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Emerald The Gemstone

All you need to know about Emeralds

Emerald fields and sources

Emerald fields and sources

EGYPT

The oldest emerald mines are those from Scythia and Upper Egypt.

Located on the coast of the Red Sea to the south of Quseir at Djebel Sabara and Djebel Sikai, these mines were worked up from the time of the Pharaohs;

It is proved by the fact that in several Egyptian mummies emeralds were found. These ancient mines were visited in the first half of the 18th century by Cailliaud in a special expedition ordered by Mehemed Ali Pascha and later were then explored by other scholars. Some of them show the work of man in superficial works, others in underground works; Some of these mines are very large, so much so that it is estimated that more than 400 men could work. It is not indeterminable that the time when they were discovered it was thought to have been exploited since 650 AD.

At the time of Alexander the Great, it was established that these mines were being worked by Greeks and then had a new impetus under the Cleopatra government; This fact is proved by the habit that the queen had to give emeralds with engravened effigy. Even in the Roman ruins of Pompeii and Herculaneum, the emeralds found proved that such gems were known and used by the Romans as well.

The Egyptian mines were also worked subsequently by the Arabs and the Turks, and then when they were discovered again they underwent other jobs then abandoned them after a short period of time.

Egyptian emeralds are found included in mica schists; They are a beautiful colour, but the gems that are a little pale are fairly common.

COLOMBIA

At the end of the 15th century emerald trade from South America began in Europe; The first to know the emeralds on this continent were the Peruvians; Later on the Spaniards took over the mines and subsequently discovered emerald mines in Colombia and Mexico.

The main production area is located in the eastern Cordillera of Bogota in Somondoco, Coscuez, Chivor and Muzo, to the left of the Rio Cararé and Minero (the latter narrow and deep) and their tributaries in the Boyaca district.

The most important mine and the most well known and the Mina Real de Muzo 50 Kilometers north of the capital of Santa Fe in Bogota, followed by those from Pefia Blanca.

The Muzo and Coscuez mines group is located in a valley close to the eastern Cordillera of the Andes, at 787 meters above sea level in mountainous and friable terrain with steep slopes. Emeralds are discovered in a scintillating complex, in calcite veins that cross clay from the lower Cretaceous age.

The emerald area of Muzo consists of four layers of perfectly distinct rock formations.

I) capas (good layer or emery layer): It is produced by carbonaceous shapes that are alternated with compact limestone, with a thickness varying from 20 to 50 meters (meaning M30), characterized by the presence of minerals such as: parisite, florite, apatite, cobalt, pyrite, quartz and, less frequently, albite and barite;

II) cem’cero (ashbin): It is contact between the capas and the underlying third layer, but it may also be lack Its thickness of around 20 centimeters. It consists of a kind of grey cement with small crystals of calcite, dolomite, baritine, pyrite, calcopyrite, quartz, often pure sulfur crystals, malachite, and azurite;

III) Gama (sack): Of a thickness varying from 10 to 20 centimeters; Is composed of layers of calcite crystals (often with albite) and quartz. On this layer lie the two upper layers as described;

IV) cambiado (changed): The denomination and due to its structure and composition completely different from the three layers above; It is also indicative of the limit of the emerald layers with a fundamental change in the terrain. It consists of benches of considerable thickness in proportion to the other layers mainly formed by dark clay schists, with superficial gloss, due to the presence of large pyrite modules and large calcite and dolomite veins; Such veins are generally transverse or oblique to the pattern of the layer.

Emeralds are contained in aragonite veins and limestones of calcite and dolomite that pass through the capas, that is in the first layer and are accompanied by the above-mentioned minerals.

Also in the fourth rocky formation, the cambiado, there are various veins and limbs, in the lower part of which are from pegmatite.

In the emerald zone of Muzo, the formation of Villeta has been subjected to intense contortions and fractures, a phenomena due to different epochs from which the various rocks forming the same formation itself originate.

