Crown Of A Diamond
Just as you’d wear a crown on your head, a diamond crown is the topmost section of the stone. It includes everything that sits above the diamond ‘girdle’.
When light passes through the crown, it's reflected back from the pavilion (base) to the viewer’s eyes. All the diamond facets reflect light in different directions for a multifaceted light show.
CROWN HEIGHT: The crown height affects a diamond’s brightness and fire (the amount of colored light reflected out of the stone).
CROWN ANGLE: The angle from the top of the girdle to the diamond table (flat top). This angle affects a diamond’s brilliance and fire from the top view. A well-cut diamond will have a crown angle between 31.5 to 36.5 degrees (you’ll find these measurements on all GIA grading reports).
Girdle Of A Diamond
The widest edge of the diamond where the crown and pavilion (base) meet. A well-cut diamond has a goldilocks girdle – not too thin and not too thick for that specific diamond. A too thin girdle can risk chipping, while an overly thick girdle puts too much weight in the middle of the diamond, making it appearing smaller than diamonds of comparable carat weight.
If the girdle thickness is off, a diamond can only receive a maximum Very Good GIA cut rating regardless of all other factors. The ideal diamond girdle rating is thin-medium, and slightly thick-thick is considered an excellent to ideal proportion.
Pavilion Of A Diamond
The bottom section of the diamond that starts at the girdle and ends at the cutlet (pointed base). Most of the diamond weight is in the pavilion.
PAVILION DEPTH: Another goldilocks measurement, a too ‘deep’ or too ‘shallow’ pavilion allows light to exit through the sides or bottom of the stone, creating a dull, lifeless looking diamond. A well-cut diamond allows light to reflect through the top of the stone, creating a brilliant, luminous sparkle.
PAVILION ANGLE: Ok, get ready for geometry class – this is “the average of the angles formed by the diamond’s pavilion main facets and its girdle plane”. What you need to know: an excellent cut diamond will have a pavilion angle between 40.6 and 41.8 degrees and will sparkle with gleaming brightness.
Table Of A Diamond
The flat, topmost (and largest) facet of the diamond – what you see from a bird’s eye view. The diamond table refracts (bends) incoming light rays which are then reflected back from the pavilion into the observer’s eyes.
TABLE SIZE: The table size is measured in relation to the girdle diameter. An excellent grade diamond has a table size of 52 to 62 percent, along with all the other corresponding dimensions and proportions that make up a well-cut diamond.
Depth Of A Diamond
The overall height of a diamond from table to cutlet – this is measured as a percentage of the girdle diameter. Diamonds graded from Very good to Ideal have a depth of 54 to 66 percent.
Cutlet Of A Diamond
The small pointed facet at the base of the diamond. It’s sized as none, very small, small, medium, slightly large, large, very large, or extremely large.
Excellent cut diamonds will fall into the ‘none to small’ range, which means the cutlet is not visible to the naked eye. Larger cutlets are less desirable as they allow light to escape through the bottom of the diamond.
This 'smaller-is-better' motto applies mostly to modern cut diamonds. Old cut diamonds had much larger cutlets which draw your eye into the stone and have their own unique beauty!