All about emerald

The emerald owes its name to the Greek “smaragdos”, comes from a word meaning “to shine” and once referred to many green-colored gems.

The history of jewelry is inseparable from this noble gem, by its quality which ensures excellent durability, and the appeal it has aroused among amateurs and collectors. Do you want to know everything about the emerald, its origins, the evolution of its price? Read our article on the subject! 

History and general characteristics of the emerald

Emeralds have been mined and collected since ancient times. The earliest known source of emerald mining dates back to Egypt. Around 2,000 years ago, the pharaohs are said to have started the trade in emeralds by exploiting the mines located near Wadi Sikait. Furthermore, this stone was widely popularized thanks to Queen Cleophearth, who was an avid collector of emeralds.

Emerald is a member of the beryl family, along with aquamarine, emerald, heliodor and morganite, but it is the most valuable of all.

Its characteristic green color is attributed to chromium and vanadium, and it is this same color that will directly define the value of the stone: the brighter and more intense the green, the more valuable the emerald. It remains very stable to light, however it changes at high temperatures (700/800 degrees). The hardness of the emerald is between 7.5 and 8 on the Mohs scale; it therefore offers good resistance to scratches, however be careful, because its crystalline structure makes it fragile to shocks.

Emerald is also a highly included stone, easily recognizable by its so-called “emerald gardens” and are a real proof of authenticity for the stone, since it is almost impossible to find a “pure” emerald without inclusions in its natural state.

The emerald also gave its name to a type of stone cutting, the emerald cut, also called RPC (rectangle pans coupés) because it is particularly adapted to the stone, making it less vulnerable to shocks. Emerald cutting is an extremely delicate task; the forces applied to the stone during this cutting process can cause it to break at any time.

Emerald deposits

The largest and most beautiful emeralds come mostly from South America, particularly Colombia, where the crystals are extracted in extremely difficult conditions: in poorly ventilated galleries at a depth of 300 metres and in temperatures of over 40°C, miners work for 8 hours amidst the deafening noise of jackhammers...

Emerald crystallization results from the action of magmatic or hydrothermal veins on metamorphic rocks. Its deposits are located near intrusive pegmatites in biotite schists, clayey schists, as well as veins crossing limestone rocks.

The extraction of emerald crystals is carried out exclusively in its veins of the mother rock (alluvial mining is not possible because the density of the emerald is too low, which makes it fragile)

Colombian Emerald

Colombia is undoubtedly the land of emeralds, it produces the most beautiful emeralds, and therefore the most sought after. Just like the Kashmir sapphire, Colombian emeralds are likely to disappear from the market due to their high extraction, which considerably increases their price, or the most beautiful specimens now exceed several thousand dollars per carat.

Their deep green hue with a subtle blue undertone is indeed rarely surpassed by emeralds of other origins. However, unlike other colored stones, the origin of an emerald can only be established beyond doubt by using a microscope. There are only tiny inclusions, undetectable under a magnifying glass, that can indicate the place of origin of emeralds.

Located in the eastern part of the Andes, the two main emerald deposits are Muzo and Chivor, each located northwest of Bogota. There, emeralds are extracted from veins of a few centimeters, between 20 and 50 meters, galleries must be dug along the veins, or by knocking down sections of the mountain using explosives in order to create open-air “terraces”. Once these pieces of rock are harvested, they are sorted by hand at the mine exit, then studied and cut once sent to the capital, Bogota.

Brazilian Emerald

Today, Brazil is the main producer of emeralds in the world, both in terms of quantity and quality, which rivals the Colombian emerald and which has positioned it as a major player in the market, since the discovery of deposits in the 16th century in the states of Bahia, and later in the states of Goias and Minas Gerais.

Brazilian emeralds are extracted using the excavation technique, which involves digging galleries into the side of the mountain to reach the emerald veins. The rocks are crushed and then sorted.

Emerald from Zambia

Discovered in the 1970s, Zambian emeralds are a deep green tinged with blue, similar to Colombian emeralds, and are found in a deposit near the Kafubu River, on the border of the Democratic Republic of Congo. Despite their undeniable quality, the weight of Zambian emeralds is less, and rarely exceed 2 carats rough, allowing stones of 0.50 to 0.70 cut to be obtained.

Historical Emeralds in Chronological Order

• The Devonshire Emerald: 1384 carats, extracted from the Muzo mine in Colombia, it was offered by the Emperor of Brazil, Pedro I to the Duke of Devonshire in 1831.
• The Isabella Emerald: 964 carats, was discovered in 1993 in the wreck of a ship in Florida. It is said to have belonged to the famous Spanish conquistador Hernan Cortez.
• The Emerald of Moctezuma: was offered by the Aztec ruler Moctezuma to Hernan Cortez.
• The Topkapi emerald: 16,300 carats, stored in the Topkapi Palace in Istanbul
• The Great Mughal Emerald: 218 carats, engraved with religious inscriptions and floral ornaments. It was discovered in India in the late 17th century and now belongs to an anonymous buyer who bought it for over $2 million in 2001.
• The Patricia Emerald: 632 carats, it is one of the most beautiful emeralds in the world, currently on display at the Museum of Natural History in New York.

Synthetic Emerald

A synthesis, by definition, is the reproduction of a stone according to its physical and chemical characteristics, with the difference that one is produced by nature and the other by man. For emerald, there are two types of synthesis, which work by dissolution: 

1) Anhydrous dissolution

Developed in the 1970s, this process is used for corundum, emerald and quartz, it is one of the longest and most expensive (8 to 12 months, the gem crystallizes by 2mm). Aluminum oxide is mixed with fluxes (allowing to lower the melting temperature). The known laboratories using this technique are: Gilson, Chatham and Ramaura.

2) Hydrothermal dissolution

This process is used for corundum, emerald and quartz. The crystals grow in water at high temperature (500 degrees) and high pressure (1000) to simulate the natural conditions that exist underground when the crystals are created. The most famous laboratory in hydrothermal dissolution: Tairus.

Emerald Treatments

Oiling

As said before, the emerald is a naturally included stone. In order to hide these inclusions, it is possible to dip the emerald in natural oil that will penetrate the stone, which is called a beautification technique, natural and still practiced on emeralds, having a low impact on its price.

Filling

On the other hand, the filling - the impregnation - of emeralds with resin is considered a treatment that denatures the stone, since the resin is synthetic and not natural and creates a coloring in the emerald.

In fact, in addition to hiding the inclusions of the stone, it improves its color (artificially). This is why it is essential to have a certificate of authenticity from a laboratory, where the different treatments used on the emerald will be mentioned.

Evolution of emerald prices 

Among colored gemstones, emerald is the third most popular gemstone in the market, accounting for 18% of colored gemstone purchases for jewelry, just after rubies (23%) and sapphires (49%). 

In terms of price appreciation, in addition to the quality and the presence of treatment, we focus on the geographical origin of the emerald (also read above, the different emerald mines).

Among the origins, the Colombian emerald, of an intense green, which is the most prized. Then comes the emerald from Brazil and Zambia.

To illustrate the point, in 2017, an 18-carat Rockefeller emerald was sold to Harry Winston for $5.5 million ($305,000 per carat), a record price per carat.

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