Unanswered Questions about GE/POL
GIA's first round of findings about the treated diamonds
The Gemological Institute of America's study of almost 900
GE/POL diamonds hints at some identifying characteristics but
leaves a multitude of unanswered questions on the treatment.
Leon Tempelsman, president of Lazare Kaplan International and
subsidiary POL, which distributes the diamonds, has stated publicly
the studied diamonds were early samples and some gemological
features GIA identified are not found in later samples because
the process was subsequently improved.
Tempelsman also dashed hopes that a determination of a diamond's
type could be used as an identifying characteristic of the treated
diamonds. GIA said most diamonds it examined were Type IIa, but
Tempelsman said General Electric, which developed the process,
hopes to apply the treatment to a wide range of diamond types.
Though frustrating to gemologists, this news doesn't negate
the progress GIA is making in its research. It will continue
to examine later samples of treated diamonds to reveal identifying
Several other leading laboratories, such as the Gübelin
Gem Lab in Lucerne, Switzerland, are studying GE/POL diamonds
Diamonds in Question
The GE/POL diamonds GIA studied range from 0.18 carat to 6.66
carats. Eighty-five percent are fancy shapes, and 80% are in
the D-G color range. The report's authors James Shigley,
Thomas Moses, Shane McClure, John Koivula and Mark Van Daele
expressed surprise about the high clarity of the studied
diamonds. Sixty-one percent are IF or VVS1 and the rest are in
the VVS2-VS range, with a small percentage of SI and I clarities.
The vast majority of the diamonds GIA examined are Type IIa.
Studies at other labs confirm GE's statements that GE/POL
diamonds are more than just Type IIa. Chris Smith, director of
the Gübelin Gem Lab, says that in the infrared region of
the spectrum, the GE/POL diamonds would be classified as Type
IIa. "Upon closer inspection and expansion of the region
where nitrogen impurities may be found [a defined area of the
spectrum from 1000 to 1400 cm-1], very minor concentrations of
nitrogen absorption typical of Type Ia diamonds have been recorded
in a small percentage of the diamonds examined to date,"
GIA's report adds information to previously announced findings
that 75% of the diamonds exhibit internal graining, creating
a hazy appearance. It also says surface-reaching cleavages in
the diamonds in some cases have a black area, with one black
mass identified as graphite. A number of included crystals are
surrounded by a roughly spherical black patch (see photo at right).
Also, 80% of the gems emit no fluorescence.
Among the questions all the labs are trying to answer is exactly
what high temperatures and pressures are involved in the treatment
(GE has confirmed it uses high temperature and high pressure
to whiten the diamonds). A high-temperature/high-pressure situation
causes diamonds to occur in the first place. For this reason,
experts say lab-induced HTHP may change the color and the basic
structure of a diamond crystal. If the temperature and pressure
leave the crystal unaltered, another mechanism or catalyst could
be involved in improving the color.
Martin Haske of Adamas Gemological Laboratories, Brookline,
MA, wonders whether the treatment might include a cleaning mechanism.
"The hazy appearance and generally high grade of the stones
would support that view," he says. Haske points to a patented
process involving the removal of impurities from diamonds that
involves HTHP and the use of acids or alkalis to leach out impurities.
"A lot of clues might be detected in unpolished rough before
they are polished away in the cutting process."
But the most important unanswered question remains: Are there
any tests on the horizon to identify these diamonds if the GE/POL
girdle inscription that POL agreed to place on them has been
removed after the diamonds reach the market? Only time and more
research will tell.
by Robert Weldon. G.G.
|This GE POL diamond shows a banded strain pattern
when viewed under cross-polarizers. A large number of GE/POL
diamonds show strain patterns, says GIA.
|A partially healed cleavage has
an unusual granular appearance. GIA saw surface cleavages less
frequently than internal graining.
||Characteristics such as this small
solid inclusion surrounded by a black patch thought to be graphite
and then an outer layer of tiny outward radiating cracks were
seen in some GE/POL diamonds.
Copyright © 1999 by Bond Communications.