The price of a diamond depends on its weight, its color, its purity and also on the quality of its cut and its degree of fluorescence.
The most common cut is named «round brilliant» and consists of 58 facets.
A perfect cut ideally lets the light shine through the gemstone and makes it glitter.
Cutting techniques remained relatively rudimentary until the beginning of the 20th Century. Research in physics, optics and refraction of the light into gems led to the discovery of the principles ruling over the symmetry by which the cutter must abide, except in rare cases.
In 1919 Tolkowsky published a treaty in which he indicated how a diamond had to be shaped in order to glitter as much as possible. This technique consisted of 58 facets : the table facet, 32 facets between the table and the girdle and 24 facets between the girdle and the culet (which is no longer facetted). This technique is seen as being the original version of the modern one.
The unit of mass used to weigh gemstones is named: «carat». A carat is equal to 0,20g and is divided into 100 «points» or hundredths. The weight indicates the size of a gemstone but is in itself not sufficient to determine its value.
Diamonds contain impurities which are the traces of the crystallization process. International norms codify the various degrees of purity.
Diamonds can be of any color. Highly colored as well as colorless diamonds are very rare and valuable.
When a diamond is exposed to ultraviolet rays it sometimes gives out a visible shade which can be blue, white, purple, yellow, green or orange. A cut diamond has a lower value if it is too fluorescent because when it is exposed to light it gives the impression to be of a quality which seems superior to what it really is. A highly fluorescent gemstone tends to look milky. Fluorescence, according to its intensity, can reduce the value of a diamond from 5% to 20%.
on a laboratory report.