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Fracture Filled Diamonds

Jan 6, 1995 12:07 PM  
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The increasing numbers of fracture-filled diamonds present a major

challenge to the diamond industry. This proliferation can be

explained in part by the fact that several firms are now offering

commercial services and/or diamonds already so treated. Three firms

in particular appear to be especially visible in the marketplace.

Perhaps the best known of these is Yehuda Diamond Co./Diascience

Corp., New York, the first to enter this field with the product

developed in the 1980's by Zvi Yehuda of Ramat Gan, Israel. They were

followed by Genesis II - Enhanced Diamonds Ltd., New York, a division

of Israel-based firm Koss & Schechter Diamonds Ltd. Their product is

often referred to in the trade as "Koss clarity-enhanced diamonds";

more recently, it has been marketed in the U.S. and elsewhere under

the trademark name of "Genesis II" clarity-enhanced diamonds. Yet

another firm marketing its own product is Clarity Enhanced Diamond

House, a division of Goldman Oved Diamond Company, New York.

In part because several companies are now offering treated stones,

some confusion has developed about the identifying features of filled

diamonds. Claims--and counterclaims--have also been made concerning

the stability and durability of various products. To address these

issues, a team of researchers at the Gemological Institute of America

and the GIA Gem Trade Laboratory undertook a study to update their

earlier findings, published in the Summer 1989 and Spring 1990 issues

of Gems & Gemology. This report summarizes some of the key results of

this study, which focused on filled diamonds obtained recently form

the Yehuda, Koss, and Goldman Oved firms - both directly and through

third parties.

Effectiveness of the Filling Treatments The effectiveness of the

Yehuda filling process in improving apparent clarity had been

previously documented by the investigators. In summary, the Yehuda

process can significantly decrease the eye visibility of treatable

features. The present study showed that both the Koss and Goldman

Oved filling procedures are also very effective in improving the

faceup appearance of treatable diamonds by reducing the eye-visibility

of surface-reaching breaks.

Microscopic Features In all the stones examined during the recent

study, the fact that the diamond had been fracture-filled could be

determined by careful microscopic examination. While in many

instances standard darkfield/brightfield illumination was sufficient

to detect one or more diagnostic features, in some cases additional

lighting methods - such as pinpoint fiber-optic, oblique overhead, and

shadowing - were critical. The key features are described below.

Flash Effects: We observed flash effects, which are characteristic of

filled diamonds, in all of the stones we studied. In the first

Yehuda-treated stones we examined, these were yellowish orange

(darkfield) and "electric" blue (brightfield). In subsequent stones

from this firm, we noted a second flash pair: vivid pinkish purple

(darkfield) and bright yellowish green (brightfield). In the most

recent Yehuda-treated stones, we documented darkfield colors of violet

to purple to pink and brightfield colors of vivid bluish green to

greenish yellow. In Koss-treated stones, the most prevalent flash

colors were vivid pink, vivid purple, and a less saturated pinkish

orange (darkfield), and bluish green, yellow and green (brightfield).

Predominant flash colors in Goldman Oved-treated stones included

violet, purple, pink, and (less frequently) blue and green

(darkfield), and green, yellow, and bluish green (brightfield).

In the recent products from all three firms, it was not unusual to

detect more than one flash color at a single angle of observation. We

also noted that, in general, the Yehuda flash effects were the

brightest and the Goldman Oved flash effects were the least obvious.

Flow Structure: A filled break may look as if a glassy substance has

flowed into it. This feature was very subtle or absent in the most

recent Yehuda-treated stones and in the Koss-treated diamonds. It was

very subtle to fairly prominent in the Goldman-Oved treated stones.

Trapped Bubbles: Trapped bubbles - areas of incomplete filling - were

noted in all "generations" of Yehuda-treated diamonds. We also

detected at least some gas bubbles in all of the Koss-treated stones,

although they were often very small. Bubbles were also seen in

virtually all of the Goldman-Oved treated diamonds.



Incomplete Filling at the Surface: These extremely shallow areas of

incomplete filling at the surface often resemble fine white scratches

when seen in darkfield illumination. They were noted in virtually all

of the Goldman Oved-treated diamonds, in most of the Yehuda-filled

breaks and, least frequently, in Koss-treated stones.

Crackled Texture: Cracks in the filling material, often with a web-

like texture, were noted in the thickest filled fractures of early and

recent Yehuda-treated stones. We did not see this feature in Koss-

treated diamonds (possibly because the Koss firm reports that diamonds

with wide breaks are unsuitable for filling) or in any of the Goldman

Oved-treated stones.

