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The 4Cs

The first thing to learn about diamonds is the "four Cs": Cut, Clarity, Color, and Carat (weight). And there is another "C" that has become important: Certificates.


The cut is probably the most important of the four Cs, because the brilliance of a diamond is heavily reliant on on the way it is cut.
The diagram below shows when a diamond is perfectly cut because it lets light enters through the table (the top flat part of the diamond) and travels to the pavilion (the lower part) where it fully reflects before exiting via the table.


A diamond's clarity relates to whether it has internal flaws, or inclusions, which are formed during the time it was formed in the ground. The visibility, number and size of the inclusions relate to the clarity of a diamond. Meanwhile, blemishes found on the surface of a diamond also affect the clarity. There are five levels of clarity.

IF – Internally Flawless and means there are no internal flaws, but some surface flaws. Understandably, these are very rare.

VVS1-VVS2 – Very Very Slightly Included (two grades). The stone has tiny inclusions which are very difficult to detect without a 10x magnification by a trained gemologist.

VS1-VS2 – Very Slightly Included (two grades). Minuscule inclusions seen only with difficulty under 10x magnification.

SI1-SI3 – Slightly Included (two grades). Very small inclusions more easily detected using 10x magnification.

I1-3 – Inclusions which are large enough to be visible both using 10x magnification and to the human eye.


The color of a diamond also plays an important role. Diamonds without any color are the most in demand as they allow the most refraction of light, or sparkle. By contrast, off white diamonds absorb light, thus preventing the brilliance from coming through.

Grading the whiteness, or lack of color, in a diamond is almost universally done according to the Gemological Institute of America's color scale. This starts with D, the highest rating for a colorless stone, and goes down the alphabet to grade stones with elements of very faint or light yellowish or brownish color. The color scale continues all the way to Z.


The weight of a diamond is measured in carats – in general, the heavier the stone, the more it costs. However, the other three C's also play a critical role.


The diamond certificate, also known as a grading report, is a full appraisal of the diamond carried out by a qualified professional with the assistance of special gemological instruments. A diamond certificate provides the individual characteristics of the stone.

There are several leadings labs, including gia, hrd, igi, ags and egl. There are also local labs in some countries, such as NGTC in China.
At Eliyahu Yona Diamonds Ltd., we mostly work with the GIA, which is the leading lab in the world.

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