GEMSTONE ENHANCEMENT
AND DETECTION IN THE 1990S
By Shane F. McClure and Christopher P. Smith
Gemstone enhancements and their disclosure
became the most important gemological issue
for the jewelry trade in the 1990s. Growing
public awareness of treatments and the greater
use of sophisticated technology to enhance the
color and/or apparent clarity of gem materials
brought to the forefront the need to maintain
(or in some cases regain) the consumer confidence that is so vital to this industry. The
treatments with the greatest impact were
those that affected the gems that were commercially most important: heat and diffusion
treatment of ruby and sapphire, “oiling” of
emeralds, and fracture filling of diamonds. At
the end of the decade, the decolorization of
diamonds by high pressure and high temperature posed one of the greatest identification
challenges ever faced by gemologists worldwide. Yet most other gem materials were also
subjected to enhancements—ranging from traditional processes as with quench-crackled
quartz to novel “impregnation” techniques
such as the Zachery treatment of turquoise.
This article discusses the treatments that were
new or prominent during the ‘90s and suggests
methods for their detection.
ABOUT THE AUTHORS
Mr. McClure (smcclure@gia.edu) is director of
West Coast Identification Services at the GIA
Gem Trade Laboratory, Carlsbad, California.
Mr. Smith is director of the Gübelin Gem Lab,
Lucerne, Switzerland.
Acknowledgments: The authors thank John
Koivula, Tom Moses, Alice Keller, and Brendan
Laurs for their help in preparing this article.
Gems & Gemology, Vol. 36, No. 4, pp. 336–359
© 2000 Gemological Institute of America
336
Enhancement in the 1990s
A
t the time the previous retrospective article on
gemstone enhancements was published by
Kammerling et al. (1990a), enhancement disclosure was a concern of the jewelry industry, but it was still
not a major international focal point. Since then, the issue of
disclosure has caused a major upheaval throughout the
trade, which has extended to all areas of the jewelry business, including diamonds (figure 1). In some cases, treatment disclosure—or the lack of it—has severely damaged
the sale of certain gem materials by eroding the confidence
of the consuming public in those gems. When consumers
feel—rightly or wrongly—that a product is not being represented honestly, they are likely to stop buying that product.
One of the most drastic of these situations in the 1990s
concerned emeralds. As a result of several events during the
decade, consumers became aware that emeralds are routinely fracture filled, a fact that retailers typically were not disclosing. This new awareness coupled with the general lack
of disclosure caused the public to feel that there must be
something wrong with emeralds and they stopped buying
them, creating a precipitous drop in the sale and value of
these stones (see, e.g., Shigley et al., 2000a).
This is just one example of events throughout the ‘90s
that made the subject of treatments—what they involve,
how they can be identified, and how they should be disclosed—the most discussed gemological issue of the decade.
Many questions about treatment disclosure are still being
debated industry wide, and the answers are usually very
complex. For this reason, this article will not seek to address
the many ethical issues that haunt the trade. Rather, we
will describe those gem treatments or enhancements that
were first reported on or commonly performed during the
last decade, and what can be done to detect them.
It is important to recognize that, for some of these
enhancements, the detection methods needed have progressed far beyond the ability of most gemologists working
in the trade, primarily because the instrumentation required
GEMS & GEMOLOGY
Winter 2000
is often very sophisticated and expensive. We hope
that this article will provide sufficient information
to help a gemologist recognize when a stone may
have been enhanced by such a method, so that he or
she can determine whether it should be sent to a
laboratory that has the necessary equipment.
THERMAL ENHANCEMENT
Thermal enhancement, or heat treatment, continues
to be the most common type of treatment used for
gems. Heat-treated stones are stable, and the result
is permanent under normal conditions of wear and
care. Heat treatment can be identified in some gem
materials by routine gemological testing, and in others only by the use of advanced laboratory instrumentation and techniques. In still other gems, heat
treatment is not identifiable by any currently known
method. By the 1980s, virtually every gem species
and variety known had been heated experimentally
to determine if its appearance could be favorably
altered. Many of the methods used both then and
now are crude by modern standards, yet they can be
very effective. During the 1990s, applications of, or
improvements in, previously known technologies
resulted in new commercial treatments. Perhaps the
most important of these is the use of high pressure
and high temperature (HPHT) to remove color in
some brown diamonds and produce a yellow to yellowish green hue in others. These advances had a
significant impact on the jewelry industry, some
requiring the investment of enormous amounts of
time and money to develop identification criteria.
Many gemstones—such as tanzanite, aquamarine, blue zircon, citrine, and the like—have been
subjected to heat treatment routinely for several
decades. Not only has the treatment of these stones
become the rule rather than the exception, but in
most cases there is no way to identify conclusively
that the gem has been treated. Therefore, heat treatment of these stones will not be discussed here.
Ruby and Sapphire. As was the case in the preceding decade, the heat treatment of corundum
remained a serious issue for the colored stone industry around the world. This treatment was applied to
the vast majority of rubies and sapphires (figure 2)
during the ‘90s to: (1) remove or generate color, (2)
improve transparency by dissolving rutile inclusions, and/or (3) partially “heal” (i.e., close by the
recrystallization of corundum) or fill surface-reaching fractures or fill surface cavities.
The primary concern that surrounded this
Enhancement in the 1990s
Figure 1. Gemstone enhancement and its disclosure became a critical issue in the 1990s, affecting
not only rubies (here, 6.38 ct), emeralds (4.81 ct),
and sapphires (6.70 ct), but colorless diamonds
(5.05 ct) as well. Photo by Shane F. McClure.
enhancement was not the heat treatment itself, but
the mostly amorphous substances that were left
behind by the heating process in rubies (such features
rarely have been encountered in sapphires). The disclosure that such substances were present in fractures
and surface depressions caused a great deal of controversy in the industry, which contributed to the significant drop in price of heat-treated rubies in the latter
half of the decade (see, e.g., Peretti et al., 1995; Shigley
et al., 2000a). Many in the industry felt that this material was only a by-product of the heating process
(Robinson, 1995), while others felt that it was put
there intentionally (Emmett, 1999). Still others maintained that if fractures were being partially healed by
this process, they were being healed with synthetic
ruby (Chalain, 1995). Back-scattered electron images
showed recrystallized corundum on the surface of one
heat-treated ruby (Johnson and McClure, 2000).
Although the material within the fractures was typically an artificial glass or similar substance, it was
also found that natural inclusions could melt during
the heat treatment and leave behind similar residual
by-products (see, e.g., Emmett, 1999).
GEMS & GEMOLOGY
Winter 2000
337
Figure 2. The vast
majority of rubies
and sapphires are
now routinely heattreated. The color or
clarity (or both) can
be improved in many
different types of
corundum by this
process. Photo by
Shane F. McClure.
This debate was fueled primarily by the discovery of large quantities of ruby near the town of
Mong Hsu in the upper Shan State of Myanmar
(formerly Burma). Virtually all of this material had
to be heated to improve its quality, either by
removing the blue “cores” that typically occur
down the center of the crystals or by filling or partially healing the many fractures (see, e.g., Peretti
et al., 1995). The fluxes used during the heat-treatment process melt, flow into surface-reaching fractures and cavities, and subsequently re-solidify on
cooling as an amorphous, vitreous solid (i.e., a
glass). Because the fluxes can dissolve solid material in the fractures or even part of the corundum
itself, the treatment process also may result in the
formation of polycrystalline and/or single-crystal
material in the fissure (see, e.g., Emmett, 1999).
Currently, researchers and other gemologists are
investigating the nature of the materials left behind
after the heating process in Mong Hsu ruby. It is
important to note, however, that heat-treated
rubies from any locality (including Mogok) could
338
Enhancement in the 1990s
contain these materials. In fact, the filling of surface-reaching pits, cavities, and fractures with
“glassy” solids was first identified in ruby from
Mogok and various deposits in Thailand during the
early 1980s (Kane, 1984).
As the decade began, glassy materials were seen
less frequently at the surface of heat-treated rubies,
where they appeared as areas of lower surface luster
in fractures and cavities. Recognizing that this was
the evidence many laboratories used to detect such
fillings, heat treaters and others in the trade began
to routinely immerse the rubies in hydrofluoric acid
to remove the surface material (figure 3). Consequently, gemologists had to focus more on the
material that was still present in the fractures
within the interior of the stone, which is much
more difficult (if not impossible) to remove with
acids. Note that the amount of residual glassy
material left in partially healed or filled fractures is
typically minuscule.
