Title: Gem Characterization Abstract: Figure 1. The 3161 cm–1 series mid-IR feature, assigned to structurally bonded OH and associated with Mg2+, displays side bands at ~3352 and 3240 cm–1 in natural sapphires and at ~3277 and 3220 cm–1 in synthetic material. Natural sapphires also displayed CO2-related bands at ~2456 and 2418 cm–1.
3161 cm–1 Infrared Feature in Synthetic Sapphires
Gagan Choudhary and Sandeep Vijay
Gem Testing Laboratory, Jaipur, India
The 3161 cm–1 mid-infrared (IR) spectral feature (figure 1) is an important tool in the identification of unheated sapphires, especially in material from low-iron metamorphic environments such as Sri Lanka. This feature is a series of bands, composed of a strong peak at ~3161 cm–1 and smaller side bands at ~3075, 3240, and 3355 cm–1. A few researchers have attributed these features to OH groups involved in charge compensation with Si4+, while some have assigned them to structurally bonded OH, associated with Mg2+. The 3161 cm–1 series is more commonly observed in natural-color yellow sapphires than any other color of corundum; occasionally it is encountered in blues and pinks. These authors, however, have encountered a strong feature at ~3161 cm–1 in a few specimens of yellow synthetic sapphire grown by the flame-fusion (Verneuil) process. Their synthetic origin was determined on the basis of inclusion study, which revealed the presence of clouds of minute gas bubbles, along with some bomb-shaped gas bubbles, typically associated with corundum or spinel grown by the flame-fusion process. Milky zones of fine pinpoints and a “plato” effect were also present.
The 3161 cm–1 mid-IR feature in these synthetic yellow sapphires displayed side bands at approximately 3220 and 3277 cm–1, as opposed to 3240 and 3355 cm–1 in natural sapphires.
Agate Analysis by Raman, XRF, and Hyperspectral Imaging Spectroscopy for Provenance
Aaron Celestian1, Arlen Heginbotham2, Rebecca Greenberger3, Bethany Ehlmann3, Bibek Samanta4, Alyssa Morgan1, and Sergey Mamedov5
1Natural History Museum of Los Angeles County
2J. Paul Getty Museum, Los Angeles
3California Institute of Technology, Pasadena
4University of Southern California, Los Angeles
5Horiba Scientific, Edison, New Jersey
The Getty Institute in Los Angeles recently acquired the Borghese-Windsor Cabinet (figure 1, left), a piece of furniture extensively decorated with agate, lapis lazuli, and other stones. The cabinet is thought to have been built around 1620 for Camillo Borghese (later Pope Paul V). It was traditionally thought that all agate gemstones acquired during the sixteenth and seventeenth centuries were sourced from the Nahe River Valley near Idar-Oberstein, Germany. While Brazilian agate began to be imported into Germany by the 1800s, it is possible that some was imported in the eighteenth century or earlier. A primary research goal was to determine if the agates in the Borghese-Windsor Cabinet are of a single origin, or if they have more than one geologic provenance.

Figure 1. Left: The Borghese-Windsor Cabinet on display at the Getty Center, being imaged by the hyperspectral analyzer (center, on tripod). Right: This Brazilian agate from Rio Grande do Sul is part of the NHMLA collection. Transect A-A′ is where the Raman map was collected. Photos by Arlen Heginbotham (left) and Aaron Celestian (right).
Both quartz and moganite will crystallize together as agate forms, but moganite is not stable at Earth’s surface and will convert to quartz over tens of millions of years (Heaney, 1995; Gíslason et al., 1997; Moxon and Rios, 2004). Thus, older agate contains less moganite. Agate from Idar-Oberstein is Permian in age (around 280 million years old), while agate from the Brazilian state of Rio Grande do Sul generally formed during the Cretaceous (around 120 million years ago). It is thought that Rio Grande do Sul would have been a primary source of material exported to Europe because it is one of Brazil’s oldest and largest agate producers.
When examining the cryptocrystalline parts of agate from comparative collections, Brazilian agates from the collection of the Natural History Museum of Los Angeles County (NHMLA; figure 1, right) had 8% or higher moganite concentration, whereas the Idar-Oberstein agate (on loan from the Smithsonian National Museum of Natural History) had less than 2% moganite. The moganite distribution in the agate is heterogeneous, likely due to different growth stages and changing geological conditions during agate formation. Using the Raman maps, we were able to isolate the areas that contained moganite + quartz and measure the ratios in those specific bands (figure 2). This narrow-band approach to determining quartz to moganite ratio, when compared to broad-brand and whole-sample approaches, was shown to be more reproducible in distinguishing Brazilian from German agates.

Figure 2. Raman analyses of two Brazilian agates (blue) and two German agates (red) in the diagnostic region between 400 and 550 cm–1 show the strongest peaks for quartz at 463 cm–1 and moganite at 501 cm–1. These data were taken from narrow-band analysis (summing all spectra in the narrow agate bands that contained quartz + moganite). Each band was used as a separate analysis. Note the strong moganite presence in the Brazilian agates.
These same agates from the Brazilian and German localities were then taken to Caltech to collect hyperspectral imaging data (on a custom-built Headwall Photonics co-boresighted visible/near-infrared and shortwave infrared sensor). Imaging data were compared to the NHMLA laboratory Raman and X-ray fluorescence analyses, and correlation analysis of combined datasets from the three different experimental procedures allowed us to establish a unique characterization pattern for the different localities.
REFERENCES
Gíslason S.R., Heaney P.J., Oelkers E.H., Schott J. (1997) Kinetic and thermodynamic properties of moganite a novel silica polymorph. Geochimica et Cosmochimica Acta, Vol. 61, No. 6, pp. 1193–1204, http://doi.org/10.1016/S0016-7037(96)00409-7

Heaney P.J. (1995) Moganite as an indicator for vanished evaporites: A testament reborn? Journal of Sedimentary Research, Vol. 65, No. 4A, pp. 633–638, http://dx.doi.org/10.1306/D4268180-2B26-11D7-8648000102C1865D

Moxon T., Ríos S. (2004) Moganite and water content as a function of age in agate: An XRD and thermogravimetric study. European Journal of Mineralogy, Vol. 16, No. 2, pp. 269–278, http://dx.doi.org/10.1127/0935-1221/2004/0016-0269
Beryllium Heat Treatment of Blue Sapphire from Sri Lanka
Sutas Singbamroong1,2, Panjawan Thanasutthipitak1, Thawatchai Somjaineuk3, and Nazar Ahmed2
1Department of Geological Science, Chiang Mai University, Thailand
2Dubai Central Laboratory Department, Dubai, United Arab Emirates
3Chanthaburi Gem and Jewelry Manufacturer Association, Chanthaburi, Thailand
Since at least 2000, corundum has been subjected to a beryllium (Be) heat treatment technique in Chanthaburi, Thailand. For this study, samples of transparent to translucent milky-white to yellow, purple to violet, and light to medium blue sapphires from Sri Lanka (metamorphic origin) were heat treated with Be in three types of furnaces (gas, electric, and fuel) at various temperatures and in both oxidizing and reducing atmospheres. The technique of Thai gem heating specialist Thawatchai Somjaineuk was used to intensify blue color, improve clarity, and distribute uneven color. Somjaineuk’s technique has been used to enhance Sri Lankan corundum with a milky/silky appearance since 2004, and supplies approximately 50 kg of beryllium-treated blue sapphire per year to the gem market.
The samples were studied after each step of heating for basic gemological properties, spectroscopic properties using ultraviolet/visible/near-infrared (UV-Vis-NIR) and Fourier-transform infrared (FTIR) absorption spectroscopy, and chemical composition using laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS). The corundum samples were first heated in a traditional O2/LPG mixed-gas furnace to about 1500°C for two hours in an oxidizing atmosphere. The white to yellow and light to medium blue sapphires turned colorless, whereas the purple to violet sapphires became pink. The second step of heating was performed with Be in an electric furnace at about 1700°C for 48 hours in an oxidizing atmosphere. After this process, the milky/silky colorless sapphires became a more transparent yellow, while the pink sapphires turned orange-pink. These stones were enhanced in the final step by reheating in a fuel furnace at about 1700°C for 72 hours in a reducing atmosphere. All samples became blue with light to strong saturation and tone.

Figure 1. UV-Vis spectra of a violet sapphire before treatment (A), after a first heating in a reducing atmosphere (B), after a second heating with beryllium in an oxidizing atmosphere (C), and after a third heating in a reducing atmosphere (D).
The combination of the color appearance, the absorption spectra analyzed after oxidation with Be and reduction heating (figure 1), and the chemical data suggest that Be and/or Mg trapped-hole yellow color centers—created during oxidation heating with Be—were made inactive after reduction heating. The blue coloration is mainly caused by strong broad absorption bands of Fe2+/Ti4+ intervalence charge transfer (IVCT) mechanism without Fe2+/Fe3+ IVCT. However, chemical data were analyzed for those samples and showed relatively high Mg and Be concentrations in comparison with the Ti composition, which does not fit well with the model that indicates [Ti4+] > [Mg2+ + Be2+] causes blue coloration. This heating technique is still not well understood. Further experiments and analyses are being carried out to confirm the role of beryllium in blue sapphires.
Gemological and Spectroscopic Characteristics of Australian Sapphires
Yafen Xu and Jingru Di
Gemmological Institute, China University of Geosciences, Wuhan
Although Australia has assumed a major role in the production of sapphire, research on this material has not been comprehensive. This study aims to analyze the gemology and spectroscopy of Australian sapphires and provide a theoretical basis for their treatment.
Under the optical microscope and other conventional instruments, hexagonal color zones were blue and yellow. Healing fissures and inclusions were extremely common. Raman spectroscopy showed that the inclusions were two-phase: CO2 and H2O with sapphire, rutile, zircon, diaspore, and amphibole, among others. Sulfur on the healing fissures indicated that S was filled during transportation. The IR spectra of the Australian sapphires typically revealed a 3310 cm–1 absorption peak (figure 1, left). This absorption feature is related to structural OH groups within the sapphire and revealed that these samples grew in reducing conditions. LA-ICP-MS indicated that the Cr/Ga ratio was less than 1 and the Fe/Ti ratio was generally 10–100 (figure 1, right), the typical ratio of magmatic sapphire. The iron content was between 3230 and 9431 ppm. Color varied with the content of Fe, Ti, Si, and Mg. UV-Vis absorption peaks (figure 2) at 377, 387, and 450 nm were caused by the d-d electronic transition of Fe3+ and Fe2+-Fe3+ in the region with less Ti; the absorption band centered at 559 nm in the yellow-green region indicated the charge transfer of Fe2+-Ti4+→Fe3+-Ti3+ and higher Ti content in this area. Fe2+-Fe3+ charge transfer often occurs together with Fe2+-Ti4+→Fe3+-Ti3+ charge transfer and causes the wide absorption band at 700–800 nm centered at 754 nm. The center may shift with different ratios of the charge transfer of Fe2+-Fe3+ and Fe2+-Ti4+→Fe3+-Ti3+.

