Gemstone Treatments And Disclosure

By Derek Parnell

When you purchase your next gemstone be sure to ask if the gemstone has had any treatments, as this can affect the value and durability of the gemstone. A good jeweller will automatically make this disclosure as part of the sale.

If you are purchasing a high-value gemstone such as Ruby, Emerald or Sapphire make sure it has a certificate from a laboratory that has the expensive equipment required to be able to detect some of these treatment. Most jewellers and gemologists have equipment that can detect certain levels of treatment, but it is only the laboratory equipped grading companies such as Gemological Institute of America and European Gemological Laboratory that can detect all the treatments available.

There are 10 major gem treatments that require disclosure from the seller to the buyer.

Bleaching, Cavity Filling, Colorless Impregnation, Dying, Fracture Filling, Heat Treatment, Irradiation, Sugar & Smoke Treatment, Surface Diffusion, Surface Modifiers. In this article we will look at 5 of them.

Cavity filling This type of treatment refers to those gemstones that have defects on the surface of the gemstone; these cavities and surface reaching fractures reduce the appearance and value of the gemstone. To enhance the value these imperfections are filled with different resins, plastic or glass, which improves the appearance and increases the gemstone weight. Due to the different Reflective Index of the filler material most gemologist can detect the fillers.

Dying. Is used to enhance the color of gemstones such as Chalcedony, Lapis, Jadeite, Cultured Pearl and Turquoise. These gemstones have one thing in common they are all porous, which enables the dye to reach just below the surface. To assist in having the dye penetrate, some gemstones are heated and then cooled quickly by quenching in water, this causes minute surface cracks into which the dye will flow. The more color a gemstone has the more appealing to the consumers.

Heat Treatment This is the most common among treatments and is used extensively on corundum (Sapphire, Ruby) to enhance the color of the gemstone. Heat can also be used to remove internal blemishes, or color centres to improve the gemstones color consistency. Most gemstones that are heated result in enhancing or changing the color are stable, however they are still enhancement and should be disclosed.

Irradiation You will find this treatment in some colored gemstones and colored Diamonds. This process began in the early 1990s and is used widely today, there are minimal traces of radiation in the gemstone but its never harmful if the correct procedures have been followed. The challenge in gemstones is the lack of stability and its sensitivity to heat once the process has been completed. Therefore it is important that you know the gemstone has been irradiated, if you ever have a jewellery item repaired make sure the stone is removed, as the heat will change the color. Most colored Diamonds are made affordable by irradiating the natural browns and yellow, which can turn them into blue, green and red colors making them more attractive and increasing their value. The process in diamonds is more stable but is still susceptible to changes with heat.

Surface Diffusion This treatment is becoming more common today with the enhancement of more valuable gemstones such as corundum. The gemstone is heated just below melting point, and then chemicals are used to penetrate the surface to become part of the crystal structure. This process is also used to produce stars (asterism) in some gemstones, again increasing value.

Disclosure It is not only unethical, it is also against the law to sell a natural gemstone that has been treated and not disclose the treatment. If a jeweller or gemologist does not know if a gemstone has had a treatment then he should assume it has and disclose it, or send to a laboratory to confirm one way or another. All treatments must be disclosed at the time of sale to the consumer. Unfortunately, today there are a lot of treated gemstones being sold as natural.

The reason sellers fail to disclose falls into four main categories:

Ignorance, they believe their suppliers, who mostly live in countries where these rules are not adhered to or do not exist.

Competitive Pressure, they feel they will be disadvantaged in a sale if their competitors do not disclose.

Resistance, they do not believe in the rules and do what they think is right.

Calculated Risk, If they don't disclose how often will they get caught and if they are caught they can probably make the problem go away by refunding or replacing the item.

A reputable seller will always provide disclosure, but its not a perfect world.


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