What is a GIA Diamond Certificate?

It’s an official diamond grading report issued by GIA (Gemological Institute of America), the world’s leading gemological laboratory. A diamond certificate is to ensure the authenticity and provide an accurate grading of a diamond.

The 4Cs grading was established by the GIA. Color, Clarity, Cut and Carat of diamonds provide a way to compare one diamond to another. A detailed certificate includes full analysis of grading of carat weight, measurement, color, clarity, cut, polish, symmetry, fluorescence and plotted clarity diagram. Each certificate provides a unique GIA report number to represent one particular diamond. With the report number, you can easily view the certificate information from the GIA website report database.



Every diamond shape has its own unique look. Diamond shapes include Round as well as Asscher, Cushion, Emerald, Heart, Marquise, Oval, Pear, Princess, Radiant, Trilliant, etc. The traditional round brilliant cut has always been the most popular among all other fancy cut diamonds.



Color relates to the amount of bodycolor in a diamond. The GIA color scale range from D (highest grade) to Z (lowest grade). The grading is based on how noticeable the color is, and each letter grade represents a range of color. Truly colorless diamonds (D color) are extremely rare and valuable.

GIA Color


Fluorescence is the diamond’s reaction to ultraviolet (UV) light. Some diamonds glow in different colors under UV light. If the diamond state as 「None」 means it doesn’t fluoresce. But if a diamond glows strong blue, the diamond may look dull in sunlight.



Clarity is the relative absence of blemishes and inclusions. Blemishes are confined to the surface of a polished diamond. Inclusions are totally enclosed in a diamond or extend into it from the surface. Diamonds are form under tremendous heat and pressure, it is extremely rare to find a diamond that without clarity characteristics. Inclusions normally have more impact on a diamond’s beauty and value than blemishes, so diamonds without internal and external clarity are extremely rare and valuable.


GIA clarity scale includes 11 clarity grades ranging from FL to I3

FL (Flawless) – no inclusions or blemishes

IF (Internally Flawless) – only insignificant blemishes and no inclusions

VVS1 & VVS2 (Very Very Slightly Included) – very very small inclusions like pinpoint, extremely difficult to see and completely clear to naked eye

VS1 & VS2 (Very Slightly Included) – very small inclusions like crystal or feather, eye clear diamond, inclusion only visible under 10x magnification

SI1 & SI2 (Slightly Included) – small inclusions and usually centrally located, easily visible under 10x magnification

I1 & I2 & I3 (Included) – obvious inclusions, visible to naked eye, and seriously affect the diamond’s durability



Cut refers to a diamond’s proportions and the quality of its finish. A well-cut diamond captures the light around it and makes that light perform in breathtaking ways, which determine the sparkle of the diamond. A diamond’s face up appearance based on three attributes. Brightness is the effect of all the internal and external reflections of white light. Fire results when white light is dispersed into its spectral color. Scintillation is a combination of sparkle and pattern. It is the extend of spots of light that flash when the diamond, the observer, or the light source moves; also describes the contrast of bright and dark areas of a diamond.


The round brilliant cut diamond has 58 facets (57 if there is no culet). There are 33 Facets on the Crown (top portion of the Diamond), and 25 Facets on the bottom of the Diamond (the Pavilion).


A shallow cut diamond will usually have a larger diameter. However the more shallow the stone, the more light is lost out from the bottom part and can cause it to look lifeless and transparent.

An ideal cut diamond has the correct proportions to reflect all the light that enters the diamond from the top and bounce within the diamond and reflected back out through the top center to create maximum fire and sparkle.

A deep cut diamond tends to have a smaller diameter. A very deep cut diamond escape light out from the sides and causing loss of brilliance and fire.

Cut 2


Polish and Symmetry

Polish refers to the quality of the diamond surface due to the finishing process or the blemishes created by cutting. Polish characteristics frequently seen on diamonds. Polish line might be traces left by the polishing wheel or from polishing too fast or against a polishing direction.


Symmetry is the general comment regarding the symmetry of the diamond. Most diamonds have at least a few symmetry variations, but typically have little effect on appearance, at least to the unaided eye. The round outline of a diamond, the missing or extra facets are the factors to evaluate symmetry.


Carat Weight

Carat weight is simply the weight of a diamond, not size. Diamonds are weighted in metric carats. A carat equals one-fifth of a gram (0.200 grams). One carat is divided into 100 units called points, 0.50ct = 50 points, and 0.75ct = 75 points. Depending on quality, large diamonds are rarer and more valuable than smaller one as large rough diamonds are less frequently found during mining.

The mm size of a diamond relative to its carat weight, it could be the key to estimate its weight. A 1.00ct diamond is approximately 6.4mm in size.

Carat Weight