Figure 1. The absorption band of 3310 cm–1 in IR spectra (left) and the Cr/Ga versus Fe/Ti ratios (right) indicate that the Australian sapphires are magmatic and grew in a reducing environment.

Figure 2. The UV-Vis spectra of the color zones in sapphire A-4 (left) and A-2 (right) are different because of different chromogenic ions (pairs).
REFERENCES
Kan-Nyunt H.-P., Karampelas S., Link K., Thu K., Kiefert L., Hardy P. (2013) Blue sapphires from the Baw Mar mine in Mogok. G&G, Vol. 49, No. 4, pp. 223–232, http://dx.doi.org/10.5741/GEMS.49.4.223
Yimiao L., Tao C. (2015) Gemmological characteristic of ruby and sapphire from Muling, Heilongjiang Province. Journal of Gems & Gemology, Vol. 17, No. 4, pp. 1–7.
A Grading Method of Jadeite Jade Transparency Based on Digital Image Analysis
Danlu Cui
Gemmological Institute, China University of Geosciences, Wuhan
In the jadeite jade market, transparency is an important feature judged by experienced practitioners observing with the unaided eye under reflected light. However, this method is easily influenced by subjective factors.
This research simulates human observation of characteristics that could help in judging jadeite transparency through certain visual information features. This approach could allow gemologists to evaluate transparency rapidly while effectively avoiding subjective factors, especially under the same test conditions used to judge jadeite jade color.
Some promising research results have been obtained, through comparing the lightness value of each image pixel in jadeite jade pictures and then using the maximum between-class variance method (OSTU) to obtain a binarization threshold. Thus, the image data is classified into a relatively bright area and a relatively dark area. When a beam of light is directed across an oval-cut jadeite jade with different degrees of transparency, different results are obtained from the images.

In oval-cut jadeite jade with a high degree of transparency, a beam of light arrives at the underside and then converges in the other side of its curved surface, forming a relatively bright area.
In oval-cut jadeite jade with a medium degree of transparency, a beam of light is divided into two parts—one part reflected at the point of incidence or absorbed during the light transmission, and the other part arriving at the underside and then converging in the other side of its curved surface. Therefore, the brightness of the whole image is even.
In oval-cut jadeite jade with a low degree of transparency, most of the light is reflected at the point of incidence or absorbed. Little light reaches the underside, and therefore a relatively dark area forms at the other side of the curved surface.

Based on these three characters, oval-cut jadeite jade with different degrees of transparency can be judged objectively and automatically.
Inclusion Characteristics of Wax-Like Amber After Hydrothermal Treatment
Yamei Wang1,2 and Yan Li1 (presenter)
1Gemmological Institute, China University of Geosciences, Wuhan
2Gem Testing Center of China University of Geosciences, Wuhan
Amber products can be hydrothermally treated (figure 1) in order to improve the transparency of the material. In this process, an abundance of tiny nano- or micro-sized bubbles penetrate the amber in the presence of an aqueous solution (with some catalyst) through controlling the temperature and pressure and selecting an inert atmosphere environment (figure 2). After the treatment, the inner layer of the weathered skin of rough amber material will generate a layer with various thickness of a yellowish white or greenish yellow “hydrothermally treated skin” or a corrugated crust containing pores. The finished amber shows residues with white hydrothermally treated spots of various sizes, which may enter into the amber’s interior or remain on the finished surface. The treated wax-like amber displays abundant gas-liquid inclusions with small and dense flat or disc-shaped bubbles accompanied by tiny stress fracture patterns. The bubbles are uneven in size and densely distributed, forming a cloud-like effect. Because the infrared spectra data of the experimental samples before and after the treatment showed little difference, identification required the support of statistical FTIR data. A series of comprehensive tests are needed to identify hydrothermally treated amber, including the diagnostic evidence of the crust-like skin containing spots.

Figure 1. Variations in the appearance of amber samples before and after hydrothermal treatment: sample 1, sample 2, and sample 3. Note that there was no weight change in the amber before and after hydrothermal treatment. Photos by Yamei Wang.

Figure 2. A: Sketch of the pressure furnace used for hydrothermal treatment. B: Evaporation of H2O steam on amber in the chamber under inert atmosphere. C: Hydrothermal treatment from bubbles in the flowing water. Illustrations by Yan Li.
Interesting Inclusions in Peridot from Jilin, China
Zhiqing Zhang, Min Ye, and Andy H. Shen
Center for Innovative Gem Testing Technology
Gemmological Institute, China University of Geosciences, Wuhan
Recently we received 50 gem-quality rough peridot from the Yiqisong Nanshan olivine ore district, a new mineral occurrence in Dunhua City in China’s Jilin Province. These peridot crystals exhibit a yellowish green hue, rather high transparency, and some visible inclusions. Study of the inclusions showed interesting results (figure 1 left, A–D).

Figure 1. Left: “Lily pad” inclusions with patterns of decrepitation halos are typical in peridot (A). Deep-colored minerals are exposed on the host’s surface with brownish impregnation, or appear ochre with a columnar, schistose form (B). Blocky and schistose green diopside appears on or near the surface (C). Brownish green enstatite is discernible (D). Right: The spectrum of mineral A matched diopside, B matched lizardite, and C matched enstatite. Double or triple peaks near 823 and 855 cm–1 occur in the peridot, not the inclusions.
For precise observation and accurate testing, the crystals were windowed and doubly polished. Comprehensive microscopic and Raman spectroscopic analysis indicated the following typical inclusions: “lily pads,” round transparent inclusions, strongly colored minerals with or without healed secondary fractures, green crystals of enstatite and diopside, and a rare dark mineral inclusion of lizardite, identified by Raman spectroscopy and by referencing the RRUFF database (figure 1, right). Further gemological research is being carried out on these samples, and more data will be published in a full article.
IR Absorption Spectrum of Type Ib HPHT-Created Diamonds as an Indicator of Their Growth Conditions
Viktor Vins1, Alexander Yelisseyev2, Dmitry Bagryantsev1, and Alex Grizenko3
1Velman, Ltd., Novosibirsk, Russia
2Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia
3Lucent Diamonds, Inc., Los Angeles
Donor nitrogen atoms are the simplest crystal lattice defect, and their one-phonon absorption spectrum is well studied. The spectrum shows two main features: a main band at 1130 cm–1 and a narrow peak at 1344 cm–1. The absorption intensity and exact position of these two peaks give information about diamond growth conditions and crystal lattice perfection. In particular, our results showed that a decrease in growth rate corresponded to a decrease in the μ1130/μ1344 absorption intensity ratio. The ratio decreased from 2 to 1.5 in samples grown in the Fe-Ni-C system and from 1.64 to 0.95 in samples grown in the Fe-Co-C system. Since the μ1130/μ1344 ratio is sensitive to growth conditions, it could serve as a criterion for diamond quality, showing the content of impurity defects as well as the amount of internal tensile stress.
Studying isotopically modified diamonds is also informative. For example, if the carbon part of the growth system was 50% 12C graphite and 50% 13C graphite, an isotopic shift at 1344 cm–1 was observed, while the main band at 1130 cm–1 did not shift. The samples containing 15N isotope, conversely, revealed a 15 cm–1 shift toward long wavelengths of the 1130 cm–1 band, whereas the 1344 cm–1 peak remained at its frequency. It can be concluded that the 1130 cm–1 band is associated with the resonant vibrations of the N-C bond, while the 1344 cm–1 peak is related not to the donor nitrogen atom but to local vibrations of the carbon atom, which is bonded to the unpaired electron of the impurity nitrogen. The position of the Raman peak on the spectra taken at different points of the sample with 47% 13C showed that the biggest shift of the diamond peak (ν = 1312.8 cm–1) was seen in parts of the crystal immediately adjacent to the seed region. The Raman peak varied from 1321.1 to 1322.5 cm–1 in other parts of the sample, which corresponds to 25 ÷ 27% of 13C. The full width half maximum (FWHM) of the Raman peak was the largest (7.8 cm–1) at ν = 1312.8 cm–1. In all other points it ranged from 6.2 to 7.4 cm–1. In addition to an unusually high μ1130/μ1344 intensity ratio, which in “traditional” nickel-containing diamond ranges from 1.5 to 2.0, this indicates that isotopically modified diamonds have a rather imperfect crystal lattice. This could be caused by internal stress resulting from the incorporation of an isotope with a larger atomic size than that of 12C.
This work was supported by grant 16-05-00873a from the Russian Foundation for Basic Research and by the state assignment project 0330-2016-0006.
Laue X-Ray Backscatter Spot Patterns: A Novel Way of Identifying Various Gemological Crystals
Hollis Milroy and Sandra Hektor
University of Toronto
Although Laue X-ray backscatter imaging of crystals dates back to the 1920s, the application of this technique to the study of gemology is very much a new concept. This study investigates the use of Laue backscatter spot patterns (also called Laue-grams) to positively identify several gem crystals of varying crystal structure and atomic complexity. Approximately 50 exposures were taken using a tungsten filament running at 2000 W (50 kV × 20 mA), with the resulting Laue backscatter images captured on medical X-ray film. Using a high-resolution scanner, the spot patterns from the developed film were compared to computer-generated models, which agreed with the film images to a high degree of accuracy.

