Emeralds are a specifically colored green variety of the mineral species beryl Be3Al2Si6O18, along with many other varieties.
By definition, natural emeralds are emeralds that formed through geological processes in the earth. Most emeralds on the market are natural emeralds, though the vast majority of them have been treated.
The vast majority of natural emeralds are also treated emeralds. Over 99% of emeralds on the global market have clarity enhancements, using either oil or resin to fill any fractures that may have formed.
The most widely used and accepted treatment is oiling. Over time the clarity-enhancing oil does dry out and become visible, and at this point the emerald needs to be cleaned and re-oiled. While oiling is a relatively simple process, it is something that needs to be done by a nearby jeweler and not at home. Furthermore, a specialty high-viscosity oil is required for this process (usually a type of cedar oil).
Another possible treatment is fracture-filling with resin instead of oil, which dries out slower. However, resin cannot be completely cleaned out of the emerald the way oil can and visibly leaves residue with the next cleaning. There is one place that claims they can completely clean and repair emeralds with a patented in-house resin formula, but there is no evidence of this currently.
Since resin is problematic, oiling is the most popular treatment on the market.
Untreated emeralds are emeralds that have not been treated in any way, meaning no oiling. These types of emeralds are also extremely rare, even in the inventory of the Natural Emerald Company. Less than 2% of emeralds that go through our inventory are completely untreated. Being untreated does not necessarily mean they are 100% clear. A number of treated emeralds have equal clarity to the untreated one.
Emerald ID: E1498
Weight: 0.55 Carats
Emerald ID: E1004
Weight: 1.50 Carats
Emerald ID: E1007
Weight: 0.94 Carats
Emerald ID: E1009
Weight: 1.18 Carats
Emerald ID: E1018
Weight: 1.17 Carats
Emerald ID: E112
Weight: 1.19 Carats
Without treatment, most of these emeralds above would not look even half as nice as the first one (E1498).
Synthetic emeralds are emeralds that were made in a lab instead of the ground. They share all the chemical and structural properties of natural emeralds since they are the same material. However, a natural emerald is much rarer than a synthetic emerald. Furthermore, there are fundamental trace differences between the two chemically speaking.
Nature mixes whatever is available in the ground without hesitation, while in a lab only the stuff that forms emeralds is used. This is why labs are able to differentiate between natural and synthetic gems reliably.
Not everything called “emerald” is necessarily an emerald. There are a number of trade names for green gems with nice green colors.
Emerald sourced from Africa
Emerald ID: E1182
Weight: 2.41 Carats
Though these terms are occasionally used, they can be very confusing and misleading even within the industry. A general rule of thumb is aside from using origin terms to describe emeralds (Colombian emerald, Zambian emerald, Brazilian emerald, etc), other terms attached to the word emerald implies that they are something other than an emerald. These terms are also avoided by credible dealers when discussing emeralds with clients who have no experience with the gem industry what-so-ever.
There are also fundamentally wrong terms like Yellow Emerald. By definition, emeralds are not yellow. What “yellow emeralds” actually are is a variety of beryl (like emeralds) called heliodor.