Cut
Many people confuse cut with the shape of a diamond. The shape you select is a matter of individual taste, and your choice is limited only by the skill and imagination of the craftsman. The cutting grade is determined by their effort to maximize the refraction of light during every stage of the fashioning process. Most brilliant-cut or complex-shaped diamonds possess 58 carefully angled flat surfaces, called facets, whose placement will affect the fire, brilliance and ultimately the beauty of your diamond. The value of two diamonds with exactly the same carat weight could vary by as much as 40% depending on the quality of cut.

 
Colour
The most prized diamonds are colourless. Their beauty depends entirely upon their remarkable optical properties which reflect all the colours of the rainbow. Though most diamonds appear to be icy white, many of them have slight traces of colour – usually yellow or brown. Due to their rarity, perfectly colourless diamonds are the most valuable. With each subtle departure from colourless, there is a decrease in rarity and value. The GIA colour grades range from D (colourless) all the way to Z (yellow-brownish).
 
Clarity
Clarity in a diamond is defined by the absence of natural 'characteristics' (imperfections in the crystal structure of the diamond). A diamond is graded using a microscope at a magnification ten times more powerful than normal vision. The rarest and most valuable diamonds have no natural characteristics at this magnification. Diamonds with more and larger characteristics are less rare and have less value. As with colour, differences in clarity can be very subtle, yet have a considerable impact on value.
 
Carat Weight
Carat weight is the standard unit of weight for diamonds. One carat equals 1/5 of a gram, or .007 of an ounce. Carat weight is further divided into decimals. For example, exactly 1/2 carat is .50 carat and expressed as 50 points. Because diamonds are weighed to hundredths of a carat, they must be weighed on extremely precise and sensitive scales. All other factors being equal, as weight increases so does rarity and value.