Figure 1. Laue backscatter spot patterns for two single-crystal samples. A: Yellow tint lab-grown single crystal diamond. B: Single-crystal tungsten in [110] orientation. Photos by Hollis Milroy.
Exposure times and crystal orientations relative to the X-ray beam axis were varied. Control exposures were run to ensure background effects (e.g., from the sample holder) did not contribute at all to the spot patterns.
The advantage of the noninvasive and nondestructive Laue backscatter method is that material can be identified from any orientation of the crystal. This is helpful when gemstones are embedded in jewelry or other materials such as rocks. Furthermore, anomalies from crystal impurities will appear on the film proportionately: The spot pattern of the predominant material will appear most visible and thus always easily determinable. For instance, the small impurities that produce different-hued gemstones will not affect the produced spot pattern from the underlying crystal structure.
Multifunction Spectrometer for Color Grading and Identification of Diamonds and Gemstones
Yan Liu
Liu Research Laboratories, South El Monte, California
A multifunction dual integrating sphere spectrometer has been developed for color grading and identification of diamonds and gemstones. The spectrometer has nine functions: spectral reflectance measurement, spectral transmittance measurement, color measurement, UV fluorescence measurement, photoluminescence (PL) measurement, color grading of gemstones, color grading of colored diamonds, color grading of jadeite, and grading of alexandrite effect. The color grading by artificial intelligence and the fine spectral measurement of PL at room temperature are particularly useful for gemological laboratories and the jewelry industry. The artificial intelligence for color grading includes a neural network and a fuzzy logic algorithm. The PL measurement is calibrated by a NIST-traceable lamp to measure the relative spectral distribution of photoluminescence, and a mathematic algorithm is developed to obtain a fine PL spectrum at room temperature. In addition, the photoluminescence measurement can amplify a weak spectrum up to 1,000 times for gemological research and identification purposes. The function for color grading of jadeite has adjustments for color area percentage and shape curve for accurate color grading of carved pieces. The grading of alexandrite effect is calculated under five standard CIE illuminants: A, D65, F3, F7, and F11. The spectrometer can be used to perform most tasks of color grading, spectroscopic identification, and research in advanced gemological laboratories.
Nephrite from Luodian, Guizhou Province of China
Quanli Chen1, Xianyu Liu1, 2, Haitao Wang3, Wenjing Zhu1, Sujie Ai1, and Zuowei Yin1
1Gemmological Institute, China University of Geosciences, Wuhan
2College of Jewelry, Shanghai Jian Qiao University, Shanghai
3School of Jewelry, Guangzhou College of South China University of Technology, Guangzhou
In recent years, a new variety of nephrite has been discovered in Luodian County in Guizhou Province, China (figure 1). It lacks greasy luster but possesses a distinctive “porcelain” luster and a fine texture. The white samples tend to show a more or less gray hue.

Figure 1. Map showing the location of the Luodian nephrite deposit.
Samples with a white to bluish white colors were studied via X-ray fluorescence (XRF), X-ray diffraction (XRD), ICP-MS, and FTIR. The results reveal that Luodian nephrite (figure 2), whose SG ranges from 2.77 to 2.90 and is slightly lower than that of Hetian nephrite, is mainly composed of tremolite, and parts of the samples contain a small amount of quartz. The chemical constituents of Luodian nephrite are SiO2 (56.75–59.01 wt.%), MgO (23.69–25.03 wt.%), and CaO (11.25–12.00 wt.%, lower than the standard value of tremolite).

Figure 2. These nephrite pieces are from Luodian County in Guizhou Province, China. Photos by Quanli Chen.
Among the trace elements of Luodian nephrite, Ti, V, Cr, Mn, and Co show higher relative mass fraction, with Ti ranking top (relative mass fraction: 2.05–4.52 × 10–8). The content of these elements is exceptionally low in Hetian white nephrite, which may shed some light on the gray hue of Luodian nephrite. Light rare earth elements are relatively concentrated, and Eu shows both positive and (more frequently) negative anomalies. Compared with Hetian white nephrite, the total content of rare earth elements of Luodian nephrite is higher, especially the elements La, Nd, Sm, Tb, and Er, indicating that the ore-forming environment is different between the two localities.
Observing the microstructure characteristics using scanning electron microscopy (SEM) revealed that the tremolite in Luodian nephrite has a mainly fibrous crystalline structure, and the various microstructure features of the aggregate are based on the different aggregation modes of fibrous tremolite. Therefore, the fibrotic range, geometric size, form combination, interaction of the tremolite, and tightness of polymerization are the basis of quality in Luodian nephrite.
“Raindrop” Turquoise from China
Ling Liu, Mingxing Yang, Yan Li, Yalun Ku, Jia Liu, and Zenmin Luo
Gemmological Institute, China University of Geosciences, Wuhan
Recently, a new type of turquoise with randomly distributed spots (figure 1A) from Hubei Province, China—where there are abundant gem-quality turquoise mines—has become popular with jewelry consumers and collectors. The material is called “raindrop turquoise” because of the unique inclusions with blue, blue-green or (rarely) yellow color. The raindrop-like inclusions and the substrate always display a similar hue, but the color of the raindrop-like inclusions is much deeper, and their transparency and hardness are higher.

Figure 1. A: The circle-shaped inclusions were unevenly distributed in this piece of raindrop turquoise. Photo by Yalun Ku. B: Inclusions seen in one of the samples from this report. The sample measures 21 × 18 × 6 mm. C: Backscattered electron imaging of the sample shown in figure 1B revealed that the gray area between the raindrop and the substrate is distinct. D: A lighter and narrower (~10 μm) line observed in the vein of the sample is pure carbon-fluorapatite.
It appears that so-called raindrop turquoise has not been well studied. Several typical specimens from the jewelry market were systematically investigated for their mineral compositions and spectral characteristics using micro-XRD, micro-FTIR, Raman, and electron microprobe analysis. The raindrop inclusions (figure 1B) were mainly composed of turquoise and fluorapatite, while the substrate was mainly turquoise. The Raman spectra of the raindrop inclusions showed the characteristic peaks of turquoise, with strong and sharp peaks at 965–968 cm–1 caused by PO43– of fluorapatite. In addition, a weak shoulder at 1070 cm–1 was observed in some samples because of CO32– replacing PO43– (Awonusi et al., 2007). The micro-FTIR spectra of the raindrop inclusions showed double weak peaks near 1460 cm–1 and 1430 cm–1, resulting from the asymmetric stretching vibration of CO32– (Fleet, 2009). The backscattered electron images (figure 1C) showed that the gray between the raindrop and the substrate was distinct, indicating the difference in their mutual mineral phases. Some raindrop inclusions kept the perfect hexagonal shapes of apatite (again, see figure 1C). In addition, a lighter and narrower line (~10 μm) was also observed in the vein of the sample (figure 1D). The chemical compositions of the raindrops and veins were Al2O3, P2O5, CaO, CuO, FeOT, and F, while the narrow line mainly consisted of P2O5, CaO, and F.
From the X-ray diffraction (XRD) and Raman results, the raindrop and vein inclusions are mixed with turquoise and fluorapatite, while the lighter and narrower line is pure carbon-fluorapatite. Hence, the deeper color of raindrop-like inclusions can be attributed to the mixture of turquoise and fluorapatite/carbon-fluorapatite.
REFERENCES
Awonusi A., Morris M.D, Tecklenburg M.M. (2007) Carbonate assignment and calibration in the Raman spectrum of apatite. Calcified Tissue International, Vol. 81, No. 1, pp. 46–52, http://dx.doi.org/10.1007/s00223-007-9034-0

Fleet M.E. (2009) Infrared spectra of carbonate apatites: v2-region bands. Biomaterials, Vol. 30, No. 8, pp. 1473–1481, http://dx.doi.org/10.1016/j.biomaterials.2008.12.007
Tianhuang Stone—The Most Valuable Seal Stone in China
Tao Chen1, Yungui Liu2, and Quanli Chen1
1Gemmological Institute, China University of Geosciences, Wuhan
2State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan
Tianhuang stone, from the village of Shoushan in Fujian Province, is the most precious Chinese seal stone. It has a profound cultural heritage in China and is quite expensive. Therefore, systematic research on the identifying gemological and mineralogical characteristics of Tianhuang stone has important value implications. Tianhuang stone mainly has a yellow color, though it can sometimes be white, red, or black. Most Tianhuang stones have weathered skins, red cracks, and “turnip” inclusion veins.

Figure 1. A: This 58 g yellow Tianhuang seal stone was sold at a Chinese auction from 2017. B: Weathered skin on the surface of a Tianhuang stone. C: Fine and white “turnip” veins. D: Red cracks extending into a Tianhuang stone from its surface.
According to X-ray diffraction and FTIR results, Tianhuang stone can be divided into three types: dickitic, nacritic, and illitic. Dickitic-type Tianhuang stone can be further divided into ordered dickitic and disordered dickitic. Illitic-type Tianhuang stone is usually composed of 2M1 illite and a small amount of 1M illite.
The weathered skin and matrix have the same mineral composition. LA-ICP-MS results suggest that iron content is higher in the skin than in the matrix. These findings, along with total iron analyses, indicate that the yellow color of Tianhuang stone is caused by Fe3+ ions in the crystal structure of dickite, nacrite, or illite. Red cracks are caused by iron minerals that entered along the cracks. The iron minerals display three forms: thick film-state, short needles, and film or fine granular, as observed by scanning electron microscopy (SEM). The “turnip” vein is a kind of fine, white spiderweb inclusion in Tianhuang stone, which has no obvious boundary between matrix and vein. SEM, energy-dispersive spectrometry (EDS), and laser Raman microspectrometry results show that turnip vein is composed of svanbergite.
Unusual “Vorobyevite” Beryl from Afghanistan
Yang Hu and Ren Lu
Gemmological Institute, China University of Geosciences, Wuhan
Beryl is an important gem species that includes goshenite, aquamarine, emerald, heliodor, morganite, and red beryl varieties. An unusual blue beryl sold as “vorobyevite” or “rosterite” is sometimes seen on the market. This crystal has a special hexagonal tabular morphology, sometimes concave, convex, or fibrous-like on basal pinacoids. The material is mined from the Deo Darrah, Khash, and Kuran Wa Munjan districts in Badakhshan Province, Afghanistan. It most likely formed in granitic pegmatite, as evidenced by the associated dark blue tourmaline and spherical muscovite aggregates (figure 1, left). Characteristics of an Afghan vorobyevite sample and the use of the term are discussed here.

