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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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