Diamond Treatments
November 15, 2005
Diamond Treatments
Throughout the history of gemstones and jewelry, there have always been attempts to improve the appearance of diamonds. Some of these treatments are permanent and some are not. The controversy comes when the treatments are not disclosed to the buyer and the diamond is sold for more money than it could be if the unsuspecting buyer knew about the treatment.
Some of these treatments have become increasingly sophisticated and harder to detect with the development of new technologies.
Fracture-Filled Clarity Enhancement
Gemstone enhancement is not a new idea. The concept of oiling emeralds, a practice that dates back to the ancient Roman Empire, is a treatment where fractures in gemstones are filled with transparent oil or some other suitable material making them less apparent.
Diamond filling works on the same principle. A transparent substance that has a refractive index close to that of diamond is injected into the feathers of a diamond. The intended result is a much less visible inclusion that improves the overall appearance of the diamond to the unaided eye.
Yehuda Diamonds
In 1982, Zvi Yehuda, a famous Israeli scientist discovered a way to enhance the clarity of diamonds. The revolutionary process optically eliminates "feathers", which are naturally occurring in most diamonds. These feathers undergo a clarity enhancement or fracture filling. It involves forcing in a special filler material (a form of rare-earth glass first developed by Zvi Yehuda) under very high heat and pressure. The result is that the feathers are now almost invisible; like dropping your contact lens in a swimming pool. It's there, but you can't see it.
Only diamonds with small cracks can be treated since the process will not work for diamonds with large cracks. The enhancement process tends to improve a diamond’s clarity by one grade and does not affect the color or weight of the diamond because only a thin glass film is used.
Clarity enhanced diamonds did not begin to appear on the diamond market in substantial quantities until the 1990's. Despite FTC guidelines which require jewelers to disclose diamonds treated with the clarity enhancement process in writing to consumers as "Clarity Enhanced / Fracture Filled" many stores do not provide disclosure of any type to their unsuspecting customers.
Some fracture filled processes cause the diamond to darken, or turn grey, under sunlight and ultra-violet light because the treatment contains bromine, which is unstable in light. The Yehuda Diamond Company purports not to use bromine so does not darken. However, like all fracture filled treatments, the fill substance is susceptible to heat, acids or bases; commonly used in jewelry repair and setting.
Detecting a Yehuda diamond is fairly simple since they have has a built-in signature 'flash effect.' Easily seen under normal 10X magnification, the flash effect appears as a line of vivid color at the location of the enhancement. The flash is usually purple or green in color.
The GIA does not certify and Diamond Source of Virginia does not sell fracture-filled diamonds for three important reasons.
Unlike laser drilling, fracture filling is not a permanent enhancement.
Fracture-filled diamonds cannot be accurately graded for clarity
The fill material does not hold up to heat and prolonged cleaning methods.
Irradiation Color Treatment
In 1904 British scientist Sir William Crookes buried some diamonds in radium salt for a year and discovered that doing so caused them to turn green and become radioactive. Color treated diamonds are readily available in all of the colors found in nature and include blue-greens, yellowish greens, yellows, browns, oranges. Although quite rare, pure blues, purples, pinks, and greens are also available. Fortunately, modern treatment techniques use forms of radiation that do not leave radioactive traces.
The production of fancy colored diamonds is estimated at less than one-tenth of 1% of diamonds mined. As a result, natural fancy colored diamonds are a rare commodity and command high prices. If you see a "fancy colored diamond" advertised for just a little more than a comparable “white” diamond in the normal color range, odds are it's treated.
Since almost every natural fancy colored diamond is going to be certified by the GIA Gem Trade Laboratory, we recommend diamonds shoppers only purchase natural fancy colored diamonds verified by the GIA Gem Trade Laboratory.
High Pressure High Temperature (HPHT)
High Pressure High Temperature (HPHT) treatment was first used to change the color of diamonds in the 1970's when laboratories were able to use high pressure and temperatures above 1900° C to change diamond colors to fancy yellow and green colors. Then in early 1999, General Electric (GE) and Lazare Kaplan International (LKI) introduced High Pressure-High Temperature (HPHT) diamonds to the marketplace, initially sold under the name "GE POL," and more recently as "Bellataire." This treatment transformed inexpensive brown diamonds into colorless diamonds.
The controversy arises because HTPT diamonds are not easy to detect. It takes specialized skills and equipment to detect diamonds treated by the HPHT process. Gemological Institute of America (GIA) grading reports now indicate when HTPT treatments are detected by stating "HPHT Annealed" or "Artificially Irradiated" in the Origins portion of a report. Grading labs continue their efforts to perfect ways to detect the always-improving process so that consumers can receive full disclosure about the diamonds they purchase.
The Federal Trade Commission (FTC) requires that HPHT be disclosed but with detection so difficult, there is a great reliance on laser inscriptions for identification and disclosure.
Laser Drilling
Laser drilling is a clarity enhancing treatment that has been in practice for years. The diamonds selected for laser drilling treatment usually have large dark, eye visible inclusions. A tiny laser beam is used to drill into the diamond, tunneling-in to remove inclusions. Some inclusions are dissolved by acid bleaching by submersing the diamond in an acid and pressurizing the container. This forces the acid through the laser drill hole and into the inclusion which makes the inclusion appear white or colorless and less visible.
Laser drilling typically leaves tunnels that resemble tiny jet trails, visible under side-view magnification. Typically a tiny white dot is visible when viewing the tunnels from the top of the diamond. Laser drilling removes inclusions permanently and does not alter the strength of a diamond. Normal cleaning and the heat produced during setting repairs won't change the appearance of the stone. Laser drilled areas that are filled-in with a clear substance (fracture filled) are more difficult to detect but the filler is not permanent.
A variation of the laser enhancement creates cracks around inclusions near a diamond's surface. The inclusion is removed and the process leaves the surface looking like it occurred naturally rather than by a laser.
Diamonds that are laser drilled can be certified by the GIA but the treatment is noted in the comment section.
Learn more about laser drilled diamonds at http://www.diamondsourceva.com/Education/Clarity/diamonds-clarity-enhancement.asp
Coatings
Diamonds are sometimes coated with various materials in an effort to show a fancy color or to make a lower color diamond appear more colorless. The coating can cover the entire diamond or just a section of it. Sometimes the coating is only on the pavilion of the diamond in a bezel or flush setting so that it is not easily visible from the top. Another common coating strategy is to put a touch of blue colored coating at the culet and the stone can appear to be several color grades better than its true color. A blue coating around the girdle can have the same effect.
Coatings can wear off with normal wear, being scratched or dissolved with alcohol. Like all diamond treatments, coatings should be disclosed by the retailer but this is seldom the case.
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