Figure 1. Left: A 16.5 × 13.2 × 7.5 mm vorobyevite with tourmaline and muscovite aggregate from Afghanistan, a 31.3 × 25.2 × 7.3 mm pale blue Chinese aquamarine, and a 22.1 × 15.5 × 7.8 mm dark blue Burmese aquamarine. Right: A two-phase inclusion hosting a round bubble in the vorobyevite. Field of view 0.37 mm. Photos by Yang Hu.
This sample was pale blue with a yellow hue in the center. Parallel intergrowth and a hexagonal growth texture were shown on a two-sided basal face. Dichroism was medium, appearing pale blue along the ordinary (o-) ray and blue along the extraordinary (e-) ray. The fluorescence response was inert to both long-wave and short-wave UV. The sample had a refractive index (RI) of 1.570–1.575 and a specific gravity (SG) of 2.53. Abundant two-phase inclusions with various shapes were observed (figure 1, right). All of these gemological properties were in agreement with aquamarine.
LA-ICP-MS analysis showed that alkali content in the form of Na and Cs (Cs2O 0.03–0.04 wt.%, and Na2O 0.07–0.08 wt.%) was relatively low according to our chemical database of all beryl varieties, classified as “low-alkali” beryl in agreement with the dominance of type I water in structural channels revealed by Raman and IR spectra. In addition, Ge Sn, Nb, and Ta were relatively rich compared with aquamarine from other origins. Due to few substitutions in the Al octahedral and Be tetrahedral crystal site, this Afghan sample was identified as “normal beryl.” UV-Vis-NIR spectroscopy showed absorptions of Fe ions (FeO 0.56–0.60 wt.%) at 372, 425, 600, and 820 nm, and the blue color was stable under sunlight. Therefore, the blue color was attributed to Fe ions rather than natural or artificial irradiation. A yellowish area in the center of the sample indicated that the blue color was natural.
The term “vorobyevite” was first applied to colorless to yellowish rose beryl containing large amounts of lithium and cesium (Cs2O 3.04 wt.% and Li2O 1.43 wt.%) from Lipovka, Russia (Yakubovich et al., 2009). The term “rosterite” designated a cesium beryl of colorless or pink color from Elba, Italy, almost synonymous with “vorobyevite” (Hänni and Krzemnicki, 2003). But neither term is officially accepted by the International Mineralogical Association or normally used for a beryl variety. Based on gemological, spectroscopic, and chemical characteristics, we confirmed this Afghani vorobyevite belonged to the beryl species, specifically the low-alkali aquamarine variety. However, similar tabular beryls from Mogok (Myanmar) and Sichuan (China) with a pale blue to dark blue color (see figure 1, left) were identified as “alkali-rich” aquamarine in our study. Although the tabular morphology in this Afghan sample was quite uncommon, tabular morphology is not a criterion for identifying vorobyevite or rosterite.
REFERENCES
Hänni H.A., Krzemnicki M.S. (2003) Caesium-rich morganite from Afghanistan and Madagascar. Journal of Gemmology, Vol. 28, No. 7, pp. 417–429.

Yakubovich O.V, Pekov I.V, Steele I.M, Massa W., Chukanov N.V. (2009) Alkali metals in beryl and their role in the formation of derivative structural motifs: Comparative crystal chemistry of vorobyevite and pezzottaite. Crystallography Reports, Vol. 54, No. 3, pp. 399–412, http://dx.doi.org/10.1134/S1063774509030067
Young Blue Sapphires from Muling, China
Yimiao Liu and Ren Lu
Gemmological Institute, China University of Geosciences, Wuhan
The area around Muling, a small town located in northeastern China, produces attractive corundum in a wide variety of color, clarity, and sizes (Liu and Lu, 2016), along with gem-quality pyrope, zircon, and black spinel. Some of its facet-quality sapphires (figure 1) are comparable to those from the finest sapphire localities in the world.

Figure 1. This 0.53 ct natural, untreated blue sapphire from Muling, China, shows desirable blue color and saturation. Photo by Yimiao Liu.
Sapphire from Muling is mostly extracted from alluvial (or secondary) deposits. Information on genesis, general formation environment, and deposit type is still incomplete and being researched to support efficient exploration.
Muling is distributed along the northern section of the Dunhua-Mishan Fault, which is a lithospheric extension between the Xing-Meng orogenic belt and the Pacific subduction zone (Ling et al., 2017). The volcanic eruptions of the Dunhua-Mishan graben began at about 44.9 Ma and ended about 5,140 years before the present (Wang et al., 2001). Gemstones were found in the placer derived from Miocene (5.3–23 Ma) basalt, which is regarded as the gem carrier. The corundum-bearing layers underlie a few meters of soft sandy clay and fertile topsoil.
This study arose from a preliminary examination of 14 faceted and 74 rough corundum from the Muling deposits. During examination of the internal characteristics, we found zircon inclusions in three blue sapphires. As one of the best geochronometers, zircon provided an initial estimate of the formation age through U-Pb dating methods.
Zircon inclusions were identified by laser Raman spectroscopy. Euhedral crystals with no evidence of surface corrosion or oxidation could indicate that the zircon inclusions within the host sapphire were syngenetic and nearly unaffected by radiation (called “high” zircon in gemology). Therefore, the ages obtained on zircon inclusions are in equilibrium with the initial formation time of the host sapphire.
U-Pb dating analyses of zircon inclusions were conducted using LA-ICP-MS at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan. Due to the small size of the target inclusions (approximately 150 μm × 50 μm) and unavoidable interference from common lead, only some subsets of information could be preserved for the age calculation. The analyses of zircon inclusions gave 206Pb/238U ages ranging from 8 to 10 Ma (i.e., Miocene). Being completely enclosed within the host sapphires, the transparent euhedral zircons were protected throughout their history from interaction with permeating fluids. Thus, the obtained ages correspond to the formational ages of these sapphires. Combined with the geologic settings, this time period would have allowed numerous volcanic events to deliver the corundum as xenocrystal from the source to the top. The formation condition of Muling sapphires might be associated with the Miocene volcanic events.
The U-Pb ages of zircon inclusions (along with a full range of trace elements within zircon) can also provide distinctive provenance characteristics, because the formation ages of sapphires from various well-known deposits are different. Although the sapphires from Muling are much older than the oldest human civilization, they are among the youngest sapphire deposits known to date (e.g., Madagascar, Sri Lanka, Myanmar, and North America). Therefore, the U-Pb age of zircon inclusions is an efficient indicator in separating similar-looking sapphires from various deposits.
Once more age information on sapphires is collected, a totally new system of provenance identification will be established. It is also helpful for further understanding the genesis of gemstones and instructing people on the rational utilization of resources.
REFERENCES
Ling Y.Y., Zhang J.J., Liu K., Ge M.H., Wang M., Wang J.M. (2017) Geochemistry, geochronology, and tectonic setting of Early Cretaceous volcanic rocks in the northern segment of the Tan–Lu Fault region, northeast China. Journal of Asian Earth Sciences, Vol. 144, pp. 303–322, http://dx.doi.org/10.1016/j.jseaes.2016.12.025

Liu Y, Lu R. (2016) Gem News International: Ruby and sapphire from Muling, China. G&G, Vol. 52, No. 1, pp. 98–100.

Wang X.K., Qiu S.W., Song C.C., Kulakov A., Tashchi S., Myasnikov E. (2001) Cenozoic volcanism and geothermal resources in northeast China. Chinese Geographical Science, Vol. 11, No. 2, pp. 150–154, http://dx.doi.org/10.1007/s11769-001-0035-z Source: GIA @topic:3


Title: Update from the Responsible Jewellery Council Abstract: The Responsible Jewellery Council (RJC) has announced plans to include colored stones and silver in the next revision cycle for its Code of Practices, which RJC members are certified against. The organization has begun updating its existing standards, a process that takes place every five years. These plans dovetailed with the release of the United Nations’ 2030 Agenda for Sustainable Development, which outlines 17 goals and 169 targets for member nations to meet. The author sat down with Edward Johnson and Anne-Marie Fleury of the RJC during the 2018 Tucson gem shows to discuss the status of these efforts.

The first round of public consultation, which focused on the scope of changes to the standard, took place in 2017. As of February 2018, RJC’s Code of Practices were under review prior to a second public consultation phase, which targets industry and non-industry stakeholders, of proposed changes to the Code. These consultation phases are in line with RJC’s annual auditing of their standard-setting approach, assurance framework, and measuring impacts program.

Like previous versions, the revised Code will certify business practices rather than products. The certification will cover all the important social, environmental, and health and safety issues in the jewelry supply chain. RJC’s priorities for change, which must work for businesses of all sizes, involve several areas, including:

Due diligence for responsible sourcing: RJC recognizes that traceability does not automatically translate to sustainability. As a standard for alignment with the Organisation for Economic Co-operation and Development, RJC encourages companies to adopt a due diligence approach to managing risks in their supply chain. Traceability remains a powerful tool for making responsible sourcing claims and is a voluntary certification option.
Gender equality: RJC endorses best practices that promote diversity, including gender equality. To this end, it is partnering with Business for Social Responsibility (BSR), a nonprofit organization dedicated to sustainable business practices, to develop better guidance on gender equality in the gem and jewelry sector. Topics to be covered include working conditions, facilities, and approaches to family leave.
Updating requirements on responsible mining: Many of the most challenging issues in the industry occur at the mining stage, and RJC continues to evolve its responsible mining provisions to address these challenges.
Reducing audit duplication: As it continues to work with jewelry industry members of all sizes, RJC continues to harmonize with and cross-recognize other industry initiatives already in place from other organizations so that businesses do not have to duplicate efforts at their own cost.

The consultation phase of the Code of Practices review is scheduled to run from April to July 2018. Announcements about the process can be found at https://www.responsiblejewellery.com/standards-development/code-of-practices-review-2/. Source: GIA @topic:10


Title: Book Review: Jewellery Drawing Abstract: This book is a long-awaited English translation of “Schmuckzeichnen mit GZ,” by the same author. The book is a self-study manual intended for goldsmiths who are interested in acquiring techniques of design illustration in terms of its function. The slim volume includes exercises on crayon illustration, the effects of light and shadow, illustration of jewelry pieces made of several different materials, illustration of opaque and transparent stones, interplay of shape and color, and illustration of pearls, among others. There is also a small section on drawing materials and tools required for the tasks.

Reviewed by GIA Library Staff
Carlsbad, California Source: GIA @topic:6


Title: Low-Temperature Heating of Mogok Ruby, Copper-Diffused Feldspar, Porcelain-Treated Turquoise, and the Work of Gem Artist Chi Huynh Abstract: Welcome to the Winter 2022 issue of Gems & Gemology! This issue concludes our volume year with studies on identifying treatments in various colored gemstones and a field report on the inspiring work of an award-winning gem artist.
“Many types of solid inclusions in Mogok ruby samples…were sensitive to heat treatment at lower temperatures between 600° and 1100°C.”
In our lead article, E. Billie Hughes and Wim Vertriest examine the difficulty of detecting low-temperature heat treatment in ruby. Using careful microscopic examination, they observed that many types of solid inclusions in Mogok ruby samples, including calcite, mica, spinel, and zircon, were sensitive to heat treatment at lower temperatures between 600° and 1100°C. Additionally, Raman analysis of calcite and spinel inclusions provided complementary evidence of low-temperature heat treatment.
Next, Qingchao Zhou and colleagues present their findings on identifying copper diffusion treatment in red andesine feldspar, which has been in question for more than a decade. Conducting experiments on both colorless labradorite and light yellow andesine feldspar to modify their color, the authors studied the samples’ fluorescence characteristics and verified that strong fluorescence provided key evidence of treatment.
A team led by Liying Huang contributes our third article, which distinguishes a newer treatment technique used to mimic the color and luster of high-quality untreated turquoise. Known in the Chinese trade as “porcelain-treated” turquoise, this material can be identified by its surface features in combination with low specific gravity, strong luster, and trace element chemistry.
In our final feature article of this issue, Tao Hsu and coauthors profile the groundbreaking work and artistry of Chi Huynh, the designer behind Galatea: Jewelry by Artist. During a visit to the Galatea store and workshop, Huynh shared several of his innovative designs and patents, along with stories of inspiration as an artist and pioneer in the jewelry industry.
G&G’s regular columns continue to offer exciting gemological findings from all over the world. Highlights from Lab Notes include an extraordinarily large cat’s-eye emerald reportedly from Brazil, details of pearl submissions to GIA labs worldwide, and the largest extraterrestrial peridot examined at GIA to date. Observations of fascinating gemstone inclusions are captured in the Micro-World section, sharing a glance at spiral-like “horsetail” inclusions in demantoid, a bluish green omphacite crystal in a Fancy brown-pink diamond, aegirine crystals in two rare samples of poudretteite from Mogok, and more. Colored Stones Unearthed returns in this issue, focusing on gem minerals that form in magmatic environments. Finally, in Gem News International, catch up on the latest information from around the globe, including the observation of an extremely rare hellandite inclusion in a ruby from Mogok and coverage of the 2022 Geological Society of America annual meeting.
We hope you enjoy the latest issue of Gems & Gemology! Source: GIA @topic:1


