Cut quality
Diamond cut quality is how well a diamond was cut: the angles, proportions and finish that make it sparkle. It is graded Excellent, Very Good, Good, Fair or Poor.
- Cut is graded Excellent, Very Good, Good, Fair or Poor.
- It judges what you see: brightness (white light), fire (flashes of colour) and scintillation (sparkle as it moves).
- Round brilliants have had an official cut grade since 2006.
Cut grade chart, best first
Odds in RXXOIn RXXO
In RXXO, 1 in 10 diamonds is Excellent. Good is the most common grade, 1 in 3.
Excellent cut RXXO diamonds
Look closer
The three things you see
Brightness is white light reflected from inside and outside the stone. Fire is light split into the colours of the rainbow. Scintillation is the sparkle, and the pattern of light and dark, as the diamond moves.
What else graders check
How heavy the stone is for its width, whether its proportions make it easy to chip, how well its facets are polished, and how exactly they line up. The lowest of the seven scores decides the grade.
Where it came from
Marcel Tolkowsky drew the light paths of a round brilliant in 1919. Today's cut grade, used since 2006, rests on computer models of light and more than 70,000 observations by people.
Questions
What is the best cut grade?
Excellent, the top of the five grades: Excellent, Very Good, Good, Fair and Poor.
What is fire in a diamond?
Flashes of colour. A diamond splits white light into the colours of the rainbow, and a well cut stone shows more of them.
Do all shapes get a cut grade?
In the diamond trade, only round brilliants get an official cut grade. In RXXO, every diamond has one.
What is scintillation in a diamond?
The sparkle you see when a diamond, the light or you move, and the pattern of light and dark areas across its face.
How is the cut grade decided?
Seven things are scored: brightness, fire, scintillation, weight for its width, durability, polish and symmetry. The lowest score sets the grade.
RXXO numbers are the odds every mint draws from. Updated 8 October 2026.