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Precious stones
Semi-precious stones
Technical information
History of the stones
Characteristics :
Crystal structure : Hexagonal Composition : Beryllium and aluminium silicate
Specific gravity : 2.71 Hardness : 7.5
Refractive index : 1.57-1.58 Birefringence : 0.006
Variety : Beryl Pleochroïsm : distinct (green, green-yellow to green-blue)
Cut : Emerald  Cabochon  Pear  Oval degree

The colouring of emeralds is due to the presence of chromium and vanadium.
In general, the emeralds are not transparent (except for some stones of great quality): there are often inclusions (liquid, bubble of gas, other crystals,…). If these inclusions do not take much place, they are not regarded as defects, giving them even a seal of authenticity beside to synthetics emeralds.
The value of an emerald is not judged only on its purity but also on its color: A stone having inclusions but of a deep green color will have more value than a pure stone but of a too pale green !
Rough stone
It should be known that the way in which one cuts the stone influences its color :
  - cut of the table perpendicular to the axis of the hexagonal prism : green-yellow
  - cut of the table parallel with the axis of the hexagonal prism : green-blue
In principle, the lapidary will try to obtain the maximum mass of the crystal and not a specific color.

History :
Emerald takes from Greek “smaragdos” meaning “green stone”. At old times, almost all the green stones were called emeralds.
The most famous emeralds are :
  • Topkapi Palace in Istambul (16 300 cts)
  • Mineralogical Museum in Moscow (11 130 cts)
  • Treasury of Vienna (ointment flask of 2 200 cts)
  • British Museum of London
  • Imperial treasure of Iran
  • American Museum of New-York

Deposits :
The countries having deposits are :
Colombia Important Some stones of higher quality Mines worked by Inca
Brazil Important Ordinary stones  
Zimbabwe   Crystals of small size but of good quality  
South Africa   5% of good quality  
Ural Weak Good rare quality  
India Weak    
Pakistan Weak    
Australia Weak    
United States Weak    
Egypt Null   Mines of Cleopatra
Austria Very weak Unsuited crystals for the cut (but with a beautiful color)