Emeralds are beryls, unlike sapphires and rubies which are of the corundum family. They will, therefore, present different technical features. They share with sapphires and rubies, the public’s enduring desirability as a beautiful gemstone.
While emeralds are hard stones in their own right just trailing sapphires and rubies, they have a slightly lower ‘wearability’ rating. This is due largely to the fact that while the crystal structure that makes up emeralds is hard, it is also more susceptible to breaking due to the type and quantity of inclusions that emeralds contain. Fine quality specimens, have a wearability that can very nearly rival sapphires and rubies from the corundum family of gemstones.
Appearance to the naked eye:
Few buyers go into a retail stores with a loupe and gemological tools in tow. They rely on how appealing the gem is to them purely from a visual perspective. And this is also the case when you are out to dinner or in a social gathering; it is highly unlikely that the other guests are using sophisticated laboratory tools to admire your ring; instead they are relying on what they see with their naked eyes. That is why we want to spend a bit of time explaining what it is you can expect to see just by eyesight.
Green. Secondary hues include blue and yellow.
Transparent. The presence of groupings of inclusions, however, can give the stone a cloudy appearance, however.
Given emeralds secondary hues of blue or yellow, these may be visible depending on angle of observation or lighting conditions.
Emeralds may present a cat’s eye feature normally referred to as chatoyancy from the French “chat” meaning cat.
Emeralds are notoriously well-known for their groupings or ‘families’ of inclusions normally easily visible to the naked eye. The inclusions are (normally?) mica impurities that get trapped into the stone during the crystal’s formation.
Other interesting facts:
While emeralds are from the beryl family of gemstones, only green stones that get their colour from trace elements of chromium can legitimately be called ’emeralds’. Other green coloured beryls that derive their colour from other impurities, such as vanadium, are more appropriately called “green beryls” and not emeralds.
- Refractive Index:
lower reading in the 1.577 range; and
higher readings in the 1.583 range
0.005 to 0.009 range
- Optic character and sign:
(U-) double refractive, uniaxial, negative
- Conoscope image:
- Specific Gravity:
3.97 to 4.05 range. Average of 4.0
- Hardness (Mohs scale):
brittle (largely due more to the presence of impurities in the stone and not due to the crystals inherent hardness)
- Spectral Absorption:
Like rubies, emeralds get their colour from the presence of chromium. People familiar with gem spectroscopy will be aware of the tell-tale chromium line formation in the red end of the spectrum (which we refer to as the three classic chromium lines).
- Chelsea Filter Reaction:
As emeralds get their colour from chromium, they will present a strong red reaction. If the stone presents no reaction to the Chelsea filter, it is more appropriately referred to as a green beryl as it is likely coloured by vanadium instead of chromium.
- Dichroscope Reaction: