The emerald
It is not exactly certain but the emerald seems to owe its name to the ancient Sanskrit term "maragata" whose literal meaning was, precisely, "green stone". 
This is also to understand, since Sanskrit is among the most ancient Indo-European languages, how long man has appreciated the beauty of this gem. Already Pliny the Elder (we are in the first century AD) in his Naturalis historia describes the color of "smaragdus" (this is the Latin term) as the most beautiful green that could be seen. 
The Egyptians extracted it as a symbol of fidelity and loyalty as early as 3,500 BC. in the mines of Zabarah on the Red Sea while the Romans went up to almost 1800 meters in the Habach valley, near today's Salzburg (where even today trekking enthusiasts can follow the emerald trail) to dig emeralds, among which without doubt the other ones were used to make the lenses that the emperor Nero used to watch the circus games as it was believed that the faceted emerald helped to rest his eyesight.
It is also possible, or at least plausible, that some of these lenses used by the rich Romans of the 1st century, by an absolutely fortuitous case, were worked in such a way that they could correct (imagine the surprise) any myopia even if then for to solve this problem in a conscious way we will have to wait for the usual Arabs at the end of the first millennium. 
In any case we can safely assume that the prototypes of the first glasses had emerald lenses. The most beautiful emeralds already reached a considerable value at that time, so much so that the Romans were the first to imitate it with green colored glass. 
Emerald (we have already said this in the ruby ​​blog) is the green variety of beryl. However, not all green beryl can be defined as emerald since when its green does not have the right tone and appropriate saturation it is simply defined as "green beryl".

When the beryl has a green-yellow color it is heliodorus and when the color is blue with green as a secondary color it is called aquamarine.
The intense green color of the emerald is instead due to very small quantities of chromium in the hexagonal crystalline system of beryl. With the right tone and saturation it is a wonderful, unique green and for this reason called "emerald green". 
Inclusions are almost always present in emerald and when they are totally absent we are almost certainly in the presence of a synthetic stone. Obviously this should be considered indicative and not diagnostic. 
In the best emeralds the inclusions are faint and not visible to the naked eye and you must use the 10X lens and for truly exceptional natural emeralds even under the microscope. The inclusions, among other things, almost always reveal their origin and their color also varies with their origin. African emeralds have a yellow-green hue and Colombian emeralds have a blue-green hue. 
The most beautiful and highest carat emeralds come from Colombia where the most famous mines are those of Muzo and Chivor.

Small quantities of emeralds of medium and only exceptionally high quality come from Brazil, from the mines of Carnaiba in the state of Bahia and that of Etabira in Minas Gerais, although it must be said that in recent years good quality emeralds have been extracted from the Santa mine Teresina de Gois.  
Since the 70s of the last century, excellent quality emeralds have been mined in East Africa, Zimbabwe and Tanzania but above all Zambia. However, the most famous for their color are those of Sandawana in Zimbabwe, intense green with a light yellow shade.  
African emeralds generally have a beautiful color and fewer inclusions but only very rarely do they match the warm and enveloping green of the Colombian ones, with the characteristic three-phase inclusions (liquid, solid and gaseous) accompanied in those of Chivor by albite and multifaceted crystals of pyrite and in those of Muzo by rhombohedral inclusions of calcite and parisite.  
The main flaw of the emerald, so to speak, is its fragility.  Fragility even more accentuated by internal inclusions and fractures, even those invisible to the naked eye. It has a hardness between 7 and a half and 8 on the Mohs scale and therefore much lower than sapphire and ruby. 
It is the most delicate of the "big three" and therefore it is always recommended to treat it with extreme delicacy and care.  It is advisable to always use great care when cleaning it, avoiding corrosive products and trying to avoid strong temperature changes which could accentuate the microfractures. It is unlikely, so to speak, that a jeweler will take the responsibility of cleaning your ring that mounts an emerald in the ultrasound tank. 
It is no coincidence that you will always find it set in very protective frames such as the "bezel setting" and almost always cut with a plank and steps in that typical cut that takes its name from it, "emerald cut". 
Even when other precious stones, a diamond for example, are cut in that way it is always called "emerald cut". 
Blanks that are not of great quality with particularly evident and invasive inclusions are instead often cut into cabochons.

It is difficult to confuse a beautiful emerald with other stones. Some green tourmalines with a particularly beautiful color may deceive you for a moment but they will never have the typical green of emerald and in any case have a much more marked pleochroism and a less decisive and above all less uniform color.
Sometimes even some intense green olivines could be deceiving at the moment but these too have a marked pleochroism with a tendency towards yellow and a notable birefringence compared to emerald. 
Emerald imitations. It was the Frenchman Ebelman, in 1949, who produced synthetic emerald for the first time. Gradually over the years and consequently with the improvement of increasingly sophisticated techniques, in the 50s of the last century it was possible to obtain excellent quality synthetic emeralds that were almost indistinguishable, to the naked eye, even for an expert, from a natural emerald. The safest identification in this case is ultraviolet radiation. 
Synthetic emerald, unlike the natural one, is transparent to short-wave rays. Furthermore, you will never find small-carat synthetic emeralds because it is absolutely uneconomical for those who produce them. As we said before, it is highly unlikely to see a natural emerald with absolutely no inclusions. Your trusted jeweler, to whom it is always advisable to contact, in this case also using the microscope, will certainly give you the certainty of your purchase. 
Another important aspect of the emerald is its treatment which obviously tends to improve the visual appearance of the stone both in terms of color and its inclusions. 
It is assumed that no less than 95% of emeralds are treated in some way.  
Usually the treatment takes place with cedar oil which has the advantage of being colorless and having a refractive index very close to that of emerald. 
There are also interventions with various more or less orthodox chemical components. In this case it is essential to distinguish between irreversible and reversible treatment. The first, commonly accepted in gemology, provides a more beautiful and economically interesting stone (even if obviously its value drops significantly) which will remain unchanged over time. 
In the second case, on the contrary, we will have a stone that is undoubtedly more fragile and susceptible to slowly returning to its mediocre original color or even breaking, due to fractures filled inappropriately, due to an impact or a sudden change in temperature. 
What can I say to conclude. Emerald is one of the most beautiful colored gems ever. The beauty of its greenery has an unparalleled charm. Its value is very high.

Beautifully colored stones, over two carats, have among the highest ratings in the field of precious stones which can easily equal and often exceed those of a diamond with the same characteristics.

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