Emerald is one of the four recognized precious gemstones, along with sapphire, ruby and diamond, and the official birthstone for May. It has been one of the most desirable and valuable coloured gemstones for centuries. Today, emerald is one of the most expensive and sought-after gems due to its unique green colour, durability and rarity.
Emerald Origin and Formation
Emerald is the green to a greenish-blue variety of beryl family gemstones that form in igneous, metamorphic and sedimentary rocks under heat and pressure for hundreds of millions of years. Its name comes from the Greek word “smaragdos” and the Latin “smaragdus”, meaning green gemstone.
Emeralds are made of 4 elements such as beryllium, aluminium, silicon and oxygen. When the conditions deep in the Earth’s crust are just right, these four elements form emerald crystals.
The green colour of emeralds is caused by the presence of chromium, vanadium or iron. The most highly valued emeralds have a pure green colour with vivid saturation with no visible colour variations throughout the stone. If the gemstone is not dark and saturated enough, it is not considered a true emerald. In such a case, it is called green beryl.
Emeralds are mined from many locations around the world, such as the United States, Australia, Russia, Pakistan and Afghanistan. However, the three major sources are Colombia, Brazil and Zambia. Colombia is the most famous source of the finest deep green emeralds, and it produces 70 – 90% of emeralds for the global market today. Brazilian emeralds are valued for their high clarity and slightly yellowish-green colour, while Zambian emeralds are desirable for their slightly bluish-green shade.
Emerald Colour and Clarity
Colour is the chief determinant of value when talking about emeralds. It is evaluated by three components: hue, tonal grade and saturation.
Hue describes the type of green the emerald has, for example, bluish-green, yellowish-green, etc. Tonal grade refers to the level of lightness or darkness of the green, while saturation refers to the intensity of the colour.
There are many shades of emeralds from medium to dark green, blue-green and sometimes slightly yellowish or bluish-green. However, the most popular and valuable colour for emerald ranges from slightly bluish-green to pure green in a medium-dark tone with strong or vivid saturation.
Clarity is important for emeralds, but their inclusions are tolerated more than in any other gemstone. According to the Gemological Institute of America (GIA), emerald is a Type III clarity gemstone, meaning even good quality emeralds used in fine jewellery today are in I2 to I3 clarity range. These imperfections are not looked upon as negative attributes as they would be for other gemstones. In opposite, flaws are considered part of the character of emeralds, and a lack of inclusions is often a sign of a fake emerald.
Unlike diamond, emerald clarity is graded by the eye. If an emerald has no inclusions visible to the naked eye, it is considered flawless.
Types of Emeralds
Emeralds are differentiated by their place of origin or the presence of a certain type of impurities. Below are the most popular emerald varieties.
As the name suggests, Colombian emeralds are mined in Colombia. These gems are known for their exceptional quality and high value.
Brazilian emeralds are mined in Brazil. They have a lighter green colour than those from Colombia. It is worth mentioning that the term “Brazilian emerald” sometimes refers to green tourmaline.
Zambian emeralds come from mines found in Zambia, and they were not that favoured by the high-end market until 1989. Things changed when Tiffany and Co. began to promote Zambian emeralds for their distinctive characteristics.
Cat’s Eye Emeralds
This type of emerald got its name due to a cat’s eye effect called chatoyancy, an optical reflectance effect caused by aligned inclusions in a stone. Cat’s eye emeralds are very rare and can only be found in paler green emeralds.
Star emeralds are extremely rare, and most are found in either Brazil or Madagascar. This type of emerald exhibits the rare occurrence of asterism, which is the appearance of a rayed star moving inside the gem.
Trapiche emeralds are the rarest type of emeralds, a combination of emeralds and lutite found in Colombia. Because of the hexagonal structure of emeralds, these two minerals alternate and form a pattern looking like the spokes on a wheel.
Russian emeralds are one of the finest quality gemstones sourced from the emerald mines in the Malysheva region of the Ural Mountains. These unique gems are prized for their light to medium and slightly dark green colour, high clarity and considerable size. Fine quality Russian emeralds are quite rare on the market, making them highly sought-after by gem collectors.
Panjshir emeralds, also known as Afghan emeralds, come from the Panjshir Valley, located north of Afghanistan’s capital Kabul. This area is rich with more than 172 mines and produces unique bluish-green emeralds comparable to the very finest of Colombian emeralds.
Swat emeralds, also known as Pakistan emeralds, come from the Valley of Swat, Pakistan, one of Asia’s largest deposits of emeralds. These rare and highly prized gemstones are recognized for their unique green colour ranging from medium to deep green, distinctive smoothness and flawless transparency.
Torrington emeralds from New South Wales, Australia, are among the rarest of all emeralds in the world since this little deposit has already been exhausted. This unique variety of emerald exhibits alternating bands of green and clear running along the length of the gemstone, giving it a very unusual appearance.
Sandawana emeralds come from an important source of superb quality gemstones Sandawana mine in Southern Zimbabwe. This mine produces highly included gems of intense colour and small size. Sandawana emeralds are known for their deep, balanced, vivid green colour and reputation for being easier to cut and polish than emeralds from other locations.
Emerald is one of the most valuable gemstones in the world. As a naturally included gemstone, emerald is priced in a slightly different way than all other coloured gems. The price of natural emeralds is mainly determined by their colour. The most valuable stones have a green hue, vivid and deep tone, and not too dark or light saturation consistent throughout the gem.
Although emeralds can be cut into any shape, the cuts which enhance the gem’s natural colour and sparkle add to its price.
Another price determinant is the size of the gem. Larger emeralds are harder to find, so they are much more expensive than smaller ones. And the final indicator for the price is the source. Gems coming from Colombia are the most valuable, with those from Zambia and Brazil just behind.
Emerald Care and Cleaning
Although emeralds are durable gemstones, 7.5 to 8 on the Mohs hardness scale, they require more care than other beryl forms. It is recommended to remove your emerald jewellery before household cleaning since this gem is sensitive to chemicals such as ammonia, alcohol, bleach and other acids. Also, it is better to remove your emerald jewellery before exercising and other physical activity, as it can be scratched by other harder materials. As a general rule, you should put your emerald jewellery on last when dressing. Chemicals from makeup, hairspray, perfume and body creams can change the gem’s colour or make it look hazy.
To clean emeralds at home, you use some mild dishwashing soap liquid and warm water. Carefully place your gemstones in the liquid you have prepared and soak them for about 20 – 30 minutes. Next, use a soft toothbrush to remove the dirt. Rinse out your piece of jewellery with clean water and dry it with a soft and lint-free cloth.
Due to their naturally included and flawed formation, emeralds are commonly treated to enhance their durability and bring out colour richness. That is why it is important to ask the jeweller if the gemstone you are about to buy has been fracture-filled or oiled. If so, you should avoid ultrasonic and steam cleaners. Ultrasonic vibrations may destroy the filling, and hot steam may cause the oil and filling sweat out of fractures. Also, it is better to avoid using commercial jewellery cleaners on your emeralds as they are usually harsh and can damage the stones.
When storing emerald jewellery, keep it separated from other softer gemstones to prevent them from being scratched. Similarly, you will want to protect your emeralds from harder gems such as diamonds, meaning it is a good idea to store them in individual cloth jewellery bags.
|Chemical Name||Beryllium aluminium silicate|
|Colours||Emerald-green to green, yellowish-green to bluish-green|
|Hardness||7.5 - 8 on the Mohs scale|
|Refractive Index||1.565 - 1.602|
|Specific Gravity||2.7 - 2.8|
|Transparency||Transparent to opaque|
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