Numerous criteria are utilized to assess the quality of emeralds. However, experts largely agree that the primary factor is color. For millennia, the deep green hue of emeralds has been the standard in the world of precious gemstones.

In addition to color, other factors influence the quality and value of emeralds. Some of these can only be analyzed by experienced specialists. This is true for “subtle qualities”: characteristics that cannot be evaluated by the naked eye.

Color

The ideal shades of emerald are pure green and bluish-green, with deep saturation and uniform, not overly dark, tone. Furthermore, the most valuable stones possess high transparency. The color of such emeralds is distributed evenly, without visible lighter or darker areas. If the hue is too yellowish or too blue, it’s not an emerald but another type of beryl.

The rich, unparalleled green color of emeralds is determined by the presence of three elements: chromium, vanadium, and iron. They must be present in balanced proportions. If any element is too scarce or too abundant, the color of the emerald changes.

Some jewelers associate the color of emeralds with their origin. For example, Colombian emeralds are considered “warm,” with rich green hues, while Zambian ones are “cool,” tinted in bluish-green tones. However, gemstones of various colors can be mined from the same deposit.

Transparency and Inclusions

Emeralds often contain inclusions, visible to the naked eye. This is a natural phenomenon, so jewelers do not consider them “critical” defects. Emeralds without inclusions are extremely rare and highly valuable.

Inclusions in emeralds often have a tree-like structure or resemble moss. They are called “jardin,” which translates from French as “garden.”

Jewelers familiar with the nature of emeralds may use gemstones with visible inclusions to create jewelry. Additionally, minor defects do not affect the price of the stones. However, if the transparency or color of the emerald is compromised due to inclusions, it can significantly reduce its value.

In the early 2000s, the GIA laboratory began analyzing the clarity and transparency of emeralds. Its specialists examine unset gemstones and then compile reports describing the color and presence of inclusions. Depending on the size and quantity of inclusions, their impact on transparency is classified as minimal, moderate, or significant. However, GIA emphasizes that these reports are used only for evaluating the quality of cutting, not the overall quality of the stone.

Cut

When deciding on the cutting method, a jeweler must consider the depth of color, strength, and presence of inclusions in the emerald. Errors can result in cutting off excessively large fragments from the mineral, thereby reducing the mass of the finished gemstone.

Emeralds are complex gemstones to cut. Four factors influence this:

  1. Almost all emeralds have significant fractures. Therefore, the cutter must process the rough stone in a way that reduces or eliminates their impact on the finished gemstone.
  2. Emeralds are more fragile than, for example, corundum, due to these same fractures. Because of fractures, an emerald may split during cutting, polishing, setting into jewelry, or even during careless everyday wear. To enhance durability, a technique called “emerald cut” is used: the stone is faceted in a way to conceal and protect potentially vulnerable areas when set into jewelry.
  3. The cutter must maximize the color, saturation, and hues of the emerald. Color has the most significant influence on the stone’s price. Therefore, the cutter may darken light emeralds (greater “depth,” smaller table, fewer facets), while lightening dark emeralds (less “depth,” larger table, more facets).
  4. Some crystals contain two or more tones, which is a flaw. For example, a stone may transition from yellowish-green to bluish-green. This effect can be corrected by correctly orienting the emerald’s table (wide flat facet) perpendicular to the crystal’s vertical axis. Thus, the finished gemstone will have the bluish-green color highly sought by connoisseurs.

For example, Colombian rough emeralds often have a distinct color gradient. Their surface may be green, while the crystal’s center is yellowish-green. If a Colombian emerald is cut incorrectly, the resulting gemstone will have a significantly less saturated hue than the original crystal.

Carat Weight

Emeralds can vary in size. In museums and private collections, one can find stones weighing hundreds of carats. In inexpensive jewelry, tiny emeralds weighing only a few carats are used.

Emeralds from the Sandawana mine in Zimbabwe usually have small sizes but a bright, saturated color. The stone’s area may be less than 1 square millimeter, but the hue will be intensely green. Most Zimbabwean emeralds have weights ranging from 0.05 to 0.25 carats, although stones over 1.5 carats are sometimes found.

Different-sized emeralds are used in jewelry making:

  • Small (size: 1–5 square millimeters, weight: 0.02–0.5 carats) – in inexpensive jewelry and inlays;
  • Medium (1–5 carats) – used as the central stone in jewelry;
  • Large (over 20 carats) – used in premium jewelry.

All else being equal, the price of an emerald increases with its size. The larger the stone, the more expensive it is.