Characteristics of good emeralds

Emeralds are unique precious gems in the world, and as we have mentioned before, there is no emerald the same as another. 

Therefore, each emerald lies with different characteristics, such as color, clarity, weight and many other qualities that make one stand out from the other. 

Below we will present some of the main characteristics of these precious gems, and also, we will give you some tips to apply when purchasing an emerald. 

Characteristics of emeralds 

Color: 

Green is the generic color of Colombian and world emeralds, however, not all stones retain such purity in their hue. In this order of ideas, there are five distinguished classes of emeralds:

• bluish green
• slightly bluish green
• faint bluish green
• green slightly yellow 
• deep green

The deep green color being the most beautiful, rarest, most valuable, and also the most exclusive tone, a tone that is only found in the mountains of Colombia.

Clarity: 

The fewer impurities an emerald has, the higher its value. In the natural emerald you can find different  inclusions (natural cracks) such as gauze, coals, other minerals and impurities that can affect the clarity of the stone. 

Depending on the transparency of the stone and the degree of inclusions, emeralds can be classified as follows: 

• Transparency : depending on the level of clarity of the stone, emeralds can be:

1. Transparent : its color is intense and the background in which the stone is located is observed 
2. Translucent: the color is faint and the background in which the stone is located is observed 
3. Opaque or bland: its color is intense, however the background in which the stone is located cannot be distinguished. 

• Inclusions: they are classified according to the intensity of the inclusions as follows: 

1. Grade B: low level, the emerald has many inclusions.
2. Grade A: weak level, the emerald has moderate inclusions.
3. Grade AA: good level, the emerald has only a few inclusions.
4. Grade AAA: excellent level, the emerald has very fine inclusions, not very noticeable to the human eye. 

Cut or size :

The cut of an emerald is a very important aspect, since it not only defines the shape of each stone, but also influences the final weight, color and brilliance of the gem. 

Emeralds, diamonds, sapphires, and all other stones can be cut in many different ways. These are the main cuts of the emerald: 

• Emerald cut or cut: The shape is rectangular, with cut corners. It is a traditional and demanding carving since it is easy to detail the defects of the stone.
• Baguette cut or cut: reminiscent of typical French bread, it is elongated and rectangular with octagonal corners. This cut adds character to the jewel, but it is not easy to use in jewelry stores. That is why it is usually worked together with other forms.
• Cabochon cut or cut: it is found in very old jewelry, in fact it is the oldest cut. It is cushion cut with rounded corners. It requires very high quality stones.
• Cut or cut oval: it is a simple and regular shape. The advantage is that its elongated shape makes the stone appear larger than the round cut.
• Round cut or cut:  it is the same brilliant cut, difficult to make but it adds shine to the stone.
• Teardrop-pear cut or cut: it is widely used in jewelry because it enhances light and adds asymmetry to the design

Weight :

Weighing diamonds, gems and precious stones requires a carat scale that is accurate and reliable. Remember, however, that you won't necessarily find a specific formula to find the exact value of a gemstone.

The weight of an emerald is measured in carats , one carat equals 0.02 grams. Taking the above into account, the weight of an emerald is exponential, so a one-carat emerald will not be worth the same as a two-carat emerald, since the larger an emerald is, the more scarce it is. 

Treatments:

Most emeralds have not only numerous internal inclusions and fractures, but also small fissures or cracks on the surface. For this reason, the vast majority of emeralds are treated to improve their clarity. The most common treatments performed on emeralds are:

• Cleaning: Cleaning is a simple overnight soak in a jar of the cleaning medium on a hot plate with which you want to clean the emerald. This is done in warm, not hot conditions.
• Organic Solvents: Safe organic solvents to use with emeralds are acetone, methyl alcohol, ethyl alcohol, and a solution of methylene chloride for dissolving cured epoxy and polyester resins
• Oiling : The traditional treatment of the emerald is oiling with cedar oil. Cedar oil is a natural product of cedar trees and is colorless and viscous. Traditionally this cedar oil has been used to fill emerald fractures because it has a refractive index that is similar to emerald.
• Acids: when organic solvents do not remove contaminants, acids are used for intense cleaning. Normally a mixture of one part nitric acid to three parts hydrochloric acid is used.

Likewise, it is important to know that institutes such as the GIA ( Gemological Institute of America ) have developed a classification scheme in which the level of fissures that reach the surface of the emerald and that have been filled or treated is evaluated, classifying them as: 

• Minor: little treatment 
• moderate: measured treatment  
• significant: subjected to exhaustive treatment 

Tip: 

If you have doubts when buying an emerald, not sure if it has treatments or if it is natural, the only way to ensure that you receive an authentic gem is through a certificate issued by the GIA. If you want to make a good purchase, you can ask the seller to test the stone to verify its veracity.

Paula A. Bonilla 

Social communicator and journalist from Sergio Arboleda University in Colombia. She is also a jeweler and is passionate about constantly learning about precious gems and national high jewelry.

Currently, she is working for one of Bogotá's most important jewelry stores, Emerald by Love. This jewelry store has over 40 years of experience and has 2 physical branches in the capital city of Colombia, located in the city center.