The four factors that determine the value of the diamond are the four C’s, from the initials of these four words: Carat, Cut, Clarity and Colour.
As well as the 4 C’s, one can add another of extreme importance, that is, the Certificate of the diamond.

Carat (weight)

Diamonds are weighed in carats, an ancient measuring unit that used the seeds of the carob tree. A carat is equivalent to 0.2 grammes. The carat can be sub-divided into granules equivalent to 1/20 of a gramme, and into points equal to 1/100 of a carat.


To obtain two brilliant cut diamonds from a rough diamond with the shape of an octahedron, one can consider various options, depending on the inclusions, the growth lines and the quality of the final cut that one wishes to obtain.

Reflecting light

A cut diamond can be perfectly shiny or can present some problems, for example: growth lines, caused by the way the diamond has formed, more or less intense; and scratches on the facets, which can form during the cutting process of the stone.


The characteristics of symmetry can be magnified more than 10 times and assessed on the basis of measures of frequency and visibility.


During the cutting phase scratches can form in some facets of the diamond which will determine the quality stated in the certificate under the term “polish”.


The inclusions of the diamond are internal characteristics caused by various factors. They can be natural or they can be caused during the cutting process of the stone.

It is worth remembering that these are not imperfections but natural characteristics that each diamond possesses rendering it unique. When the diamond is put under pressure, it can provoke fractures and breakages.


Diamonds can assume almost all colours, due to impurities or structural defects: yellow and brown are the most common. Black diamonds contain numerous inclusions that give the gem its dark look.

When the colour is quite saturated in yellow or brown diamonds, the stone can be defined by the gemmologist as a fancy color diamond, otherwise it can be classified for colour according to the normal scale of colour of white diamonds.

Colour scale

The Gemmological Institute of America (GIA) classifies yellow and brown diamonds of low saturation as diamonds on the normal colour scale, and applies a graded scale from “D” (exceptional white) to “Z” (clear yellow.) The GIA classifies diamonds that have more colour than a “Z” as fancy color, together with those that have colours that are different from yellow or brown. The rarest colour diamonds are red, which never reach notable sizes, followed by intense green and blue.


Some diamonds subjected to ultraviolet radiation (366 nm) can show fluorescence, which consists of the emission of energy under a type of light caused by the temporary disruption of electrons in a substance, when it receives particular treatments such as heating, irradiation with X rays , irradiation with ultraviolet light etc.

Fluorescence ends when what causes it ceases. Fluorescence, depending on the extent of it, makes the diamond appear more or less veiled, that is not completely transparent, which influences negatively on the final price.

Fluorescence scale