The word emerald comes from the Latin word smaragdus, deformation of the Persian word zamarat which means "heart of stone". Like other metals and precious stones, myths and legends mingle with the historical reality of this gemstone. We already mention its presence in Babylon, in the second millennium BC. J. - C., where it served as currency of exchange. In the ancient period of Egypt, near the Red Sea, were emerald mines, which were made jewelry for the great of the empire. These mines of Djebel Zabarah, rediscovered in 1816 by the French explorer Frédéric Cailliaud, were wrongly nicknamed mines of Cleopatra. They were already exhausted, but they probably only contained gems of poor quality.
In Antiquity, authors such as Theophrastus, Herodotus or Pliny the Elder mention the presence of emeralds and sometimes describe statues, or even columns or obelisks carved in this stone. We now know that they were not real emeralds. In these remote times, other stones with green highlights could easily give the change, and there were already imitations, including glass. On the other hand, it is conceivable that statuettes were carved out of raw mineral blocks of lower quality.
In Roman times, this precious gemstone blade was used as an optical instrument by the Emperor Nero, who would have used it to correct his myopia when he watched the gladiatorial fights4. At that time, there was mainly one mine in Europe, that of Habachtal (de) in Austria. Discovered by Celtic tribes, it was also exploited by the Romans.
In the sixteenth century, Spaniards discovered new deposits in South America, mainly in Colombia. The Chivor mine will operate from 15455 and the Muzo mine in 15945.
In India, the "Great Mughal" stone, discovered in 1695, weighs 217.80 carats and measures about 10 cm. She wears religious inscriptions. She was bought for $ 2.2 million by an anonymous.
Until the beginning of the 20th century, it was also called "eastern emerald" a radically different stone: green corundum, whose composition is similar to that of ruby and sapphire.
Criteria for determination
The emerald is composed of aluminum silicate and beryllium, to which are added chromium, vanadium and iron. Its hardness varies between 7.5 and 8 on the Mohs scale. The emerald is slightly dichroic (green-yellow or green-blue). Its break is conchoidal and its line is white. Its density varies from 2.7 to 2.9.
The identification of this precious gemstone, in particular to establish links between known deposits (62 deposits in 19 countries) and ancient stones, is done by mass spectrometry, by measuring the proportion of its isotopes of oxygen. The 18O / 16O ratio varies from 7 to 25 depending on the deposits.
Emerald is soluble in hydrofluoric acid. She gives a bright green pearl when heated.
The crystalline system of the emerald is hexagonal, its space group is P6 / mmc. Its structure is very similar to that of beryl, the atoms Al and M (M = Cr, Fe, V) being located on octahedral mixed occupation sites connecting Si6O18 rings.
Emeralds are rare because their formation requires exceptional geological conditions:
beryllium, the principal component of beryl, is in fact mainly found in the magma of the earth's crust;
chromium, vanadium and iron, which transform beryl into emerald, are rather located in the Earth's mantle.
Between two known types of deposits, Brazil and Colombia, there are marked differences:
in Brazil, these precious gemstones were formed for some two billion years ago and others about 600 million years ago. The crystals have solidified by mixing with black mica and possess mineral inclusions. They often lack purity;
in Colombia, the formation dates back to 65 million years, when tectonic movements brought minerals to 300 ° C in contact with a sedimentary layer dating from the early Cretaceous, about 135 million years before our era.
Exploitation of the deposits
Map of the main emerald producing countries in the world.
Roman emerald necklace, third century, treasure of Lyon-Vaise.
In jewelry, it is mainly cut in "emerald" (rectangle with cut sides), "cabochon", "pear" or "oval". this precious gemstone is one of the most expensive gems. The very frequent presence of inclusions, graciously called "frost" or poetically "garden", is not a handicap, because it can attest to the origin of the stone; certain crystallographic originalities are much sought after by collectors (six-pointed star, called trapiche emerald).
Most emeralds are treated with oils or resins, which is why it is not recommended to clean them by the ultrasound technique, especially because of their fragility (inclusions or fractures).
Extraction and production
Colombia is the world's largest producer (60% of world production, 6 million carats for the year 1995): Chivor, Muzo, Peñas Blancas and Coscuez mines called the Golden Triangle. Not only is Colombia a champion of quantity, but also of quality. Its emeralds are generally purer than those from other sources. The Bank of the Republic of Colombia has a collection of beautiful stones.
The distribution among the main producing countries is as follows8:
Country Fields% production
Colombia Chivor, Muzo, Peñas Blancas, Coscuez 60%
Zambia Miku, Kufubu, Mufulira 15%
Brazil Santa Terezinha of Goïas, Belmont, Carnaïba 12%
Russian Urals 4%
Zimbabwe Sandawana 3%
Madagascar Ankadilalana 3%
Afghanistan (Pandjchir Valley)
The most important size center is located in India, in Jaipur, where the number of lapidaries is estimated at 100,000. The size of emeralds has grown because of the great predilection of the maharajah for precious stones and especially the emeralds from around the world. The size is practiced by looking for the minimum of losses, as in Brazil. Stones cut in Colombia were cut according to the same principle until the principles of European size, favoring the quality rather than the yield, were adopted by the cuttings of Bogota. The most beautiful stones are usually resized in Paris. In addition, Israel has developed a state-of-the-art center in Ramat Gan.
The most beautiful emeralds
Devonshire, a raw green crystal of 1,384 carats, is perhaps the most famous emerald. Extracted in the mine of Muzo (Colombia), it was offered in 1831 to William Cavendish, the 6th Duke of Devonshire by the Emperor Peter I of Brazil. In 1956, an emerald of 11,000 carats was found in South Africa. The most famous (and exposed) of these precious gemstones are in the following cities:
Topkapi Palace in Istanbul (16,300 carats);
Mineralogical Museum of Moscow (11,130 carats);
Kunsthistorisches Museum of Vienna: emerald called "Moctezuma", limestone block covered with this precious gemstone crystals that was offered to Hernán Cortés by the Aztec ruler; perfume bottle (2,680 ct);
Vienna (2,200 carats);
Imperial Treasury of Iran in Tehran;
British Museum in London;
The American Museum of Natural History in New York has an exceptional raw emerald in its purity and color, the Patricia (632 carats);
The 964 carat Isabella emerald that belonged to the family of Hernán Cortés, recovered in 1993 from a sunken wreck in 1757 off the coast of Florida by Victor Benilous9,10;
We can also mention this precious gemstone Saint Louis, cabochon of 51 carats which adorned the central fleur de lys of the so-called Saint Louis crown. This crown was part of the Regalia of the Kingdom of France since at least the end of the thirteenth century and was kept in the Treasury of Saint-Denis. If the crown was destroyed at the time of the revolution (1791), the stone is still preserved in the national museum of natural history, in Paris.
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