Emerald
The name emerald is derived from the Greek word “Smaraydos” which means green stone and in ancient times, reffered not only to emeralds but also probably to most green stones. Emerald is the most precious stone in the beryl group. Its green is incomparable and therefore it is it is called‘emerald green’. The coloring agent for the real emerald is chromium.Beryl that are colored by Vanadium ought to be called ‘green beryl’ are not emerald. The color of emerald is stable against light and heat and only alters at 700 c- 800 c. The distribution is often irregular, a dark slightly bluish green is most desired.
Only the first specimens are transparent. Often the emerald is clouded by inclusion. These are not necessarily classified as faults, but are evidence to the geniusness of the stones, as compared with synthetic and other imitation. The gemologist named these inclusion as JARDIN which is a French word meaning garden.
DEPOSITS
Emeralds are formed by Hydrothermal process associated with magma and also by metamorphism.
Most of the emerald used in historical jewellary would have been form cleoplatra’s mines in Egypt, which now yield only quality emeralds.
Significant deposits are in Colombia especially in Muzo mine located in North-West of Bagota. Firstmined by native tribes, the Muzo deposit was abandoned and re-discovered in the 17th Century.The mine yields fine quality quality stones of deep green color.
Another important Colombian deposit is the Chivor mines is in North-East of Bagota. It was also mined by Native Americans. During recent decades further emerald deposits, which promise to be successful and have been found in Colombia. There is always high demand for the rare so-called Trapiche emeralds found exclusively in Colombia. In Brazil there are various deposits in Bahin, Goias and Minas Geriasstones are lighter than Colombia ones, mostly yellow-green, but they are often free of inclusion.
The most important deposit is in Zimbabwe is the Sandawana mine. Crystal are small but are of good quality.
In the Northern transraal, the cobra and the Somerset mines Emeralds are mined by modern methods using machinery. Only Five percent of production is of good quality. Most of them are suitable for cabochous.
Further Emerald deposits are in Russia in the Urals North of Yekaterinburg (Sverdlovsk), Afghanistan, Australia, Ghana, India, Madagascar, Mozambique, Namibia, Nigeria, Pakistan, Tanzania and the United States (North Carolina).
PROPERTIES
The various properties of Emerald are
| Species | Beryl |
| Variety | Emerald |
| Chemical Composition | 3 BeO AI2O3 6Sio2 (Silicate OfAluminium and Beryllium) |
| Crystal System | Hexagonal |
| Color | Light to dark green, slightly yellowish green and blueish green. |
| Cause of Color | Chromium |
| Hardness | 7.5 |
| Specific Gravity | 2.61 to 2.78 |
| Pleochroism | Dichroic (strong to weak) |
| R.I. Range | 1.56 – 1.57 to 1.59 – 1.50 |
| Optic Sign | U –ve |
| Birefringence | 0.005 to 0.009 |
INCLUSION
There are different types of inclusion found in Emerald
| India | Coma like inclusion, two phases and mica are seen. | ||||||
| Brazil | 2-Phases, dolomite, pyrite and chromite are seen. | ||||||
| Zimbabwe (Sandawana) | Tremolite needles are seen. | ||||||
| Zambia | Black dravite, Biotite-phlogopite mica and orange red rutile are seen. | ||||||
| Pakistan | Calcite and jagged, 3 phases are seen. | ||||||
| Austria | Yellowish brown Mica plates are seen. | ||||||
| Australia | Biotite mica present. | ||||||
| South Africa | Brownish mica present. | ||||||
| Russia | Actinolite needles present. | ||||||
| Madagascar | 2-3 Phases and brown mica are seen. | ||||||
| Colombia |
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FAMOUS EMERALDS
The 1759-Carat Guinness Emerald Crystal
The stone was found at the Coscuez in Colombia and is one of largest gem quality emerald crystals in the world. Today it is the part of the collection of the BancoNazionale de la Republica in Bagota, Colombia.
The Patricia Emerald Crystal
The Patricia Emerald Crystal was discovered in the Colombian Andes Chivor mines in 1920 and is named after the mine owners daughter. Not only is it one of the largest gem-qualityemeralds in the world, but it is also dihexagonal and measures 2.5” * 1”. The stone resides New York Museum of Natural history.
Maximillian Emerald Ring
A ring containing a 21.04 carat step cut emerald, donated to the Smithsonian museum by Marjorie Marriweather Post.
Hooker Emerald brooch
A 75.47 Carat emerald set in abrooch, part of the Smithsonian museum’s collection.
The Mackay Emerald Necklace
The stunning 167.97 carat Mackay Emerald was mined in Muzo, Colombia. The largest cut emerald in the National Gem Collection, it is set in an art Deco Diamond and Platinum necklace designed by Cartier Inc.
SIMULANTS
The simulants of Emerald are,
Tsavorite, Massive, Hydrogrossular, Green Zircon, Green Sapphire, Green Beryl, Tourmaline,Chalcedony, Diopaste, Fluorite, Green Paste and Synthetic Emerald.
