To determine the value of a diamond, note its color, clarity, cut and carat. Diamonds are more valuable when they have less color, lack spots and imperfections, have higher cut grades and weigh more. Compare each of these four factors to reach an actual market value of a diamond.
To determine the value of a diamond pertaining to color, jewelers place it on a scale from colorless to light yellow. The less color a diamond has, the more valuable it is. The differences between each grade of diamond are very subtle and require a trained jeweler to differentiate.
The clarity of a diamond refers the amount and location of any flaws or blemishes. To spot these, use a 10x magnifying glass and inspect each facet for blemishes on the inside or surface of the diamond. Since blemishes can block light passing through a diamond, the more significant they are, the less valuable the diamond is.
A diamond's cut refers to the fineness of the cuts, called the grade. A skilled gemsmith cuts each diamond according to its proportions to allow the maximum amount of light to reflect. If a diamond is cut in such a way that it allows light to escape through the bottom, the diamond appears darker and is therefore less valuable.
The carat of a diamond refers to its weight; one carat is equal to 200 milligrams. One carat is divided into 100 to reach its carat weight, so a 4 milligram diamond is 0.20 carats. The heavier a diamond is, the more valuable it is.