(via ICA Early Warning Flash, No.65, December 21, 1992) GAGTL writes:
A pink cut-cornered square modified brilliant diamond was submitted to the Gem Testing Laboratory for the determination of the origin of its color—whether it was of natural or treated color and for the determination of the color grade.
The diamond weighed 3.35 carats and measured approx. 8.32x8.08x6.53mm. Upon examination with a 10x lens, one was struck by the many feathers visible within the stone. Viewing the diamond from various angles and by transmitted light, one could detect many surface reaching fractures displaying iridescent colors implying these were filled with air. But also noticeable were the tell-tale blue and orange flashes in some fractures indicating that these had been filled with an artificial material.
Spectroscopic investigation of the stone proved it to be a diamond of natural color and of type IaAB. The nature of the internal colored grain lines and the frosted appearance of some of the fractures indicated that the diamond may have been mined in Argyle, Australia.
If graded, the color grade would be fancy pink and the clarity grade would be pique III. However, The Gem Testing Laboratory does not issue grading reports on fracture filled diamonds. The poor clarity grade apparent subsequent to fracture treatment and the presence of untreated air-filled fractures indicate that the clarity enhancement process was not successful.
Although the Laboratory has tested fracture-filled diamonds before, this is the first instance we have seen of a fancy colored diamond being so treated.
Tuesday, April 24, 2007
Hydrothermal Synthetic Rubies
(via ICA Early Warning Flash, No.66, January 28, 1993) GGL writes:
Background
During the Fall season of 1991, we first became aware of a production of hydrothermal synthetic rubies being made in Russia. At that time, we were informed that the production was only consisting of very small stones and therefore this seemed to be more of a scientific than commercial interest. During the next year and a half, we did not receive any additional information concerning further developments of this product. While on a recent trip to Bangkok though three samples were acquired which were reportedly from a recent production of Russian hydrothermal synthetic rubies. Seeing as how this represents a new and therefore unfamiliar synthetic ruby on the market, we felt it would be beneficial to inform the colored stone industry of their presence through the ICA Early Warning Alert system.
Gemological properties
The three sample stones tested, weighed 1.69, 0.69 and 0.62 ct. possessing colors ranging from Burma to Thai types with high saturations and medium to dark tones. Standard gemological testing revealed properties of refractive index (1.76-1.77), birefringence (0.008), specific gravity (3.99-4.00), UV fluorescence (LW: weak-med, red; SW: inert-weak red) and spectrum, consistent with other natural and synthetic rubies.
Microscopic examination revealed the presence of very strong graining features throughout the stone. These graining features are visually reminiscent of the type of graining observed in the Russian production of hydrothermal synthetic emeralds. In most directions, this graining is generally in a striated pattern, although in one direction the graining takes on a strongly roiled appearance resembling an aggregation of graining features. The presence of this graining is so strong, as to have an effect of slightly reducing the transparency of the stone enough to give it a sleepy appearance. This also caused a slightly diffused image of the pavilion back facet edges when viewed through the table. Certain fluctuations of color zoning could also be observed interwoven with the graining patterns. Distinctive as well were the presence of numerous, small, golden colored, highly reflective metallic inclusions. These inclusions were present in small collective groups as well as sparsely located individually. Additionally observed were healed fracture systems creating fingerprint inclusions which occasionally contained a secondary gas phase and other fracture systems.
Discussion
While these rubies represent a completely new kind of synthetic which could be encountered in the market today, their identification should not prove to be difficult. Just as with other synthetic rubies, mass sampling by means of UV fluorescence will not separate these synthetics from their natural counterparts. Microscopic examination identifying the very strong graining features which are unlike any of the swirled or planar growth characteristics observed in natural rubies from various localities and the presence of golden colored metallic inclusions, provide clear and easy proof of the synthetic origin for these hydrothermally grown rubies.
Background
During the Fall season of 1991, we first became aware of a production of hydrothermal synthetic rubies being made in Russia. At that time, we were informed that the production was only consisting of very small stones and therefore this seemed to be more of a scientific than commercial interest. During the next year and a half, we did not receive any additional information concerning further developments of this product. While on a recent trip to Bangkok though three samples were acquired which were reportedly from a recent production of Russian hydrothermal synthetic rubies. Seeing as how this represents a new and therefore unfamiliar synthetic ruby on the market, we felt it would be beneficial to inform the colored stone industry of their presence through the ICA Early Warning Alert system.
