The rarest types of emeralds are the ones seen in depicted in TV shows and cartoons; huge, perfectly green gems with no inclusions.
How Rarity is Quantified
While initially developed for diamonds, the 4Cs of color, clarity, cut, and carat weight quantify rarity into a price tag for many varieties of gemstone.
The title of “Emerald” is only given to green beryl that shows outstanding color. Whatever beryl is green and not vivid enough to be an emerald is called green beryl. The most desirable emerald color is a bluish green with no yellow tones. Emeralds from the Chivor mine in Colombia are known for this description, but that does not mean every emerald from the mine displays those features. Other emerald mines are fully capable of producing this quality in notable amounts too.
E1569 | play | medium | “Emerald ID: E1569, Weight: 1.01 Carats, Origin: Zambia”
Common Emerald Appearances:
Emerald ID: E590, Weight: 0.82 Carats, Origin: Zambia
Emerald ID: E285, Weight: 0.37 Carats, Origin: Zambia
Emerald ID: E759, Weight: 0.60 Carats, Origin: Zambia
Rarely is the clarity of an emerald transparent. They are almost always included as a Type III gemstone, to the point where over 99% of all emeralds are oiled to improve clarity. Even at the Natural Emerald Company, less than 2% of all gems that come through our inventory are completely untreated. Any emeralds that are clear without oiling treatments are extremely rare, and will go for at least 2-3 times the price of treated emeralds of comparable appearance. In larger sizes over a few carats, the price will increase exponentially more.
Examples of our few untreated emeralds:
Emerald ID: E1332, Weight: 1.60 Carats, Origin: Colombia
Emerald ID: E1497, Weight: 0.32 Carats, Origin: Colombia
Emerald ID: E862, Weight: 3.32 Carats, Origin: Ethiopia
Faceting & Cuts
Originally emeralds could only be faceted into an emerald cut, due to their eye-visible inclusions. However, with current cutting techniques, emeralds can be cut in just about any shape without too many issues from inclusions. The only restriction is that all cuts will be dictated by the shape of the original, uncut emerald. Gem cutters will always aim to get the largest amount of carat-weight out of rough gems, though they have to compromise between a number of factors like windowing , extinction , brilliance , symmetry, inclusions, and more to make the gems look good. As a result, the proportions of the cut are always slightly off with few exceptions.
The final C, carat weight, acts as a gauge to how rare all the other factors are. While weight is straightforward in and of itself, larger weight increases the price exponentially due to rarity. A 4.00 carat emerald will not be twice as expensive as a 2.00 carat emerald of equal quality. It will be something like four times more expensive because it is four times as rare. When all these factors come together, you have a one-in-a-lifetime emerald.
A super-famous example of this is the Rockefeller emerald. This emerald is by no means the largest gem-quality emerald, but it is the best quality emerald for its carat size the entire world over. It would be very surprising if another gem like it ever came onto the market.
For comparison, above is the Rockefeller ring next to an emerald of comparable size. The first thing you see is just how clear it is in comparison to the second emerald. This is because the Rockefeller emerald is visibly inclusion free, requiring magnification to see any distinguishing features. Next, the bluish tint in it is textbook perfect, which is difficult to find for any colored gem. This is slightly easier in emeralds because they have a very limited color definition (any green that isn’t good enough is called green beryl instead). As far as this rarest emerald goes, it has the price tag and a famously rich family name to match.