It is a common practice in the trade that virtually all emeralds have been fracture-filled by oil, resin, or other substances to enhance their clarity, sometimes to enrich their color, or even durability. The geological conditions where emerald grows just make it very rare for emerald to be eye-clean. Therefore, emerald is classified as Type 3 according to the GIA colored stone grading system.
Whatever the substance is to fill the emerald's fractures, they want to use the one that has the refractive index (RI) closest to that of emerald possible, so the substance can blend well in the emerald's interior and doesn't make a big difference when light strikes through it. They also prefer a substance that is able to remove and refill in the future. Cedarwood oil with high viscosity is one of the favorable fillers for emeralds.
There have to be surface-reaching fractures in emerald in order to accept fillers. Gemologists often look for blue or yellow flashes in emeralds under the microscope, or chalky colors under UV lighting to tell if that emerald is clarity enhanced. If it is, it must be noted in the report. Sometimes, it requires more sophisticated technology to spot fillers in an emerald. If that is the case, sending that emerald to GIA laboratory is recommended.
Clearly, if all other factors are equal, an eye-clean emerald commands the top price and is highly sought-after. The intensity of clarity enhancement in an emerald will affect its clarity grading; hence affecting its price per carat. GIA will record the indications of clarity enhancement in their reports, and classify them as minor (F1), moderate (F2), and significant (F3).
Many other factors will come into play when valuing emeralds. If color is the most important factor, clarity is the second, cut and carat weight are to be followed. Origin is also a factor that could change emerald value significantly. Emeralds can range from $20.00 to hundreds of thousands of dollars a carat. You would want to hire a professional to appraise your emerald or give you some advice before you invest your money in an emerald.
Because most emerald is fracture filled, it is susceptible to heat and chemicals from the jewelry torch, ultrasonic jewelry cleaner, steamer, etc. Emerald is also not recommended to set on daily-wear jewelry such as engagement rings. Daily activities and the interaction with household chemicals can do huge damage to fracture-filled emeralds.
Now let's look at these admiring natural emeralds:
The photo below is an emerald crystal that exhibits its perfect six-sided hexagon crystal habit. A magnificent specimen like this one is usually displayed in the museum or in the collectors’ possession rather than being cut and faceted for the jewelry industry.
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