Gemological properties
The three sample stones tested, weighed 1.69, 0.69 and 0.62 ct. possessing colors ranging from Burma to Thai types with high saturations and medium to dark tones. Standard gemological testing revealed properties of refractive index (1.76-1.77), birefringence (0.008), specific gravity (3.99-4.00), UV fluorescence (LW: weak-med, red; SW: inert-weak red) and spectrum, consistent with other natural and synthetic rubies.
Microscopic examination revealed the presence of very strong graining features throughout the stone. These graining features are visually reminiscent of the type of graining observed in the Russian production of hydrothermal synthetic emeralds. In most directions, this graining is generally in a striated pattern, although in one direction the graining takes on a strongly roiled appearance resembling an aggregation of graining features. The presence of this graining is so strong, as to have an effect of slightly reducing the transparency of the stone enough to give it a sleepy appearance. This also caused a slightly diffused image of the pavilion back facet edges when viewed through the table. Certain fluctuations of color zoning could also be observed interwoven with the graining patterns. Distinctive as well were the presence of numerous, small, golden colored, highly reflective metallic inclusions. These inclusions were present in small collective groups as well as sparsely located individually. Additionally observed were healed fracture systems creating fingerprint inclusions which occasionally contained a secondary gas phase and other fracture systems.
Discussion
While these rubies represent a completely new kind of synthetic which could be encountered in the market today, their identification should not prove to be difficult. Just as with other synthetic rubies, mass sampling by means of UV fluorescence will not separate these synthetics from their natural counterparts. Microscopic examination identifying the very strong graining features which are unlike any of the swirled or planar growth characteristics observed in natural rubies from various localities and the presence of golden colored metallic inclusions, provide clear and easy proof of the synthetic origin for these hydrothermally grown rubies.
Diamond Fracture Filling Extensive Treatment, Subtle Features
(via ICA Early Warning Flash, No.68, April 5, 1993) GIA GTL writes:
Background
The diamond described herein is a 0.88 carat heat-shaped brilliant that was initially submitted to the GIA Gem Trade Laboratory for grading. During preliminary examination, however, a staff gemologist noted at first appeared to be an extremely low relief fingerprint inclusion containing minute voids. As this would be very atypical for diamond, the stone was brought to the identification and research lab for investigation.
Microscopic features
Examination under magnification using standard darkfield illumination revealed several very transparent, colorless, filled fractures. These all contained minute voids as mentioned above, as well very subtle orange and, to a lesser extent, blue flash effects. Difficulty in detecting these effects was compounded by the very shallow angles of the fractures to the surface of the diamond.
The treatment became more apparent when a pinpoint fiber optic illuminator was used. This lighting technique revealed the extent of the filled breaks, including one very large fracture beneath and nearly parallel to the table. The intense illumination made the flash effects significantly more noticeable, as well as revealing hairline fractures in the filling material. The outlines of the filled areas were also found to be easier to detect when examined in transmitted lighting with a single polarizing filter placed between the microscope’s objectives and the diamond.
Additional testing
Qualitative chemical analysis using energy dispersive X-ray fluorescence detected lead, an element previously detected in diamond fillings, X-radiography further confirmed the presence of the filling in the form of white, X-ray opaque areas on the radiograph.
Discussion
Although the diamond under investigation contained extensive filled fractures, the diagnostic microscopic features of the treatment were quite subtle. These might easily be overlooked if only darkfield illumination were used. It is therefore recommended that additional lighting techniques be used when examining diamonds for possible filled breaks, including pinpoint fiberoptic illumination and polarized light.
Background
The diamond described herein is a 0.88 carat heat-shaped brilliant that was initially submitted to the GIA Gem Trade Laboratory for grading. During preliminary examination, however, a staff gemologist noted at first appeared to be an extremely low relief fingerprint inclusion containing minute voids. As this would be very atypical for diamond, the stone was brought to the identification and research lab for investigation.
Microscopic features
Examination under magnification using standard darkfield illumination revealed several very transparent, colorless, filled fractures. These all contained minute voids as mentioned above, as well very subtle orange and, to a lesser extent, blue flash effects. Difficulty in detecting these effects was compounded by the very shallow angles of the fractures to the surface of the diamond.
The treatment became more apparent when a pinpoint fiber optic illuminator was used. This lighting technique revealed the extent of the filled breaks, including one very large fracture beneath and nearly parallel to the table. The intense illumination made the flash effects significantly more noticeable, as well as revealing hairline fractures in the filling material. The outlines of the filled areas were also found to be easier to detect when examined in transmitted lighting with a single polarizing filter placed between the microscope’s objectives and the diamond.
Additional testing
Qualitative chemical analysis using energy dispersive X-ray fluorescence detected lead, an element previously detected in diamond fillings, X-radiography further confirmed the presence of the filling in the form of white, X-ray opaque areas on the radiograph.
