05/22/20 09:30 - ID#60803
Gemstone Color Enhancements
When colored gemstones are treated artificially, we say that they have been enhanced. Most colored gemstones have been enhanced. Stones may be treated while still in their rough crystal form or after they have been cut into polished gemstones. Colored stones are enhanced for four reasons:
To intensify, deepen and/or make the color more uniform
To remove a modifying color, leaving the rarer hue more visible
To mask or eliminate unsightly inclusions
To stabilize the structure of the gemstone
All treatments of colored gemstones must be disclosed to the buyer, so consumers can make informed decisions about the value of their stones before they purchase. All enhancements affect the cost of colored stones, some by a little, others by a lot. Because most colored gemstones are enhanced, those that are not commanding premium prices.
There are many degrees of enhancements. Some alter color just a bit, while others are so extensive they create almost the full color of the polished gem. Some mask only a few unsightly inclusions, while others “burn out” an entire field of internal markings, leaving the stone nearly flawless — something that is fairly rare in nature. Any enhancements can be detected by experienced gemologists with standard laboratory tools. Other enhancements require advanced laboratory identification. Some enhancements are permanent; others are temporary, allowing a strong color to fade or inclusions to re-appear under certain circumstances. Your jeweler can provide an independent laboratory document identifying any enhancement to the stone. This is especially important for the purchase of an expensive ruby, emerald or sapphire. Customers should understand how this enhancement affects a stone’s quality, current cost and potential future value, especially if the treatment may not be permanent.
Surface coating is the process of adding a thin layer of colored foreign material to all or part of a gemstone’s surface, with the intent of either masking the underlying body color or enhancing a desirable color. Most often, this coating is applied to the pavilion and/or girdle of the diamond; the way that light refracts as it passes through a diamond creates the illusion of uniform color distribution.
The durability of diamond coatings vary considerably, depending on materials used and methods of coating applied. Original coating techniques date far back in history when a simple paint or ink was applied to the girdle of a diamond, easily removed by rubbing with a solvent. Most recent advances in technology employ a very thin optical or chemical film which is more durable, but still readily worn away by heat, scratching, abrasion, polishing, and just everyday wear.
In terms of detection, coated diamonds are identified without much difficulty by a trained gemologist in a laboratory.
Irradiation is the process of exposing diamonds to various types of high-energy particles in a nuclear reactor, which slam into the diamond and become embedded in its matrix, in order to change their color. Irradiation with these high-energy particles alters the internal atomic structure of the diamond, and produces ‘color centers’. Color centers are electronic defects in the diamond’s crystal structure, which change the way a diamond absorbs light and therefore its color. During the irradiation process, diamonds are bombarded with gamma rays, neutrons, protons, deuterons, or electrons.
The effects of these different methods of irradiating a diamond vary; each process produces a different kind of radiation, with different energies and degrees of penetration through a diamond. In other words, the resulting color depends on the type of irradiation selected and the length of exposure time. Most often, irradiated diamonds are subsequently annealed to further modify their color into the desired hue, a process described in the following section.
Irradiated diamonds are very difficult to identify using standard gemological equipment; advanced testing by a recognized laboratory is thus imperative.
Annealing is the process of slow heating diamonds at moderate temperatures to deepen, or further alter, the color of a diamond most often after irradiation. Annealing will frequently enhance a colored diamond to brighter shades of yellow, orange, or pink. The resulting colors are dependent on the original diamond’s composition, temperature and length of annealing process.
- This information was taken from www.tomtivoljewels.com and www.dcla.com**
Last Modified: 05/22/20 09:30