Title: Quarterly Crystal: Diamond in Diamond Abstract: Figure 1. With a weight of 0.71 ct and measuring 5.88 mm in longest dimension, this glassy colorless diamond octahedron contains an eye-visible diamond inclusion. Photo by Diego Sanchez.
Mineral inclusions in diamonds are always very interesting to gemologists and other geoscientists, and the colorful minerals such as bright green chromium diopside and orange almandine-pyrope usually attract the most attention. This Quarterly Crystal is slightly different, in that the inclusion is both transparent and colorless, with relatively low relief compared to the diamond crystal host. The parent diamond, a transparent colorless, gem-quality glassy octahedron, weighed 0.71 ct and measured 5.88 × 3.99 × 3.01 mm (figure 1). Reportedly from South Africa, the diamond was purchased at the Tucson shows from David New.
When inclusion-host pairs are composed of the same mineral, it causes a low-relief situation bordering on invisibility. Such inclusions become visible when the orientation of the inclusion is different or when there is an interface or partial interface between the host and the inclusion. In the case of diamond in diamond, if the inclusion is visible, then the interface can consist of various fluids and gases, other minerals (most commonly graphite formed through graphitization), combinations of all of these, or nothing at all.

Figure 2. Polarized light shows an elongated modified diamond octahedron displaying various degrees of interfacing with the host diamond crystal. Photomicrograph by Nathan Renfro; field of view 2.18 mm.
Examining the outline of the diamond inclusion in figure 2, there are areas at the interface where the inclusion and host diamond appear to blend perfectly and the interface seems to completely disappear. These are areas of perfect contact where the diamond inclusion and the diamond host merge, without any form of interfacial separation. Source: GIA @topic:4


Title: Diamond-Shaped Cloud in Diamond Abstract: Figure 1: This 0.53 ct round brilliant diamond contained a unique cloud that resembled the profile view of a diamond. Photomicrograph by Nathan Renfro; field of view 2.60 mm.

Diamonds can show some interesting surprises when examined by microscopy. Recently, the authors examined a D-color, 0.53 ct round brilliant diamond with an intriguing cloud inclusion that bore a remarkable resemblance to the profile view of a faceted round brilliant (figure 1). Due to the prominent diamond-shaped cloud under the table, the clarity grade of the stone was SI2 (figure 2).

Figure 2. The D-color, 0.53 ct round brilliant diamond has SI2 clarity due to a distinctive cloud inclusion under the table facet. Photo by Marco Martinez.
Photomicrography was used to chronicle the depth of the cloud, which indicated that it was three-dimensional and part of its center reached the diamond’s surface. When focusing through the inclusion beginning at the surface of the table facet, the cloud spanned ~320 microns of focal distance. This is not the first instance of a faceted diamond showing a cloud inclusion with diamond-related geometry. Gemologists have shown other natural diamonds with clouds resembling diamond octahedra (Winter 2015 Lab Notes, pp. 428–429; Renfro et al., Winter 2018 G&G, pp. 428–429). However, this is the first cloud with such a shape the authors have encountered.
The infrared absorption spectra showed a type Ia diamond with saturated concentrations of nitrogen. Photoluminescence maps were collected with 532 nm and 455 nm excitation. A false-color map corresponding with the normalized intensity of a peak at 700 nm (figure 3A) was detected almost solely within the cloud. This peak at 700 nm has been ascribed to nickel and can be seen in hydrogen-rich diamonds, particularly within hydrogen-rich clouds (e.g., Fall 2020 Lab Notes, pp. 416–419).
In the 455 nm PL map, we detected the H3 center at 503.2 nm (figure 3B), which is identified as an A-aggregate decorated with a vacancy. The especially dense area along the “girdle” showed a distinct chemistry as that portion of the cloud had an elevated 700 nm peak intensity (figure 3A) and an elevated H3 concentration (figure 3B). Figure 3C shows the intensity of the diamond Raman peak. The Raman signal detected within the cloud shows decreased intensity; additionally, the diamond outline in this map corresponds well with the image in figure 1 (as the presence of the cloud reduces the Raman signal reaching the detector). Prior research has shown that oftentimes such clouds form preferentially within the {100} growth sectors (W. Wang and W. Mayerson, “Symmetrical clouds in diamond – the hydrogen connection,” Journal of Gemmology, Vol. 28, No. 3, 2002, pp. 143–152).

Figure 3. Photoluminescence maps were compiled from thousands of spectra (each pixel is 10 microns in size). A: Intensity of a peak centered at 700 nm (associated with nickel and often seen in hydrogen clouds). This peak intensity is normalized by ratioing to the diamond Raman peak. B: Intensity of the normalized H3 center at 503.2 nm; much of the cloud has a lower intensity than the surrounding diamond, but a portion of the “girdle” section of the cloud shows a higher H3 intensity. C: The map of the diamond Raman intensity corresponds well with the visual image, including the cloud resembling a diamond outline seen in figure 1.
While this diamond-shaped cloud formation may cause some concern over the natural origin of such an inclusion (see an example of a 3D subsurface laser engraving in quartz in Fall 2020 Micro-World, pp. 427–430), the cloud in this diamond appeared to be completely natural when examined in the microscope. Generally, the absence of inclusions or clarity characteristics increases the beauty and value of a diamond, but not always. In this diamond, the cloud’s presence adds beauty, value, and distinction. Thanks to an observant and skillful polisher, we get to see another “brilliant” example of an intriguing cloud inclusion in diamond. Source: GIA @topic:4


Title: Large Diamond Inclusion in Diamond Abstract: Figure 1. Trigons seen on a diamond crystal inclusion visible through the crown of a round brilliant diamond. Photomicrograph by A’Dhi Lall; field of view 2.11 mm.
Recently, the authors examined a 2.01 ct Faint green round brilliant diamond with a fascinating diamond crystal inclusion that displayed a transparent, ghost-like appearance. Due to the large size of this nearly invisible crystal, the stone was given a clarity grade of SI2.

Figure 2. Strain between the host diamond and the diamond inclusion is revealed by the interference colors in cross-polarized light. Photomicrograph by A’Dhi Lall; field of view 13.55 mm.
Photomicrography was used to document the features of this inclusion. Triangular etch features, also known as trigons, were seen on the inclusion (figure 1). These are typically natural growth markings of diamonds, confirming the inclusion as diamond. The diamond crystal inclusion appeared to have sharp and easily recognizable faces. Images with cross-polarized light show strain between the inclusion and the host diamond (figure 2). A DiamondView image also reveals the diamond crystal inclusion (figure 3).

Figure 3. DiamondView image of the diamond inclusion in the diamond host. Image by Luthfia Syarbaini.
Generally, the beauty and value of a diamond increase with the absence of inclusions. Yet the presence of a diamond inclusion gave this diamond a certain distinction, which in the authors’ opinion added to its beauty and value. Source: GIA @topic:4


Title: Enormous South Sea Cultured Pearl Filled with Cultured Pearls Abstract: Figure 1. The large 49.55 ct South Sea cultured pearl (left) is shown alongside a typical 13 mm South Sea cultured pearl. Photo by Jian Xin (Jae) Liao.

              Known for their size, South Sea cultured pearls can attain a diameter of 20 mm or more. A massive baroque white South Sea cultured pearl weighing 49.55 ct and measuring 27.12 × 23.23 × 21.67 mm (figure 1) was recently submitted to the New York laboratory for identification. Besides its remarkable size, we noted a small corner section with a circular gap highlighted by a yellowish glue-like material (figure 2). This feature suggested that a smaller pearl with similar color and luster had been used to fill an opening in the baroque cultured pearl.

	Figure 2. A small pearl was plugged into this opening in the baroque pearl. Photo by Jian Xin (Jae) Liao.
Microradiography revealed that this smaller pearl was a nonbead-cultured pearl with an irregular linear dark central growth feature (figure 3, left). Both pearls originated from a saltwater environment, according to energy dispersive X-ray fluorescence (EDXRF) spectroscopy. Surprisingly, microradiography revealed three additional bead-cultured pearls within the large baroque specimen (figure 3, right). These three cultured pearls showed their own distinct bead demarcations and had all been drilled through. The large void was filled with an unknown substance that prevented the three pearls from moving around.

	Figure 3. The baroque pearl’s internal structure suggested a non-bead cultured pearl (left). X-radiography showed that three bead cultured pearls were used to fill the void (right). Photo by Surjit Dillon Wong.
Although we occasionally see filled or plugged pearls (see D. Hargett, “Unusually large worked and plugged cultured pearl,” Winter 1991 Lab Notes, p. 251), this was the first time we had encountered a South Sea cultured pearl filled with multiple bead-cultured pearls. We believe this enormous pearl was originally cultured with a single bead nucleus, but that somehow the bead emerged through an opening. To maintain the specimen’s weight and durability, the three bead-cultured pearls were used to fill the void and the opening was plugged with a smaller nonbead-cultured pearl. Source: GIA @topic:5


Title: Book Review: Exotic Gems, Volume 4: How to Identify, Evaluate & Select Jade & Abalone Pearls Abstract: By Renée Newman, softcover, 136 pp., publ. by International Jewelry Publications, Los Angeles, 2016, $19.95.

Exotic Gems, Volume 4 is the latest book in a series focusing on jadeite, with a bonus section on abalone pearls. This volume is geared for the consumer and the professional, but is accessible to jewelers, sales associates, gem dealers, collectors, gemology students, and appraisers. Its 136 pages are visually rich, with 338 color photos, diagrams, and tables. Author Renée Newman has packed the book with information about jadeite’s historical significance, countries of origin, and defining characteristics.