Discussion
Although the diamond under investigation contained extensive filled fractures, the diagnostic microscopic features of the treatment were quite subtle. These might easily be overlooked if only darkfield illumination were used. It is therefore recommended that additional lighting techniques be used when examining diamonds for possible filled breaks, including pinpoint fiberoptic illumination and polarized light.
Diffusion Treated Corundum In Pink To Red To Purple Color Range
(via ICA Early Warning Flash, No.69, May 14, 1993) GIA GTL writes:
Background
The diffusion treated stones described herein were provided for examination by United Radiant Applications, a Southern California-based firm that has been involved in the commercial production of blue diffusion treated sapphires. The faceted specimens, which included 27 stones in the red to pink to purple color range, were made available so that their gemological properties and identification criteria could be documented prior to any commercial release.
Visual appearance
Face-up some of the stones appear uniform in color, while other exhibit uneven color distribution, the latter apparently due to an absence of color on some pavilion facets.
Magnification
A number of features previously documented with blue diffusion treated sapphires were noted in these stones. These include uneven coloration from one facet to another, color concentrations in surface-reaching cavities and fractures, and color reinforcement of facet junctions, although the latter was often significantly more subtle than what we have encountered with blue diffusion-treated stones. Also noted was a type of surface and near surface damage, including minute spherical voids that we had not previously documented in blue diffusion treated sapphires.
Refractive indices
Values were generally higher than those normal for corundum, including some reading over the limits of the conventional refractometer (1.80 +).
Pleochroism
Some stones exhibited atypical dichroism, including a brownish yellow dichroic color.
Short wave UV luminescence
The majority of the stones showed a patchy bluish white luminescence to this wavelength at the surface that was sometimes confined to specific facets or groups of facets.
Absorption spectra
These were generally consistent with those of both natural and synthetic corundums of comparable color, although some absorption features were less pronounced.
Discussion
The diffusion treated corundums described herein are not difficult to identify. Key features include unusually high refractive index readings, atypical dichroism and UV luminescence, patchy surface coloration, color concentrations along facet junctions, and spherical voids just below the surface.
Background
The diffusion treated stones described herein were provided for examination by United Radiant Applications, a Southern California-based firm that has been involved in the commercial production of blue diffusion treated sapphires. The faceted specimens, which included 27 stones in the red to pink to purple color range, were made available so that their gemological properties and identification criteria could be documented prior to any commercial release.
Visual appearance
Face-up some of the stones appear uniform in color, while other exhibit uneven color distribution, the latter apparently due to an absence of color on some pavilion facets.
Magnification
A number of features previously documented with blue diffusion treated sapphires were noted in these stones. These include uneven coloration from one facet to another, color concentrations in surface-reaching cavities and fractures, and color reinforcement of facet junctions, although the latter was often significantly more subtle than what we have encountered with blue diffusion-treated stones. Also noted was a type of surface and near surface damage, including minute spherical voids that we had not previously documented in blue diffusion treated sapphires.
Refractive indices
Values were generally higher than those normal for corundum, including some reading over the limits of the conventional refractometer (1.80 +).
Pleochroism
Some stones exhibited atypical dichroism, including a brownish yellow dichroic color.
Short wave UV luminescence
The majority of the stones showed a patchy bluish white luminescence to this wavelength at the surface that was sometimes confined to specific facets or groups of facets.
Absorption spectra
These were generally consistent with those of both natural and synthetic corundums of comparable color, although some absorption features were less pronounced.
Discussion
The diffusion treated corundums described herein are not difficult to identify. Key features include unusually high refractive index readings, atypical dichroism and UV luminescence, patchy surface coloration, color concentrations along facet junctions, and spherical voids just below the surface.
Mixed Diamonds & Octahedral Cubic Zirconia Baguettes
(via ICA Early Warning Flash, No.73, August 13, 1993) GII writes:
Recently we have encountered in a packet of rough diamond one octahedral shaped cubic zirconia. The person who had done this also must be having some idea of crystallography for he has taken the trouble to etch out trigons on the octahedral faces. Fortunately, the trigons are parallel to the sides of the octahedral faces, whereas in diamonds they are not; this gave us the first doubt and other tests confirmed our suspicion.
Another interesting case of cubic zirconia fraud has also been detected at our laboratory. In a packet of diamond baguettes as well as round brilliant same sized cubic zirconia baguettes and round brilliants were detected. The suspicion was first triggered off when similar dimension baguettes were weighing 0.029 carats and some 0.05. The difference was obvious when the weight of some more number of pieces was compared and other tests were performed.