At the beginning of this decade, gemological laboratories had vastly different policies (see below)
GEMS & GEMOLOGY
Winter 2000
concerning the nomenclature used to disclose these
substances, which included “glass,” “glassy,” “glasslike,” or “a solid foreign substance.” In 1995, the
Asian Institute of Gemmological Sciences in
Bangkok became the first laboratory to introduce a
system to denote the amount of this material that
was present in a particular ruby. At the same time,
they introduced the term residue to denote this substance (Johnson, 1996a). Their system described the
presence of residue as minor, moderate, or significant. Most internationally recognized laboratories
have since adopted similar terminology.
In fact, during this period, discussions took place
in the trade and among laboratories specifically to
address these nomenclature issues. Nevertheless, it
will be very difficult for all international gemological laboratories to reach a consensus on how to present or describe this form of treatment, because different regions of the world have quite differing
views on the subject. In the U.S., the trade demands
more open disclosure because of legal concerns (see,
e.g., Weldon, 1999a). On the opposite side of the
spectrum are Southeast Asia and the Far East,
where the trade typically wants little disclosure
(see, e.g., Hughes and Galibert, 1998). Between these
two is Europe, which traditionally follows the rules
and regulations set out by CIBJO (International
Confederation of Jewellery, Silverware, Diamonds,
Pearls and Stones [see Editions 1991 and 1997]).
All of these factors served to confuse people in the
trade and consumers alike. They not only contributed to a dramatic decrease in the price of heated
rubies, but they also created greater demand for nonheated rubies and sapphires by the end of the decade.
Besides the continuation of the heating practices
described in the previous retrospective article
(Kammerling et al., 1990a), there were some significant new developments during the 1990s relating to
the heat treatment of sapphire as well as ruby. First,
equipment became increasingly more advanced. In
addition to the more sophisticated control of temperature and atmosphere, some electric furnaces
were also equipped for elevated pressure (Karl
Schmetzer, pers. comm., 2000). Such advanced
techniques led to the successful heat treatment of
blue sapphires from Mogok, which was previously
not commonplace (Kenneth Siu, pers. comm.,
1997).
Heat treatment alters many of the properties and
internal characteristics of rubies and sapphires. For
those laboratories that provide locality-of-origin determinations, such modifications—coupled with the
greater number of corundum sources found during the
decade—only added to the complexity of determining
the geographic origin of a ruby or sapphire (see, e.g.,
Schwarz et al., 1996). However, a number of articles
did address the techniques used and the effects of heat
treatment on sapphires from localities such as
Kashmir (Schwieger, 1990), Sri Lanka (Ediriweera and
Perera, 1991; Pemadasa and Danapala, 1994), Montana (Emmett and Douthit, 1993), Australia
(Themelis, 1995), and Mogok (Kyi et al., 1999).
Proving that a stone has not been heat treated is
often no simple matter, and it may require a significant amount of experience. Little new information
was published in the ‘90s concerning the identification of this treatment in corundum. The criteria of
the ‘80s, most of which require the use of a microscope, still apply. These include spotty coloration,
cottonball-like inclusions, broken or altered rutile
silk, internal stress fractures around solid inclusions,
altered mineral inclusions, and chalky bluish to
greenish white fluorescence to short-wave ultraviolet radiation (see, e.g., Kammerling et al., 1990a). It
has been suggested that enhancement can be effected in some rubies and sapphires by heating them at
lower temperatures, which might not produce the
evidence normally seen in heat-treated corundum
(John Emmett, pers. comm., 2000). This would make
identification of the treatment even more difficult.
Figure 3. Rubies that have been
fracture filled with a glassy substance can be detected by the lower
luster in reflected light of the glassy
material within the fractures (left).
In the mid-‘90s it became common
for treaters or dealers to immerse
these stones in hydrofluoric acid to
remove this surface evidence (right).
Photomicrographs by Shane F.
McClure; magnified 40×.
Enhancement in the 1990s
GEMS & GEMOLOGY
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339
Figure 4. The color enhancement of diamond
moved to the forefront late in the decade, when
it was learned that new high pressure/high temperature techniques had been developed that
could turn brown type IIa diamonds colorless
and turn brown type Ia diamonds, similar to the
rough diamonds shown here, yellow-green
(inset, 4.45 ct). Photo by Shane F. McClure;
inset photo by Maha Tannous.
Diamond. The close of the decade witnessed a dramatic new development in thermal enhancement.
Beginning in approximately 1996, intense yellow to
greenish yellow to yellowish green type Ia diamonds
began to enter the international diamond market
(see, e.g., Reinitz and Moses, 1997b). Soon thereafter
it became known that the color in these diamonds,
which were primarily thought to have originated in
Russia, had been produced in type Ia
diamonds by high pressure/high temperature annealing techniques (figure 4).
On March 1, 1999, Lazare Kaplan International
subsidiary Pegasus Overseas Limited announced
that they planned to market diamonds that the
General Electric Company (GE) had enhanced by a
proprietary new process (Rapnet, 1999). GE scientists soon confirmed that they were using HPHT
annealing to remove color from type IIa brown diamonds (figure 5; see box A of Moses et al., 1999).
This development sent a shockwave throughout the
international diamond industry (see, e.g., Barnard,
1999; Weldon, 1999b,c). Gemological and research
laboratories around the world soon began the task of
developing a means to detect these HPHT-enhanced
diamonds (see, e.g., Moses et al., 1999; Chalain et al.,
1999, 2000). Currently, several characteristics have
been identified that may indicate if a diamond has
been exposed to HPHT conditions. Unfortunately,
most are not within the scope of techniques available to the average gemologist, because they depend
heavily on absorption and/or photoluminescence
spectral features present at low temperatures (see,
e.g., Fisher and Spits, 2000; Reinitz et al., 2000b;
Smith et al., 2000). Nevertheless, the process may
produce some indications that are visible with a
microscope. These relate primarily to damage
caused by the extreme conditions of the treatment,
such as etched or frosted naturals, or fractures that
are partially frosted or graphitized where they come
to the surface (figure 6). It must be emphasized that
these are indications only, and they may be difficult
to recognize for all but the most experienced
observers.
By the end of the decade, a number of different
groups in various countries were modifying the
color of diamonds by exposure to HPHT conditions
(see, e.g., Moses and Reinitz, 1999). The majority of
these stones are the yellow to yellowish green type
Ia diamonds, but more than 2,000 “decolorized”
type IIa diamonds had been seen in the GIA Gem
Figure 5. This 0.84 ct piece of type
IIa diamond rough was HPHT
annealed by General Electric for
GIA researchers. The original dark
(approximately equivalent to Fancy)
brown material (left) was changed
to approximately “G” color (right)
after being subjected to the process.
Photos by Elizabeth Schrader.
340
Enhancement in the 1990s
GEMS & GEMOLOGY
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Trade Laboratory by the end of 2000. Most recently,
HPHT-processed pink type IIa diamonds and even a
limited number of blue type IIb diamonds have
appeared (Hall and Moses, 2000).
Tourmaline. The 1989 discovery of elbaite tourmaline in Brazil’s Paraíba State revealed colors that had
never before been seen in this gem species. It was
soon determined that exposure to high temperatures could produce a vivid blue or green hue in
some crystals from this deposit; the “emerald”
green was not known to occur naturally (Fritsch et
al., 1990). The heat treatment of these tourmalines
(commonly referred to as “Paraíba” tourmaline)
continued throughout the 1990s, even though finds
of this material declined as the decade progressed.
Other types of tourmaline from various countries
also continued to be heat treated during the 1990s.
However, as with the Paraíba material, such treatment cannot be identified in these tourmalines by
standard gemological methods.
Topaz. Pink topaz continues to be produced by
exposing brownish yellow to orange “Imperial”
topaz from Brazil to elevated temperatures (figure
7). This color does occur naturally in topaz from a
number of localities, including Brazil.
The most recent report on the mining and heat
treatment of Imperial topaz was done by Sauer et al.
