The most complete analysis identifying, in addition to the naturality of the diamond, all the evaluation criteria: size, carat, colour and purity, treatment and diamond type.
The patterns of proportions and inclusions are also graded by our gemologists.
The Laboratoire Français de Gemmologie gives a unique number to each deposit. This number identifies the object at each stage of analysis. When a stone has already been viewed and reexamined following a recut or a preliminary examination, it is given a new number.
The date corresponds to the end of the analysis and the day on which the report is published.
Identification refers to the nature of the stone analysed.
The research and identification of the treatment will be carried out for all the stones using all the state-of-the-art equipment and expertise of the Laboratoire Français de Gemmologie.
Our nomenclature is based on the recommendations of recognised international bodies such as the LMHC and the CIBJO, as well as on Decree No. 2002-65 of 14 January 2002, which governs the trade in gemstones and pearls in France.
A diamond showing no treatment will be identified as ‘Diamond’ and the information ‘No indication of treatment’ will be noted on the report.
If a diamond has one of the treatments listed below, it will be identified as a ‘Treated Diamond’ and the nature of the treatment will be noted on the report.
Nomenclature of diamond treatments :
For all these treatments, except laser drilling, LFG will not gradate the stone.
The shape, cut and dimensions (obtained with the Sarine Diamension HD digital measuring instrument) describe the external appearance of the stone.
When you deposit a jewel with several stones, or batches, we indicate the diametrical variation of the batch.
The weight of the stones is indicated in carats (1ct = 0.2 g) to two decimal places.
Rounding is done according to the 3rd decimal place: if it is less than 9 then no rounding, if it is equal to 9 then round up. For example: 0.9990 ct is 1.00 carat but 0.9989 ct is 0.99 carat.
If the jewel is set with stones, it is weighed in grams.
The colour of a colourless diamond is established by comparison with our diamond masterstone set. The latter has been established in comparison with the CIBJO masterstone set. (https://cibjo.org/wp-content/uploads/2022/10/CIBJO-Diamond-Blue-Book-2022-1.pdf).
The rating corresponds to the following scale, which you will find on your reports:
For coloured diamonds, the LFG uses commercially accepted terms to qualify the colour of these diamonds according to the following scale:
The colour described is the main shade with secondary shades.
Ex: ‘Fancy’ vivid pink, slightly purple
The internal inclusions and surface defects present in a stone determine its purity.
The grading nomenclature used at the LFG corresponds to the CIBJO recommendations (https://cibjo.org/wp-content/uploads/2022/10/CIBJO-Diamond-Blue-Book-2022-1.pdf)
You will find this same scale on your reports:
The cut grade is established according to strict standards that combine information on the proportions, symmetry, polish and thickness of the girdle.
It is indicated by one of the following criteria: Excellent - Very good - Good - Average - Fair
The polish is graded with one of the following criteria: Excellent - Very good - Good - Average - Fair.
These characteristics are taken into account when assessing the grade of the cut.
Symmetry is graded using one of the following criteria: Excellent - Very good - Good - Average - Fair.
This characteristic is taken into account when assessing the cut grade.
Fluorescence is indicated by one of the following criteria: None - Weak - Medium - Strong - Very strong.
It is graded by comparison with the LFG's fluorescence standards under long UV light (365 nm).
The LFG is one of the few gemmological laboratories to specify the type of diamond in its reports using infrared spectrometry:
In this section, the LFG indicates additional information concerning the treatment, the natural or non-natural origin of the colour in the case of coloured diamonds, the presence of an additional facet, a rough indicator or a growth zone.
In the interest of transparency, the LFG will tell you which scientific instruments have been used to test your stone.
Scientific instruments used
Diagram of the stone's proportions obtained with the Sarine Diamension HD digital measurer
Girdle : Very thin to medium, faceted
Clarity diagrams, table view and culet view, showing the specific characteristics of your stone:
Natural