Recently we have encountered in a packet of rough diamond one octahedral shaped cubic zirconia. The person who had done this also must be having some idea of crystallography for he has taken the trouble to etch out trigons on the octahedral faces. Fortunately, the trigons are parallel to the sides of the octahedral faces, whereas in diamonds they are not; this gave us the first doubt and other tests confirmed our suspicion.
Another interesting case of cubic zirconia fraud has also been detected at our laboratory. In a packet of diamond baguettes as well as round brilliant same sized cubic zirconia baguettes and round brilliants were detected. The suspicion was first triggered off when similar dimension baguettes were weighing 0.029 carats and some 0.05. The difference was obvious when the weight of some more number of pieces was compared and other tests were performed.
Synthetic Diamonds: Rough And Treated, Faceted
(via ICA Early Warning Flash, No.74, August 13, 1993) GIA GTL writes:
Background
Recently a 0.74 carat yellow rough crystal was submitted to the GIA Gem Trade Laboratory in New York for routine identification. Shortly thereafter, a 0.55 carat dark brownish orangy red round brilliant was submitted to GIA GTL for an origin of color determination. Examination of both specimens revealed that they were synthetic diamonds. It was further determined that the rough specimen had been annealed and that the faceted one had been irradiated and subsequently annealed.
Appearance
The habit of the rough crystal was predominantly cubic, with some octahedral and dodecahedral faces. Smooth cube, and to a lesser extent, dodecahedral, faces are seen only on synthetic diamonds.
Magnification/magnetism
Both the rough and faceted pieces contained fairly large inclusions with a metallic luster. When suspended at the end of a thread, both were attached to a magnet, actually attaching to it. This reaction has been noted to date only with synthetic diamonds containing large, magnetic inclusions derived from the metallic flux in which they are produced.
The two showed similar patterns of ultraviolet luminescence and color zoning, forming essentially a square; the faceted piece also revealed this in the form of graining. This growth pattern was centered roughly in the middle of the base of the crystal and on the table of the round brilliant. Octagonal to square patterns are commonly seen in synthetic diamonds, but not in natural diamonds.
Ultraviolet luminescence
The ultraviolet luminescence of both pieces was stronger in short wave than long wave radiation. They both emitted a moderate to strong green fluorescence along the pattern described above in short wave UV radiation, with a weaker green reaction in long wave. The round brilliant also emitted a moderate orange fluorescence in short wave. Gem quality yellow synthetic diamonds previously examined by GIA Research and GIA GTL personnel have shown luminescence in short wave exclusively. The reactions noted in the two specimens under discussion would therefore appear to be from a source other than those we have previously documented in the gemological literature.
UV/Visible/IR spectroscopy
Spectroscopy helped to further characterize the specimens. Infrared spectroscopy showed them both to be essentially type Ib, as are most yellow synthetic diamonds. However, they both also showed a IaA character. This has not previously been observed in gem quality synthetic diamonds.
In the visible range, the round brilliant showed a number of sharp lines between 500 and 700bn at liquid nitrogen temperature. These features were noted both in the hand held spectroscope and on the chart of the spectrometer. Some of these lines have never been observed in natural diamond but have been reported in synthetic diamonds.
Finally, the presence of the features typical of treated pink diamonds in the spectrum of the red brilliant (in addition to other lines mentioned above) and a small HIb peak in the infrared prove that it had been irradiated and subsequently annealed. The yellow crystal also shows a line at about 637nm, which suggests that it, too, had been subjected to annealing.
Conclusion
The above characteristics clearly identify both the crystal and round brilliant as synthetic diamonds. However, some of their properties are slightly different from what we have observed before in yellow gem quality synthetic diamonds. Interestingly, virtually all the features noted are consistent with those of a group of Russian yellow synthetic diamonds currently being studied by GIA Research and the GIA GTL.
Background
Recently a 0.74 carat yellow rough crystal was submitted to the GIA Gem Trade Laboratory in New York for routine identification. Shortly thereafter, a 0.55 carat dark brownish orangy red round brilliant was submitted to GIA GTL for an origin of color determination. Examination of both specimens revealed that they were synthetic diamonds. It was further determined that the rough specimen had been annealed and that the faceted one had been irradiated and subsequently annealed.
Appearance
The habit of the rough crystal was predominantly cubic, with some octahedral and dodecahedral faces. Smooth cube, and to a lesser extent, dodecahedral, faces are seen only on synthetic diamonds.
Magnification/magnetism
Both the rough and faceted pieces contained fairly large inclusions with a metallic luster. When suspended at the end of a thread, both were attached to a magnet, actually attaching to it. This reaction has been noted to date only with synthetic diamonds containing large, magnetic inclusions derived from the metallic flux in which they are produced.
