ENCYCLOPEDIA
EMERALD FULL GUIDE
CHARACTERISTICS OF EMERALD
Etymology: From the Ancient Greek smaragdus, meaning green stone.
Family: Beryl
Chemical composition: Aluminum silicate and beryllium
Hardness: 7.5 on the Mohs scale
Density: 2.67 – 2.78
Optical properties: Uniaxial birefringent
Refractive index: 1.56 – 1.58
Birefringence: 0.006 – 0.01
Crystal system: Hexagonal
THE ORIGIN OF EMERALD
First discovered in 3500 BC in the mines surrounding the Red Sea, which have now run dry, in the present day emerald is sourced from deposits in South America, Africa and Asia.
Although the most famous emeralds in the world are undoubtedly those sourced from Colombia, they have been mined intensively for many years and reserves are becoming increasingly scarce as a result. Brazil has now overtaken Colombia as South America's largest producer of the famous green gemstone. There are very few mines in the world that produce such high quality emeralds as Brazil. It also has some of the most environmentally friendly mining practices in the world.
On the African continent the largest producer of emeralds is Zambia. In fact, its highly sophisticated mining technology gives us 35% of the world's emerald supply. It is closely followed in the rankings by Russia and Afghanistan, where some of the most beautiful emeralds in the world can be found.
Last but not least, Pakistan (where production is irregular due to the country's political turmoil) and the Yunnan province in China. This latter deposit was discovered at the start of the 1990s and has not yet seen much mining exploitation. The Chinese government has only recently begun to show interest in it. China could therefore soon become one of the world's major players in emerald production.
Although the most valuable emeralds tend to be cut in Israel, most emeralds are cut in Jaipur, India, where untreated stones sourced from around the world are sent.
CARAT
The carat value of a stone, not to be confused with the karat (a unit used to determine the purity of precious metals), is used to assess the weight of precious stones. The more a stone weighs in carats, the more valuable it is. For example, a 1-carat emerald weighs 0.2 grams, which means that a 5-carat emerald will weigh 1 gram.
Emeralds are very popular for celebrating engagements and emerald wedding anniversaries. The most common sizes range from 1 to 5 carats. However, it is possible to find exceptional stones weighing over 20 carats.
Emeralds have a lower density than other gemstones, which means that even if an emerald weighs the same as a diamond or sapphire, it will still be larger than them.
THE COLOR OF EMERALD
Emerald is a green gemstone belonging to the beryl mineral family. In order to qualify as an 'emerald', beryl minerals must have a certain level of saturation and green color intensity. If the green of a stone is too pale it is simply called a green beryl. Similarly, if a stone is too blue or too yellow it is not classified as an emerald but as a different variety of beryl and its value will drop significantly.
The most sought-after colors for emeralds are green with a slight blue hue and 'pure' green with an intense saturation level. As well as boasting a beautiful color, emeralds must be transparent and the color must be homogeneous.
Emerald is slightly dichroic, which means that it displays different colors depending on the angle from which it is looked at (yellow-green or blue-green). The way in which lapidaries cut the stone is therefore a crucial factor in displaying its color well.
Like ruby, the origin of an emerald can also affect its color. For example, Colombian emeralds are known for their pure, warm and intense green color. And Zambian emeralds are renowned for the touch of blue in their beautiful green color.
HUE
The hue of a gemstone describes its shade. Emeralds have many different hue combinations that make each stone completely unique.
SATURATION
Saturation refers to the degree of color intensity of a gemstone. This is an essential indicator in the valuation of emerald.
TONE
Tone refers to the brightness of a gemstone, describing whether the color falls towards the light or dark end of the spectrum. The most sought-after emeralds tend to have a medium to medium-dark tone.
THE CLARITY OF EMERALD
Emerald has more inclusions than any other gemstone. Its inner fractures and imperfections, which are also poetically dubbed 'jardins' (French for garden), can be easily seen from the outside, as can tiny cracks on the stone's surface. Emeralds without inclusions visible to the naked eye are extremely rare. However, inclusions should not affect the transparency of the stone, which is one of the most important factors to consider when buying an emerald.
Although Colombian emeralds are renowned for their beautiful color, they nonetheless tend to have more inclusions than Zambian emeralds which tend to be 'cleaner'.
CUTS & SHAPES
Cutting an emerald is a delicate art because its many inclusions and cracks make it a highly fragile stone. Each and every part of the cutting, polishing and setting process must be carried out with the utmost precision in order to prevent the stone from breaking.
The rectangular emerald cut has traditionally been the most common shape for emeralds. It was invented specifically for this gemstone so as to protect its fragile angles and consists of one large rectangular face with step cut sides. However, this green stone can now also be found in many other shapes including cushion, oval, pear, heart and round.
ROUND EMERALD
CUSHION EMERALD
PEAR EMERALD
OVAL EMERALD
CALENDAR
The emerald is the birthstone of anyone born in the month of May. It is also used to celebrate 40 years of marriage in France and 35 years of marriage in the US (emerald wedding anniversary).
FAMOUS EMERALDS
Devonshire Emerald
One of the most well-known emeralds in the world is the 1384-carat Devonshire Emerald. It was discovered in the famous Muzo mine in Colombia in 1831 and was given to the Duke of Devonshire by Emperor Pedro I of Brazil.
Patricia Emerald
The world-famous 632-carat Patricia Emerald was discovered in Colombia and is renowned internationally for its unrivalled clarity and radiance. It is currently on display at the American Natural History Museum in New York.
Hooker Emerald
The 75.47-carat Hooker Emerald was sourced from Colombia and is set into a platinum brooch and surrounded by diamonds. It is currently on display at the American Natural History Museum in New York.
Elizabeth Taylor Emerald
This brooch contains a gorgeous 23.46-carat emerald surrounded by diamonds and was given to Elizabeth Taylor by Richard Burton. It was sold at Christie's in 2011 for $6,578,500.
TREATMENTS
Embellishment, which enhances the natural beauty of the stone, is done to practically all emeralds on the market. It is carried out with pure natural cedar oil, which was chosen because it is colorless and has a similar refractive index to the emerald. Firstly, the emerald is placed in a hydraulic cylinder. Then heat and pressure is applied so that the oil enters the cracks of the stone. This method is called fracture-filling using cedar oil. The amount of fracture-filling carried out depends on the quantity of inclusions in the stone.
Other types of stone modification carried out using colored or synthetic oils, resins, glass or wax alter the natural stone and significantly decrease its value.