Many say cut is probably the most important, and most challenging, of the four Cs to understand. Cut refers not to a diamond's shape (e.g. round, oval, pear, etc.) but to a diamond's proportions, symmetry and polish. The beauty of a diamond depends more on cut than any other factor. The proportions of an ideal cut diamond reflect almost all the light that enters it, showcasing its brightness, scintillation, and overall sparkle.
Carat is the weight of a gemstone or diamond on a gem scale. Carat is often the first thing to come to mind. Shape and cut of a diamond also play a role in whether the stone appears visually larger or smaller than its actual carat weight.
Some may say color is the second most important factor in the beauty of a diamond. A Diamond's color is all about what you can’t see. Diamonds are valued by how closely they approach colorlessness – the less color, the higher their value. The one exception to this is rule is with fancy colored diamonds.
A diamond's clarity is the visibility, number and size of natural inclusions within each stone. Diamonds that are clear, create more brilliance, and thus are more highly prized, and priced. For a natural diamond, the clarity characteristics are ones that occur during the formation process; they give each diamond a unique fingerprint.