Information From a Grading Certificate

setting a diamond

Under the date you will see some basic information on the shape (see below). In this case the diamond is referred to as a “Round Brilliant”.

Shape and Cutting Style:

This indicates that the outline of the diamond is round, and the diamond is brilliant cut which refers to the modern style of diamond cutting which has fifty seven or fifty eight facets.

Measurements:

The minimum and maximum diameter followed by the depth measured from the table to the culet.

Weight:

Is measured in carats and rounded off to the hundredth.

gia diamond report

Proportions

The proportions of the diamond are also included in the certificate. These are the most basic indicators of how the diamond is cut.

Depth:

The depth here is shown as a percentage. The percentage is the physical measurement of the depth divided by the average girdle diameter. This can indicate how deep the diamond is for it’s diameter. This is one basic way to gauge how well the diamond is cut.

The most preferred total depth percentage for a round diamond is between 58.5% and 62.5%. If you compare the depth listed below (63.2%) to the diameter listed above (9.15 – 9.27 mm) and take into consideration the carat weight (3.04 carats) you can surmise that alot of the diamonds weight is in the depth rather than in the diamonds diameter (size face up).

In other words the deeper a diamonds depth for a given carat weight, the smaller the diamond will appear.

Table:

The table here is shown as a percentage. The percentage is the physical measurement of the table divided by the average girdle diameter. This can indicate how large or small the table of the diamond is compared to the size. The table percentage affects what kind of light the diamond will most reflect.

If the stone has a larger table (60% to 65%) most light will reflect off of the table giving the diamond a majority of brilliance (white flashes) seen by your eye. If the diamond has a small table (50% to 55%) most light will enter the diamond and exit through the crown facets breaking into spectral colors called fire (red, green, and blue flashes). The most preferred table percentage range is between 53% and 57%.

Girdle:

The girdle here is given a verbal description of the thickness. The thicker a girdle is the more effect it will have on the overall depth of the diamond. The key to girdles is not to go to extremes. The girdle protects the side of the diamond from damage.

If the girdle is too thin, it is far more likely to chip the diamond when it is set. If the girdle is too thick, the cutter is just adding depth (and weight) to the stone without making the diamond appear larger. The GIA ratings for diamond girdles are;

o Extremely Thin
o Thin
o Medium
o Slightly Thick
o Thick
o Extremely Thick

Culet:

The culet of the diamond is the facet on the bottom point of the stone. If the GIA report lists the culet as “None” as in the case above, it means there is no facet on the point. In modern round brilliant cut diamonds you most likely see none, very small or small. Any of these listings on a GIA certificate are acceptable, however anything listed as medium, or large should be avoided.