Title: 2015 Sinkankas Symposium Abstract: This Mexican opal in rhyolite is from the Iris mine, Hacienda Esperanza, in Querétaro. The Mineralogical and Geological Museum at Harvard University, received this specimen as a donation from James Garland in 1892, facilitated by George Frederick Kunz. It measures 7 × 6 cm and is the finest opal in the museum’s collection. Photo by Robert Weldon/GIA, courtesy of the Mineralogical and Geological Museum, Harvard University.

The thirteenth annual Sinkankas Symposium was held April 18 at GIA headquarters in Carlsbad, California. Co-hosted by the Gemological Society of San Diego, GIA, and Pala International, the event drew a capacity crowd eager to learn about opal.

After welcoming remarks from organizer Roger Merk, the morning presentations began with an overview by Dr. Eloïse Gaillou (Paris School of Mines) on geology, color, and microstructure. Andrew Cody (Cody Opal, Melbourne) chronicled the Australian opal market before delving into fossilized specimens. Dr. Raquel Alonso-Perez (Mineralogical and Geological Museum, Harvard University, Cambridge, Massachusetts) spoke on the history of the museum and shared photos and data of specimens from its collection. Photographer Jack Hobart showed superb images from his extensive database of Mexican opals. Bill Larson (Pala International, Fallbrook, California) described his personal collection of Mexican, Australian, Ethiopian, and Brazilian opals, many of which were on display throughout the campus.

The afternoon sessions began with a presentation by Alan Hart (Natural History Museum, London) on the museum’s opal collection. Noted lapidary Meg Berry (Megagem, Fallbrook, California) described various techniques for cutting and carving. Buying guide author Renée Newman (International Jewelry Publications, Los Angeles) discussed the jewelry uses of matrix and common opal. Helen Serras-Herman (Gem Art Center, Rio Rico, Arizona) followed with additional insight on the many varieties of common opal. Robert Weldon (GIA, Carlsbad) discussed the challenges of photographing opal’s shifting flashes of color, as well as the instruments and post-production techniques best suited to the task. Nathan Renfro (GIA, Carlsbad) looked at the gem’s internal features and the wide range of mineral inclusions that create vibrant, colorful scenes. Dr. George Rossman (Caltech, Pasadena, California) examined causes of color and offered closing remarks.

Sapphire will be the theme of the 2016 symposium. For more information on the event or to purchase the proceedings volume, visit www.sinkankassymposium.net. Source: GIA @topic:1


Title: Transparent Rhodonite with Clarity Enhancement Abstract: Figure 1. A large 11.32 ct rhodonite showing vivid orangy red color and visible needle-like inclusions. Photo by Diego Sanchez.

Recently the Carlsbad laboratory received a transparent vivid orangy red rhodonite for identification service (figure 1). Standard gemological testing revealed a double refractive index of 1.727–1.738, and a specific gravity of 3.66 was obtained. The stone was inert to both long-wave and short-wave UV light. These properties were consistent with rhodonite (R. Webster, Gems, 5th ed., rev. by P.G. Read, Butterworth-Heinemann, Oxford, 1994, p. 365). Rhodonite, with the formula CaMn3Mn[Si5O15] (mindat.org), is a member of the triclinic crystal system and occurs in manganese-bearing rocks.

Figure 2. These scattered randomly oriented curved needle-like inclusions are likely the mineral cummingtonite. Photomicrograph by Nathan Renfro; field of view 2.56 mm.

Figure 3. Low-relief fractures with high-relief trapped gas bubbles offer proof of clarity enhancement in the faceted transparent rhodonite. Photomicrograph by Nathan Renfro; field of view 3.12 mm.
During microscopic analysis, scattered curved needle-like inclusions (figure 2) were observed as well as fractures with clarity-enhancing residue that also contained high-relief areas where gas bubbles were trapped (figure 3). Although the source of this particular rhodonite is unknown, curved needle inclusions in transparent rhodonite from Brazil were previously reported in 2004 and 2008 (Fall 2004 GNI, pp. 260–261). The appearance of the needle-like inclusions was consistent with those previously identified as cummingtonite (P. Leverett et al., “Ca-Mg-Fe-rich rhodonite from the Morro da Mina mine, Conselheiro Lafaiete, Minas Gerais, Brazil,” The Mineralogical Record, 2008, Vol. 39, pp. 125–130).
In addition to Brazil, Australia is a well-documented source of gem-quality rhodonite (P. Millsteed et al., “Inclusions in transparent gem rhodonite from Broken Hill, New South Wales, Australia,” Fall 2005 G&G, pp. 246–254). Despite being clarity enhanced, this saturated gem-quality rhodonite was exceptional for its bright vivid color, transparency, and size. Source: GIA @topic:2


Title: Copper-Bearing Minerals of Colorado Abstract: Between 1868 and 1922, Colorado produced almost 260 million pounds of copper. Nearly 100 million pounds came from the Leadville district, with another 50 million mined in San Juan County. During the 20th century, the Gilman district surpassed Leadville in total copper production, yielding more than 210 million pounds. Total Colorado production prior to 1958 reached 585 million pounds.

