Russian technical requirements for emeralds clarity TU 95 335-88
Samples of Russian emerald from the collection of Gokhran of the Russian Federation. Photos provided by the Gemological Center of Moscow State University
The main indicators of emeralds are color, purity, group by weight, type of cut, proportion and quality of processing.
The color of emeralds is characterized by color tone and lightness.
Depending on the color tone and lightness, emeralds are divided into five color groups :
1 – dark green;
2 – medium-dark green;
3 – medium green;
4 – medium light green;
5 – light green.
Emerald standards set by the Gokhran of Russia
Some samples of emerald selected according to the standards of Gokhran of Russia
The purity of emeralds is characterized by their transparency, the manifestation of internal natural inclusions, cracks that determine the appearance of a faceted stone.
Depending on the manifestation of these parameters, emeralds are divided into :
1) faceted, into three purity groups (G1, G2, G3);
2) cabochons – into two groups of purity (K1 and K2).
| Parameter | Faceted stones | ||
| 1 | 2 | 3 | |
| Clarity | transparent | transparent | partially lost transparency in the peripheral zone of the stone |
| Inclusions and cracks | rare, barely visible to the naked eye | thickening and network in certain zones of the stone, visible to the naked eye | forming condensations and a network in the volume of the stone, visible to the naked eye |
| Сabochons group | |||
| Parameter | K1 | K2 | |
| Clarity | partially lost transparency in the peripheral zone of the stone | lost transparency in the central zone or in the volume of the stone | |
| Inclusions and cracks | forming a network in volumes of stone | forming a dense network in the entire volume of the stone, visible to the naked eye here |