The Four Cs - Cut

Cut

Diamonds are the Earths treasure. The exemplified beauty in their color and clarity are an effect of natural phenomena; but a diamond’s cut is solely the result of the talent and craftsmanship of the master cutter. Master craftsmen reveal the concealed beauty of a diamond in the rough. A well cut diamond can attain and demonstrate brilliance regardless of color or clarity. How much a diamond reflects and releases of its inner beauty is determined by how well it plays with light – essentially its Cut's overall brilliance and symmetry. Cut is the factor that fuels a diamond’s fire, sparkle and brilliance.

The AGS and GIA Laboratory approach cut grading differently. Diamonds awarded the top grade by these laboratories; Excellent with GIA or Ideal (0) with AGS are near the top cutting quality of diamonds available today. The AGS Ideal Cut grade is considered to be a 3D Cut score based on 3D modeling of a diamond as opposed to a 2D Cut score resulting from strictly numerical proportions and percentages.

Two Rounds; Poor Cut (left) vs. an Ideal Cut (right) CIH Diamond

The AGS Cut Grade

AGS or the American Gem Society assesses cut grades on round diamonds and some fancy shapes. The AGS cut grade system includes numeric ratings from 0 (Ideal) to 10. From its foundation AGS focused on cut assessment for both the trade and consumers. They pioneered the "Ideal" cut grade for the round brilliant diamond and provided user-friendly guidelines. AGS created the first scientifically reviewed, impartial, and repeatable cut grade method in the industry. For these reasons AGS is far stricter and only less than 3% of the world's round brilliant diamonds can earn the AGS top grade of 0 or 'Ideal’ with regards to cut. The grading system takes into account 11 factors: brightness, dispersion, leakage, contrast, girdle thickness, culet, weight ratio, durability, tilt, polish and symmetry.

The AGS Cut grade is recognized as a 3D Cut grading system in comparison to GIA's 2D Cut grade. AGS scores a cut grade using a combination of specific proportions plus 3d modeling. The 3d modeling entails the scanning of a diamond into a computer and then running 3d models on that scan to confirm the performance of the diamond. This is advantageous in that the exact proportions and angles of the diamond and the performance of those facets in 3D space is tested. This is in contrast to other laboratories with 2D cut scores which match up numerical ranges and proportions (which have already been roughly averaged) and then award a cut score based solely on those numbers. For this reason, an AGS Ideal cut grade can not be reverse engineered using 2d proportions.

The GIA Cut Grade

Currently, GIA only assesses cut grades on round brilliant diamonds in the D-Z color range. The GIA cut grade system includes ratings of Excellent, Very Good, Good, Fair and Poor. A diamond's initial cut grade is estimated by the GIA Cut Estimator, the final assessment is determined upon proportion and performance of the diamond. Each diamond is blindly assessed in the grading process by multiple gemologists. The grading process takes into account five major factors: proportions (measurements, critical crown and pavilion angles), girdle thickness, culet size, polish and symmetry. Because the GIA cut grading system provides an objective assessment of a diamond's overall cut quality, each cut grade represents a range of proportion sets and diamond appearances, each of which may conform in different ways to the characteristics of that grade.

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