	Jadeite is inherently inscrutable. There are so many factors to be considered—color, luster, transparency, to name a few—along with confusion over its counterpart nephrite and the many jade imitations on the market. The two large charts in the "Imitation or Real Jade?" chapter help the reader to discern jadeite’s unique characteristics, such as refractive index reading, specific gravity, and hardness. The charts help to separate the simulants from jadeite and nephrite. The chapter ends with visual clues: closed-back settings, warm surface, and a low sales price are among the many hints.

	The "Treated or Untreated" chapter indicates the instruments in a gemologist's arsenal can be used to identify treatments, such as the Chelsea filter, and what the results express about the integrity of the material. Ms. Newman further delves into advanced detection tools are found in gemological laboratories, including various spectrometers, thereby making the laboratory reports more comprehensive.

	Jadeite is traditionally sold by the piece, rather than by carat weight, and the chapter on price factors discusses at length the three quality factors that have the most impact on jadeite values: transparency/translucency, treatment, and color saturation and tone. The next five chapters explore jade sources and its impact on world cultures such as China, Myanmar (Burma), Guatemala, Canada, and the United States. Minor sources of jadeite such as Russia, New Zealand, and Taiwan are covered briefly, with a review of the region’s history mining or cultural uses of jade. Color photos give great examples of jadeite from these areas.

	The last chapter concentrates on abalone pearls, an increasingly respected colorful pearl product. Sourcing, pricing factors, gemological characteristics, and general appreciation for the material are explained with Renee Newman's typical thoroughness.

	For the consumer, there are sections on historical significance, therapeutic powers and, of course, advice on caring for jadeite, nephrite, and abalone pearl. For the professional, The book helps professionals navigate the complexities of "exotic" jadeite through increased awareness of a commonly imitated, treated, enhanced, and faked gemstone. Source: GIA @topic:13


Title: The Geographic Origin of Diamonds, Sapphire from China, and Pigments Sourced from Gem Materials Abstract: Welcome to the Fall 2022 issue of Gems & Gemology! This issue delivers fascinating new content, offering four feature articles ranging from the hot topic of diamond origin to an in-depth look at the role gem materials have played in art throughout history.
“…the only definitive method to establish diamond origin depends on preserving and retaining origin information from the time of mining”
In our lead article, Evan Smith and coauthors explore the methods and challenges associated with determining the geographic origin of diamonds. Current approaches have attempted to associate trace element characteristics with specific origins, but there is still no scientifically robust method to determine the geographic origin of a given diamond. The authors conclude that the only definitive method to establish diamond origin depends on preserving and retaining origin information from the time of mining rather than determining it analytically.
Next, authors Yimiao Liu and Ren Lu of the Gemmological Institute, China University of Geosciences in Wuhan, examine sapphire from a lesser-known source in Muling, China. Comparing their samples with sapphire from well-known sources worldwide, the authors report on the quality, gemological characteristics, and origin-related features with comprehensive analytical results. They determine that Muling sapphire is from a more diverse geological environment than the sapphire from many other regions.
In our third article, join Britni LeCroy for a lesson in art history as she researches pigments historically sourced from gem materials. Covering hematite, azurite, malachite, lapis lazuli, bone, ivory, and cinnabar, the study investigates the evolution of pigments in a wide array of artistic mediums, from ancient cave drawings to modern paintings.
Finally, Yicen Liu and coauthors present their spectroscopic investigation of the color mechanism of pink spinel reportedly from Kuh-i-Lal in the Pamir Mountains of Tajikistan. To determine the cause of color, the group examines the mechanism of color change from room temperature to 1000°C using spectroscopic techniques and trace element analysis.
Meanwhile, our regular features continue to deliver interesting findings from all over the globe. Highlights from the Lab Notes section include an exceptional natural-color 1.21 ct red diamond, a gota de aceite–like effect in a Brazilian emerald, and the first report of a natural pearl discovered in a Telescopium shell. Micro-World is packed with illuminating observations from the inner landscapes of gemstones, offering a glimpse at an unusual brightly colored purple fluid in quartz, “smoke ring” inclusions in heated blue sapphire, and a large orange rutile inclusion in a “chameleon” diamond. Diamond Reflections returns with an exploration of fluid inclusions in natural diamond, highlighting the scientific value these inclusions offer from the great depths of the earth. In Gem News International, you’ll find an update from Mozambique’s ruby mines, a report on the first-ever Turquoise United conference in Albuquerque, and highlights from current gem and mineral exhibits at the San Diego Natural History Museum and the Perot Museum of Nature and Science in Dallas.
We hope you enjoy the latest issue of Gems & Gemology! Source: GIA @topic:1


Title: Oscar Jewels: Diamonds, Opaque Gems and Yellow Gold Shine Abstract: Best Actress winner Cate Blanchett stunned in white opal and diamond chandelier earrings by Chopard. Photo courtesy of JoeSeer/ Shutterstock.com

                      Like host Ellen DeGeneres, who donned a series of black and white tuxedos, many celebrities attending the 2014 Academy Awards opted for classic black, dark blue, or pale-hued gowns such as beige, off-white, or white. Bold colors and printed fabrics were almost absent from the red carpet, which gave the stars and their stylists the opportunity to select an abundance of statement necklaces and earrings that took center stage.

Black played a role in providing a setting for some truly outstanding gems. Charlize Theron took the conventional “little black dress” to the next level in a gown with almost invisible tulle straps. Her plunging neckline framed a stunning necklace from the Harry Winston Incredibles collection featuring a 31 carat D-color, IF-clarity center diamond. “August: Osage County” Best Supporting Actress Oscar nominee Julia Roberts chose diamond earrings, rings, and stackable bracelets by Bulgari to complement her black lace sleeveless peplum gown.

Olivia Wilde gave new meaning to maternity style in an elegant black and white gown. She added glamour to the simplicity of her attire with Lorraine Schwartz jewels: a pair of white jade and diamond drop earrings in platinum; black and white jade, diamond and platinum bangles; and a black and white diamond and platinum ring.

	Charlize Theron’s 31 carat diamond necklace from the Harry Winston Incredibles collection took center stage at the 2014 Oscars. Photo courtesy of JoeSeer/ Shutterstock.com
Platinum made an impression among this year’s attendees. Anne Hathaway wore platinum bracelets with 100 carat total weight of diamonds, a square-cut emerald and platinum ring, and diamond stud earrings by Neil Lane to complement her black silk crepe, crystal-embellished column dress. Best Actress nominee Sandra Bullock opted for a pair of platinum and pear-shaped diamond cluster climber earrings by Lorraine Schwartz.

Blue, in various tones and saturations, was one of the most represented hues on the red carpet, and jewelry reflected the trend. Amy Adams, Best Supporting Actress nominee for her performance in “American Hustle,” accessorized with statement pendant earrings of rhodochrosite, lapis, turquoise and diamonds in yellow gold, as well as a fire opal ring, all from Tiffany & Co.

Many attendees of the 2014 Oscars wore beige or soft-colored gowns, which were particularly conducive to showcasing opaque or diamond jewelry. “Blue Jasmine” star and Best Actress winner Cate Blanchett revived an era of classic Hollywood glamour with a form-fitting beige sequined gown. Her Chopard jewels included a large pair of 33-carat iridescent white opal and diamond chandelier earrings, a Toi et Moi diamond ring, and yellow diamond line bracelets.

Calista Flockhart stepped on the red carpet in an ivory cap-sleeved gown she adorned with round emerald and diamond cluster earrings by Jacob & Co. jewels. Naomi Watts accessorized her lace and sequined snowy white gown with a Bulgari spider-web necklace.

Not to be outdone by their female counterparts, men sported some notable accessories this year. Ice-skater and Olympic commentator Johnny Weir wore a pave-set diamond ring by Le Vian and a Demarco diamond brooch. Singer Pharrell, who performed the Oscar-nominated “Happy,” turned to Lorraine Schwartz for gold and yellow diamond studs; he also wore Be Happy gold bracelets, along with Ofira Jewels gold ball bracelets with multicolor diamonds. Brad Pitt’s yellow gold and diamond tuxedo buttons and cufflinks by Robert Procop coordinated with partner Angelina Jolie’s ensemble. Jolie, the 2014 Humanitarian Award recipient, donned a sleek metallic beaded gown accented by a pair of 42 carat total weight diamond and yellow gold bezel-set earrings by Robert Procop Exceptional Jewels.

Last but not least, yellow gold jewelry made a strong comeback. Kristin Chenoweth paired her gold corset outfit with yellow gold Neil Lane jewels, including pinwheel diamond earrings, a chain bracelet, and a diamond ring. Best Supporting Actress winner Lupita Nyong’o accessorized her ethereal light-blue pleated gown with Fred Leighton jewels: a dazzling gold and diamond headband, a 19th-century coiled yellow gold and diamond snake bracelet, yellow gold and rose-cut diamond crescent earrings, several diamond rings, and a 1960s turquoise and diamond gold ring.

View Gallery Source: GIA @topic:6


Title: Gem-Quality Synthetic Diamonds Grown by a Chemical Vapor Deposition (CVD) Method Abstract: Brown-to-gray and near-colorless single-crystal type IIa synthetic diamonds grown using a chemical vapor deposition (CVD) technique by Apollo Diamond Inc. have gemological properties that are distinct from those of both natural diamonds and HPHT-grown synthetic gem diamonds. The tabular crystals typically range up to 1 ct or more and a few millimeters thick, and consist of an overgrowth on a natural or synthetic diamond substrate. Faceted CVD synthetic diamond usually cannot be separated from natural diamond with standard gemological techniques; although when portions of the substrate are still present, an experienced gemologist may be able to recognize differences in luminescence or color between the overgrowth and substrate. In all cases, however, the CVD synthetic diamonds examined to date could be identified in a gemological laboratory by the combination of a strong orangy red fluorescence seen with the De Beers DiamondView deep-ultraviolet imaging system, a characteristic anomalous birefringence (strain) pattern, and distinctive features in their infrared absorption spectra (e.g., at 3123 cm-1) and photoluminescence spectra (strong 575 and 637 nm emissions, a doublet at 596 and 597 nm, and a line at 737 nm). Source: GIA @topic:4


Title: Color Grading of Colored Diamonds in the GIA Gem Trade Laboratory Abstract: The GIA Gem Trade Laboratory (GIA GTL) presents the system it uses to color grade faceted colored diamonds, and the information on which it is based. This system involves a trained grader establishing the characteristic color in a standardized illumination and viewing environment, using various reference materials for color comparison. Here, the Munsell color system is used to illustrate the relationships between the different color terms used. GIA GTL "Fancy grade" nomenclature for colored diamonds has been expanded to better address all colors. This color terminology will soon be incorporated into a new GIA GTL colored diamond report. Source: GIA @topic:4