In this article, 106 minerals from the Colorado Mineral Belt (COMB) are listed and 39 are discussed in the text. The Eagle mine in the Gilman district is probably Colorado’s most prolific producer of mineral specimens. Gilman pyrite, sphalerite, chalcopyrite, siderite, barite, and galena are found in collections all around the world. The Sweet Home mine in Buckskin Gulch, a source of world-famous rhodochrosite, is also well known for fine specimens of two copper-bearing minerals, bornite and tetrahedrite. The Creede mining district is one of the most extensively studied mineral deposits and volcanic areas in the country. A detailed study of the Creede ore deposits has been conducted in an attempt to develop a model for epigenetic precious-metal deposits. Summitville is well known as the source of the state’s finest covellite specimens. The Good Hope mine is the type locality for four copper-bearing tellurides: rickardite (Cu3-xTe2), weissite (Cu2-xTe), vulcanite (CuTe), and cameronite (AgCu7Te10). Turquoise was mined from the King mine deposit in Conejos County and from the Chief mine in the St. Kevin district of Lake County.

The state of Colorado has produced some significant copper-bearing mineral specimens. Most of its copper minerals are sulfides and sulfosalts, with chalcopyrite the most common copper-bearing mineral.

Abstracted by Guy Lalous Source: GIA @topic:1


Title: Leigha: The Creation of a Three-Dimensional Intarsia Sculpture Abstract: Traditional gem intarsia, essentially flat interlocking mosaic work, is generally restricted to two-dimensional surfaces. Taking intarsia into three dimensions “in the round” requires the use of new techniques. This article illustrates the process of creating a contemporary three-dimensional intarsia sculpture. The skirt in Leigha was executed with over 800 separate pieces that averaged 1 to 2 mm in thickness. As the skirt is over 12 inches (30 cm) long, the necessary tensile strength to hold the pieces together required the use of the relatively new ultraviolet-curing cements, as well as structural design elements that would not be concerns in two-dimensional work. Inspired by an ancient Minoan motif, this intarsia sculpture illustrates some of the expanding possibilities for gem materials in the realm of gemstone objets d’art. Source: GIA @topic:9


Title: Romancing the Source: Montana Sapphires Abstract: Montana Sapphires

	Big sky, mountains, rivers, forests, deer, and sapphires. Join the GIA field team on a speedboat ride, visit sapphire mines, see sapphires pulled straight out of the jig, witness the science of heat treatment, and feel the passion of the miners and their customers.

	Montana’s rich history of gold and sapphire goes back to the late 1800s. A GIA field team traveled to the Rock Creek and Missouri River areas, where sapphire mining is still underway, to document the current industry and collect rough sapphire samples for our research reference sample collection. During our time in Montana we visited three mining operations, each with its own business model and its own exciting story. They all shared some common traits, however: amazing natural beauty and a passion for both the area and sapphires.

After a hard day of mining, Mike Cumley pulls a pastel green Montana sapphire right out of the jig—the first time it has been seen by anyone. Photo by Andrew Lucas/GIA, courtesy Spokane Bar Mine.

	Join us on this adventure and learn about the legacy of North American gemstones as we travel by speedboat with a mine owner down the Missouri River, witnessing historical mining sites and current operations. Then visit their mine (Spokane Bar Mine) with us, where we document the entire mining process, and feel the thrill at the end of the day when we pull rough sapphires right out of the jig. The Spokane Bar Mine usually mines for tourists, but on this day we had the entire mine to ourselves to collect samples for the GIA reference collection.

	Come to Gem Mountain and see passionate tourists wash and sort sapphire-bearing gravel to find rough sapphire treasure. Witness the rarely seen world of sapphire heat treatment as Chris Cooney demonstrates the art and science of heating Montana sapphires for the excited customers who have just found them. Join us at a new, well-funded commercial venture looking to start a new golden age of Montana sapphire production, with plans to market the rough to discerning jewelers and recreate the brand name of Rock Creek Montana sapphires.

