The cut is essentially a diamond's shape, and how well it has been cut to the "ideal" standard. Common shapes include round brilliant, princess, oval, and emerald. The type of cut plays a big factor in the amount of sparkle, or fire, the diamond gives off. A round brilliant cut has much more fire than an emerald cut, for example. Some cuts are more expensive than others, but which cut is most expensive fluctuates with the market.
The cut of a diamond is also rated based on how well the cut conforms to the ideal standard set for it. This includes things like number of facets, symmetry, and angles. These factors are extremely important as they greatly affect the amount of light refracted by the diamond. A single misaligned facet can cause a diamond to look 'dead' and 'dark', thus ruining an otherwise beautiful diamond. When looking at the quality of a cut on a grading certificate, the grading will range from excellent to poor. Buy a diamond only if its cut quality is excellent or very good. Do not buy a diamond if its cut quality is only good,fair, or poor. These lower gradings can affect something as crucial as the overall shape, like a princess cut that's meant to be a square but is really rectangular! Beware any grading that doesn't follow the convention discussed above - e.g.: a grading that uses terms like sensational or magnificent. These terms are merely marketing hype and are highly misleading.
A retail or discount jeweller is likely to stock only cuts that are the most likely to sell, which are round brilliant and princess. A boutique or high-end jeweller will have a greater selection of cuts, especially including emerald, pear, and marquise. Some of these cuts are associated with more vintage designs.
At K. Amani Fine Jeweller, we are happy to modify any of our ring designs to accommodate a specific diamond cut that you prefer. We also custom-create ring designs specifically designed to showcase your chosen diamond's shape.