Diamonds I3 - IV are the most common grades. I1 and II are also found in small quantities. The quality of a diamond is determined by its color (quality) and its clarity (how well it reflects light). Diamond colors range from colorless to dark red, while clear diamonds can appear white or yellow under certain conditions. The higher the quality number, the more desirable the stone is considered to be. There are three main categories of diamond quality: superb, good and fair. Superb diamonds are extremely rare — about one in every 100,000 diamonds—and are only found in deposits with high concentrations of carbon. They are colorless or slightly colored, with no internal defects that would affect how it lights up when cut into stones. Good diamonds are more common and have qualities of excellence in color and clarity. They may have minor inclusions that do not affect their beauty but could cause problems if you plan to sell the diamond later. Fair diamonds are the most common type and include stones that are both colorless and perfectly clear. They may have surface flaws such as spots or lines that run through the stone from top to bottom.