	Come with us to Big Sky Country, where the land’s natural beauty is matched only by the beautiful sapphires it provides. Source: GIA @topic:1


Title: A Zircon with Strong Photochromic Effect Abstract: Figure 1. This 6.54 ct zircon showed a significant color change from medium light greenish blue (left) to very dark yellowish green (right) after exposure to long-wave UV for two minutes, and the color was reversible during the photobleaching process with LED white light. Photos by Kai-Yun Huang.
Recently, a 6.54 ct oval faceted gemstone with greenish blue color (figure 1, left) was sent to Taiwan Union Lab of Gem Research (TULAB) for identification. The specific gravity of this stone was 4.68, and the refractive index was over the limit of the refractometer. Microscopic observation showed strong birefringence. In addition to standard gemological testing, Raman spectroscopy and comparison with the zircon reference spectrum R050203 from the RRUFF database (figure 2) confirmed it was a zircon. It was particularly worth noting that this zircon showed a significant color change from greenish blue to very dark yellowish green (figure 1) when exposed to a long-wave ultraviolet lamp.

Figure 2. The stacked Raman spectra of the greenish blue zircon and a zircon reference spectrum from the RRUFF database; spectra are normalized and baseline-corrected.

Figure 3. Visible spectra of the zircon (after UV light exposure) during the photobleaching process were recorded every six minutes. The gradually decreasing spectral change implied that the color tended to stabilize.
To determine the extent of the color change and whether it was permanent or reversible, the zircon was first exposed to long-wave UV light for one minute and then under 10W white LED light for another minute (the light sources were placed approximately 3 cm away from the gemstone). After repeating this process several times with each exposure one minute longer than the previous time, we confirmed that the color changed from medium light greenish blue with strong saturation to a medium dark greenish yellow with lower saturation after two minutes of long-wave UV light exposure. However, the greenish yellow color gradually returned to the stable greenish blue color after photobleaching with LED white light for 30 minutes. Therefore, the stone was a photochromic zircon with reversible color change (as reported in N.D. Renfro, “Reversible color modification of blue zircon by long-wave ultraviolet radiation,” Fall 2016 G&G, pp. 246–251). After the color change reached its full extent under long-wave UV light, the zircon was analyzed by visible spectroscopy to record its continuous spectral change during the photobleaching process every six minutes (figure 3). The resulting spectra revealed that the light transmittance in the range between 450 nm and 550 nm gradually increased during the photobleaching process, and the greenish blue color finally returned to a stable state after 30 minutes.
Although this type of photochromic zircon has previously been reported, a zircon over 6 ct with such a significant photochromic effect is still rare and worth noting, especially since it exhibited a distinct difference in hue, tone, and saturation. Source: GIA @topic:3


Title: Combination of Phenomena in Star and Cat’s-Eye Color-Change Sapphire Abstract: Figure 1. This 20.49 ct star sapphire with a combination of phenomena exhibited a color change from violet (top) to purple (bottom). Side A is shown in these photos. Photos by Shunsuke Nagai.
The Tokyo lab recently examined a transparent 20.49 ct violet to purple color-change double cabochon sapphire, measuring 16.67 × 14.69 × 8.51 mm (figure 1) with a specific gravity of 3.99 and a spot refractive index of 1.77. Usually a star sapphire is only polished on one side, and the unpolished side does not show any phenomena. But this stone was polished on both sides, which resulted in a unique combination of phenomena. Side A displayed a six-rayed star. Side B also displayed a six-rayed star, but one line containing two of the rays was much stronger, which made the phenomenon reminiscent of a cat’s-eye.

Figure 2. Side A: Intersecting sets of parallel needle inclusions producing six-rayed asterism. Photomicrograph by Yusuke Katsurada; field of view 5.8 mm. Inset photo by Shunsuke Nagai. The photomicrograph is not aligned with the inset.
Chatoyancy is displayed when light reflects off a set of dense parallel elongated inclusions, such as needles; asterism occurs when such a set of inclusions is oriented in multiple directions. In the case of this stone, side A with the distinct six-rayed star had three sets of dense parallel needles and platelets close to the surface, intersecting at 60° angles (figure 2), which is common with six-rayed asterism. Side B also had three sets of these needles close to the surface, but the needles were more concentrated in one of the directions, producing a cat’s-eye effect (figures 2 and 3). Interestingly, the chatoyancy in Side B and one line of asterism in Side A are contributed by the same group of needles.

Figure 3. Side B: Set of parallel needle inclusions producing chatoyancy. Photomicrograph by Yusuke Katsurada; field of view 5.8 mm. Inset photo by Shunsuke Nagai. The photomicrograph is not aligned with the inset.
Although color-change star sapphire is not particularly rare, color-change cat’s-eye sapphire is far less common. Color-change sapphire with asterism on one side and chatoyancy on the other is without question a “phenomenal” gem. Source: GIA @topic:3


Title: Paraíba-Like Synthetic Sapphire Abstract: Figure 1. This 7.78 ct round brilliant and 4.90 ct cushion brilliant displayed a blue-green and green-blue color, respectively, that are reminiscent of Paraíba tourmaline. Photograph by Nathan Renfro.

