| HPHT
Tutorial
HPHT & Xanthic Collection what's that
?
Color enhancing process comparison
Technical description
HPHT disclosure and detecting challenge by certification
institutes
HPHT
& Xanthic Collection what's that ?
HPHT stands for High Pressure High Temperature.
“XANTHIC COLLECTION” Diamonds are extremely
rare diamonds that were originally crystallized without color
and were destined to become extraordinary gems. During their journey
to the surface of the Earth through volcanic pipes, though, these
crystals were subjected to intense heat, tremendous pressure,
and explosive turbulence.
These conditions caused some molecular misalignment in these crystals
resulting in an yellowish or a brownish color and internal stress,
so called “plastic deformation” (strain).
The HPHT process simply provides comparable conditions of heat
and pressure, allowing these crystals to spontaneously relieve
themselves of their molecular stress and return to their proper
alignment and their original state, so called “healing of this
plastic deformation”. It is this process of restoration that leads
to the description of “XANTHIC COLLECTION” Diamonds
as Mother Nature intended.
“XANTHIC COLLECTION” Diamonds are extremely rare, ultra-pure,
natural diamonds that have been restored to their intrinsic color
by a proprietary HPHT process. “Xanthic Collection”-brand diamonds
are of exceptional quality. Mostly “D” through “H” in color for
white diamonds or fancy intense color as green, yellow, orange,
chartreuse, gold, olive and occasionally pink and blue for colored
diamonds, seldom lower in clarity than “VS2”, and cut to the most
demanding standards in the diamond industry.
”XANTHIC COLLECTION” Diamonds are completely natural diamonds
and the process is permanent. Nothing is added to the natural
diamond crystal nor anything removed from it in the process of
transforming a rough diamond to a polished gem. “XANTHIC COLLECTION”
Diamonds are never laser-enhanced, irradiated, fracture-filled,
or altered in any way that would compromise their all-natural
content.
Because “XANTHIC COLLECTION” Diamonds are totally natural, they
cannot be easily distinguished from other diamonds without extremely
sophisticated equipment.
For this reason we have established a very strong disclosure policy
for all “Xanthic Collection” diamonds. To always be able to distinguish
a “Xanthic Collection” diamond from regular diamonds we have them
laser-inscribed on their girdles with the brandmark “Xanthic”,
and the HRD logo & certificate number.
We even go further to comply with the Diamond World Congress HPHT
rule passed on the October 2002 Congress in London, by asking
our dealers to sign our disclosure policy.
To understand very clearly the difference between HPHT processing
and treatment, we can say that treated diamonds usually have one
or more of the following characteristics: a change that is not
permanent, special care needed for maintenance, and/or applied
material that is not intrinsic to the natural diamond. “XANTHIC
COLLECTION” Diamonds have none of these characteristics.
In fact, the process that restores “XANTHIC COLLECTION” Diamonds
to their original natural state in many ways alters rough diamonds
less than the processes of cleaving, laser-shaping, polishing,
and acid-boiling, among others, that are accepted activities necessary
for transforming rough to polished.
Color
enhancing process comparison
| HPHT
process |
|
Natural
color .
|
|
Bombarding
processing |
Price:
In relation with white diamonds of corresponding shape
and clarity, the HPHT processed diamonds will be a little
more expensive. |
|
Price:
Very high, can't fit all budgets. Christie's auction
meet the highest selling price with over 1 million US
dollars per carat... . |
|
Price:
Very cheap, generally low end grade diamonds used
to meet inexpensive market products. |
Clarity:
Only the best clarities as IF, VVS and VS can be used
to this process, lower grade will encounter serious problems
under the high pressure.
