Like most gems, emeralds are weighted in carats (ct). For small melee sized emeralds weighing 0.2 carats or less, a measurement in points may be given too. One carat is equal to 100 points: 1.00ct = 100pt.
While carat weight is one of the 4Cs of pricing along with color, clarity, and cut, it does not measure the quality of an emerald. The 4th C instead measures how difficult finding another emerald of the same quality is. This is purely a measurement of rarity, which directly translates into price.
The limiting factor with emeralds is that they typically form with a high number of inclusions, despite a gem habit that does not limit carat weight. If an emerald is too included it can break on the cutting wheel, since gem faceting is a brutal process. This limits the amount of cuttable emerald rough.
An ideal emerald color of a bluish green is another limiting factor, though not as much as the inclusions. Emerald is in fact a very narrow color definition of green colored beryl . It ranges from a slightly yellowish green to a bluish green. If it is too light, it is no longer an emerald, and instead a piece of green beryl.
The antiques industry has a popular saying: “Try to find another one”. This is the challenge jewelers and dealers face when trying to match gems. While matching emeralds is somewhat easier due to their limited colors, finding a similar cut of emerald that is also alike in size, weight, and clarity of the two emeralds is difficult, much less finding a matched set. Large gems can even take years to match if they are not cut from the same rough and to match in size. An extreme example of matching is a strand of 35 golden south sea pearls, which took 37 years for the Jewelmer Joaillerie company to match. Most pairs of emeralds will not take decades to make, though matched sets may need a significant amount of time.
Large matched pairs or sets of emeralds will also command higher prices than single emeralds of equal weight due the time and labor it demands.
Emerald ID: PRE153 Total Weight: 2.11 Carats Origin: Zambia Price: $12,554.50 USD
Emerald ID: E872 Weight: 1.19 Carats Origin: Colombia Price: $2,975.00 USD
Emerald ID: E1516 Weight: 2.16 Carats Origin: Zambia Price: $7,992.00 USD
Notice how the matched pair costs more than double an emerald of similar individual size (a little over one carat). It is still more expensive than a 2 carat emerald of similar quality, but a much rarer size.
Gems were originally weighed against small carob seeds. This method of weighing gems and jewelry predates the measurement of grams, which is credited to International Bureau of Weights and Measures. Thought to be consistent in terms of size and weight, they were weighted using scales like the example pictured here.