The guild's emerald color grading system is based on emerald colorimetric stones. According to Munsell's color theory, color grades are divided into five levels: light, medium, thick, fresh and deep.

Guild Emerald Color Grading System

Among them, Vivid represents a color with high saturation and brightness.

Emerald (Wharton Green) refers to the green with high saturation and brightness among bright green, which represents the top color of emerald.

Relationship between green and bright green

Emerald is a color with high lightness and saturation in bright green, and it is the top color in emerald color rating. Emerald is to emeralds what pigeon blood is to rubies and sapphire is to sapphires. Emeralds that reach turquoise must meet the following requirements:

Color originated naturally, reaching VividGreen level, with higher lightness and saturation;

The place of origin is not considered as a factor to evaluate the greenness, and emeralds of any place of origin can only reach the standard in hue, lightness and saturation.

The optimal levels of transparency are none, extremely slight, slight and slight to medium.

Emerald usually needs clarity treatment because of its growing environment and gemological characteristics, but a higher degree of optimization will affect the color. Therefore, emeralds with medium and significant cleanliness optimization grades can't get the emerald grade.

Emerald usually needs clarity treatment because of its growing environment and gemological characteristics, but a higher degree of optimization will affect the color. Therefore, emeralds with medium and significant cleanliness optimization grades can't get the emerald grade.

Emerald with any of the following characteristics can't get the green grade: (1) surface coating, dyeing or other discoloration treatment; (2) There are obvious quality problems, such as obvious color bands, dark inclusions and bottom leakage; (3) There are obvious fillers on the surface; (4) obvious and widely distributed unoptimized cracks; (5) Optimal level of moderate and significant cleanliness.

Comparison between the sample to be tested and the colorimetric stone

In addition, the standard colorimetric stone is the lower limit stone, and when the color of the sample to be tested is between two kinds of colorimetric stones, its color grade is lower. For example, the color of emerald is between bright green and emerald green, and its saturation and lightness are between the two sides of the colorimetric stone (Figure 4). According to the lower limit rule of the colorimetric stone, the color grade of the sample is bright green. This means that the grading standards are stricter. Therefore, when you buy emeralds, you must choose a certificate issued by a reliable laboratory in order to follow strict testing standards and get scientific and effective color results.

Comparison of color grading standards between Wharton green and wood left green

You must like precious stones. You've heard of wood left green. What is the essential difference between it and Wharton Green?

As we know, the origin and color are not necessarily related. Although color is a reference factor to judge the origin, in fact, judging the origin is a complicated work, which needs to consider many factors such as basic gemological parameters, inclusions, spectral characteristics, trace element content and distribution.

Emeralds in wooded mining areas are rich in color.

Therefore, origin and color are two concepts, and emeralds from different origins overlap. High-quality emeralds are not only unique to Colombia, but also top emeralds in Brazil, Afghanistan and Zambia.

Some laboratories use Muzuo green to describe colors, a certain place of origin to represent the top color of emeralds, and Colombia as a color grading requirement. This is not a scientific and effective approach, mainly because:

Color and place of origin are two main factors to judge the value of emeralds in the market at present. They should exist independently of each other, not necessarily related, and should not intersect. Therefore, it is very misleading to introduce the concept of origin when judging color.

According to the introduction of gemologists from Guild Laboratory on 20 16, they visited the Muzo mining area in Colombia and had in-depth discussions with dozens of prestigious and experienced local businessmen. After collecting a large number of color standard samples and origin standard samples, they found that the emerald produced in Muzuo mining area is rich in color (Figure 5). But semantically, these gems should all be called Muzuolv.

With the continuous exploitation of various mining areas and the continuous exploration of new mining areas, high-quality emeralds have appeared in various producing areas, which is not unique to Colombia. Brazil, Afghanistan, Zambia and newly discovered Ethiopia all produce many high-quality emeralds.

Therefore, color and origin are two independent factors to evaluate emeralds, and origin should not be considered in color classification. Obviously, the grading conditions of wood for green are unfair and unscientific to emeralds in other places, and are full of contradictions and disputes. Therefore, the definition standard and implementation of Wharton Green are more conducive to the healthy and benign development of jade trading.

Guild certificate home page

1: vividgreen * stands for green.

2. For the analysis of green, please refer to the attached page.

Tips:

"Brightness" refers to the brightness of a color, such as lightness and darkness. The higher the brightness, the brighter the color.

"Saturation" indicates the depth of the color. The higher the saturation, the darker the color.

Conclusion Due to strict color grading requirements, rigorous color theory, accurately calibrated standard colorimetric stones, strictly trained color grading personnel, qualified grading environment and scientific operation, the above five requirements are indispensable.

At the time of purchase, because of the shopping mall environment, photo or video shooting environment, etc. If the classification requirements are not met, the human eye's judgment on color is easily influenced by the outside world. Therefore, it is very necessary to buy emeralds with color grading certificates. Note that the certificate needs to select an authoritative organization, such as Guild, GIA, Gübelin, etc.