The diamond certificate is commonly referred to as a cert. There are many institutions that specilize in the grading of diamonds. The most common are: the Gemological Institute of America (GIA), European Gemological Laboratory (EGL), Gemological Institute Laboratories of Israel (GILI), and Hoge Raad Voor Diamant which translates to Diamond High Council of Belgium (HRD).
When looking at a diamond report, you will notice each specific diamond is issued an identification number and the date and time that the report was done. The report lists the instruments used to examine, describe and grade the diamond. The report also describes the diamond's shape and cut, the clarity and color, and any other comments about the stone. There is also a diagram which plots the internal and external characteristics of the diamond.
Shape and Cut - Refers to the style and make of the diamond. The style is the shape of the stone; for example: round brilliant, marquise shape, oval shape, emerald cut, princess cut, radiant cut, heart shape, and baguettes. Many believe the larger the diamond the greater its value. This is not necessarily true. It is the cut that unlocks the beauty for which diamonds are valued. Larger diamonds are generally full cut, meaning they have 58 facets, each of which must be in precise symmetrical relationship. The responsibility for this precision lies solely with the cutter. (top )
Measurements - When measuring the diameter of a round diamond, the circumference and the depth of the stone are gauged. These measurements are then used to calculate the proportions of the diamond. On fancy shaped diamonds the measurements are taken length by width. (top )
Weight - Carat or carat-weight refers to the size and weight of the diamond. The word carat originated from times when the seeds of the carab tree were used on a balance scale to measure weight. Today, the standard weight of one carat is 0.2 grams or 1/5 of a gram. One carat is divided into 100 points; a diamond of 75 points weighs 0.75 carats. A large diamond is not necessarily a better or more valuable diamond. Two diamonds of equal weight can have very unequal value, depending on their cut, color and clarity. (top )
Proportions - ratio of two specific measurements of a diamond. This relationship is an indicator of the diamond's brilliance. (top )
Depth - Refers to the total depth of the stone from the table, or top, of the diamond to the culet, or point. In round brilliants the range of generally accepted depth to width ratio is between 57% and 63%. (Ideal proportions are 58.9% to 61.8%.) In fancy shapes, the total depth and other proportions are not scrutinized the same way as round brilliants. (top )
Table - The table is the largest facet of the diamond and considered the window. In round brilliants, the range of generally accepted table to overall diameter is 53% to 66%. (Ideal proportions are 53% to 57%.) Again, in fancy shapes, the table diameter and other proportions are not scrutinized in the same way as in round brilliants. (top )
Girdle - Refers to the middle of the diamond that separtes the crown, or top of the diamond from the pavilion, or bottom. The girdle generally makes up to 2%to 3% of the total depth of the stone. This can vary depending on how thin or thick the girdle actually is. Some girdles are faceted and others are granular and have a frosted appearance.
Culet - The culet is a polished facet placed at the tip of the diamond to prevent chipping. The culet ranges from none or white abraded to extremely large, which would show an octanganal outline when looking through the stone. The culet is graded through the table, with the stone face up, under 10X magnification. (top )
Polish -The polish grading rates the surface of the diamond. This includes blemishes which are surface characteristics such as: abrasions, nicks, pits, polish lines, polish marks, a rough girdle, and scratches. (top )
Symmetry - This indicates how symmetrical and aligned the facets of the diamond are to one another. Factors that can affect the symmetry include the following: off center culet or table, out of round girdle, facets that fail to point properly, misalignment of crown and pavilion facets,
a table that is not a rectangular octagon, misshapen facets, table and girdle not in parallel, a wavy girdle, a natural (a rut that can affect the clarity grade) or extra facets (which do not affect the clarity grade). Polish and symmetry are given the grades of Excellent, Very Good, Good, Fair, and Poor. (top )
Clarity Grade - Clarity refers to minute traces of non-crystallized carbon, called inclusions. Almost all diamonds have inclusions, though most are not discernable to the eye without aid of magnification. The fewer inclusions there are, the rarer the stone will be. As with color, we use the GIA scale for grading clarity. There are eleven clarity grades used by a skilled grader at 10X magnification to evaluate and determine the various clarity characteristics. (top )Flawless (FL)-A flawless diamond shows no blemishes or inclusions. The following do not disqualify a diamond from the flawless category:
- an extra facet on the pavilion which cannot be seen face up
- naturals totally confined to the girdle (which neither thickens nor distorts its outline)
- internal graining marks which are not reflective, white, or colored and do not significantly affect the transparency of the diamond.
Very Very Slightly Included (VVS1 and VVS2)- A VVS diamond contains minute inclusions that are extremely difficult to locate. VVS1 differs from VVS2 in that the the inclusion can only be seen through the pavilion.
Very Slightly Included (VS1 and VS2)-VS diamonds contain minor inclusions ranging from difficult to see (VS1) to somewhat easy to see (VS2).
Slightly Included-An SI diamond contains noticable inclusions which would be easy to see (SI1) to very easy to see (SI2). In some SI stones, inclusions are visible to the unaided eye.
Imperfect (I1,I2, and I3)- An imperfect diamond contains inclusions which are obvious and can easily be seen face up. In I2 and I3 diamonds the inclusions are usually so numerous that they can affect the transparency and brilliance of the diamond and can also pose a durability threat. Some certs use the term Pique (P1,P2, and P3) in place of imperfect. (top ) Please note: The previous clarity descriptions are most applicable to round brilliants and some characteristics may be more visible in large stones and fancy shapes.
Color Grades - Refers to color, or, more accurately, the absence of color. Most diamonds have color. Those without color are rare and so premium priced. A tinge of color is evident in most diamonds with some having a body color slightly more visible. It is important to note that these types of diamonds cost less than totally colorless diamonds because they they are less rare, not because colorless is better. In fact, a diamond with a tinge of color can hold greater appeal than icy white diamonds. To help determine the differences, the Gemological Institute of America (GIA) created a scale with colorless diamonds starting at 'D'. D, E. and F are considered colorless. G, H, I and J are near colorless which is still considered white. With the descending letters (K, L, etc.) the color becomes more intense. (top )Flourescence - Ultraviolet flourescence is an emission of visible glow stimulated by invisible wavelengths. Approximately 50% of all gem quality diamonds exhibit some degree of flourescence. Diamonds can flouresce any color; the most common color is blue. The strength of flourescence is described in the following terms:
- None - also known as inert
- faint - occurs just around the girdle's edge
- Moderate - the majority of the body glows, but not strongly
- Strong - the whole stone glows brightly (top )
Comments - This section contains any other points not already listed on the diamond report. (top )
Diagram - The diagram is the blueprint of the diamond. The diamond is plotted with different symbols for the different characteristics. Red is used for those that are internal and green for external. The first symbol listed in the key is usually the clarity grade setter or the most visible inclusion. Plotting is done to identify the diamond and document the condition and characteristics of it; plotting also serves to support and justify the clarity grade. (top )