HomeMajor Colored StonesEmeraldGemmology of Emeralds
Chemistry and Crystallography
Chemical Composition Be3Al2SiO6
Crystallographic System Hexagonal
Cleavage  
Fracture  
Fracture Lustre  
Habit  



Physical Characteristics

Hardness 7.5 to 8
Toughness poor to good
Specific Gravity  
Streak  



Optical Characteristics

Colour and Cause

Green; Chromium is the usual element claimed to be responsible for the attractive green colour of emerald. However, some emeralds from Colombia, Russia, Lake Manyara(Tanzania), Afghanistan, Nigeria, Zambia, and Carnaiba(Brazil) are characterised by unusually low contents of chromium. Indeed, some of these emeralds contain up to about 0.3% V2O3, which also may contribute to their emerald green colour(Brown, 1984; Platonov et al., 1984; Wood and Nassau, 1968). The large variation of iron content in emeralds is due to the possibility of incorporating iron, either as Fe2+ and or Fe3+, in different sites in the beryl lattice. Indeed specimens of bluish green Zambian emerald were quite distinct from other emeralds analysed as they have the highest iron content but low concentrations of chromium.

Both colombian emeralds and the synthetic emerald had less FeO than all other emeralds. In addition, the Colombian Emeralds contained considerable amounts of CuO. Bluish green Zambian emerald and emeralds from Carnaiba(Brazil) both had lower chromium contents than emerald from other locations. Some emeralds from Afghanistan and Brazil were slightly enriched in iron as well as vanadium.

Degree of Transparency  
Polish Lustre  
Refractive Index 1.56 to 1.60
Birefringence 0.003 to 0.010
Optic Character Uniaxial negative
Pleochroism  
Dispersion  
Phenomena  
X-Ray Fluorescence  
Transparency to X-Rays  
Ultraviolet Fluorescence  
Chelsea Filter Reaction  
Absorption Spectra  



Description

Appearance  
Variety and Trade Names  
Misnomers  
Typical Size Range  
Typical Cutting Styles  

Market 
Availability  
Public Recognition  
Wearability  
Recommended Disclosures  

Key Separations, Suggestions for Testing and Evaluation
Emerald imitations can be made from green glass or synthetic spinel triplets.

Synthetic emeralds may be grown using the flux of hydrothermal method.

Emerald alternatives include alexandrite, demantoid garnet, diopside, jadeite, Peridot, sapphire, tourmaline, tsavorite garnet, and zircon.
 
Possibilities for Confusion


Bibliography and Suggested Further Reading
  • Peter G. Read, Gemmology
  • http://www.gia.edu/library/4463/emerald.cfm

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