Know Your Stone

Know Your Stone

The 4 Cs and Diamond Grading Fundamentals

Any experienced and trustworthy specialist wishing to grade a diamond, needs to ascertain the factors determining its quality and value. These factors are: Color, Clarity, Cut, and Carat also known as The 4 Cs.


In the 1930’s the Gemological Institute of America created a color scale to describe the colors of diamonds. While the terms were almost romantic -“river”, for example, described the best color quality- they were soon replaced by a letter system in which the letter D represents the best color quality, followed in alphabetical order down to Z, representing Fancy Color Diamonds.


Diamonds are created deep within the earth, under immense pressure and extreme heat. The conditions which create diamonds, also leave marks, imperfections raging from barely visible through magnification to highly noticeable to the naked eye. Imperfections can appear within the diamond (called inclusions) or on the surface (called blemishes). Inclusions and blemishes may affect the way light passes through and reflects through a diamond, so efforts are made to cut the diamond so they are least visible on the finished diamond (usually, under the bezel facets and near the girdle).

Clarity of diamonds is graded on a scale ranging from Flawless to Included:


Flawless: No inclusions or blemishes are visible to a skilled grader using 10x magnification.

Extremely rare, less than 1 in 5000 jewelry quality diamonds are rated FL.


Internally Flawless: No inclusions, only blemishes are visible to a skilled grader using 10x magnification.

FL and IF diamonds appear identical unless viewed under 10x magnification by a skilled grader. Less than 3% of jewelry quality diamonds are rated IF.


Very, Very Slightly Included: Inclusions are difficult for a skilled grader to see under 10x magnification.

VVS1 inclusions are typically only visible from the pavilion, while VVS2 inclusions are visible from the crown. In each, the inclusions are invisible to the eye, appearing identical to the higher grades unless viewed under 10x magnification by a skilled grader.

VS1 - VS2

Very Slightly Included: Inclusions are clearly visible under 10x magnification but can be characterized as minor.

Inclusions are not visible to the naked eye. Perhaps 1 in 100 untrained observers can detect VS2 inclusions with the naked eye, on close inspection under ideal conditions.

SI1 - SI2

Slightly Included: Inclusions are noticeable to a skilled grader using 10x magnification.

SI1 is the lowest grade with flaws often invisible to the naked eye. SI2 inclusions are usually visible to the naked eye, although they will require close inspection.

I1 - I2 - I3

Included:Inclusions are obvious under 10x magnification and may affect transparency and brilliance.

I1 diamonds have inclusions that are almost always visible to the naked eye.


Often mistaken for shape (round, pair, rectangle etc.), the cut of a diamond actually refers to its proportions, symmetry and polish. The beauty and brilliance of a diamond depends on the cut more than any other factor. Though difficult to quantify and specify, diamond cut has three major effects on the finished stone’s appearance: brilliance (light reflections from the surface and inside the polished diamond), fire (light dispersion into visible color, seen as flashes of color), and scintillation (the sparkle created when the diamond or the light source is moved).

When cutting a diamond, the cutter must balance optimal cut and appearance against maximum yield of carat weight. Many buyers are willing to pay more for larger, fair-cut diamonds than for slightly smaller well-cut diamonds, which puts much pressure on the cutter. The Cut Grade is important because it identifies stones that were cut Fair to Poor in an effort to gain carat weight.


Diamonds are sold by the carat, which refers to their weight, not their size. “Carat” is derived from “carob”, as a carob seed used to be the original measuring unit of diamonds. A carat is 0.2 grams (roughly the weight of a paperclip) and is not to be confused with ‘karat’ which refers to the degree of gold purity.

As carat weight increases, so does a diamond’s price, because the larger a diamond is, the rarer it is. That means that not only the price of the diamond increases, but also the price-per-carat increases.

Famous Large Diamonds:

The Cullinan Diamond

Weighing more than 3000 carats in the rough, it was cut into 105 separate stones, one of which is the Star of Africa, weighing 530 carats. The Star of Africa is a pair-shaped diamond, originally set in a brooch worn by British royalty, but later put in the “Scepter with Cross.”

The Ko-Hi-Noor Diamond

its name means “mountain of light” in Persian, and it dates back to 1302, when it weighed 186 carats. In 1849 the diamond was sent to Queen Victoria, and was cut again, its weight reduced to 108.93 carats. These days it adorns the crown of Queen Elizabeth II.

The Hope Diamond

A fancy dark grayish-blue diamond, the Hope Diamond weighs 45.52 carats. The diamond was found in India in 1642 and originally weighed 132 carats. It was set in the royal crown of Luis the 14th, only to be stolen during The French revolution. In 1830 a blue diamond was bought by a diamond dealer named Henri Thomas Hope.

The Fifth C


The 4 Cs are the cornerstones of diamond grading and provide a reliable method of evaluation. However, in recent years, an additional C is required in order to know the true value of any diamond: Certification. Since diamonds are found and mined all over the world, from Australia to Africa, from America to Europe, it is essential for consumers, dealers and investors alike to know that the diamonds they possess come from a responsible source. There are a few organizations around the world providing that type of certification.


The GIA (Gemological Institute of America) was created in 1931 as a non-profit organization. The GIA remains the world’s leading authority on diamonds, colored stones and pearls. Its experts are world renowned and maintain GIA’s reputation as the leading source of knowledge, standards and education in gems and jewelry.

GIA laboratories certify both diamonds and other precious stones. While evaluating a stone, GIA experts receive precise geometrical parameters of, assess the quality of the cut and the polishing as well as its color, clarity and the presence of fluorescence.
Most GIA-certified diamonds include a laser-engraved GIA logo and the number of the diamond on the girdle (the lateral side that separates the upper and the lower parts of the diamond).

The certificate also indicates whether a diamond has been changed in any way in order to improve its quality.

GIA maintains a database of certificates which is available to the public on the GIA website.

Laser engraving along with geometric parameters and location of inclusions that are unique to each diamond is 100 % forgery-resistant. The certificate itself also has several degrees of protection.


The International Gemological Institute is a laboratory established in 1975, now operating laboratories & offices in Antwerp, New York, Hong Kong, Mumbai, Bangkok, Tokyo, Dubai, Tel Aviv, Toronto, Los Angeles, Kolkata, New Delhi, Thrissur, Jaipur, Surat, Chennai, Ahmedabad and Hyderabad. IGI Diamond Reports are issued for diamonds of any size; a plotted diagram of the characteristics and a graphic representation of proportions appear on many of IGI documents.


HRD – the High Diamond Council is located in Antwerp, Belgium. HRD Antwerp’s primary shareholder is the Antwerp World Diamond Centre (AWDC, a private foundation established in 1973 as the Hoge Raad voor Diamant (HRD) or Diamond High Council and represents the Belgian diamond industry. The HRD certification is characterized by a separate assessment of the proportions of a diamond such as the height of its crown and depth of its pavilion.


European Gemological Laboratory, first established in 1974 is a veteran among global gemological institutions around the world. The United States Headquarters of EGL is located New York City’s international diamond district. EGL certification focuses on the color and the purity of the diamond. The quality of the cut is secondary in this certification. An increased evaluation is possible at times because of features of the quality control system used in Europe. Evaluations according to the EGL procedure also exist in the United States and in Asia (EGL USA and EGL Asia). Their evaluation is generally similar to the evaluation of the European organization but includes certain features specific to the region.

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