Title: The Gemological Properties of Russian Gem-Quality Synthetic Yellow Diamonds Abstract: A group of gem-quality synthetic diamonds, grown in Russia using the "BARS" apparatus and now being sold for jewelry use, is examined. Study of seven yellow (five faceted, 0.11-0.51 ct) to orangy or brownish yellow as-grown samples, and three yellow to greenish yellow samples (all faceted, 0.14-0.21 ct) reportedly treated by post-growth annealing at high pressure and temperature, revealed distinctive gemological properties. These include: color and luminescence zoning, metallic inclusions, graining, and sharp visible-range absorption bands (some seen with a handheld spectroscope). Source: GIA @topic:4


Title: De Beers near Colorless-to-Blue Experimental Gem-Quality Synthetic Diamonds Abstract: Examination of five small boron-doped synthetic diamonds, grown by De Beers researchers for experimental purposes, reveals some diagnostic features not reported in previous studies of gem-quality synthetic diamonds. The presence of internal growth sectors that are blue, yellow, or near colorless has produced faceup colors in three faceted stones that vary from near colorless to bluish-greenish gray to blue. Because they look so different from previously reported De Beers synthetic diamonds, such faceted synthetics could go unrecognized without careful gemological testing should they ever become commercially available. Source: GIA @topic:4


Title: The Gemological Properties of the De Beers Gem-Quality Synthetic Diamonds Abstract: Gem-quality synthetic diamond crystals weighing up to 11 ct have been grown in limited numbers at the De Beers Diamond Research Laboratory since the 1970s. These crystals have been produced strictly on an experimental basis and are not commercially available. Examination of a group of 14 brownish yellow, yellow, and greenish yellow synthetic diamonds reveals distinctive gemological properties: uneven color distribution, geometric graining patterns, metallic inclusions, and, in most cases, fluorescence to shortwave but not to long-wave UV radiation. Source: GIA @topic:4


Title: The Gemological Properties of the Sumitomo Gem-Quality Synthetic Yellow Diamonds Abstract: The distinctive gemological properties of the gem-quality synthetic yellow diamonds grown by Sumitomo Electric Industries are described. These synthetic diamonds, produced on a commercial basis, are grown as deep yellow single crystals in sizes up to 2 ct. The material is currently marketed for industrial applications only, in pieces up to about 0.40 ct. The synthetic diamonds can be distinguished by their ultraviolet fluorescence (inert to long-wave; greenish yellow or yellow to short-wave); their unusual graining, veining, and color zonation under magnification; and the absence of distinct absorption bands in their spectra. Source: GIA @topic:4


Title: Challenges in Identifying Drilled Keshi Pearls Abstract: Lot of 40 drop and oval pearls, with the smallest weighing 0.62 ct and measuring 5.17 × 4.16 mm and the largest weighing 2.95 ct and measuring 9.53 × 6.65 mm. Photo by Gaurav Bera.
Distinguishing natural pearls from non-bead cultured (NBC) pearls, commonly referred to as “keshi” in the industry, has become increasingly complex. While traditional methods such as radiomicrography were once reliable for the identification of South Sea keshi NBC pearls, recent advances in pearl drilling techniques have rendered these conventional approaches less foolproof. As a result, there is a growing need for advanced data analysis to study the internal structure, chemistry, and other spectral features associated with the mollusk origin to enable reliable separation of natural from NBC pearls.
To further examine challenging structures, GIA’s Mumbai laboratory borrowed pearls represented as natural from a known source. The lot consisted of 40 white to light cream drop and oval pearls (28 undrilled, 7 drilled, and 5 partially drilled). The smallest weighed 0.62 ct and measured 5.17 × 4.16 mm, and the largest weighed 2.95 ct and measured 9.53 × 6.65 mm (see above). The pearls all looked new, with smooth, high-luster surfaces that were free of blemishes. Under 40× magnification, the surfaces showed well-defined overlapping fine aragonite platy structures that accounted for their silky surface sheen.
Energy-dispersive X-ray fluorescence revealed manganese levels ranging from below detection level to 33.80 ppm and higher strontium levels ranging from 1756 ppm to 3364 ppm. Most of the pearls showed an inert reaction under X-ray fluorescence, while some had a weak yellowish green reaction. The latter reaction accounts for the higher manganese levels recorded. The pearls emitted medium to strong yellowish green fluorescence under long-wave ultraviolet light and a similar weaker reaction under short-wave UV. Based on these analyses, a saltwater origin was confirmed for all of the pearls.
Examined with real-time X-ray microradiography (RTX), most of the pearls showed minimal growth arcs, and some revealed faint linear-looking features visible only in certain directions. External and internal features aroused suspicion that these pearls were NBC. Another important observation was related to the size and length of the drill holes. Given the importance of maintaining weight, it is customary to drill drop and oval pearls to approximately one-third of their length. These pearls, however, were drilled to a depth that covered more than two-thirds of their length, while others were fully drilled with oversized drill holes. This indicated the pearls were drilled with the specific intention of concealing internal structures (Summer 2023 Lab Notes, pp. 218–220).

RTX imaging was performed for all the pearls in three directions, with careful alignment along their lengths to detect the presence of any linear feature or its remnants resulting from the drilling process. In most cases, proving a cultured origin only through RTX imaging was challenging. Consequently, the structures were studied using X-ray computed microtomography (μ-CT) analysis, as shown in table 1. In pearls 1 and 2, both undrilled, RTX imaging revealed a few distinct growth arcs, but not much was visible at their centers. Pearl 1 exhibited a small suspicious linear feature along its length, while pearl 2 did not. Interestingly, μ-CT analysis revealed an elongated linear feature running along the length of both pearls, accompanied by a few growth arcs, with the outer nacre lacking many growth features.
Pearls 3 and 4 were partially drilled, and both exhibited drill holes of unusual length and size compared to those observed in natural pearls. RTX imaging showed a few growth arcs toward the outer nacre and minimal growth at the center around the drill hole area. When aligned along their lengths, remnants of a linear feature crossing the drill hole were clearly visible in pearl 3, whereas pearl 4 did not show any evidence of the linear feature. Similarly, μ-CT analysis on both pearls revealed remnants of the linear feature toward the end of their drill holes, indicating an unsuccessful attempt to remove the linear features. Pearl 5, which was fully drilled, had fine growth arcs along its shape in RTX imaging, with a faint shadow feature running parallel to the drill hole. Through μ-CT analysis, a linear feature near the drill hole area was clearly visible.
As observed, structures from the samples closely resembled those observed in South Sea NBC pearls from the Pinctada maxima mollusk (A. Homkrajae et al., “Internal structures of known Pinctada maxima pearls: Cultured pearls from operated marine mollusks,” Fall 2021 G&G, pp. 186–205). In particular, drop and oval pearls from this mollusk should be carefully examined to avoid misidentification as natural due to the absence of structure if only examined under RTX imaging.
Natural drop and oval pearls are highly valued, and those with exceptional appearance and size are not easy to find. In recent decades, some members of the trade have attempted to conceal the linear features visible in South Sea keshi pearls using film or dental X-ray machines and subsequent drilling to remove any evidence. This often results in remnants of the linear features being left behind, as observed in these samples. These remnants can only be identified by carefully aligning the pearls in RTX imaging and through μ-CT analysis. Such subtle features can be easily overlooked during testing, potentially leading to their misinterpretation and misidentification as natural pearls. It is therefore essential for the trade to remain alert and informed about these increasingly frequent practices. Source: GIA @topic:5


Title: Pearls from the Placunidae Family (Windowpane Oysters) Abstract: Figure 1. Two loose pearls from windowpane oysters submitted to the Bangkok laboratory and a mixed strand containing mostly windowpane and Pteria species pearls submitted to the New York laboratory. Photo by Jian Xin (Jae) Liao.
Nacreous pearls are commonly constructed from layers of stacked aragonite platelets. In recent years, however, GIA laboratories in Bangkok, Hong Kong, Mumbai, and New York have reported unusual pearls with a “nacreous-looking” surface caused by the presence of calcite instead of aragonite (figure 1) (Winter 2022 Lab Notes, pp. 477–478). These findings piqued curiosity and prompted a more comprehensive study involving research samples and mollusk shells. The study indicated that these calcite “nacreous-looking” pearls were likely produced by mollusks belonging to the Placuna genus in the Placunidae family.
These marine bivalve mollusks, commonly known as “windowpane oysters,” are found along the coasts of India, Malaysia, China, and the Philippines (C.M. Yonge, “Form and evolution in the Anomiacea (Mollusca: Bivalvia)-Pododesmus, Anomia, Patro, Enigmonia (Anomiidae): Placunanomia, Placuna (Placunidae, fam. Nov.),” Philosophical Transactions of the Royal Society of London, Vol. 276, No. 950, 1977, pp. 502–503). Placuna mollusks are widely valued for their thin, durable mica-like translucent flat shells, called capiz or kapis shells, which were once a popular alternative to glass and often used as windowpanes and decorations. Although the mollusks were also known to produce small pearls, these were not commercially available until recent decades (C.T. Achuthankutty et al., “Pearls of the windowpane oysters, Placuna placenta,” Mahasagar, Vol. 12, No. 3, 1979, pp. 187–189).

Figure 2. Characteristic surface features of mosaic pattern (A) and botryoidal structure (B) were observed on a pearl from the necklace in figure 1, compared to the typical nacreous-looking surface of fingerprint-like platy structure (C) on a loose pearl. Photomicrographs by Joyce Wing Yan Ho (A and B) and Artitaya Homkrajae (C); fields of view 7.19 mm, 9.61 mm, and 2.90 mm, respectively.
The studied pearls were variously shaped, measuring 3 to 8 mm and weighing 1 to 3 ct. Their bodycolors ranged from silver to brown or gray, with varying degrees of tone and saturation. Viewed under 40× magnification, they exhibited diagnostic surface features of distinctive mosaic or cellular patterns, and some appeared similar to a botryoidal structure. While these features are unique and have not been observed in typical nacreous pearls, a few of the samples also showed overlapping platelets typically found in nacreous pearls (figure 2).