The two showed similar patterns of ultraviolet luminescence and color zoning, forming essentially a square; the faceted piece also revealed this in the form of graining. This growth pattern was centered roughly in the middle of the base of the crystal and on the table of the round brilliant. Octagonal to square patterns are commonly seen in synthetic diamonds, but not in natural diamonds.
Ultraviolet luminescence
The ultraviolet luminescence of both pieces was stronger in short wave than long wave radiation. They both emitted a moderate to strong green fluorescence along the pattern described above in short wave UV radiation, with a weaker green reaction in long wave. The round brilliant also emitted a moderate orange fluorescence in short wave. Gem quality yellow synthetic diamonds previously examined by GIA Research and GIA GTL personnel have shown luminescence in short wave exclusively. The reactions noted in the two specimens under discussion would therefore appear to be from a source other than those we have previously documented in the gemological literature.
UV/Visible/IR spectroscopy
Spectroscopy helped to further characterize the specimens. Infrared spectroscopy showed them both to be essentially type Ib, as are most yellow synthetic diamonds. However, they both also showed a IaA character. This has not previously been observed in gem quality synthetic diamonds.
In the visible range, the round brilliant showed a number of sharp lines between 500 and 700bn at liquid nitrogen temperature. These features were noted both in the hand held spectroscope and on the chart of the spectrometer. Some of these lines have never been observed in natural diamond but have been reported in synthetic diamonds.
Finally, the presence of the features typical of treated pink diamonds in the spectrum of the red brilliant (in addition to other lines mentioned above) and a small HIb peak in the infrared prove that it had been irradiated and subsequently annealed. The yellow crystal also shows a line at about 637nm, which suggests that it, too, had been subjected to annealing.
Conclusion
The above characteristics clearly identify both the crystal and round brilliant as synthetic diamonds. However, some of their properties are slightly different from what we have observed before in yellow gem quality synthetic diamonds. Interestingly, virtually all the features noted are consistent with those of a group of Russian yellow synthetic diamonds currently being studied by GIA Research and the GIA GTL.
Saturday, April 21, 2007
Polymer-impregnated Jadeite
(via ICA Early Warning Flash, No.75, November 23, 1993) GIA GTL writes:
Background
Over the last several years polymer-impregnated jadeite has become prevalent in the jade market. This has given rise to some colors of jadeite being routinely tested for the presence of this treatment.
Recently, the GIA GTL in Santa Monica received for identification a 15 carat purple oval cabochon that we identified as jadeite. Subsequent testing determined the stone to be polymer impregnated. To the best of our knowledge, this is the first report of a jadeite of this color that is polymer-impregnated.
Polymer-impregnated ‘lavender’ jadeite
Gemological properties: Gemological testing revealed an index of refraction and visible absorption spectrum consistent with jadeite jade. Specific gravity was measured by the hydrostatic method and determined to be 3.32, which is slightly lower than the norm for jadeite. This is consistent with previous findings of polymer-impregnated jadeite. The stone was inert to longwave ultraviolet radiation. Magnification did not reveal any evidence of treatment. As is often the case with purple jadeite, the origin of the color could be be determined.
Infrared spectroscopy
The spectrum of this stone reveals intense absorptions around 2900cm¯¹ which are not found in natural jadeite. These additional features are due to the presence of an ‘opticon-like’ polymer. This is not surprising, since this type of polymer is the most commonly employed for jadeite impregnation, according to many reports and our own experience.
Discussion
This finding is particularly significant since none of the polymer-impregnated jadeite (or B jade) we have seen so far was purple in color. They have all been green or mottled green and white, some with applied spots of brown. This means that we will now have to expand our routine testing for polymer impregnation to include purple jadeites as well.
New polymers for jadeite impregnation
We have recently encountered two new types of polymer used for the treatment of jadeite, in addition to the three previously described which are wax, an ‘opticon-like’ polymer, and phthalate-like polymer. Since we do not know yet their exact nature, we will refer to them as polymer 4 and polymer 5.
Polymer 4
The infrared spectrum of polymer 4 is very similar—but not identical—to that of wax. In particular, the major absorption is slightly shifted and of different width than that for wax. Jadeites treated with this product do not ‘sweat’ when tested with the thermal reaction tester, as opposed to those impregnated with wax which do. We measured the SG of one stone showing this kind of impregnation at 3.33.