(1996). This article described a possible new test for
detecting heat treatment in topaz. The limited number of heated stones in this study showed a distinct
change in short-wave UV fluorescence from a very
weak to moderate chalky yellow-green in the
untreated stones to a generally stronger yellowish or
greenish white in the treated stones. As the authors
noted, more research is needed to determine the reliability of this test.
Figure 6. This fracture in an HPHT-annealed
yellow-green diamond has partially graphitized,
which is an indication that the stone has been
subjected to high pressure/high temperature
conditions. However, the presence of graphitization should not be construed as proof of treatment. Photomicrograph by Shane F. McClure;
magnified 31×.
As is the case with many other materials, at this
time heat treatment in zoisite is not detectable in
most cases.
Amber. Several reports in the ‘90s described a kind
of surface-enhanced amber, where a dark brown
layer of color is generated at a shallow depth by
exposing the amber to controlled heating, up to
Figure 7. Heat treatment of brownish yellow to
orange Imperial topaz from Brazil changes the
color of the material to pink, such as the piece
shown here on the lower left. The larger crystal
weighs 115.0 ct. Photo by Maha Tannous.
Zoisite. Most people in the trade are now familiar
with the fact that the color of the vast majority of
tanzanite in the market is the result of the heat
treatment of brown zoisite. In 1991, however, transparent green zoisite was discovered. Although the
finds to date have been relatively small and sporadic
at best, limited experimentation showed that only a
small percentage of this material responded to heat
treatment, changing from the original bluish green
through brownish green to a greenish blue. Barot
and Boehm (1992) suggested that green zoisite was
not routinely being heated because of the rarity of
this material.
Enhancement in the 1990s
GEMS & GEMOLOGY
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341
Figure 8. This heat-treated amber bead has been
ground down on opposite sides to show that the
color imparted by the treatment is confined to a
thin surface layer. The dark brown hue fades on
prolonged exposure to light. Photomicrograph
by Shane F. McClure; magnified 10×.
approximately 220°C (Crowningshield, 1993;
Hutchins and Brown, 1996; Safar and Sturman,
1998). In many cases, the interior of this material is
left almost colorless (figure 8). With prolonged exposure to light, however, the dark surface layer proved
to be unstable, fading to a much lighter tone.
This treated amber can be recognized by a dull,
chalky green fluorescence to long-wave UV, rather
than the stronger orange fluorescence of untreated
material, as well as by the presence of numerous
tiny gas bubbles in swirling clouds just below the
surface of the stone.
Other Gem Materials. It seems that people in our
trade have a fascination with exposing gemstones to
heat, just to see what happens. Some examples of
this reported during the past decade include changing the color of blue benitoite to orange (Laurs et al.,
1997), yellow chalcedony to carnelian (Brown et al.,
1991), and rhodolite garnet to a more brownish
color with a metallic oxide coating (Johnson and
Koivula, 1997a).
DIFFUSION TREATMENT
Corundum. At the beginning of this decade, the
trade witnessed a dramatic resurgence in diffusiontreated blue sapphire (e.g., Kane et al., 1990; Hargett,
1991). This resurgence was attributed to a new technique that allowed for a much deeper penetration of
the diffused color, which came to be known as “deep
diffusion” in the trade. For a time, these stones
seemed to have a certain degree of trade acceptance,
342
Enhancement in the 1990s
and large diffusion-treated sapphires—some exceeding 20 ct—were produced (e.g., Koivula and
Kammerling, 1991b). By the mid-‘90s, however,
interest in this material had declined dramatically
(Koivula et al., 1994). We believe that, for the most
part, these stones were being marketed and disclosed
properly, although there were several incidents of
diffusion-treated sapphires being “salted” in parcels
of natural-color blue sapphires (Brown and Beattie,
1991; Koivula et al., 1992d).
Identification of this material is best accomplished by immersing it in methylene iodide.
Diffusion treatment in sapphires is characterized
by color concentrations along facet junctions,
patchy surface coloration, and higher relief in
immersion when compared to an untreated stone
(Kane et al., 1990). It was recently reported that
some diffused sapphires do not show the characteristic concentrations along facet junctions, which
are caused by the stones being repolished after
treatment (Emmett, 1999). This was attributed to
the possible use of a molten titanium-bearing flux
instead of a powder, which could eliminate the
need for repolishing. Such stones can still be identified by the “bleeding” of color into surface-reaching
features such as “fingerprints,” fractures, and cavities, or by their characteristic higher relief in
immersion.
The most significant new development in diffusion treatment during the decade was the introduction of red diffusion-treated sapphire (often called
diffusion-treated ruby), as described by McClure et
al. (1993). This type of diffusion treatment never
seemed to gain wide usage, probably because of the
difficulties inherent in diffusing chromium into the
surface of corundum. These difficulties result in a
very shallow surface layer of color, as well as in
some unwanted colors such as purple and orange
(Koivula and Kammerling, 1991f,g; McClure et al.,
1993; Hurwit, 1998). One of the authors (CPS) was
informed that when this material first came out,
several prominent ruby dealers in Bangkok paid
very high prices for diffusion-treated “rubies” that
were represented as heated only.
Diffusion-treated “rubies” can be identified readily by their patchy or uneven surface coloration,
color concentrations along facet junctions, relatively high relief in immersion (figure 9), very high surface concentrations of chromium, very high refractive index, patchy bluish white to yellowish white
short-wave UV fluorescence, and atypical dichroism
(see, e.g., McClure et al., 1993).
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Winter 2000
Figure 9. Immersion
in methylene iodide
reveals the patchy
surface coloration,
color concentrations
along facet junctions,
and high relief (when
compared to untreated stones) of these
red diffusion-treated
sapphires. Photo by
Shane F. McClure.
Occasionally encountered were corundums that
owed their asterism, as well as their coloration, to
diffusion treatment (e.g., Crowningshield, 1991,
1995c; Johnson and Koivula, 1996c, 1997c). Even
colorless synthetic corundum was diffusion treated
(Koivula et al., 1994; Crowningshield, 1995b;
Johnson and Koivula, 1998a).
Topaz. We first encountered what was being represented as “diffusion treated” topaz in 1997 (Johnson
and Koivula, 1998d). However, it is still not clear if
the cobalt-rich powders employed during the
enhancement process actually diffuse into the lattice of the topaz. Nevertheless, the green-to-blue
colors of this material (figure 10) are quite different
from the orange, pink, or red hues we have seen in
topaz colored by a surface coating (Johnson and
Koivula, 1998d; Hodgkinson, 1998; Underwood and
Hughes, 1999). The “diffusion treated” material is
easily identified by its spotty surface coloration.
The colored layer is as hard as topaz and is so thin
that no depth was visible in a prepared cross-section, even at 210× magnification (Johnson and
Koivula, 1998d).
types of artificially irradiated gems appeared on the
market, although there were a number of changes or
improvements made to the methods used with some
already well-known irradiated gems, such as blue
topaz (Fournier, 1988; Skold et al., 1995). During this
decade, gemologists and gem laboratories continued
to see irradiated gem materials, but very little of
what they saw was actually new.
Figure 10. “Diffusion treated” green-to-blue
topaz (here, 4.50–5.86 ct) was first seen in the
late 1990s. While it has not yet been proved adequately that the color is actually diffused into
these stones, the extremely shallow color layer is
as hard as topaz. Photo by Maha Tannous.
IRRADIATION
In the 1980s, experimental and commercial irradiation played a significant role in the arena of gemstone treatment (Kammerling et al., 1990a). During
the following decade, however, the role of irradiation
diminished considerably when compared to other
forms of enhancement. In the 1990s, very few new
Enhancement in the 1990s
GEMS & GEMOLOGY
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343
Radioactivity is a word that stirs particularly
strong emotions in the public at large. This is primarily due to a widespread lack of understanding
concerning the various forms of irradiation and their
short-lived or long-lasting effects. If there is anything
that generates press quickly, it’s the detection of
residual radioactivity in an irradiated gem and the
potential threat to health it suggests. Diamond,
ruby, chrysoberyl, spodumene, and topaz are a few of
the gem materials that have shown residual radioactivity after color enhancement by irradiation.
Figure 11. The red color in this 0.55 ct synthetic
diamond was produced by irradiation and subsequent annealing. Photo by Robert Weldon.