Apparent Color of Filler: A yellowish body color was noted in

relatively thick areas of both early and recent Yehuda-treated

diamonds. We did not see any indication of inherent filler color in

any of the Goldman Oved- or Koss-treated diamonds (although there was

a drop in apparent color grade in some of the Koss-treated diamonds

documented before and after treated diamond (although there was a drop

in apparent color grade in some of the Koss-treated diamonds

documented before and after treatment).

Cloudy Surface Markings: A few of the Yehuda-treated diamonds

examined in 1990 had cloudy, circular surface markings. What appeared

to be filling residue was seen on some of the most recent Yehuda-

treated diamonds; no such indications of treatment were noted on any

of the Koss- or Goldman Oved-treated stones.

Cloudy Filled Areas: These are areas of reduced transparency in

filled fritters that resemble white clouds. We noted this feature to

some extent in treated stones from all three firms.

Durability and Stability of the Fillings For this phase of the study,

we subjected filled diamonds from all three firms to a series of

tests. However, with one exception, only one stone from each diamond

treated was used for each test. Therefore, the results of our tests

are representative, but not conclusive, and general conclusions should

not be drawn from them. We strongly recommend that readers obtain the

full report of our investigation as published in Gems & Gemology,

which provides a detailed description of the testing methods as well

as the results. With these caveats, our results are summarized below.

Steam Cleaning: Prolonged steam cleaning had no noticeable effect on

the faceup appearance of a Yehuda-treated diamond but removed small

amounts of filler from both a Koss-and a Goldman Oved-treated stone.

Ultrasonic Cleaning: Prolonged ultrasonic cleaning removed some

filler at entry points of surface-reaching breaks on a Yehuda-treated

diamond but had no noticeable effect on either the Koss- or the

Goldman Oved-treated stone.

Direct Heating: Exposure to high temperatures--both in prong-

retipping exercises and controlled furnace heating-- caused

significant damage to the filler in diamond treated by all three

firms.

Indirect Heating: No damage was noted to any of the products in

experiments involving the sizing of rings set with filled diamonds.

Repolishing: Repolishing produced different degrees of damage to the

filler in all three of the test stones.

Laser Inscribing: Laser inscribing the girdle of filled-diamonds on

an area that was close to, but not intersected by, a filling entry

point produced no noticeable deterioration in the filling in any of

the three stones.

Daylight Equivalent Testing: Exposure in a solar simulator equivalent

to 340 hours of exposure to daylight produced no obvious changes to

any of the products.

Exposure to long-wave ultraviolet radiation equating to 3,400 hoursU

exposure to daylight had no noticeable effect on a Yehuda-treated

diamond; similar results were noted in a second stone after the

equivalent of 1,700 hours of daylight exposure. A Koss-treated

diamond first showed some minor discoloration of the filling material

after the equivalent of 1,000 hours of daylight had a second stone

first shoowed some discoloration and clouding of the filler after the

equivalent of a single exposure equating to 1,700 hours of daylight.

One Goldman Oved-filled diamond showed obvious discoloration and

clouding after the equivalent of 3,400 hours of daylight; a second

stone showed no damage after a single exposure equivalent to 1,700

hours of daylight.

Low-Temperature Testing: Testing that simulated the type of cooling

warming that might occur when filled-diamond jewelry was worn in a

cold climate, going from heated building to the outdoors and back, had

no noticeable effect on any of the three samples.

Conclusion

Our recent study has shown that the fracture-filling treatments of all

three firms can be detected using a binocular gemological microscope.

However, because some diagnostic features can be quite subtle,

standard darkfield/brightfield/brightfield illumination is not always

adequate for detecting the treatment. Furthermore, it is our

experience that a 10x loupe cannot be relied on to detect

characteristic features in all diamonds. The most common diagnostic

features noted with the microscope were flash effects, high-relief

areas representing incomplete filling, and cloudy areas of reduced

transparency.

While the suites of diagnostic features for filled stones from the

three firms were not identical, there was significant overlap. In

addition, there are other firms offering treatment services and the

features of their products can be expected to overlap those of the

three firms studied. Therefore, we conclude that not individual

feature or suite of features will identify which firm treated a

specific stone.

Our durability testing showed prolonged exposure--or numerous short

exposures--to commonly employed cleaning methods may damage the

filling substances. Direct heating--like that used in jewelry repair

procedures--will damage the fillers; however, repair procedures

involving indirect heating might not damage them. Prolonged exposure

to daylight may have a negative effect on the appearance of some

fracture-filled diamonds.

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Tags: GIA, Israel, Jewelry
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