|
| |
GE Produces Pinks and Blues De Beers, GIA Develop HPHT Detection - Dec.2000
Along with their ability to treat brown diamonds and make them white, General
Electric has also developed the technology to turn lower-quality stones into
fancy colored pink or blue stones. GE’s High Pressure High Temperature process
is producing the equivalent of fancy to fancy deep pinks and very light to fancy
intense blues. The pink diamonds were type IIa, the blues were type IIb (showing
electrical semi-conductivity and characteristic boron features in the
mid-infrared). According to Bellataire Diamonds, the Lazare Kaplan-owned distributor of
the GE-processed stones, the pinks and blues will represent a small fraction of
overall production. The focus, therefore remains changing the color of diamonds in the N color range
to the D to F range. Once heralded as undetectable, these stones are now able to be flagged by a
detection unit developed by De Beers. After two years of research, meanwhile, the GIA has discovered a number of detection factors to help identify
stones treated by GE. According to a report in the GIA’s Gems & Gemology, the treated
stones have drastic changes in color, yet little change in inclusions, graining
and strain. The process alters the color via a reconfiguration of the lattice in
which defects such as unoccupied carbon sites and point defects that absorbs visible light and imparts color.
"Indicators that a diamond has been HPHT processed are provided by
inclusion features and photluminescence spectra," according to the fall
issue of Gems & Gemology.
Meanwhile, after an exhaustive study, the GIA determined that there is still not
single feature by which a GE diamond can be identified, yet there are features
that conclusively establish that a diamond is not HPHT treated. these include a
wide variety of inclusions, some types of graining, the IR spectra and various
photoluminescence and cathodoluminescence activities. Some of the identification
criteria may also apply to the pink and blue treated stones.The De Beers detection unit, meanwhile, deep freezes each diamond to minus 196
Celsius in liquid nitrogen and employs tests that the company is not
revealing. Right now, there are no plans to mass produce the units for use by
retailers.
v
|