Likewise, there was little progress in detection
methods. For many gems, no test or series of tests,
destructive or nondestructive, is currently available to
establish whether they have been subjected to irradiation. Unless the technique used produces a visually
distinctive pattern in a treated stone, such as the
“umbrella effect” seen around the culet of a cyclotrontreated diamond, the use of irradiation to improve a
gemstone’s color still can be difficult or impossible to
detect gemologically. For example, although treaters
have used irradiation to produce intense pink-to-red
colors in near-colorless to light pink tourmaline for
many years, this well-known form of color enhancement is still not detectable. This is also the case for
blue topaz, as well as for many other gem materials
that are routinely irradiated.
Yet another factor to consider in the detection of
any suspected means of treatment, including irradiation, is economics. While it may be economically
feasible and even imperative to attempt to detect irradiation-induced color enhancement in a fashioned
green diamond, the same is usually not the case with
respect to smoky quartz or blue topaz. The low value
of the starting materials, and the limited potential
gain in value of those materials after color enhancement, does not warrant a significant expenditure in
laboratory time to attempt to detect the treatment.
344
Enhancement in the 1990s
Diamond. Irradiation to improve or induce color in
diamond is generally performed on faceted stones,
because usually the need for color improvement can
be determined accurately only after a stone has been
cut. However, rough diamonds are also occasionally
irradiated. A 13.12 ct treated-color yellow rough diamond was reported late in the decade (Reinitz, 1999).
Treatment of rough is a highly questionable practice,
since such material is often misrepresented. The fact
that some treatment methods produce only a shallow layer of color that can be removed easily on
faceting strongly suggests that the treatment is only
done to deceive.
Unfortunately, most radiation-induced color patterns in faceted diamonds, such as those produced
by electron bombardment, are subtle and difficult to
detect. Careful inspection with a gemological
microscope, however, may show color zoning that
is directly related to the facet shape of the diamond
(Fritsch and Shigley, 1989). Artificially irradiated
diamonds that show subtle but diagnostic forms of
color zoning in blue to green (Hargett, 1990;
Hurwit, 1993; Moses and Gelb, 1998) and reddish
purple (Reinitz and Moses, 1998) were encountered
regularly throughout the 1990s. Diffuse transmitted
light is useful in the detection of treatment in these
stones if the light can be directed through the diamond. To facilitate light transmission, total or partial immersion of the diamond in methylene iodide
is often helpful.
A number of treated pink to purplish pink diamonds encountered in the ‘90s (Crowningshield
and Reinitz, 1995; King et al., 1996) did not show
color zoning that could be related to irradiation.
In such cases, both the diamond’s reaction to UV
radiation (bright, chalky orange to both long- and
short-wave) and its spectrum (sharp absorption lines
at 595, 617, and 658 nm) are distinctive of treatment. Although irradiation-produced pink in diamonds was previously rare and usually accidental
GEMS & GEMOLOGY
Winter 2000
(Kammerling et al., 1990a), significant quantities of
laboratory-irradiated pink diamonds (typically meleesize) appeared on the market in the latter half of
the decade.
Also encountered in the 1990s were diamonds
irradiated to such a dark green that they appeared
essentially opaque and black in all jewelry applications. These diamonds are identified by the fact
that they are dark green instead of the dark gray of
natural black diamonds, which is caused by inclusions (Kammerling et al., 1990b). Some of these
“black” stones are treated in a nuclear reactor,
which can result in residual radioactivity. One
such treated diamond examined in the GIA laboratory was sufficiently radioactive to render it
unlawful to sell for almost 37 years (Reinitz and
Ashbaugh, 1992). Another report on “black” irradiated diamonds stated that the residual radioactivity was related to metallic polishing residues in
surface-reaching cracks that became radioactive
when the stones were irradiated. Prolonged boiling in acid removed the radioactive residues and
rendered these treated diamonds safe (Koivula et
al., 1992h).
Irradiation and annealing also can change synthetic diamonds from yellow and brownish yellow
to red (figure 11—Moses et al., 1993; Kammerling
and McClure, 1995c). These treated synthetic
stones do not present significant identification problems because they have distinctive spectra (the
same as for treated pink diamonds mentioned
above) and all the internal characteristics expected
of synthetic diamonds. The short-wave UV fluorescence is particularly distinctive, as these treatedcolor red synthetic diamonds almost always show a
bright green “cross” in the middle of the table with
orange throughout the rest of the stone (figure 12;
Moses et al., 1993).
Ruby. Radioactive rubies were new to the gem trade
in the 1990s. These stones first appeared on the
market in Jakarta, Indonesia, and were reported in
the trade press in mid-1998 (“Indonesia: Irradiated
ruby…,” 1998). Two of these stones were examined
by Ken Scarratt at the AGTA Gemological Testing
Center, who subsequently loaned them to GIA for
photography and further study (Johnson and
Koivula, 1998c). The slightly brownish red stones
closely resembled rubies from East Africa. Both
showed clear evidence of heat treatment and were
partially coated with a black crust of unknown origin that appeared dark brown along thin edges.
Enhancement in the 1990s
Figure 12. A characteristic property of irradiated
red synthetic diamonds is their short-wave UV
fluorescence, which typically shows a strong
green “cross” in the center of the stone surrounded by weak orange. Photomicrograph by
John I. Koivula; magnified 15×.
The isotopes responsible for the residual radioactivity in these stones were not determined, so we do
not know just how long the stones would remain
radioactive. To date, no information has become
available as to the precise source of these rubies and
their original starting color.
These radioactive rubies cannot be recognized by
any standard gemological means. The only indications are their brownish color and the black crust.
However, these indications are unreliable. Fortunately, we know of no further reports of these
stones in the marketplace.
Chrysoberyl. Yet another form of radioactive gem
material appeared in the 1990s. Hundreds of carats
of cat’s-eye chrysoberyl of an unusual dark brown
color were sold at gem markets around the world.
These cat’s-eyes showed a dangerous level of
radioactivity—50 times greater than that which is
legally acceptable in the United States—and were
thought to have been treated in a nuclear facility in
Indonesia (perhaps the same source as for the
radioactive rubies described above). The original
starting material is believed to have come from
Orissa, India (Weldon, 1998b). All dark brown cat’seye chrysoberyls are suspect until they are tested for
radioactivity by a properly equipped gemological
laboratory.
GEMS & GEMOLOGY
Winter 2000
345
No tests are presently available to detect the treatment in these stones.
Beryl. Maxixe beryl, the dark blue beryl that owes
its color to natural or (usually) artificial irradiation,
appeared again in the 1990s, in at least one instance
as a substitute for tanzanite (Reinitz and Moses,
1997a). Another report reviewed its susceptibility to
fading (in most cases, dark blue is an unstable color
in beryl) and the gemological properties used to recognize this type of beryl (Wentzell and Reinitz,
1998).
Figure 13. These two “Ocean Green” irradiated
topazes (3.00 and 3.13 ct) were originally the
same color, but after being taped to a south-facing window for one day, the stone on the left
lost almost all of its green component. Photo by
Maha Tannous.
Topaz. Large amounts of irradiated blue topaz continued to be seen in the international gem market.
Irradiated green topaz with unstable color (figure
13) was reported (see, e.g., Koivula et al., 1992f;
Ashbaugh and Shigley, 1993). It was marketed
under the trade name Ocean Green Topaz. Because
the color is produced by irradiation in a nuclear
reactor, like other reactor-treated gems this green
topaz has the potential to be radioactive. The color
ranges from light to medium tones of yellowish
and brownish green through a more saturated green
to blue-green. On exposure to one day (or less) of
sunlight, the green component fades, leaving a typical blue topaz color. The relative tone and saturation remain the same.
The original starting material is said to have
come from Sri Lanka. Green topaz has been reported to occur in nature, but it is very rare. With this in
mind, any green topaz should be suspected of some
kind of treatment.
Quartz. Pale gray cat’s-eye quartz was being irradiated to a dark brown to enhance the appearance of
the chatoyancy by having the bright, reflective,
inclusion-caused “eye” appear against a dark background (Koivula et al., 1993a). Also reported was the
gamma irradiation (followed by heat treatment) of
colorless quartz to produce colors ranging from
green through yellow and orange to brown (Pinheiro
et al., 1999). All of the colors were stable to light.
