For the classification of diamonds it was necessary to find a recognized and valid method in the world to give an accurate market value to every single stone. GIA, in the mid-30s, developed a method for classifying diamonds. This method was then modified and updated periodically to adapt to the needs of the market. The 4 C, respectively; Colour, Clarity Grade, Carat, Cut.
The diamonds have internal features that are formed during the long process of creation under the earth's crust at about 150 km depth, in a particular condition of high temperature and high pressure. To determine the degree of clarity of the gemologist must consider the size, the position, the number of inclusions having a loupe 10X. The diamonds without any characteristic of clarity are considered pure, or internally pure, and hand-hand that these features increase, the degree of purity is lowered.
The Salvadori diamonds have a high degree of clarity, from pure to VS2, in which the inclusions can't be seen with the naked eye.
In a colour scale ranges from D to Z, the closer one gets to the absence of color, the higher the degree of color assigned. Salvadori uses a very high quality colour ranging from D to G. However, for Fantasy Colour diamonds, such as yellow diamonds, it is exactly the opposite; their value grows with the strength and intensity of colour.
The size of a diamond is given by its weight in carats, divided into points. One carat equals 100 points, or 1/5 of a gram. The carat originates from ancient times when merchants discovered that the dried seeds of the carob tree had a relatively constant weight and could become an excellent standard measurement. This is not to be confused with Karats which is the unit of measurement used to describe how much pure gold is in an alloy. Generally diamonds with higher carats, being less frequent in nature, have greater value. However, you can not only consider the weight to give it a value, because the number of carats is only one of several factors to consider when evaluating a diamond.
The cut determines how well a diamond has been cut, not to be confused with the way in which it was cut. (The most common way is the brilliant cut, followed by the oval, the tear-drop, the marquise and the heart cuts). The aspects of cutting that contribute to the beauty and to a return of light are optimal proportions, cleaning and symmetry. The parameters for assessing these factors are; excellent, very good, good, faint. The Salvadori diamonds are all excellent or very good.