CIBJO Diamond Grading Reports:

Colourless to near colourless loose diamonds are usually submitted to SSEF for a 4C (Carat, Colour, Clarity, Cut) quality grading. This quality determination follows the CIBJO rules, edited in the CIBJO Diamond book which may be ordered from the SSEF Secretariat (gemlab@ssef.ch). Stones under 0.20 ct are not graded. A simplified CIBJO diamond report is issued for stones between 0.20 and 0.46 ct. For stones over 0.46 ct, the following rules apply:

Determination of colour authenticity of diamonds

Following the determination of the nature of a coloured diamond (synthetic or natural), a colour authenticity test can be performed. Treatments applied to fancy coloured diamonds tend to improve their colour.  These treatments consist either in coating the surface with a coloured substance, or in irradiating the whole or part of a diamond. This last treatment is the most common and is generally followed by a heat treatment (annealing).

Diamonds with a reduced colour (high-pressure high-temperature treated diamonds) are disclosed as Treated Diamond.