Polymer 5
The infrared spectrum of polymer 5 shows similar absorption features as polymer 4, plus five more in the range of 2950-3150 cm¯¹. The three jadeites impregnated with this material that we studied are inert in ultraviolet radiation. We could measure the SG on only one of them, and the stone floated in the 3.32 SG liquid (methylene iodide). It is interesting to note that two of these stones displayed ‘sweating’ when tested with T.R.T.
Conclusion
These two new polymers have been seen on a few jadeites submitted for identification, and laboratories involved in B-jade detection should be aware of them. They demonstrate the growing variety of polymers that are being used for jade treatment. One reason for this could be the increasing number of companies involved in this treatment.
Background
Over the last several years polymer-impregnated jadeite has become prevalent in the jade market. This has given rise to some colors of jadeite being routinely tested for the presence of this treatment.
Recently, the GIA GTL in Santa Monica received for identification a 15 carat purple oval cabochon that we identified as jadeite. Subsequent testing determined the stone to be polymer impregnated. To the best of our knowledge, this is the first report of a jadeite of this color that is polymer-impregnated.
Polymer-impregnated ‘lavender’ jadeite
Gemological properties: Gemological testing revealed an index of refraction and visible absorption spectrum consistent with jadeite jade. Specific gravity was measured by the hydrostatic method and determined to be 3.32, which is slightly lower than the norm for jadeite. This is consistent with previous findings of polymer-impregnated jadeite. The stone was inert to longwave ultraviolet radiation. Magnification did not reveal any evidence of treatment. As is often the case with purple jadeite, the origin of the color could be be determined.
Infrared spectroscopy
The spectrum of this stone reveals intense absorptions around 2900cm¯¹ which are not found in natural jadeite. These additional features are due to the presence of an ‘opticon-like’ polymer. This is not surprising, since this type of polymer is the most commonly employed for jadeite impregnation, according to many reports and our own experience.
Discussion
This finding is particularly significant since none of the polymer-impregnated jadeite (or B jade) we have seen so far was purple in color. They have all been green or mottled green and white, some with applied spots of brown. This means that we will now have to expand our routine testing for polymer impregnation to include purple jadeites as well.
New polymers for jadeite impregnation
We have recently encountered two new types of polymer used for the treatment of jadeite, in addition to the three previously described which are wax, an ‘opticon-like’ polymer, and phthalate-like polymer. Since we do not know yet their exact nature, we will refer to them as polymer 4 and polymer 5.
Polymer 4
The infrared spectrum of polymer 4 is very similar—but not identical—to that of wax. In particular, the major absorption is slightly shifted and of different width than that for wax. Jadeites treated with this product do not ‘sweat’ when tested with the thermal reaction tester, as opposed to those impregnated with wax which do. We measured the SG of one stone showing this kind of impregnation at 3.33.
Polymer 5
The infrared spectrum of polymer 5 shows similar absorption features as polymer 4, plus five more in the range of 2950-3150 cm¯¹. The three jadeites impregnated with this material that we studied are inert in ultraviolet radiation. We could measure the SG on only one of them, and the stone floated in the 3.32 SG liquid (methylene iodide). It is interesting to note that two of these stones displayed ‘sweating’ when tested with T.R.T.
Conclusion
These two new polymers have been seen on a few jadeites submitted for identification, and laboratories involved in B-jade detection should be aware of them. They demonstrate the growing variety of polymers that are being used for jade treatment. One reason for this could be the increasing number of companies involved in this treatment.
Yellow And Orange Sapphires
(via ICA Lab Alert, No.1, June 2, 1987) AIGS writes:
Background
In 1981, we at AIGS were asked to identify what was undoubtedly among the first heat treated Sri Lankan yellows to come out of ovens of Bangkok. We were told that the stone was treated by an unknown process (which was later found to be heat), and were asked to determine the color stability. This we proceeded to do by performing our usual fade test. This consisted of exposing the stone to heat and light at 1cm distance of a 150 watt spotlight for up to one hour. We were truly surprised when, after a few minutes exposure, the color had become much darker and more brownish (stones treated with irradiation would fade; some untreated Sri Lankan yellows will fade, but in most the color will not change). This change was temporary only; as the stone cooled to room temperature the color returned to normal.
Since this time we have tested over a thousand Sri Lankan yellow/orange sapphires and have found that all of the heat treated yellow to orange stones react in this way. Thus, a simple test for detection of heat treatment in Sri Lankan yellow/orange sapphires is possible.
The test
Place the stone in close proximetry to a source of mild source of heat, such as an incandescent bulb.
Results
Heat treated Sri Lankan yellow/orange sapphire —The color darkens temporarily, becoming more brownish. The deeper the original color, the greater the change. As the stone cools, the color returns to its original state. Control stones should be used so as to detect even slight changes in color.
