The LFG relies on the recommendations and precautious measures of recognised international bodies such as the LMHC and the CIBJO, as well as the decree no. 2002-65 of 14th of January 2002, which governs the trade in gemstones and pearls in France.
If a diamond shows no treatment, it 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 grade the stone.
Emeralds often show cracks that have a negative impact on the appearance of the stone. To remedy this, they are usually impregnated with colorless substances of varying fluidity to improve transparency and reduce the visual impact of these cracks. These substances are generally oil, resin (natural or artificial) or wax.
The LFG will identify the nature of the impregnation, oil, resin (without detailing whether it is artificial or natural) or wax, and quantify the impact of the latter on the degree of improvement in transparency as a function of the cracks (F) and cavities (C). Quantification can be weak (1), moderate (2) or strong (3).
If no impregnation is detected, the LFG will state ‘N – No indication of clarity improvement’. Very weak or insignificant impregnation will be qualified as ‘Weak’ by the LFG.
Similarly, the presence of resin in outcropping cavities and its quantification will be noted as ‘C’; a combination of F + C is possible. In accordance with decree no. 2002-65 of 14th of January 2002 on the trade in gemstones and pearls, any emerald marked ‘C’ or impregnated with coloured oil will be identified as a ‘Treated Emerald’.
Corundum can be heated to improve its colour,’ TE – Indications of thermal modifications ’. No distinction is made between ‘low temperature’ treatments and ‘conventional’ heat treatments.
If cracks are present, additives may be added during heating (borax, leaded glass, etc.), which is common for rubies and less common for sapphires, in order to improve transparency. The quantity of residue resulting from the addition of this additive will be notified ‘TE + quantity’ according to the following chart: low filling (TE1/TE2), moderate (TE3/TE4) or high (TE5/TE6).
Based on the same principle, this nomenclature identifies and quantifies the presence of outcropping cavities in terms of size and/or number, and will then be marked ‘C’. A combination of TE + C is possible.
If lead-doped glass (Pb) or eventually cobalt (Co) is present, the wording ‘F(Pb/Co)’ for filled cracks or ‘C(Pb/Co)’ for filled cavities will identify and quantify the treatment.
In accordance with decree no. 2002-65 of 14th of January 2002 on the trade in gemstones and pearls, any corundum marked ‘C’ or containing lead, titanium or any other heavy metal will be identified as a ‘treated ruby/sapphire’.
A ruby will be identified as a ‘composite ruby’ if the cohesion of the stone is only due to the abundance of leaded glass in the cracks and/or cavities, or if it is an agglomerate of rubies held together by leaded glass.
Diffusion treatments, beryllium (Be) or titanium (Ti), aim to improve the colour of sapphires and coloured sapphires (rare for rubies) and/or to generate asterism in the case of Ti diffusion.
They will be notified on the report:
If no heat treatment is detected, it will be marked ‘NTE – No thermal modification observed’.
All treatments, even less common ones (dyeing, impregnation, irradiation, etc.), will be mentioned according to the LMHC nomenclature and recommendations.
Paraíba tourmalines are commonly heated to improve their colour. If no treatment is detected, it will be marked ‘N – No indication of treatment’. On the other hand, if a heat treatment is identified, it will be marked ‘TE – Indications of thermal modifications’.
Oil can sometimes be detected in cracks in order to improve the transparency of the stone. This will be mentioned and quantified in accordance with LMHC recommendations.
In rare cases, spinel may undergo heat treatment, which will be mentioned on the report ‘TE – Indications of thermal modifications’. On the contrary, the report will state ‘N – No indication of treatment’.
Jade jadeite is frequently treated by resin or wax impregnation and/or dyeing to improve its colour or translucency.
The LFG advises the following treatments on jadeite:
In accordance with decree no. 2002-65 of 14th of January 2002 on the trade in gemstones and pearls, any jadeite that has been impregnated and/or dyed will be classified as ‘treated jadeite’.
Tanzanite is commonly heated to improve its colour. In this case, the LFG report will state ‘TE – Indications of thermal modifications’. When appropriate, the report will state ‘N – No indication of treatment’.
Pearls can be treated to improve their colour or surface appearance.
Nomenclature of treatments to improve colour :
Nomenclature of treatments to improve surface appearance :
In accordance with decree no. 2002-65 of 14th January 2002 on the trade in gemstones and pearls, any pearl that is coated and/or tinted will be classified as a ‘treated pearl’. In the case of a Mabé, the report will bear the words ‘Composite cultured blister’.
The purpose of the treatments is to darken the background colour to bring out the play of colour in the noble opals.