A polished diamond’s proportions, or “cut,” affect its light performance, which in turn affects its beauty and overall appeal. Diamonds with fine proportions, symmetry, and polish optimize their interaction with light and have increased brightness, fire and scintillation.

The weight of a diamond is measured in carats. It is the easiest of the four characteristics to determine.

A carat is 200 milligrams (1/5 of a gram) and is divided into 100 points (like pennies to a dollar). Thus a half carat stone is a diamond of 50 points and is listed as 0.50 carat.

Clarity is determined by the number and size of internal characteristics (called inclusions) and external characteristics (called blemishes) which both occur naturally in diamonds. Small inclusions that are visible only under magnification are not likely to diminish the beauty of a diamond. The smaller the inclusion, the less likely that it will interfere with light as it passes through the diamond.

• 

  VVS

  These grades contain minute inclusions so small they are difficult to locate under 10x magnification. Pinpoints, faint clouds, tiny feathers, bruises or internal graining characterize the VVS grades.

• 

  VS

  These grades contain minor inclusions of a size, number and location between those difficult to locate and those somewhat easy to locate under 10x magnification. Small included crystals, small feathers and distinct clouds characterize the VS grades.

• 

  SI

  These grades contain noticeable inclusions which are easily visible under 10x magnification. Diamonds in these grades may disclose inclusions to the unaided eye when placed table down on a white background, but rarely when viewed face up

• 

  I

  The imperfect categories contain inclusions which are obvious when viewed under 10x magnification and which may be visible to the unaided eye in the face-up position.

Although many people think of gem quality diamonds as colorless, truly colorless diamonds are actually very rare. Most diamonds used in jewelry are nearly colorless with tints of yellow or brown.

Color grades are determined by comparing each diamond to a master set. Each letter grade represents a range of color and is a measure of how noticeable a color appears.

GIA Color Scale