Interesting news on a scientific study on the Colombian emerald is carried out by Prof. A.M. Barriga Villalba. The author notes that the presence of pegmatite dams at the bottom of the Villeta formation, as well as the appearance of quartz, albite, apatite and other minerals, suggest that the source of mineralization comes from a very deep infrared intrusion, which penetrated through the clay schists of Villeta during cataclysms in the tertiary period.

According to Dr. J.E. Pogue, the emeralds were formed by pneumatolytic mineralization at temperatures below 575 °C. Mineralizing solutions penetrated the interstices and fractures of the sedimentary layers, whose lower extremities were occupied by calcium carbonate, while the gaseous elements reached the higher crack slits crystallizing emeralds and associated minerals under special weather conditions, temperature and pressure.

However, from other news it seems that the emeralds of Muzo are not found in calcite or dolomite veins, but in veins or cavities within clay sections.

The green colour of the emerald of Muzo more or less intense, produced by the chromium oxide solution and iron entering the cracks at the time of crystallization. The colour variation, sometimes even almost colourless, is due to the amount of the above-mentioned oxides intervened in its formation.

It has been noted that well-coloured emeralds and with good crystallization are found in veins of a small vessel (6-10 cm) and rarely in those over 20 cm. It seems that this is due to the greater pressure that the solutions and the gases have entered into narrow cracks, thus favoring a more perfect crystallization.

These emerald veins are branched out and they often have interruptions or other accidental deviations, but always cross the sedimentary layers at right angles or oblique; In horizontal veins or parallel to the cover is hardly given to find emeralds.

About 30 km north of Muzo, at a much lower altitude, the mines of Coscuez are located. In this area, emerald rocks are tougher due to infiltrations, through the covering layers from calcium solutions. Coscuez’s formations suffered periods of great upheaval; In fact, even the crystals are found in large numbers fractured.

These mines can not be exploited in an open-cut manner as those from Muzo, especially because the water is at an altitude higher than the sea uranium and it would therefore be too expensive to transport it to the mines; The tunnel system is therefore adopted in areas of minor erosion.

At 180 km from Bogota, at 1,850 meters above sea level, there are the Chivor Mines. Emerald formation is in the direction of south to north and, unlike those of Coscuez and Muzo, has not undergone telluric upheavals, therefore the stones are less fractured.

In these Colombian fields, the emeralds are generally of a very good quality, but there are no pale gems, uneven or blackish gems for strong inclusions.

RUSSIA

The ancient lands of Scythus are likely to be the same ones that were discovered in the Urals in 1830 by a coal, which found several green stones at the foot of an eroded tree. The examined gems and proven to be emerald and in 1832 the work began in several quarries located along the upper course of Starka Tokowaja in the Yekaterinburg area. The main centres of these mines are: Troitsky, Makaroff, Mariinsky, Cristovich and Lioublinsky, where the work was repeatedly suspended and then reactivated.

Troitzky is, however, the main center from which the Ural emeralds come from.

The crystals, together with aquamarine, phenacytes, etc., are located at depths of 30 meters included in micascists intercalated between schists and actinolytic scintars. Excavation works are carried out in tunnels on a wide range.

According to M.A. Viullerme, the best emeralds are generally found in black micascists and they have a beautiful green colour and excellent transparency, while those found in feldspathic or limestone rocks are just translucent, sliced and irregular in colour.

Summarizing: Ural emeralds, like those from Colombia, are generally very beautiful, but there are species in this latter area, of gems that have abundant crevices and faded colours.

BRAZIL

Brazil’s lands have gained immense importance in recent years.

In fact, even though it seems like a fairy tale, it would appear that since 1554 research into the forests of Rio Doce began in an area which lies in the precisely in the valley of the actual Serra das Esmeraldas.

Through various successive initiatives, it arrived in 1612 when some of Brazil’s green stones were brought to Portugal, which after a while it was said to be green-coloured tourmalines (but who knows, perhaps they were emeralds).

Anyway, there were still other research news up until 1713.

However, the first emeralds were found in 1913 at Bom Jesus das Meiras (present day) in the southern part of the Bahia state; Later they were also found in the state of Minas Gerais where emeralds are abundantly along the Aracuai River and along the course of some tributaries of the Mucuri, whose springs are in the chain of the mountains bearing the name of Serra das Esmeraldas.