.
|
|
Clarity:
All clarities are found. |
|
Clarity:
Generally low end grade diamonds are used and
mostly the diamonds are also passed through a crack filling
treatment to enhance the clarity. |
Radioactivity:
None. .
|
|
Radioactivity:
None. |
|
Radioactivity:
? !! |
Durability:
The process is permanent. What ever you can do with your
diamond, the color will resist. |
|
Durability:
So long as you don't re-cut your diamond, the color is
permanent. As the color of the diamond can be located
just at a point of the diamond and shining throughout
all the stone, you run the risk of loosing part or all
the color if for any reason you choice to re-cut your
diamond. |
|
Durability:
By this treatment the color is put into the diamonds by
breaking the atom during an acceleration made within an
atomic reactor. . |
Processing
disclosure:
All Xanthic Collection diamonds come with a certificate
that clearly specify the HPHT processing. We also request
from all our dealers to sign our disclosure policy and
to clearly inform all their customers as manufacturers,
jewelries and the general public. |
|
N/A
|
|
Processing
disclosure:
No commentaries. |
Technical
description -
HPHT processing
HPHT
processing involves subjecting the diamond, polished or rough,
to very high temperatures and pressures in specialized equipment.
Depending on their size, only a few diamonds can be processed
at one time in such equipment. As a result of this process,
which in some instances takes only a very short time, the color
of the diamond can be dramatically changed.
Diamonds are classified scientifically into two “types” with
subcategories for each. “Type I” diamonds — the most abundant
in nature — contain nitrogen. They usually vary from colorless
to yellow or brownish yellow. “Type II” diamonds — which are
rare in nature — lack all but tiny amounts of nitrogen. They
are sometimes colorless, but more often brown; if they contain
boron, they can be blue to gray. These two categories of diamonds
display differences in some physical properties and in their
absorption or luminescence spectra. The brown coloration in
diamonds of both types results when they have been subjected
to plastic deformation (i.e., “strain”) deep in the earth during
long periods of geologic time.
As a result of HPHT processing, type II brown diamonds can be
transformed to colorless or near-colorless. The same procedure
can transform a limited number of brown-pink or brown-to-gray-blue
type II diamonds to pink and blue, respectively. In both cases,
heating at very high pressures results in a “healing” of the
plastic deformation mentioned above, thereby removing the cause
of the brown coloration so that the type II treated diamond
is colorless, pink or blue.
The transformation of type II brown diamonds to colorless was
the first product introduced into the market, and to date these
diamonds represent the overwhelming majority of what is offered
for sale.
Within
the past few years, the HPHT process has also been used for
the processing of more common type I brown diamonds to transform
them to yellow-green, yellow and orange-yellow. This expanded
range of diamonds being treated by HPHT continues to make this
a difficult identification problem.
The specialized equipment needed for HPHT processing is not
common, existing at only a few high-technology companies and
research institutes around the world. Despite having the equipment,
not all of these companies and institutes have ready access
to the appropriate precursor diamonds for HPHT processing.
HPHT
disclosure and detecting challenge by
certification institutes
We
at S.L. Maxfield & Associates, owner of the Xanthic Collection
trademark, affirm to disclose all processed diamonds. We work
closely with all major labs for certification on all Xanthic
Collection diamonds.
Colorless
to near-colorless HPHT-annealed diamonds have proven to be a
difficult identification challenge. GIA researchers have now
carefully documented over 8,000 such diamonds and have systematically
compared their properties to those of type II natural-color
diamonds, thereby allowing them to develop robust criteria to
separate them.
Since
1999, several organizations have become involved with HPHT processing
of diamonds, and their “recipes” for transforming the colors
of diamonds at high temperatures and pressures may be slightly
different. Consequently, certification institutes are constantly
updating their research to ensure that practical identification
criteria are established.
After the introduction of HPHT-processed diamonds, GIA focused
their HPHT research efforts almost exclusively on detecting
decolorized type II brown diamonds. They expanded these efforts
when a wider range of colors produced by HPHT processing entered
the diamond market. Although recognizing decolorized type II
brown diamonds is a challenge, in some ways the identification
of HPHT treatment in type I diamonds can be even more challenging
because of the wider variation in properties they exhibit. HPHT
processed type I diamonds produces a range of colors from yellowish
green to orange. Because of their varying amounts and configurations
of nitrogen, these diamonds respond differently to HPHT processing,
and the resulting color changes range from subtle to dramatic.
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