346
Enhancement in the 1990s
DYEING
Although dyeing is one of the oldest treatments
known, the 1990s witnessed a number of apparently
new variations on beryl, corundum, jade, and opal,
among other gem materials. Especially convincing
were dyed quartz and quartzite imitations of gems
such as amethyst and jadeite. At the same time, the
proliferation of inexpensive cultured pearls brought
with it a multitude of colors produced by dyes.
Beryl. In addition to the standard dyeing techniques
used to enhance pale green beryls to an emerald color
or colorless beryl to aquamarine (e.g., quench crackling, or drill holes coated with dye; Koivula et al.,
1992b), the market saw the continued use of green
oils and the introduction of green Opticon as fracture
fillers (Koivula and Kammerling, 1991a). Using a
combination of heat (to increase porosity and thus
color penetration) and dye, Dominique Robert of
Switzerland turned massive beryl with intergrown
quartz into imitations of ornamental materials such
as charoite and sugilite, as well as turquoise and coral
(Koivula et al., 1992e). As is the case with most dyed
stones, the treatment was readily identifiable by the
presence of dye concentrations in the fractures.
Corundum. Although the red staining of quartz that
has been heated and quenched (“crackled”) to induce
fissures dates back hundreds of years, for the first
time gemologists identified corundum in which fractures had been induced and the pale sapphires then
dyed a purplish red. These stones were recognized by
the irregular color distribution and the presence of a
yellow fluorescence confined to the stained fractures; they also lacked the red fluorescence and Cr
lines in the spectroscope that are characteristic of
ruby (Schmetzer et al., 1992). A similar process was
also seen in dyed natural star corundum (Schmetzer
and Schupp, 1994). Dyed red beads examined in the
GEMS & GEMOLOGY
Winter 2000
GIA Gem Trade Laboratory responded to a simple
acetone test; removal of the dye from one bead
revealed that it originally was a pale green sapphire
(Crowningshield and Reinitz, 1992).
Jadeite. Colored substances have been used to fill
cavities in bleached and impregnated jadeite (Johnson and McClure, 1997b). These fillers are readily
visible with a microscope.
Of particular concern was the identification of
dye in a green jadeite bangle that did not show the
typical dye band with the handheld spectroscope
(Johnson et al., 1997). This piece first aroused suspicion when the expected absorption bands for
chromium were not seen in the spectroscope. The
bangle was of sufficient color that these bands
should have been present if the color was natural,
so the piece was examined very carefully with a
microscope. Fortunately, in this case the dye was
evident as color concentrations along grain boundaries (figure 14).
Opal. Because of its porosity, opal has long been
subjected to enhancements such as the “sugar”
treatment commonly used on Andamooka material
to darken the background so the play-of-color is
more prominent (see, e.g., Brown, 1991). During the
1990s, however, we also saw opal darkened by silver
nitrate (similar to the treatment used to produce
black in pearls). As with the sugar-treated material,
the silver nitrate treatment is evidenced by the presence of dark irregular specks (Koivula et al., 1992i).
In still another process, opal-cemented sandstone is
soaked in an organic solution and then carbonized
at temperatures over 500°C to produce an attractive
carving material (Keeling and Townsend, 1996).
Particularly interesting was the introduction of dark
blue enhanced opal, produced by soaking a highly
porous chalky white hydrophane opal in a mixture
of potassium ferrocyanide and ferric sulfate (Koivula
et al., 1992c). This material looks black to the
unaided eye, but strong transmitted light reveals its
unnatural dark blue body color.
Figure 14. Careful microscopic examination
revealed dye concentrations in this piece of
jadeite, which did not show the dye spectrum
typical of this type of material. Photomicrograph by Shane F. McClure; magnified 34×.
they were dyed. Other indications of silver nitrate
staining include damage to the nacre layers or, occasionally, a dimpled surface (Moses, 1994). Of particular concern toward the end of the decade was the
prevalence of dyed “golden” South Sea cultured
pearls. Unfortunately, the natural or treated origin
of these pearls often cannot be determined (“Pearl
treatments...,” 1998). Whereas the colors of dyed
saltwater pearls are usually fairly limited (black,
brown, dark green, and “golden”), freshwater cultured pearls have been dyed in a wide array of hues,
including “silver,” “bronze,” and bright “pistachio”
Figure 15. This cultured pearl was turned black
with a metallic oxide, most likely by the use of a
silver nitrate solution. Photo by Jennifer Vaccaro.
Pearls. Numerous examples of black cultured saltwater pearls that had been dyed with a silver nitrate
solution (figure 15) were seen during the ‘90s,
including some mixed with natural black pearls in a
fine necklace (DelRe, 1991). The treated pearls were
first spotted by the lower contrast on the X-ray film
between the shell bead and the nacre; their chalky
green appearance to long-wave UV confirmed that
Enhancement in the 1990s
GEMS & GEMOLOGY
Winter 2000
347
fact, many of these issues have continued into the
new millennium.
Figure 16. Quartzite dyed green to imitate
jadeite, as illustrated by these 8 mm beads, was
commonly seen in the 1990s. Photo by Maha
Tannous.
green (Johnson and Koivula, 1999). In many cases
these dyed pearls can be identified by their unnatural color alone, or by the presence of dye concentrations around drill holes or just under the surface of
the pearls.
Quartz. For literally thousands of years, quartz has
been quench-crackled and dyed to imitate more valuable gem materials such as ruby and emerald. During
the last decade, we observed for the first time quartz
beads that had been quench-crackled and dyed to
imitate amethyst (Reinitz, 1997b). In at least one
sample, green dye had been mixed with an epoxy
resin such as Opticon before it was introduced into
the quench-crackled stone (Koivula et al., 1992j).
Of particular interest were unusual dyed quartzites
(a metamorphic rock composed primarily of quartz
grains) in colors such as purple (to imitate sugilite;
Reinitz and Johnson, 1998). One of the most convincing of such imitations was quartzite dyed to imitate
jadeite, both lavender (Koivula and Kammerling,
1991c) and green (figure 16; Kammerling, 1995a). As
with most dyed gems, though, dye concentrations in
the fractures and between grains provided a strong
indication of treatment.
CLARITY ENHANCEMENT
The previous retrospective article titled this section
“Oiling/Fracture Filling.” Since that time, it has
become commonplace to refer to such treatments as
clarity enhancement, because that is the objective.
As mentioned in the introduction to this article, the
issue of disclosure of clarity enhancement had some
damaging effects on the trade during the 1990s. In
348
Enhancement in the 1990s
Diamond. Clarity enhancement of diamonds by
fracture filling began in the late 1980s, with the first
comprehensive article on the subject published by
Koivula et al. (1989). This first article focused on the
product from Yehuda Diamond Corp., the only
company performing this treatment at the time.
Five years later, another comprehensive article
(Kammerling et al., 1994b) dealt not only with the
then-current Yehuda product, but also with filled
diamonds from newer players in this field, especially Koss and Goldman-Oved (figure 17).
Clarity enhancement of diamonds became a serious issue when the lack of disclosure by certain
U.S. retailers led to devastating exposés in the
national media (see, e.g., “Everyone’s best friend,”
1993). In particular, two St. Louis jewelers were
accused of selling filled diamonds without disclosing the treatment (“Five on your side,” 1993), which
eventually led to the destruction of their business
and even the tragic death of one of them (“Rick
Chotin…,” 1994).
The key identifying feature for fracture-filled diamonds remains the flash effect: the different colors
seen when the fracture is viewed at an angle nearly
parallel to its length, first in darkfield and then in
brightfield. Colors seen perpendicular to the fracture are not flash colors and are due to diffraction
within feathers that most often contain only air.
The 1994 article by Kammerling et al. showed that
while the identifying features of filled diamonds
from the three manufacturers were similar in many
respects, there were differences in the intensity and
hue of the flash colors from one product to another;
however, no flash effect was sufficiently unique to
identify a particular manufacturer. This was also
the case with other microscopic features typical of
filled stones, such as trapped gas bubbles, areas of
incomplete filling (particularly at the surface), and
cloudy fillings.
A number of other studies concerning clarity
enhancement of diamonds were published during
the first half of the 1990s (Scarratt, 1992; Nelson,
1993, 1994; Sechos, 1994; McClure and Kammerling,
1995). All were aimed at disseminating the identification criteria for this treatment to as many people
in the trade as possible.
