Emeralds, the gemstone variety of green beryl, are well-loved for their unique green colour and are one of the most popular gemstones available today. The vivid green exhibited by emeralds is a result of the presence of chrome and, sometimes, vanadium, in the crystal structure. Colombia, Brazil and Zambia are today the top producers of quality emeralds, but Russia, India, Austria are also significant producers. Despite being a relatively hard gemstone (7.5 - 8), they are relatively fragile stones and are subject to cracking and breaking.
The long, shallow shape defined by the emerald cut is best for showing off the fire of a quality emerald. A good cut will enhance the quality of any gemstone and in emeralds, a shallow cut may bring more colour saturation than a deeper cut. In emeralds, cut is especially important as a good cut will minimize the effect of natural inclusions and prevent these flaws from penetrating deep into the gem. Emeralds may be cut into other shapes such as round, pear, oval and heart shapes.
Emeralds exist in a variety of shades of green with varying degrees of hue, tone and saturation. Emeralds exhibiting a colour of fresh green grass are considered to be the finest quality emeralds and increasing amounts of chromium in an emerald will dictate the darkness of the green colour. The colour of an emerald is often a strong indication of the origin of a stone - Columbian emerald is deep green with a slight blue undertone whereas African emerald has a slight darkening effect which may undermine its value. Consumers should look for uniform colour distribution in any emeralds they wish to purpose.
The clarity of an emerald is defined by the presence and amount of internal and external inclusions and flaws. A flawless emerald is almost impossible to find and inclusions are commonly used to verify the authenticity of an emerald. Given the likelihood of inclusions occurring in an emerald, the positioning of the inclusions becomes more important and inclusions occurring around the sides of an emerald would be preferable to inclusions found on the table.
As with other coloured gemstones, emeralds are typically enhanced during the gemstone preparation processes. Very few emeralds are found without fissures or surface cracks and it is thus common for them to have been oiled, waxed or filled with resin in order to create a smooth surface. These fissures are filled prior to the initial gemstone processing. Later, the stone will be treated with colourless oil or wax to make these flaws less prominent. Oiling is one of the oldest methods used for enhancing the clarity of an emerald.