Irradiated Sri Lankan yellow/orange sapphire —The color will fade, usually within one hour.
Untreated Sri Lankan yellow/orange sapphire —Generally no change, however some stones may show some fading.
Thai/Australian yellow/orange sapphire, heat treated or untreated—no change has been observed in the color of these stones.
(To: Mr N Horiuchi; Subject: Response to comment on Lab Alert No.1) AIGS writes:
Discussion
Mr N Horiuchi has commented on the test we previously described in Lab Alert No.1 to detect heat treatment in Sri Lankan yellow/orange sapphires. Mr Horiuchi stated that this color also did not fade under the same condition as reported on (by) AIGS.
From the above statement it appears that Mr Horiuchi has not understood the text of Lab Alert No.1. As others may also have misunderstood the text, we will describe the test again below.
Heat treatment in Sri Lankan yellow to orange sapphires may be detected by applying a simple fade test. (Caution: This test only works for Sri Lankan stones). Once a yellow/orange sapphire has been identified as definitely originating from Sri Lanka, its color is tested by applying a simple fade test. The stone in question should be placed on a glass (or other nonflammable) platform within ½ cm of a hot 150 watt (or more) spotlight. The idea is to expose the stone to lots of light and heat. After about 15 minutes exposure (as the stone heats up), the color of a heat treated yellow/orange sapphire will have been found to have become slightly darker and more brownish (the deeper the starting color before the test, the deeper and more brownish the color after heating up). This change is temporary only. As the stone cools its color will fade back to the color before the test was started, not, we repeat, not back to the color before the stone was heat treated (by someone else presumably). We believe that is where Mr Horiuchi misunderstood the original Lab Alert.
Other possible reactions
If the stone has been irradiated (either by nature or by man) the color will fade, usually within one hour’s exposure. In most natural Sri Lankan sapphires, however, the color will show no change. Natural yellow/orange sapphires from other sources and synthetic yellow/orange sapphires also show no change.
To make this test more accurate, control stones of similar color to the stone being tested should be used. Then after the stone in question heats up it can be compared to the color of the control stone. In the case of heat treated yellow/orange Sri Lankan sapphires, the change is not subtle in deeply colored stones, and anyone with normal vision should easily detect it, but the comparison must be made quickly before the stone tested cools down.
Dr Kurt Nassau has informed us that under certain conditions, yellow/orange sapphires may get darker upon exposure to some kinds of visible light. We have absolutely no information on exactly what kinds of stones do this or under what conditions. However he has promised us that the subject will be described in detail soon in an article he has written for Gems & Gemology. We have also written an article on the subjects covered in Lab Alerts Nos. 1 and 2 and submitted it to Gems & Gemology. We don’t know when it will appear (or if it will appear). We have had no reply of any kind, even though we sent it 8 weeks ago.
The subject of color in yellow sapphires is extremely complex. We have no illusions that the above information is the last word on the subject. However, over the past ten years we have tested thousands of pieces of yellow/orange sapphire from all sources and this is what we have found. If anyone else could she additional light on the subject, we would love to hear from them.
Dr K Schmetzer replies:
A. Fe³+ or by Fe³+ and Ti³+: Type 1, originating from Nigeria, Thailand, Australia or
B. By a yellow color center: Type 2, originating from Sri Lanka.
By heat or irradiation heat treatment, yellow stones with similar color centers, i.e with absorption spectrum similar to the spectrum of Type 2, but with different stabilities to light or heat are produced.
C. Irradiation treatment, color center: Type 3
D. Heat treatment, color center: Type 4
According to my experience and knowledge, AIGS describes a test for Type 4 stones, and N Horiuchi is dealing with Type 3 stones. Dr Nassau describes Type 2 stones in Alert No.9, and this type of yellow color center may be connected with natural irradiation. The reason for the higher stability of this naturally irradiated yellow compared to artificially irradiated yellow is an unknown but similar results were found by myself with natural irradiated yellow quartz (citrine) and artificially irradiated yellow quartz.
Background
In 1981, we at AIGS were asked to identify what was undoubtedly among the first heat treated Sri Lankan yellows to come out of ovens of Bangkok. We were told that the stone was treated by an unknown process (which was later found to be heat), and were asked to determine the color stability. This we proceeded to do by performing our usual fade test. This consisted of exposing the stone to heat and light at 1cm distance of a 150 watt spotlight for up to one hour. We were truly surprised when, after a few minutes exposure, the color had become much darker and more brownish (stones treated with irradiation would fade; some untreated Sri Lankan yellows will fade, but in most the color will not change). This change was temporary only; as the stone cooled to room temperature the color returned to normal.
