Cut: The art of polishing a diamond is to maximize its brilliance and fire (dispersion). A diamond that is cut too deep or too shallow will be less brilliant and ultimately, less valuable. The cut is the only factor of a polished diamond's value that is controlled by human hands.

Colour: The smallest variation in colour makes a difference. Colourless diamonds are the most admired, but diamonds are found in all colours of the rainbow. The rarer the colour, the more valuable is the diamond.

Clarity: Most diamonds contain inclusions, which developed during their formation in the earth. The number, type, size, position and brightness of these inclusions can affect the clarity of a diamond.

Carat: The weight, which will reflect its size, of a diamond is expressed in carats.
Five carats is equivalent to 1gram and is divided into 100 'points'.

By

More on this subject:

Israel Diamond Exchange

Diamond Certificates

Diamond Knowledge