4. Diamond Cut

Nature is responsible for the cooler and the clarity of a diamond. The cut, that aspect that unlocks a diamond's hidden beauty, is the skill and craft of a talented diamond cutter.
Lacking an accepted industry wide standard for cut grading, as there are for clarity and cooler, GRA has developed a scale of cut grading as described below. In general terms this is what it means:

Excellent Cut (HW Grade 1 to 1+)
Diamonds cut to "ideal" proportions, as shown in the diagram. This cutting yields a diamond of maximum brilliance and beauty. A stone cut to these proportions will be considerably more expensive than a diamond of the same clarity and cooler but of poorer cut.

Good Cut (HW Grade 2 to 3)
Diamonds cut just outside the tolerances of the ideal cut.

Average Cut (HW Grade 4)
Diamonds cut to average proportions, with somewhat reduced brilliance and beauty to trained observer.

Commercial Cut (HW Grade 5 to 6)
Diamonds cut with reduced brilliance to the untrained eye, or significant retention of weight from the rough.

Irregular Cut (HW Grade 7 to 8)
Diamonds cut with distinctly reduced brilliance to the untrained eye, or significant retention of weight from the rough.

Below you can see how we place an "ideal" cut stone on our scale and also a fairly average "deep" stone. In general given the same weight (carat) the stone on the left will command a premium in price, and exhibit more fire and brilliance.