate also includes a proportions chart, which shows the proportions of the certified stone. It is these proportions that determine the cut grade.
Coloured stone certificate
1. IGE report number
By providing this number you will be able to request the details of any certificate that has been issued by this laboratory. At the IGE we keep copies of all the documents issued over more than 40 years of operation of our Laboratory. This number can also be used to access the certificate data through our section Report check if it has been issued since 2015.
2. Species / variety
This is the most important piece of information on the certificate as it defines the authenticity and origin of the gemstone, i.e. the mineral or gemstone in question and whether it is natural or synthetic (artificial).
3. Shape & cut
Shape refers to the appearance of the outline of the gemstone (round, oval, rectangular, square, triangular, etc.) in the girdle plane.
The cut reflects standards followed in the stoning process, in terms of the number and arrangement of the facets (brilliant, emerald, princess, radiant, barion, etc.).
4. Weight
The unit of weight used for gemstones is the carat, which is equivalent to 0.2 grams.
For the indication of the weight on the certificate, no arithmetical rounding is carried out, the third decimal place is only rounded up to the upper hundredth if it is a nine (this is the general rule for all international laboratories). For example: 1.498 ct is 1.49 ct on the certificate, or 1.499 ct is 1.50 ct on the certificate.
5. Measurements
Measurements are determined in millimetres with a Leveridge precision gauge to two decimal places.
In the most common case, the round brilliant cut, several measurements are made of the diameter of the diamond and the maximum and minimum values obtained are considered. The height is then measured.
For the other sizes, the three main measurements are given: length, width and height.
6. Color
Colour is expressed by indicating hue, saturation and tone.
7. Transparency
The degree of transparency is indicated as follows: transparent, semi-transparent, translucent, semi-translucent, opaque
8. Clarity grade
This term defines the degree of internal cleanliness of the gemstone. The degree of purity is determined by the presence, more or less manifest, of inclusions.
9. Cut grade
This section assesses the quality of the cut of the gemstone.
10. Tratamientos
This section Is mainly dedicated to the indication of the presence or not of some kind of treatment, as well as the severity of the treatment (if any).
In this sense, the Laboratory of the IGE tries to be as objective as possible when describing these processes and adopts four different behaviours depending on the type of manipulation, always considering that there may be some cases in which the presence of treatment is not demonstrable.
11. Comments
Any peculiarity of the gem that deserves to be commented on is reported in this section.
12. Photograph
A photograph of the gemstone is included in this section. You can find it in higher resolution by accessing, with the certificate number, at Report check.
13. QR code
By scanning the QR code, the authenticity of the certificate can be verified. It also allows you to find more information about treatments, if any.
14. Date of issue of the original document and signature of the responsible Chief Gemologist