Since this time we have tested over a thousand Sri Lankan yellow/orange sapphires and have found that all of the heat treated yellow to orange stones react in this way. Thus, a simple test for detection of heat treatment in Sri Lankan yellow/orange sapphires is possible.
The test
Place the stone in close proximetry to a source of mild source of heat, such as an incandescent bulb.
Results
Heat treated Sri Lankan yellow/orange sapphire —The color darkens temporarily, becoming more brownish. The deeper the original color, the greater the change. As the stone cools, the color returns to its original state. Control stones should be used so as to detect even slight changes in color.
Irradiated Sri Lankan yellow/orange sapphire —The color will fade, usually within one hour.
Untreated Sri Lankan yellow/orange sapphire —Generally no change, however some stones may show some fading.
Thai/Australian yellow/orange sapphire, heat treated or untreated—no change has been observed in the color of these stones.
(To: Mr N Horiuchi; Subject: Response to comment on Lab Alert No.1) AIGS writes:
Discussion
Mr N Horiuchi has commented on the test we previously described in Lab Alert No.1 to detect heat treatment in Sri Lankan yellow/orange sapphires. Mr Horiuchi stated that this color also did not fade under the same condition as reported on (by) AIGS.
From the above statement it appears that Mr Horiuchi has not understood the text of Lab Alert No.1. As others may also have misunderstood the text, we will describe the test again below.
Heat treatment in Sri Lankan yellow to orange sapphires may be detected by applying a simple fade test. (Caution: This test only works for Sri Lankan stones). Once a yellow/orange sapphire has been identified as definitely originating from Sri Lanka, its color is tested by applying a simple fade test. The stone in question should be placed on a glass (or other nonflammable) platform within ½ cm of a hot 150 watt (or more) spotlight. The idea is to expose the stone to lots of light and heat. After about 15 minutes exposure (as the stone heats up), the color of a heat treated yellow/orange sapphire will have been found to have become slightly darker and more brownish (the deeper the starting color before the test, the deeper and more brownish the color after heating up). This change is temporary only. As the stone cools its color will fade back to the color before the test was started, not, we repeat, not back to the color before the stone was heat treated (by someone else presumably). We believe that is where Mr Horiuchi misunderstood the original Lab Alert.
Other possible reactions
If the stone has been irradiated (either by nature or by man) the color will fade, usually within one hour’s exposure. In most natural Sri Lankan sapphires, however, the color will show no change. Natural yellow/orange sapphires from other sources and synthetic yellow/orange sapphires also show no change.
To make this test more accurate, control stones of similar color to the stone being tested should be used. Then after the stone in question heats up it can be compared to the color of the control stone. In the case of heat treated yellow/orange Sri Lankan sapphires, the change is not subtle in deeply colored stones, and anyone with normal vision should easily detect it, but the comparison must be made quickly before the stone tested cools down.
Dr Kurt Nassau has informed us that under certain conditions, yellow/orange sapphires may get darker upon exposure to some kinds of visible light. We have absolutely no information on exactly what kinds of stones do this or under what conditions. However he has promised us that the subject will be described in detail soon in an article he has written for Gems & Gemology. We have also written an article on the subjects covered in Lab Alerts Nos. 1 and 2 and submitted it to Gems & Gemology. We don’t know when it will appear (or if it will appear). We have had no reply of any kind, even though we sent it 8 weeks ago.
The subject of color in yellow sapphires is extremely complex. We have no illusions that the above information is the last word on the subject. However, over the past ten years we have tested thousands of pieces of yellow/orange sapphire from all sources and this is what we have found. If anyone else could she additional light on the subject, we would love to hear from them.
Dr K Schmetzer replies:
A. Fe³+ or by Fe³+ and Ti³+: Type 1, originating from Nigeria, Thailand, Australia or
B. By a yellow color center: Type 2, originating from Sri Lanka.
By heat or irradiation heat treatment, yellow stones with similar color centers, i.e with absorption spectrum similar to the spectrum of Type 2, but with different stabilities to light or heat are produced.
C. Irradiation treatment, color center: Type 3
D. Heat treatment, color center: Type 4
According to my experience and knowledge, AIGS describes a test for Type 4 stones, and N Horiuchi is dealing with Type 3 stones. Dr Nassau describes Type 2 stones in Alert No.9, and this type of yellow color center may be connected with natural irradiation. The reason for the higher stability of this naturally irradiated yellow compared to artificially irradiated yellow is an unknown but similar results were found by myself with natural irradiated yellow quartz (citrine) and artificially irradiated yellow quartz.
Subscribe to:
Comments (Atom)