Also noteworthy was the discovery that rough
diamonds were being filled and then shipped to
Africa to be sold (Even-Zohar, 1992). This obvious
GEMS & GEMOLOGY
Winter 2000
Figure 17. Clarity enhancement
of diamonds can be very effective, as illustrated by these
before (left) and after (right)
views of a 0.20 ct diamond that
was treated by the GoldmanOved Company. Photomicrographs by Shane F. McClure.
attempt to defraud buyers was quickly condemned
by the diamond industry, and a resolution was
eventually passed by the combined leadership of the
International Diamond Manufacturers Association
and the World Federation of Diamond Bourses that
prohibited the filling of rough or the selling of filled
rough (Even-Zohar, 1994).
Filled fractures were observed in several colors of
fancy diamonds, including yellow (McClure and
Kammerling, 1995), pink (Reinitz, 1997a), and
brown (Sechos, 1995). The yellow-to-orange flash
effect normally seen in darkfield illumination was
almost not visible in the yellow diamond, although
the dark blue brightfield flash color stood out quite
nicely on the yellow background. The color appearance of the pink diamond improved as the numerous large fractures in the stone were made transparent by the treatment.
Variations in the flash effect were reported occasionally. One diamond showed a vivid blue flash
color that resembled a dark “navy” blue ink splotch
(Hargett, 1992a). In some filled diamonds, the flash
colors are so subtle as to be easily overlooked; in
such cases, the use of fiber-optic illumination is
invaluable (Kammerling and McClure, 1993a).
Conversely, another note reported flash colors that
were so strong as to appear pleochroic in polarized
light (Johnson, 1996b).
Johnson et al. (1995) reported a filling material
with an unusual chemical composition: It contained thallium in addition to the more typical trace
elements found in fillers, Pb and Br. They speculated that this might have been one of the earlier filled
diamonds, as there were rumors that some of the
first fillers contained thallium.
Even though much has been published about the
inability of diamond filler materials to withstand
heat, gemological laboratories commonly see filled
diamonds that were damaged during jewelry repair
procedures. In almost all cases seen to date, the jew-
Enhancement in the 1990s
eler was not told that the stone had been clarity
enhanced and did not take the time to look at the
diamond with magnification for the telltale signs.
Such were the circumstances with a 3.02 ct diamond that was eye clean before the jeweler started
repair work on the ring in which it was mounted
(Hargett, 1992b). The large, eye-visible fractures that
appeared in the center of the stone when the
mounting was heated created a difficult situation
for the jeweler. This scenario has been played out
many times since then. A later report described
filler material that actually boiled out of the fractures and deposited on the surface of the diamond
in small droplets (Johnson and McClure, 1997a).
Emerald. There has never been a better example of
the impact that a gem treatment can have on the
jewelry business than what occurred with emeralds
during the last decade. Even though emeralds have
undergone some sort of clarity enhancement for
centuries (figure 18), not until the 1990s did this
treatment and its disclosure become a critical issue
for the trade. A series of unfortunate events created
a loss of consumer confidence, particularly in the
United States, that had a devastating effect on the
emerald market. Bad press in the form of high-profile lawsuits, and local and national television
exposés on programs such as Dateline NBC
(“Romancing the stone,” 1997), contributed to this
problem, but they were certainly not the only
cause. One noted emerald dealer pointed out that
this lack of consumer confidence started in 1989,
when a synthetic resin called “palm oil” or “palma”
became prevalent for fracture filling in Colombia
(Ringsrud, 1998). He attributed the problem to the
fact that this substance, which has an R.I. of 1.57,
hides fractures too efficiently and is notoriously
unstable. He estimated that in approximately 20%
of the stones treated with “palm oil,” the filler
would turn white and become translucent in only a
GEMS & GEMOLOGY
Winter 2000
349
Figure 18. Clarity enhancement
of emeralds has been done for
centuries, but it became a significant issue for the trade in the
1990s. Many saw the dramatic
effect this treatment can have on
an emerald for the first time
with the publication of photos
that showed stones before
enhancement (left) and after
(right). Photos by Maha Tannous.
few months, so that fractures that had been virtually invisible became obvious to the unaided eye. One
can only speculate as to the potential impact of
such deterioriation on the consumer, who probably
was not told the emerald had been filled at the time
of purchase.
These and other aspects of the issue were heavily debated in the trade press (see, e.g., Bergman,
1997; Federman, 1998; Schorr, 1998). Three major
concerns surfaced: (1) what types of fillers were
being used, (2) how permanent or durable each filler
was, and (3) how much filler was present in any
given stone.
The types of fillers being used for clarity
enhancement of emeralds have expanded dramatically during the last decade. Kammerling et al.
(1991) noted that in addition to traditional fillers
such as cedarwood oil, treaters had started to use
epoxy resins, the most popular of these being
Opticon. This article also mentioned that proprietary filling substances were being developed by
several other companies (Zvi Yehuda Ltd. of Israel,
CRI Laboratories of Michigan, and the Kiregawa
Gemological Laboratory of Japan).
Since that time, many other fillers have been
introduced, and the infamous “palm oil” was identified as probably being the liquid epoxy resin
Araldite 6010 (Johnson et al., 1999). Treaters also
started to use hardened epoxy resins, with the idea
that they would be more durable than the liquid
materials, which tended to leak out over time. The
formulas for these resins are considered proprietary
and carry names such as Gematrat, Permasafe, and
Super Tres.
The durability of the individual fillers remains
the subject of ongoing research. There is little
debate as to the nonpermanence of “palm oil” or
cedarwood oil (see, e.g., Kammerling et al., 1991;
Federman, 1998; Kiefert et al., 1999). However,
those who use other fillers have made various
350
Enhancement in the 1990s
claims regarding their ability to hold up under normal conditions of wear and care. In fact, this feature has been the focus of marketing efforts by several of the treaters who offer hardened resins
(Johnson and Koivula, 1997b; Weldon, 1998a;
“New type of epoxy resin,” 1998; Fritsch et al.,
1999a; Roskin, 1999).
An interesting development during this debate
came when many in the industry claimed that a
desirable feature of a filler would be the ability to
remove it. Because some of these resins decompose
and turn white or cloudy with time, dealers recognized that they eventually would need to be
removed so that the stones could be retreated. This
was a valid concern, as attempts to remove these
unstable fillers often have been unsuccessful
(Themelis, 1997; Hänni, 1998).
Also during this decade, a number of laboratories
maintained that they could comfortably make the
distinction between specific types of fillers and
began to offer such a service (see, e.g., Hänni et al.,
1996; Weldon, 1998c; Hänni, 1998, 1999; Kiefert et
al., 1999). Others believe that while these fillers
may be separated into broad categories, it can be difficult or even impossible to identify mixed fillers or
stones that have been treated multiple times with
different fillers (Johnson et al., 1999).
In light of this debate, many have suggested that
the amount of filler in a given emerald is perhaps
more important than the kind of filler used
(Johnson and Koivula, 1998b; Drucker, 1999). Thus,
many laboratories offer a service that classifies the
degree of enhancement. In most cases, the system
uses four or more classifications, such as none,
minor, moderate, and significant (see, e.g.,
McClure et al., 1999).
The criteria used to detect fillers in emeralds
have been described at length by various
researchers (see, e.g., Johnson and Koivula, 1998b;
Hänni, 1999). These criteria primarily consist of
GEMS & GEMOLOGY
Winter 2000
flash effects (figure 19), incomplete areas of filling
or gas bubbles (figure 20), and whitish or deteriorated
filler within the fractures—all of which can be seen
with magnification.
Additional information about emerald fillers was
published throughout the decade. Hughes
Associates, the manufacturer of Opticon, reported
that the refractive index of Opticon can range from
1.545 to 1.560, depending on the amount of hardener added (Koivula et al., 1993b). The chemistry of
fillers was closely examined to determine if it could
be an aid in identification (Johnson and
Muhlmeister, 1999). Unfortunately, the answer was
no. The new hardened filler Permasafe was characterized by Fritsch et al. (1999a). Early on, two
Brazilian dealers reported that some treaters were
adding a green coloring agent to Opticon (Koivula
and Kammerling, 1991a), a practice that is not
acceptable in the trade.
Other Gem Materials. Of course, it was inevitable
that clarity enhancement would find its way into
other gem species. We know of two reported incidences in the ‘90s: one in alexandrite (Kammerling and McClure, 1995a), and the other in a
pyrope-almandine garnet (Kammerling and
McClure, 1993b).
