The practice of over grading the diamond to increase the perceived value. This practice is illegal. See link for more information. Rapaport.
In natural diamond the colour is related to a lattice imperfection. This can be mimicked in synthetic or treated diamond by a variety of treatments including annealing, heating or irradiating. The heat and pressure or irradiation can result in the lattice deviation resulting in the brown or pink colour.
The ultimate colour for the collector, Orange is extremely rare in diamond. To be certified fancy orange colour, there cannot be any brown in the stone.
Lines left on the surface of the diamond which are visible under magnification, normally removed during the final diamond polishing process. Polish lines can affect the polish grade of the diamond.
Plastic covering that provides a safeguard against loose diamonds being lost or damaged. Laboratory sealing has a number of security features including electrostatic security bars, pressure-sensitive transparent adhesive and cryptoprint text which only becomes visible after opening the seal.
Diameter is a reference measurement against which most of the proportions on a diamond are calculated. On a round brilliant cut diamond, this is the length in millimeters of a straight line going through the center of a diamond. Click here to learn which standard diameter measurements correspond to specific well-proportioned carat weights. On a fancy shaped diamond, this is the average measurement in millimeters of the length and width.
Set of certified and registered diamonds, with known colours from which other master sets may be derived.
A coloured diamond with a natural yellow body colour. Yellow must be the predominant colour, but it may be modified by shades of green, orange, or brown. The colour in natural yellow diamonds is created by the presence of nitrogen as an impurity when the diamond is growing. Natural yellow diamonds are common; canary diamonds are however more rare.