Cut is the only one of the 4Cs shaped by human hands. It refers to how expertly a diamond is proportioned, faceted, and finished, directly determining how light returns to the eye as brightness, fire, and sparkle. Because cut quality has such a profound impact on a diamond’s beauty and value, it is widely considered the most important of the 4Cs.
In diamond trading, cut is a primary search filter on platforms like Rapaport Trade both in terms of the cut shape and quality. The quality scale ranges from Fair to Ideal as seen in thi screenshot. In addition, Rapaport maintains two dedicated diamond Price Lists based on cut style: one for Round diamonds and one for Pear cuts (which serves as the pricing benchmark for all fancy shapes).
Cut quality is evaluated on three main factors:
- Proportions
- Polish
- Symmetry
A poorly cut diamond, whether cut too deep or too shallow, leaks light and appears dull. Consequently, it commands a substantially lower price than a well-cut diamond of equivalent weight, color, and clarity.