A diamond’s cut grade is determined by how well its facets interact with light to create visual effects in both the diamond’s interior and its exterior (aka sparkle). Of the all the 4Cs, cut is the most important factor in how the stone appears to the naked eye. If the cut is too shallow, light will escape from the side. An ideal cut diamond directs light to the bottom of the stone and back up through its top (or what gemologists call the table). It will cost you more but is arguably what makes diamond so special.
Nearly all diamonds have some imperfections. But often, these flaws – called inclusions and blemishes- are microscopic. Diamonds with the fewest and smallest imperfections get a higher clarity grace –and price.
With diamonds, the less color there is, the more light and sparkle and the higher the quality. A D-grade diamond is the top of the color chain, as it has no color at all, while Z is the lowest and most yellow.
Think of carats like pounds – they measure how much a diamond weighs. A single metric carat is defined as 0.2 grams. For diamond shapes like round, princess, and Asscher, the greater the distance in millimeters across the top of the stone, generally the greater carat weight.