Recently GIA’s Carlsbad laboratory received for identification two gemstones weighing 7.78 and 4.90 ct (figure 1) that showed a neon green-blue to blue-green color similar to that of Paraíba tourmaline. Standard gemological testing yielded a refractive index of 1.76–1.77 and a specific gravity of 4.00, consistent with corundum. Microscopic examination revealed curved color banding (figure 2) when viewed with diffused light and immersed in methylene iodide. Plato lines were observed when examining the stones parallel to the optic axis using cross-polarized light. Curved color banding and Plato lines are the two most important pieces of evidence to separate natural from flame-fusion synthetic sapphire using standard gemological testing. Also observed were wavy, finely textured clouds associated with the blue color zones (figure 3). Pink emission caused by the presence of trace-element magnesium was seen only with fiber-optic light. This stone does not react to fluorescent light.

Figure 2. Subtly curved color zoning was seen in this vibrant blue-green synthetic sapphire, confirming its flame-fusion origin. Photomicrograph by Forozan Zandi; field of view 5.33 mm.

Figure 3. Blue color zones in the Paraíba-like synthetic sapphires showed wispy clouds when observed with fiber-optic illumination. Photomicrographs by Forozan Zandi; fields of view 4.95 mm.
Trace-element chemistry measured by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) showed the presence of cobalt (105–158 ppmw, with detection limit at 0.652 ppmw), which is presumably responsible for the vibrant color, and magnesium (0.52–1.05 ppmw, with detection limit at 0.044 ppmw). Other trace elements such as Ni, Fe, Cr, and Ti were under the detection limits.
This is the first time GIA’s Carlsbad lab has examined flame-fusion synthetic sapphire with a color similar to Paraíba tourmaline. Source: GIA @topic:3


Title: Copper-Bearing Minerals of Colorado Abstract: Between 1868 and 1922, Colorado produced almost 260 million pounds of copper. Nearly 100 million pounds came from the Leadville district, with another 50 million pounds mined in San Juan County (Henderson 1926). During the twentieth century, the Gilman district surpassed Leadville in total copper production with more than 210 million pounds mined (Beaty, Landis, and Thompson, 1990). Total Colorado production prior to 1958 reached 585 million pounds (Del Rio 1960). In this article 106 minerals from the Colorado Mineral Belt (COMB) are listed and 39 are discussed in the text. The Eagle mine in the Gilman District is probably Colorado’s most prolific producer of mineral specimens. Gilman pyrite, sphalerite, chalcopyrite, siderite, barite, and galena are found in collections all around the world. The Sweet Home mine in Buckskin Gulch, source of world-famous rodochrosite, is also well known for fine specimens of two copper-bearing minerals bornite and tetrahedrite. The Creede mining district is one of the best-studied mineral deposits and volcanic areas in the country. A detailed study of the Creede ore deposits has been made in an attempt to develop a model for epigenetic precious-metal deposits. Summitville is well known as the producer of the state’s finest covellite specimens. The Good Hope mine is the type locality for four copper-bearing tellurides: rickardite (Cu3-xTe2); weissite (Cu2-xTe); vulcanite (CuTe), and cameronite (AgCu7Te10). Turquoise was mined from the King mine deposit in Conejos County and from the Chief mine in the St. Kevin district, Lake County.

The state of Colorado has produced some significant copper-bearing mineral specimens. Most of the Colorado’s copper minerals are sulfides and sulfosalts with chalcopyrite being the most common copper-bearing mineral.

Abstracted by Guy Lalous Source: GIA @topic:1


Title: Quartzite Bangle with Fuchsite Inclusions Abstract: Figure 1. This bangle, weighing 40.10 g, was identified as quartzite. Photo by Su Xu.
Jadeite jade bangles are always popular in the Chinese market. With high prices and rising demand for these products, a bangle with an appearance similar to jadeite was encountered recently.
The bangle was submitted to the National Gold-Silver Gem & Jewelry Quality Inspection Center (Sichuan) for identification. It was semitransparent with a white and green bodycolor resembling that of jadeite (figure 1). However, standard gemological testing showed a refractive index of 1.54 and a specific gravity of 2.67, values that were both significantly below those of jadeite and more in line with quartz. It showed no reaction under Chelsea filter. Using a polariscope, the material was found to be composed of polycrystalline aggregates. Microscopic examination revealed a granular aggregate structure and different microcrystalline mineral inclusions.