In the State of Bahia in 1950 the findings attracted the attention of green pebbles in Fazenda São Thiago, near Salininha in the Pilào Acado District and in 1962 the research began which led to the emergence of new emerald fields; In 1963 again in the state of Bahia, other more important fields were found in Carnaiba near Campo Formoso and Anagé in Serra dos Pombos. Later on emeralds were also found in Tau, in the state of Cearà in the extreme north of Brazil.

In Brazilian fields, the mother rock is a dolomite marble, with layers of talc, in the vicinity of which emeralds are found in cavities associated with quartz and calcite and they are joined in quartz veins. There are only isolated crystals within the marble.

The emeralds of the lands in the State of Minas Gerais are not very beautiful in colour, as they are greenish-yellow (dominating this second colour), but in return they are pure and without cracks; Those from the lands in the state of Bahia are instead a good colour, but very easily impure.

A lot of raw material is exported to various parts of the world; The local cutting operation began in 1970 and the main cutting machines are those from Rio de Janeiro and Sao Paulo.

INDIA

Indian lands generally decanted in the jewellery environment as they are considered ancient producers of the finest emeralds are not at all such. It is at least very doubtful that emeralds traded in India for over 1500 years came from Indian mines. It was only in 1943 as a result of exploration of coal, iron, mica and beryl necessary for the needs of the Second World War that emeralds emerged in the mountains of Arawalli, Rajasthan in the state of Rajputana. A real exploration for emeralds has been in the area of Kaliguman Udaipur, Ajmere-Merwara, Rajgarh and Bhilwara since 1945, where the mineral is found in mild biotite mica and in soft talcum with biotite.

The colour and quality of Indian emeralds, at least the ones so far found, are not very nice for poor transparency.

PAKISTAN

Recently in 1958, it is the discovery of emerald fields in the Swath village on the Himalayan hills west of the Kashmir border area, which is still very difficult to reach. The exploitation of the mines occurs by pit excavations; The material obtained is a good colour and also with good transparency. However, we do not yet have precise information on geologic and petrographic characters regarding the conditions of origin of these Pakistani emeralds.

SOUTH AFRICA

Transvaal. – A significant importance was found in emerald lands in 1927 in the Leydsdorp district in Transvaal, where the mineral is found in biotite schists. Some specimens with an excellent colour and transparency were found, but the emeralds of this origin are of rather poor quality.

Rhodesia. – In October of 1956, two South African colonizers, who for more than two years spent time researching beryl, tantalite and lithium minerals in the Sandawana valley in southern Rhodesia, had the chance to discover a prime emerald field and a second, much more important in May of 1957.

These lands are located in an isolated location on the southern part of the Mweza mountain range, composed of ancient rocks dating back to the pre-Cambrian period. The emeralds are joined to pegmatite formations in tremolite shapes, resulting from metamorphoses of contact between granite magma and tremolite scintillations; They are a beautiful intense green colour, but in small crystals; In memory of the discovery, the discoverers named the emeralds Sandawama emeralds a denomination still in use on the market today. Also from Chikwanda come high quality emeralds, as well as from Mayfield For Victoria.

Tanzania. – In February of 1970, there were evidence of the discoveries of emerald deposits in metamorphic rocks on the shores of Lake Manyara, near the village of Maji Moto (an area known as the hot springs of sulfur hot water).

It is a matter of good sized hexagonal crystals with very good green-grass, yellowish-green or a bluish-greenish colour, often similar to the Sandawana emeralds described above usually found with chrysoberyl (alexandrite).

Zambia. -The deposits discovered up until 1931 in the Kitwe district in northern Zambia about 50 km from the Zaire (ex Congo) border, but only explored and processed since 1970. These deposits are referred to as Miku or Kafubu (tributary first of the Kafubu River). A pale to greenish colour to an excellent bluish-green and sometimes similar to those from the Sandawana mine.

Mozambico. -Emeralds recently found in pegmatites at Marne are a nice green colour, but very sliced.

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