Color is designated by letters with the rarest colorless diamonds starting with the letter DEF and going to KLM for diamonds with more color. Cut - the cut can determine how much a stone costs. If your diamond has a little bit of color or a few tiny inclusion inside it can still look magnificent if properly cut. Clarity - most diamonds have little hidden birthmarks. A diamond is considered flawless and more expensive if you don't see tiny dark spots or specks under 10X magnification.
Most diamonds have some inclusions.
Carat - carat designates the weight of the diamond. The larger and clearer the diamond, the more expensive. Customers should always try to buy the largest diamond with the highest quality they can afford - without breaking the budget. Be sure the stone is certified by an independent laboratory and not the jeweler. This report tells the buyer everything about the stone's characteristics.