Figure 2. The bangle’s infrared reflectance spectrum exhibited characteristic peaks at 489, 537, 691, 778, 798, 1105, and 1178 cm–1 that are typical for quartzite.
The identity was further confirmed by analytical testing. Fourier-transform infrared (FTIR) reflectance spectroscopy showed peaks at 489, 537, 691, 778, 798, 1105, and 1178 cm–1 that were consistent with the characteristic spectrum of quartzite (sometimes referred to as “quartzose”) (figure 2) (X. Jin et al., “Gemmological and vibrational spectrum characteristics of micaceous quartzose jade ‘strawberry crystal’,” Journal of Gems & Gemmology, Vol. 23, No. 3, 2021, pp. 20–28). Energy-dispersive X-ray fluorescence (EDXRF) analysis revealed trace amounts of iron throughout and chromium exclusive to the green inclusions.

Figure 3. Photomicrographs and Raman spectra of inclusions in the bangle (black) and the reference spectrum in the RRUFF database (red): flaky fuchsite (A), brassy yellow pyrite (B), white dolomite (C), and brown rutile (D), shown in darkfield illumination (A) and reflected light (B–D). Photomicrographs by Su Xu; fields of view 0.2 mm (A), 1 mm (B), 0.8 mm (C), and 0.05 mm (D). See B. Lafuente et al. (2015), https://rruff.info/about/downloads/HMC1-30.pdf. Spectra are offset vertically for clarity.
These green flaky inclusions were slightly oriented. Raman combined with EDXRF analysis identified them as fuchsite (K(Al,Cr)2(AlSi3O10)(OH)2), a green chromium-colored variety of muscovite (figure 3A) (Fall 2013 GNI, pp. 183–184). Additionally, brassy yellow inclusions in a range of sizes were confirmed as pyrite (figure 3B) using Raman spectroscopy. Raman also identified some white blocky inclusions in a nearby area as dolomite (figure 3C), as well as some tiny brown rutile inclusions found as irregular, randomly scattered grains (figure 3D).

Figure 4. The UV-Vis spectrum of the green area showed two broad absorption bands centered at 423 and 600 nm in addition to a weak peak at 684 nm, indicating the presence of chromium.
Ultraviolet/visible spectroscopy corresponding to the green areas showed two broad absorption bands at about 423 and 620 nm, with a weak peak at 684 nm (figure 4). These features have been assigned to Cr3+ in fuchsite.
To our knowledge, fuchsite contained in quartzite is usually uniformly scattered in the form of tiny flakes. The uneven distribution of green fuchsite that resulted in patches of green in this bangle is noteworthy. The patchy green spots resemble the color concentrations often observed in jadeite. Despite the bangle’s resemblance to jadeite, gemological tests such as refractive index, microscopic observation, and infrared and Raman spectroscopy readily identify it. Source: GIA @topic:13


Title: Remarkably Large Iridescent Healed Fissures Resembling Play-of-Color in Sapphire Abstract: Figure 1. Large iridescent healed fissures in an oval mixed-cut sapphire. Photo by Shunsuke Nagai; field of view 12.20 mm

An interesting iridescent pattern was recently observed in a blue sapphire. Gemological properties and inclusions indicated a natural sapphire, and the UV-Vis-NIR spectrum suggested basalt-related origin (e.g., A.A. Levinson and F.A. Cook, “Gem corundum in alkali basalt: Origin and occurrence,” Winter 1994 G&G, pp. 253–262). The characteristic inclusions of blue color concentrations surrounding exsolution particles of rutile and numerous partially dissolved needles provide evidence of heat treatment (J.I. Koivula, “Internal diffusion,” Journal of Gemmology, Vol. 20, No. 7/8, 1987, pp. 474–477).

Figure 2. Iridescent dendritic healed fissures in sapphire. Photomicrographs by Makoto Miura; field of view 2.10 mm (left) and 1.30 mm (right).
Notably, this sapphire included unique large partially healed fissures showing attractive iridescence (figure 1). Similar iridescent healed fissures in sapphires and rubies from basaltic deposits have been previously documented (e.g., E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Vol. 3, Opinio Verlag, Basel, Switzerland, 2008, pp. 110 and 216–220); however, the healed fissures in this sapphire were remarkably large and visible to the unaided eye (figure 1). The fissures nearly parallel to the table facet showed variously colored iridescence with dendritic patterns (figure 2). Trapped air in a cemented plane of a doublet can also show such patterns (see Spring 2019 Lab Notes, p. 92), but this stone has no assembly feature. These attractive iridescent colors, resembling the “play-of-color” of precious opal, result from thin-film interference. This is a unique visual effect created by internal features in heat-treated corundum. Source: GIA @topic:3


Title: Star Opal Abstract: Figure 1. This 2.39 ct transparent opal with a light brownish yellow bodycolor possessed a six-rayed star. Photo by Lhapsin Nillapat.

