Expert evaluation: a diamond evaluation procedure that comprises the comparison of the diamond to other diamonds based on specific criteria. The set of such criteria constitutes an expert evaluation system. Typically, expert evaluation of diamonds is implemented according to four parameters (4 “C”):
The first “C” is the carat weight.

At this stage, the precise determination of the diamond weight is performed by weighing on the scales or calculating with the use of formulas if the diamond is attached to a product. The weight of a diamond is expressed in carats (1 ct = 0.2 gram).
The second “C” is the color.

Diamonds that have no color (are completely colorless) are of a particular value. The color scale is divided into groups beginning with completely colorless diamonds (the most valuable), which is followed by a smooth transition with an increase in yellow-color saturation, and ends with the last group, which has a clear yellow color.
The third “C” is the clarity.

At this stage, all the internal imperfections (defects) of the diamond are identified. The evaluation of the impact of defects on the purity takes into account the size, the nature, the quantity, the position, the brightness / color of internal features, and – in some cases – external features.
The fourth “C” is the cut.

At this stage, the characteristic of the shape of a diamond, the cut quality, and the finishing is provided.