Evaluating Natural Emeralds: A Guide to Grading

Emerald Color and Emerald Color Chart

When assessing the color of natural emeralds, three categories are considered: hue, tonal grade, and saturation. The tonal grade assesses how dark or light the green shade in the gem appears. Natural emeralds exhibit a wide spectrum of green tones, ranging from Very Light to Medium Light, Medium, and Medium Dark. Differences in these tones can be observed in our emerald color chart below.

Typically, emeralds of high quality fall within the Medium to Very Dark tonal range. However, this does not solely determine the quality of an emerald; hue and saturation are equally important.

Hue describes the specific green color of an emerald. For instance, a natural emerald might be described as “bluish-green” or “yellowish-green.” Most emeralds from Colombia exhibit a “bluish-green” hue.

Saturation gives intensity and strength to the emerald’s color. The saturation scale ranges from very dull to pure and vivid green. For example, a “Medium Dark” emerald is generally regarded as high quality, but a low saturation can diminish its overall appeal. Conversely, a “Medium Light” emerald with vivid saturation can be highly attractive. Hence, emeralds are graded considering all three categories.

Emerald Grading Scale

All gemstones, including emeralds, are typically evaluated using the Natural AAA, AA, or A grading system.

• Natural AAA: Representing the highest quality, these emeralds constitute the top 10% of gemstones. They are rich green, have slight inclusions, and exhibit very high brilliance.
• Natural AA: The second-highest category, encompassing 20-30% of gemstones. These emeralds are medium green and may have moderate inclusions.
• Natural A: Covering 50-75% of gemstones, these are dark green, heavily included, and opaque. While still good, they are considered lower quality compared to the preceding categories.

Another category, Heirloom/Rare Emerald, surpasses AAA quality. Such emeralds are extremely rare and highly valuable.

Emerald Clarity

Clarity pertains to the internal appearance of the gemstone. Unlike other gemstones, emeralds often contain inclusions like gasses, other minerals, crystals, and liquids acquired during crystallization. It’s common, with around 99% of natural emeralds having inclusions. According to the Gemological Institute of America (GIA), colored gemstones fall into three clarity types: Type 1, Type 2, and Type 3. Emeralds belong to the Type 3 category.

• Type 1 gemstones: Typically free or nearly free of inclusions.
• Type 2 gemstones: Usually include inclusions.
• Type 3 gemstones: Almost always contain inclusions.

Inclusions in Emeralds

Inclusions are inherent in emeralds, but an excessive amount can reduce their crystal-like appearance and compromise durability, especially if near the surface. Low-clarity emeralds are characterized by numerous inclusions. Nevertheless, their presence is a natural trait of emeralds, and their absence often indicates a synthetic or imitation stone.

Emerald Treatments

Due to the prevalence of inclusions, it is standard practice to treat emeralds with oils or resins to enhance their clarity and overall quality. Cedar oil is most commonly used for this purpose.