                      Opal is best known for displaying play-of-color. It may also display asterism, though star opal has only been reported from Idaho, and a perfect six-rayed star is exceptionally rare (J.V. Sanders, “The structure of star opals,” Acta Crystallographica, Vol. A32, 1976, pp. 334–338). The Bangkok laboratory recently had the opportunity to examine a transparent star opal (figure 1). The 2.39 ct light brownish yellow cabochon displayed a distinct six-rayed star.

Standard gemological testing gave a spot RI reading of 1.43 and a hydrostatically calculated SG of 2.10. When exposed to ultraviolet radiation, the stone fluoresced strong bluish white under long-wave and weak bluish white under short-wave UV. It phosphoresced green after exposure to long-wave UV. Advanced gemological testing by energy-dispersive X-ray fluorescence (EDXRF) confirmed a silica-rich material with some additional trace elements, including aluminum and iron. All of these properties were consistent with opal.

Microscopic examination revealed large parallel planes with play-of-color intersecting to form a hexagonal pattern (figure 2). This is responsible for producing the six-rayed star. This unusual stone serves as a reminder that, unlike asterism in other gem materials, the star in opal is caused by diffraction of light from faults or imperfections in the packing arrangement of silica spheres.

	Figure 2. This photomicrograph of the opal shows the intersection of large parallel planes with play-of-color, producing asterism. Photomicrograph by Charuwan Khowpong; magnified 15×. Source: GIA @topic:12


Title: Multi-Color Sapphires Reportedly from the Garba Tula District, Isiolo County, Kenya Abstract: Figure 1. Color-calibrated photos of sapphires (0.602–7.133 ct) reportedly from the Garba Tula area in the Isiolo region of Kenya. The black arrow indicates the color-change sapphire. Photo by Sasithorn Engniwat.
The Garba Tula sapphire deposit, located in Isiolo County in central Kenya, is a unique igneous gem-corundum producing area. It is a productive source of blue, green, and yellow sapphires (C. Simonet et al., “The Dusi (Garba Tula) sapphire deposit, Central Kenya–A unique Pan-African corundum-bearing monzonite,” Journal of African Earth Sciences, Vol. 38, 2004, pp. 401–410). Figure 1 shows the overall color appearance of 28 Garba Tula sapphires recently examined in this study. They were purchased from a reliable dealer at the Tucson gem shows in 2019. It was noticed that their color varied from dark blue to yellow through various shades of blue and green. Some showed strong yellow and blue zoning, while samples with bluish and greenish color banding were also observed. Interestingly, one of the sapphires exhibited a color-change appearance (indicated by the black arrow in figure 1). Windows were polished into the samples in order to study their internal features and collect chemical data. For some samples, windows were polished parallel to the c-axis for spectroscopic measurements.
The studied materials revealed a slightly higher refractive index (1.761–1.773) than typical metamorphic sapphires. The other standard gemological properties were typical of natural corundum. The vast majority of these Garba Tula sapphires (75%) displayed no fluorescence under long-wave UV radiation, while 18% fluoresced red and the remainder showed zoned orange fluorescence (with very weak red fluorescence or none). The fluorescence intensity to long-wave UV of Garba Tula sapphires is generally very weak to weak. However, they were totally inert to short-wave UV light.

Figure 2. Typical inclusions presented in the sapphires from Garba Tula, Kenya. Left and center: A plane of irregular reflective needles that showed brownish color using fiber-optic lighting and diffused lighting, respectively; field of view 2.88 mm. Right: Numerous single and clusters of zircon crystals, some with tension fractures; field of view 4.8 mm. Photomicrographs by C. Khowpong and S. Wongchacree.
The characteristic inclusions observed from these 28 Garba Tula sapphire samples are presented in figure 2. More than 90% were included with irregular brownish needles and platelets identified by Raman as hematite/ilmenite (Y. Katsurada et al., “Golden sheen sapphire and syenite/monzonite–hosted sapphire from Kenya,” Fall 2018 G&G, pp. 322–323), formed either as planes along the color banding or as a group or cloud. These multiple twinning planes, commonly associated with parallel and/or intersecting growth tubes, were found in more than 80% of the stones. A few samples contained numerous single and scattered clusters identified by Raman spectroscopy as zircon crystals (figure 2, right), sometimes with fine rutile needles and reflective particle clouds, but with fewer irregular brownish platelets. Fingerprint inclusions as well as the other crystal inclusions identified using Raman spectroscopy and the RRUFF reference database, such as apatite and mica, were occasionally observed in the Garba Tula sapphires studied. Moreover, crystals of carbonate minerals were also previously reported in Garba Tula sapphire (Y. Katsurada et al., 2018). However, they typically lack sharp growth structure and milky clouds, as frequently seen in Madagascar and Sri Lanka.
FTIR spectra obtained from the sapphires often showed one or more diagnostic features: a single 3309 cm–1 peak as well as OH-related mineral features such as boehmite, kaolinite, and gibbsite. It was noticed that every sample exhibited a single 3309 cm–1 peak without any subordinate peaks, while the boehmite and kaolinite were observed often (>70%) with a small percentage (18%) showing the gibbsite mineral feature.
Interestingly, the UV-Vis-NIR spectrum of greenish blue to blue sapphires from Garba Tula exhibited a metamorphic-type sapphire spectrum, with strong Fe3+-related absorption features at 377, 388, and 450 nm and also an Fe2+-Ti4+ intervalence charge transfer (A.C. Palke et al., “Geographic origin determination of blue sapphire,” Winter 2019 G&G, pp. 536–579). A broad band centered at 880 nm, which is typically used to indicate basalt-hosted sapphire, was not observed.