IMPREGNATION
Impregnation of porous gem materials with different
kinds of polymers to improve their appearance or
durability has been widespread for many years. The
1990s saw major developments concerning the use
of this treatment technique on a number of important gem materials.
Jadeite. The most significant gem material affected
by impregnation during the last decade was jadeite.
The treatment process, which is often referred to as
“bleaching,” caused such an uproar in the jade
industry that jadeite sales in Japan fell as much as
50% over a three-month period in the beginning of
the decade (“New filler threatens jadeite sales in
Japan,” 1991).
“Bleaching” actually involves a two-step process. First the jadeite is immersed in an acid to
remove the brown iron oxide staining that is so
common in this material. This staining gives the
stone a brown coloration that is less desirable and
therefore detrimental to its value. The result after
“bleaching” is a color such as pure green or green
and white. Unfortunately, this process leaves
Enhancement in the 1990s
Figure 19. The flash effect is one feature that can
be used to identify if an emerald has been filled.
The two most common colors, orange and blue,
are seen in this stone in a fracture that is otherwise almost invisible. Photomicrograph by Maha
Tannous; magnified 15×.
behind voids in the structure of the jadeite, which
make the grain boundaries of the aggregate material
readily visible, and many fractures may appear. Not
only do these voids and fractures adversely affect
the translucency of the gem material, but they also
can affect the durability of the jadeite, so that it is
more susceptible to breakage (Fritsch et al., 1992).
It is because of these adverse effects that the sec-
Figure 20. Another feature that can help determine whether an emerald has been filled is the
presence of gas bubbles or unfilled areas within
a very low relief fracture. Photomicrograph by
Shane F. McClure; magnified 22×.
GEMS & GEMOLOGY
Winter 2000
351
Figure 21. All of these jadeite cabochons have
been bleached and subsequently impregnated
with a polymer to improve their appearance.
The overall result is usually quite effective.
Photo by Maha Tannous.
ond step of the process is necessary: The “bleached”
jadeite is impregnated with a polymer (usually an
epoxy resin) to fill the voids and return the stone to
an acceptable translucency (figure 21). This addition
of a foreign material created the need for a new classification of jadeite. The bleached and polymerimpregnated material came to be known as “B
jade.” “A jade” refers to jadeite that has not been
treated at all, and “C jade” is used for dyed jadeite.
Figure 22. Structural damage caused by the bleaching process is clearly seen in this treated jadeite.
Also visible is a large fracture filled with the
impregnating polymer. Photomicrograph by Shane
F. McClure; magnified 30×.
352
Enhancement in the 1990s
The origins of this treatment lie somewhere in
the mid-1980s, and an early report was given by
Hurwit (1989). The beginning of the ‘90s saw an
explosion of bleached jadeite on the market. Since
no in-depth studies had been done on the material
at that time, there were no procedures in place to
identify it. Once this became widely known, and
all jadeite became suspect, the price of jadeite
plummeted.
The first comprehensive study on the identification of bleached and impregnated jadeite was published by Fritsch et al. (1992). These researchers
found that the only conclusive way to detect if a
piece had been treated was to examine its infrared
spectrum for the telltale “signature” of the polymer
filler. Subsequently, a number of other identification methods were described, such as the use of Xray photoelectron spectroscopy (Tan et al., 1995)
and diffuse reflectance Fourier-transform infrared
(FTIR) spectroscopy (Quek and Tan, 1997), as well
as the use of a simple drop of acid (described in
Fritsch et al., 1992, and elaborated in Hodgkinson,
1993). Some of these methods were even used to
identify polystyrene as one of the polymers used
(Quek and Tan, 1998). However, infrared spectroscopy remains the easiest test to perform, provided one has the necessary equipment. By the end of
the decade, several jadeite dealers had purchased an
FTIR spectrophotometer so they could personally
test all the jadeite they handle.
It was also noted early on that the structural
damage caused by the bleaching process could be
seen in reflected light with a microscope (figure
22—Ou-Yang, 1993; Moses and Reinitz, 1994;
Johnson and DeGhionno, 1995). This surface texture has been referred to as having an etched or
honeycomb-like appearance, which is a manifestation of the gaps or voids left between the individual
grains in the jadeite structure. Articles were published on the use of a scanning electron microscope
to study and document this phenomenon so that it
might be used as an aid in identification (Tay et al.,
1993, 1996).
Tests conducted on the durability of this material found that long-term exposure to detergents
could damage or remove some of the filler. Also,
heating at 250°C can turn the treated jadeite brown
(Johnson and Koivula, 1996b).
Some particularly unusual examples were
reported: a bangle bracelet with internal gas bubbles
generated by the filling of cavities that were created
when the acid etched out carbonates within the
GEMS & GEMOLOGY
Winter 2000
Figure 23. These
turquoise cabochons
were treated by the
Zachery process,
which decreases the
porosity of the material, making it less likely to discolor with
time and wear. Photo
by Maha Tannous.
jadeite (Koivula, 1999), a necklace that had a mixture of treated and untreated jadeite beads
(Kammerling, 1995b), and the first reported instance
of a bleached and polymer-impregnated lavender
jadeite (Kammerling et al., 1994a).
The most important thing for the gemologist to
remember about this treatment is that it can be
identified conclusively only by sophisticated means
such as infrared spectroscopy. There may be some
indications, such as a yellow fluorescence, low specific gravity, or coarse surface texture, but these do
not prove that a piece of jadeite has been treated.
Turquoise. Turquoise is notorious for being impregnated. Because its inherent porosity makes it subject to discoloration from wear, treatment is very
common. As one might expect, impregnation of
turquoise with plastics (Kammerling, 1994a,b) and
oils (Koivula et al., 1992g, 1993c) was still prevalent
in the 1990s.
The most significant turquoise treatment that
came to light in the ‘90s may not be an impregnation
at all. Called Zachery treatment after the man who
developed it, this process actually was introduced in
the late 1980s, although the first major study did not
appear until 1999 (Fritsch et al., 1999b). During this
decade, millions of carats of Zachery-treated
turquoise entered the trade (figure 23).
The process is still a closely guarded secret, so
exactly how it effects the change in turquoise is not
completely understood. We do know that Zachery
treatment reduces the porosity of turquoise, but
Enhancement in the 1990s
there is no evidence that it adds any polymers or
other foreign material. The end result is turquoise
that does not absorb oils or other liquids during
wear and therefore does not discolor, as most natural turquoise does in time. The turquoise can be
treated without changing its original color, or the
color can be darkened, depending on the wishes of
the client.
Regardless of the actual enhancement mechanism, the only way to prove conclusively that an
individual piece of turquoise has been treated by
this process is through chemical analysis, since
Zachery-treated turquoise usually has an elevated
potassium content. Visual indications of this treatment include a slightly unnatural color, a very high
polish, and blue color concentrations along surfacereaching fractures (figure 24).
Opal. While there were no new advances in the
impregnation or “stabilization” of some kinds of
matrix opal, which has been a common practice for
many years, there were a few other notable developments with regard to opal.
The hydrophane opal mentioned in the Dyeing
section, which was treated to resemble Australian
black opal, was also impregnated with a plasticized
liquid to seal the porosity and improve the transparency after the dyeing process (Koivula et al.,
1992c).
Impregnated synthetic opal appeared on the market during this decade. It is not difficult to identify,
because the specific gravity (around 1.80–1.90) is
GEMS & GEMOLOGY
Winter 2000
353
Figure 24. Although Zachery treatment can be
proved only through chemical analysis, the presence of color concentrations along fractures in the
turquoise is a good indication. Photomicrograph
by Shane F. McClure; magnified 10×.
too low for untreated material (Kammerling and
McClure, 1995b; Kammerling et al., 1995; Fritsch,
1999). However, controversy arose when some in
the trade objected to the use of the term synthetic
in association with this material, because it is
impregnated with plastic. This nomenclature issue
is still being investigated and discussed.
SURFACE COATINGS
Changing the color of gem materials by the use of
colored surface coatings was a very popular treatment throughout the 1990s, as it has been for centuries. We continue to see different kinds of coatings on various gems, sometimes to imitate more
valuable stones and sometimes to create a unique
look not associated with a natural material.