Figure 3. Three variously colored windowpane shells and a brown windowpane pearl, shown in daylight (left) and long-wave UV light (right). Joyce Wing Yan Ho (top) and Kwanreun Lawanwong (bottom); shells courtesy of Robin Willis.
Under long-wave ultraviolet radiation, the pearls displayed a striking reddish fluorescence, particularly from the darker areas, which is comparable to the reactions observed on the windowpane oyster shells (figure 3). Similar reddish fluorescence has been observed in dark pearls from the Pteria species (L. Kiefert et al., “Cultured pearls from the Gulf of California, Mexico,” Spring 2004 G&G, pp. 26–38; Winter 2014 Lab Notes, pp. 295–296). However, it is important to note that the composition of calcite in windowpane pearls and aragonite in Pteria species can be distinguished using Raman spectroscopy.
Ultraviolet/visible (UV-Vis) reflectance and photoluminescence (PL) spectra from a laser excitation at 514 nm collected on the darker areas unveiled features similar to those typically observed in natural dark nacre of Pteria species, as well as Pinctada margaritifera and Pinctada maxima. The UV-Vis spectra exhibited absorption features at 405 and 495 nm. The 405 nm feature is related to uroporphyrin, a type of pigment responsible for gray to black tones in some pearl oyster species (Y. Iwahashi and S. Akamatsu, “Porphyrin pigment in black-lip pearls and its application to pearl identification,” Fisheries Science, Vol. 60, No. 1, 1994, pp. 69–71). All the samples showed bands at approximately 620, 650, and 680 nm in their PL spectra. These three PL bands have been commonly recorded in darker-colored pearls from the species mentioned above.
The saltwater origin was confirmed by energy-dispersive X-ray fluorescence spectrometry, which revealed very low or below detection limit manganese content and high levels of strontium ranging from 1000 to 1500 ppm.

Figure 4. RTX images revealed concentric growth rings typical of the internal structure commonly observed in windowpane oyster pearls.
Intriguingly, real-time X-ray microradiography (RTX) uncovered a distinct, evenly spaced fine concentric ring structure throughout most of the inner area of the pearls (figure 4). This structure was identified in most of the submitted pearls as well as the research samples studied. With these combined unique characteristic features, we were able to confidently conclude that the mollusks producing these pearls were from the Placunidae family. The first GIA Pearl Identification report for a pearl from this mollusk was issued in May 2023.
While most shelled mollusks have the potential to produce pearls, identifying the exact species remains a challenge, particularly with less commonly encountered species. Conducting continuous research studies with known samples from reliable sources is crucial and greatly assists in identification. As a continuation of this lab note, a comprehensive article featuring detailed studies will be prepared. Source: GIA @topic:5


Title: Parasite Channels in a Saltwater Natural Pearl Abstract: A parasite channel with a surface opening and finer branch-like etch channels in a natural saltwater pearl. Photomicrograph by Emiko Yazawa; field of view 4.79 mm.
Shell-boring parasitic worms are commonly found inside the shells of various pearl-producing mollusk species. Consequently, mollusk shells may exhibit elongated channels indicating the presence of such organisms. Recently, the author observed interesting parasite channel features inside an 8.25 mm natural saltwater pearl (see above) set in a brooch with other pearls and near-colorless stones.
Microscopic examination revealed a Y-shaped channel with numerous finer branches that likely formed as the parasite searched for a way out of the pearl. The channel opening was observed at the surface of the nacre, while the tunnel was located slightly beneath the nacre. This interesting feature matched the pearl’s internal structure, with a similarly Y-shaped structure visible in the X-ray image. Although such channels are often found in shells, they are rarer in pearls, and this channel’s unique shape and morphology are noteworthy. Source: GIA @topic:5


Title: Imitation Cat’s-Eye Pen “Pearls” Abstract: Figure 1. With fiber-optic illumination, a sharp, bright pink chatoyant band extends across the surface of a 1.89 ct dark brown button-shaped imitation pearl perpendicular to its internal fibrous structure. Photo by Robert Weldon/GIA.

	Chatoyancy is an optical phenomenon commonly seen in gemstones that have an abundance of parallel solid or hollow long acicular inclusions in which an eye-like band is produced when viewed in strong light. Fine cat’s-eye gemstones of various mineral species are prized; however, natural chatoyancy in pen pearls would be an extraordinary occurrence. During a recent study on reportedly non-nacreous pearls from the Dr. Eduard J. Gübelin Collection, the author found three dark brown button-shaped samples stated to be from a Pinna species mollusk. All three samples displayed an attractive cat’s-eye effect when illuminated under a fiber-optic light or any single white light (figure 1). In each specimen, the chatoyant band manifested as a single bright pink line extending across the surface in a direction perpendicular to the internal fibrous structure.

	Evidence of human manipulation includes fine linear features present in random directions across cellular structures; these are proof of work carried out during the fashioning of the samples into cabochons. Microscopic examination revealed the fibrous structure as numerous well-formed, minute parallel acicular crystals. Infrared spectroscopy subsequently confirmed the crystals to be calcite. The calcite was arranged in a vertical columnar orientation rather than in a radial and concentric structure characteristic of non-nacreous Pinna (pen) pearls, which led to further doubts concerning the “pearl” identity of the samples.

	Microradiography of all three samples revealed tight internal structures. The obvious radial structures that would be expected in pen pearls were not observed (N. Sturman et al., “Observations on pearls reportedly from the Pinnidae family (pen pearls),” Fall 2014 G&G, pp. 202–215). Based on its external and internal features, this material was almost certainly the same type of imitation pearl previously reported in G&G (Winter 2011 GNI, pp. 330–332).

	Fluorescence images taken of one specimen using a polarizing microscope and an ultraviolet excitation filter with a wavelength range of 330–380 nm (figure 2, left) reveal a prominent banded structure at right angles to the calcite columns. When viewed at right angles to their lengths under the same conditions, the long, thin calcite crystals reveal a hexagonal cross-section, creating a striking mosaic or cellular pattern (figure 2, right). The cells varied in form, and their approximate diameters ranged from 15.50 to 38.00 microns.

	Figure 2. Fluorescence images reveal banded features, typical of shell, at right angles to the vertical columnar structure of the calcite crystals (left). A mosaic pattern (right) is apparent looking down the hexagonal cross-section of the calcite columns. Photomicrographs by Artitaya Homkrajae; fields of view 2.88 mm and 1.44 mm, respectively.

	These samples were appealing for the magnificent kaleidoscopic colors that were seen using fiber-optic illumination (figure 3). The semitranslucent to translucent nature of the crystals allowed light to pass through and produce vibrant, colorful scenes owing to the interference of the light rays that were reflected and refracted when interacting with the crystals. As one can see, exploration of the micro-world is not only important to forensics—it can also be quite beautiful.

	Figure 3. Under fiber-optic light, magnificent reflective kaleidoscopic colors of pink, yellow, and green are revealed from the well-formed acicular calcite crystals after mineral oil is applied to the sample’s surface. Photomicrograph by Artitaya Homkrajae; field of view 3.57 mm. Source: GIA @topic:5


Title: Unusual Large Nacreous Pen Pearls Abstract: Figure 1. Left to right: Three large nacreous pearls weighing 24.47 ct (pearl 1), 36.58 ct (pearl 2), and 36.70 ct (pearl 3). Photo by Gaurav Bera.
GIA’s Mumbai laboratory has received a wide variety of interesting pearls for identification since opening its pearl testing department in May 2022. One recent submission included three baroque pearls weighing 24.47 ct, 36.58 ct, and 36.70 ct and measuring 28.22 × 18.04 × 9.84 mm, 28.79 × 19.48 × 10.40 mm, and 32.49 × 20.50 × 18.35 mm, respectively (figure 1).

Figure 2. Features characteristic of pen pearls shown on pearl 1. Left: Striated nacre on the white and light gray areas; field of view 3 mm. Right: Non-nacreous structure consisting of a network of cells observed on the dark brown region; field of view 1.3 mm. Photomicrographs by Karan Rajguru.
Visual observation revealed a combination of nacreous and non-nacreous surface structures. The pearls were white to light gray and brown and exhibited a strong orient with variations in saturation and tone. In some areas, their surface quality was poor to slightly damaged. Viewed under 40× magnification, the white to light gray areas displayed a striated and much finer form of nacre growth structure than observed in most nacreous pearls from Pinctada and Pteria mollusks (figure 2, left). The dark brown areas showed a characteristic non-nacreous cellular structure consisting of a network of closely packed cells (figure 2, right). These observations were consistent with previous studies (N. Sturman et al., “Observations on pearls reportedly from the Pinnidae family (pen pearls),” Fall 2014 G&G, pp. 202–215).
Raman analysis using a 514 nm and 830 nm laser excitation was performed on different surface areas. The nacreous areas on all three pearls showed a doublet at 701 and 704 cm–1 and a peak at 1085 cm–1 indicative of aragonite. However, the brown non-nacreous areas on pearls 1 and 2 showed a peak at 712 cm–1 indicative of calcite. Photoluminescence analysis for all pearls revealed weak bands at 620, 650, and 680 nm, suggesting natural coloration (S. Karampelas et al., “Raman spectroscopy of natural and cultured pearls and pearl producing mollusc shells,” Journal of Raman Spectroscopy, Vol. 51, No. 9, 2020, pp. 1–9).

Figure 3. RTX images, μ-CT images, and photomicrographs of the three pearls. The dark organic-rich voids are marked with red arrows, and the external weakened organic-rich areas on the surface are marked with blue arrows. Photomicrographs by Karan Rajguru; fields of view 9 mm (pearl 1) and 16.3 mm (pearls 2 and 3).
Despite the possibility of these three being large blister pearls, closer examination of them did not reveal any indications of previous attachment to the shell such as signs of heavily worked or sawn areas (“Natural shell blisters and blister pearls: What’s the difference?” GIA Research News, August 26, 2019). The lack of such features indicated they were whole pearls. The few small organic-rich areas visible on the pearls’ surfaces (figure 3), along with the non-nacreous and nacreous surfaces, were possibly damaged because the organic-rich material weakened over time.
X-ray fluorescence analysis revealed an inert reaction for all the samples. Energy-dispersive X-ray fluorescence spectrometry showed very low manganese levels (below detection limit in both pearls 1 and 2 and 9.9 ppm in pearl 3) and high strontium levels (1535 ppm, 1682 ppm, and 1250 ppm, respectively). Both analytical results were indicative of a saltwater origin.
Real-time microradiography (RTX) and X-ray computed microtomography (μ-CT) revealed a combination of large voids with some dark organic-rich material surrounded by white walls and fine growth arcs (figure 3). A chambered effect was notable in all three samples. The complex appearance of the voids differed from those observed in most non-bead cultured pearls from the Pinctada species, yet they were similar to nacreous and non-nacreous pen pearls reported in Sturman et al. (2014). The outline of the voids was consistent and followed the shape of the pearls’ surfaces, unlike the irregular and inconsistent voids found in the non-bead cultured pearls. In addition, μ-CT imaging revealed light gray and dark gray areas associated with the presence of organic matter within the voids, a characteristic commonly observed in natural pearls (“Non-bead cultured pearls from Pinctada margaritifera,” GIA Research News, April 27, 2018).
Based on the external and internal structure analysis, the samples were identified as natural pearls from the Pinnidae family (pen pearls). Visual observation, combined with the absence of any evidence of commercial culturing, played a crucial role in their identification. Their size and appearance further supported their classification as natural whole pearls. Source: GIA @topic:5