LA-ICP-MS showed comparable trace element chemistry profiles between the different color areas of the stones, as presented in table 1. The Garba Tula corundum contains significant amounts of Fe and small amounts of Ti. High Fe content ranging from 1555–3177 ppma and 2121–2943 ppma were detected in greenish blue to blue and yellowish to greenish zones, respectively, while the Ti concentration ranged from 3–41 ppma. The high amounts of Fe were also higher than those of Mogok (Myanmar) and Tunduru (Tanzania) sapphires, which have been previously reported as high-Fe metamorphic sources (W. Soonthorntantikul et al., “An in-depth gemological study of blue sapphires from the Baw Mar mine (Mogok, Myanmar),” GIA Research News, 2017, https://www.gia.edu/gia-news-research/blue-sapphires-baw-mar-mine-mogok-myanmar). Therefore, the chemical composition of the Garba Tula sapphires, particularly their high Fe, is not common for metamorphic sapphire deposits.
The discovery of this source for yellow, green, and blue sapphires could be interesting for the gem trade. The material represents a true challenge for gemologists working on origin determination, as their formation is quite complicated. Although some properties and chemistry of the Garba Tula sapphires are comparable to the corundum xenocrysts originating from alkali basalt fields, their UV-Vis-NIR and FTIR spectra and their internal features are not consistent with typical basalt-related sapphires. The inclusion scene might, in some aspects, overlap between high-Fe metamorphic and basalt-related sapphires. The reflective/iridescent brownish platelets can be seen in metamorphic sapphires from Mogok, Myanmar, as well as in basalt-hosted sapphires from Thailand and Ethiopia. But none of the glassy melt inclusions usually observed in basalt-related sapphires were noticed in the Garba Tula sapphires. One hypothesis is that they formed in the same way as the basalt-related stones but just were not brought to the surface by the basalt. Therefore, a combination of multiple techniques can be useful in the origin determination of sapphires from Garba Tula. Source: GIA @topic:3


Title: Blue Gahnite from Nigeria Abstract: Figure 1. Three single octahedra of natural gahnite, approximately 1.5 ct each, from Kaduna State, Nigeria. Photo by Robison McMurtry.

In recent years, Nigeria has gained considerable attention in the gem trade for the discovery of sapphires reportedly from the Mambilla Plateau in Taraba State. In addition to sapphires, spinels have been sporadically mined in Jemaa and recently in Kagoro, both in Kaduna State (figure 1). The spinel group of minerals, with a general chemical formula AB2O4, has a total of 22 different species. Four of these species have Al predominantly occupying the octahedral site: spinel (MgAl2O4), galaxite (MnAl2O4), hercynite (FeAl2O4), and gahnite (ZnAl2O4). The spinels from Kagoro have been identified as gahnite, the zinc end member. Gahnite is one of the rarer members of the spinel group of minerals, typically found at zinc deposits. Most crystals are very small, included, and translucent to opaque. Faceted gems are very collectible due to their rarity and color.
The geology of the Nigerian spinels has been previously studied (R. Jacobson and J.S. Webb, “The pegmatites of central Nigeria,” Geological Survey of Nigeria Bulletin, No. 17, 1946, pp. 1–61), and the deposits can be subdivided into three groups based on their mineralogy: (1) microcline-quartz pegmatites, which commonly occur within the calc-alkaline granitoids and are rarely mineralized; (2) microcline-quartz-mica pegmatites, found within metasedimentary sequences; and (3) quartz-mica veins, which occur in schists and gneisses or marginal to group 2 pegmatites. Gahnite occurs in groups 2 and 3. Knowledge of the composition of zinc-rich spinels is useful in separating a wide variety of source environments. For example, Zn content is high in spinels occurring in rocks that have experienced low-grade metamorphism and high oxygen and sulfur fugacity (fO2 and fS2), whereas Zn content is lowest in high-grade metamorphic rocks (A. Heimann et al., “Zincian spinel associated with metamorphosed Proterozoic base-metal sulfide occurrences, Colorado: A re-evaluation of gahnite composition as a guide in exploration,” Canadian Mineralogist, Vol. 43, No. 2, 2005, pp. 601–622).
Standard gemological examination of three rough octahedra (figure 1) gave the following properties: color—blue; pleochroism—none; refractive index—1.791 to over the limit (flat reading from polished crystal face); hydrostatic specific gravity—4.180–4.294; fluorescence reaction—inert to both long- and short-wave UV; and color filter reaction—red. Internal characteristics observed with a gemological microscope were colorless unidentified crystals, fingerprints, and a red-brown crystal inclusion identified by Raman spectroscopy as sphalerite (figure 2).