Plastic remained a popular coating substance. To
improve transparency and luster, treaters used both
plastic and wax to coat jadeite (Koivula and Kammerling, 1990b, 1991i). Plastic also provided stability
to fossilized ammonite that was unstable due to natural frost shattering in surface deposits (Koivula and
Kammerling, 1991h). A transparent colored plastic
coating was used to impart an emerald-like appearance to beads fashioned from light green beryl
(Crowningshield, 1995a). The presence of air bubbles
and abnormal surface irregularities visible with magnification, as well as reaction to a “hot point,” are
the best means to identify this type of coating.
354
Enhancement in the 1990s
The surface coating of colorless topaz was widespread, with different processes being used by the
end of the decade. Orange, pink, and red material
(see, e.g., figure 25) showed a spotty surface coloration (detected with low magnification) that was
easily scratched by a sharp object. Although the process was originally represented as diffusion treatment, these colors (unlike the green-to-blue surfacetreated topaz described in the earlier Diffusion
Treatment section) were probably produced by sputter coating (Johnson and Koivula, 1998d).
Thin metallic coatings remained popular for
treating both quartz and topaz, as crystals and as
faceted stones (figure 26). Microscopic examination
of gold-coated blue to greenish blue “Aqua
Aura”–treated samples, which made their debut in
the late 1980s, revealed unnatural coloration at
facet junctions and an irregular color distribution on
some facets (figure 27—Koivula and Kammerling,
1990a; Kammerling and Koivula, 1992). Durability
testing of these gemstones showed that even though
the coating is relatively hard and chemically inert
(Koivula and Kammerling, 1990a), care must be
taken to avoid damage during jewelry manufacturing or repair (Koivula and Kammerling, 1991d).
New colors and effects were created in coated
quartz by using different combinations of metallic
elements. These included purple, yellow, green, and
red hues created by Au, Bi, Pb, Cr, Ti, and other elements (Johnson and Koivula, 1996a), as well as a
“rainbow” iridescence that was reportedly caused
Figure 25. These topazes were originally represented as being diffusion treated, but they actually were coated with a color layer that was easily scratched off. The pink stone is 3.19 ct and
the red one, 3.29 ct. Photo by Maha Tannous.
GEMS & GEMOLOGY
Winter 2000
by an Ag/Pt coating (Koivula and Kammerling,
1990e). A colorless sapphire with a yellowish orange
coating that was seen in the early 1990s also might
have been treated by such a process (Moses and
Reinitz, 1991).
The demand for certain colors of sapphire led to
the resurfacing of some “old tricks” in Sri Lanka
that used organic compounds to create surface coatings (Koivula and Kammerling, 1991b). Pale or colorless rough was turned yellow by boiling in water
(sometimes with wax added) that contained the
branches or bark of a local tree. Some Sri Lankans
took a similar “low-tech” approach to imitate pink
sapphire rough: The treater placed the pale or colorless sapphire in his mouth along with a local berry,
chewed the berry to create the pink coating, and followed this by smoking a cigarette (which reportedly
improves the durability of the coating). These treatments may seem unimportant, but to the gem
buyer alone in a remote area of Sri Lanka, knowing
about them could mean the difference between a
successful trip and a disaster.
Coated diamonds were still encountered in the
laboratory during the 1990s, although less frequently. One such stone showed a brownish purple-pink
color that rarely occurs naturally in diamonds
(Crowningshield and Moses, 1998). Although the
exact nature of the coating substance could not be
identified, its speckled appearance over the entire
stone suggested a sputtering process. Diamond-like
carbon (DLC)—an amorphous brown material with
a hardness between that of diamond and corundum—was used experimentally at the beginning of
the decade to coat several gemstones, which resulted in greater durability (Koivula and Kammerling,
1991e). More recently, DLC was identified on a
treated-color “black” diamond by Raman analysis;
researchers used the same method to tentatively
identify a carbide compound on a treated-color
green diamond (Reinitz et al., 2000a).
New pearl coatings presented some significant
identification challenges in the 1990s. A strand of
lustrous black circled cultured pearls was found to
be coated with a form of silicone called polydimethyl siloxane (Hurwit, 1999). A peculiar
smoothness, sticky feel, and slight anomalous reaction to a thermal reaction tester were the only
clues to the presence of the coating; advanced techniques were needed to identify it. Mabe assembled
blister pearls also were coated, but Hurwit (1991)
reported that the lacquer coating was applied to the
plastic dome under the layer of nacre. The effect
Enhancement in the 1990s
Figure 26. Aqua Aura treatment was still used
extensively on quartz (the two inside stones)
and topaz (the two outside stones) throughout
the ‘90s. Photo by Robert Weldon.
was to improve the luster and overtone of the
white mabe pearls. A spotty, uneven color distribution suggested the presence of an enhancement, but
only by disassembling a sample could the coating
be confirmed.
To produce a dark background and thus bring
out the play-of-color, opal was subjected to several
coatings, including: (1) black paint on the base of
diaphanous opal from Australia (Brown et al., 1991),
Figure 27. Aqua Aura treatment is easily detected
by the presence of unnatural surface coloration on
the facets of a stone. Photomicrograph by John I.
Koivula; magnified 12×.
GEMS & GEMOLOGY
Winter 2000
355
(2) a dark plastic-like material on portions of a
Mexican opal (Koivula and Kammerling, 1990c),
and (3) sugar-treated opal that appeared to be further
coated with a plastic-like substance (Koivula and
Kammerling, 1990d). All of these coatings were
readily apparent with microscopic examination.
Two other relatively isolated occurrences of
coatings deserve mention. A brittle glass-like coating was responsible for the dark violet-blue color
of some drilled quartz beads (Kammerling and
McClure, 1994). This coating, possibly applied by
an enameling process, was identified though a
combination of microscopic examination of the
drill holes, hardness testing, and advanced techniques. Koivula et al. (1992a) noted that acrylic
spray could be used to enhance the luster of massive gem materials such as lapis lazuli and jadeite.
Such a coating is easily identified: With magnification, slight concentrations are seen in surface
irregularities, and the acrylic can be easily
removed if it is rubbed with a cotton swab that has
been dipped in acetone.
It is interesting to note that the use of coatings
has spread to some laboratory-grown materials. A
company in northern California trademarked the
name Tavalite (Johnson and Koivula, 1996d) for
cubic zirconia that had been treated with an optical
coating. The process created six different colors that
had a different appearance in reflected and transmitted light. This product was very easy to identify, in
that it does not resemble any other material.
CONCLUSION
It can safely be said that events of the 1990s
changed the attitude of the entire industry toward
treatments and disclosure, which today constitute
the single most important issue facing the trade.
Identification of some of the significant treatments—such as glass-filled rubies, HPHT-processed
diamonds, and a variety of irradiated gem materi-
als—continues to challenge many gemologists.
Within the last year, we have already seen significant new developments in the laser drilling of diamonds (McClure et al., 2000), as well as in the
material used to fill fractures in diamonds (Shigley
et al., 2000b). In addition, there has been recent talk
of new filling processes that will bring true clarity
enhancement to higher-refractive-index colored
stones such as ruby, sapphire, and alexandrite
(Arthur Groom, pers. comm., 2001). Also, the technology being used to create the “diffusion treated”
blue-green topaz can be applied to other gem materials, and it is likely that some of these will reach
the market in the future. One of the authors (SFM)
has already seen colorless quartz turned pink by this
process. All of these developments will undoubtedly create more identification challenges.
Some of the issues regarding disclosure may not
have solutions that will be agreeable to everyone in
the industry. However, there were a number of
meetings in the latter half of the ‘90s at which leaders of prominent gemological laboratories and trade
organizations worldwide met to establish better
communications and greater consistency in reporting terminology. These meetings illustrate the
determination of the jewelry industry to address
these issues and find solutions that will benefit
members of the trade and consumers alike.
The 1980s retrospective article asked the question, “What new treatments might face us in the
not-too-distant future?” Yet technological advances
in the last 10 years have produced treatments, such
as removing the color from brown diamonds, that
most of us would not have thought possible at the
beginning of the decade. Without a doubt, technology will continue to advance at an even faster rate
during the next decade. The only thing we can guarantee is that there will be no end to fresh challenges
in treatment identification and disclosure as we
enter the new millennium.
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