Color
The value of a gemstone’s color is determined by three key factors: hue, tone, and saturation. Hue refers to the specific tint of green present. Tone indicates how much light the gemstone absorbs, influencing the color’s intensity. Saturation measures the vividness of the dominant color. Emeralds that exhibit a primary green color are typically more valuable compared to those with hints of yellow.
The most admired emerald shades are either bluish-green or pure deep green, without an overly dark tone. In high-quality emeralds, the green color is uniformly spread throughout. Emeralds from various mines and countries, such as those from Colombia and Zambia, display distinct colors. Colombian emeralds are known for their pure intense green, while Zambian emeralds exhibit a bluish-green hue. However, the origin of the color alone doesn’t guarantee the source. Emeralds with saturated and darker greens are valued more highly, whereas pale or icy green emeralds are less appreciated and may even be classified as green beryl if very light. Emeralds with less than 15% secondary color are considered premium, commanding higher prices.
Opacity
Nearly all natural emeralds feature visible inclusions, which are small internal growths that form during the stone’s creation. These inclusions often give emeralds a mossy appearance, sometimes referred to as a “garden.” Emeralds with fewer visible inclusions are more valued. The most prized emeralds hover around 75% on the transparency scale, where 0% signifies a clear stone and 100% an opaque black stone. Additionally, emeralds often have surface-breaking fissures due to their softer nature compared to rubies, sapphires, and diamonds.
Treatment
To enhance their appearance and reduce inclusion visibility, many emeralds undergo heat treatment. This permanent process involves applying oil, heat, and pressure to bring out and improve the stone’s natural qualities. Alternative treatments, such as using resin fillers to fill cracks, can enhance the emerald’s look but are considered less desirable as they detract from the stone’s overall value.
