Coloured stone identification


Unique reference number

The Laboratoire Français de Gemmologie gives a unique reference number to each item submitted for examination. This number identifies the item at each stage of analysis. When a stone has already been seen and comes back after a re-cutting or a preliminary examination, a new number is assigned to it.


The date of the report is the date when analyses are completed and when the report is issued.


The Nature indicates the variety of the stone. On this specimen, ruby belongs to the same family as sapphire: corundum.

Shape, cut and dimensions

The shape, cut and dimensions describe the external appearance of the stone. When you submit a piece of jewellery with several stones, or lots, we indicate the diametrical variation of the lot.


The weight (mass) of the stone is shown in carat weight with a precision of two decimals. The third 9 after the decimal point is rounded up to the nearest hundredth. For instance: 0.9990 will be shown as 1.00 carat, 0.9989 shown as 0.99 carat. If the item is a jewel set with stones, then it is weighed in grams.


The colour gives an indication of the hue (on our specimen: red), the tone if necessary (for instance : orange) and of saturation (here : vivid).

Instruments scientifiques

Dans un souci de transparence, le LFG vous indique par quels instruments scientifiques votre pierre a été testée. Vous trouverez la description et l’utilité de chaque machine dans notre section >> Notre matériel


The Identification refers to the type of stone which has been analysed


La nature indique la variété de la pierre. Sur ce specimen, le saphir vient d’une famille commune au rubis : les corindons.


According to the French Decree no. 2002-65, published on the 14th of January 2002, on trade in gemstones and pearls, treatments should be disclosed either with the word “treated” or with the information on the type of treatment applied, when the stone has undergone, as the case may be, irradiation treatment, treatment by laser, dye, surface diffusion, filling, possibly as a residue of a heat treatment, solidified colourless foreign matter in external cavities that present reflection breaks visible under the 10 x loupe, or by any other laboratory method that alters their appearance, colour or clarity.


It is in the comments section that the LFG provides additional information related to origin or treatments. For example, impregnation with a colourless fluid substance, heat treatment or bleaching without the addition of colouring products or varnish.


A high resolution photography shows the stone on its arrival in the laboratory (dimensions in the photo are not binding but as representative as possible). The stone might have been re-cut or changed colour since it left our premises.

(+33) 01 40 26 25 45
30, rue de la Victoire - 75009 Paris
Monday - Thusday : 9H30 to 17H00
Friday : 9h30 to 16h30
Withdrawal files at same days and time


Share This