Figure 2. Raman identification of this inclusion was consistent with sphalerite. Photomicrograph by Nathan Renfro; field of view 0.91 mm.

Figure 3. The visible spectrum of the Nigerian gahnite from Kagoro. The absorption bands from ~500 to 650 nm are largely due to Co2+, but with modification from iron absorption bands. Absorption bands around 462 and 470 nm are related to iron chromophores.
Advanced spectroscopic testing was performed on the three samples. The Raman spectra were typical of gahnite, with peaks at 420, 510, and 661 nm. The visible spectrum showed significant cobalt absorption bands (figure 3) between 500 and 620 nm, with additional contribution from iron absorption bands modifying the cobalt absorption spectrum (e.g., A.C. Palke and Z. Sun, “What is cobalt spinel? Unraveling the causes of color in blue spinels,” Fall 2018 G&G, pp. 262–263).
Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) analysis was used to obtain the accurate chemistry of the three stones. The chemical composition was acquired by a ThermoFisher iCAP Q ICP-MS coupled with an Elemental Scientific Laser NWR213 laser ablation system. NIST 610 and 612 were used as external standards, and 27Al was used as an internal standard. LA-ICP-MS results (see appendix 1) showed that the three stones were predominantly composed of more than 90 mol.% gahnite (ZnAl2O4), with minor other end members of Al-spinel species. They should thus be classified as gahnites.

Figure 4. A vertical line 1 and a horizontal line 2, containing a total of 44 spots, were selected to apply LA-ICP-MS analyses across the whole section. Mol.% end member vs. position profiles revealed that the stone was predominantly composed of gahnite with minor hercynite, spinel, and galaxite. Detailed information on major element chemistry, site distribution, and species for each spot can be found in appendix 1. Spot spacing is 200 microns.

Figure 5. Trace element vs. position profiles revealed that the outer rims had higher concentrations of V and Co, but lower concentration of Ni than the inner rims and core. Detailed information on trace elements for each spot in lines 1 and 2 can be found in appendix 2.
To better understand the composition of this type of spinel, we prepared a cross-section cut from the middle of one octahedral crystal, sample NBS3 (figure 4). A vertical line of 22 spots (figure 4, line 1) and a horizontal line of 22 spots (figure 4, line 2) were selected to cross the whole section from outer rims to the opposite outer rims for LA-ICP-MS analyses. All the spots showed more than 90 mol.% gahnite with hercynite as the second most abundant species (figure 5). Spots near the outer rims contained more hercynite than spots on the inner rims and core. The mol.% end member distribution was very consistent throughout the whole section. Nine trace elements for each spot in lines 1 and 2 were plotted in figure 5. In general, the outer rims had higher concentrations of V and Co but lower concentration of Ni than the inner rims and core. Source: GIA @topic:2


Title: Sapphires from Colombia Abstract: Figure 1. Five unheated Colombian sapphires, ranging from 0.41 to 3.65 ct. Photo by Diego Sanchez.

Colombian sapphires were first reported in G&G nearly 35 years ago and are still circulating in the market today (see P.C. Keller et al., “Sapphire from the Mercaderes–Río Mayo area, Cauca, Colombia,” Spring 1985 G&G, pp. 20–25). The deposit is located in southern Colombia in the Cauca Valley, in the small town of Mercaderes. This location is notorious for being politically unstable and dangerous. This deposit continues to produce in small quantities, with most material extracted from riverbeds using picks and shovels. Independent miners collect year-round and go to Bogotáto sell the material. Vanessa Van Horssen (Carlsbad, California) recently purchased several unheated Colombian sapphires and learned about the active mines from a third-generation miner in Bogotá. She loaned GIA’s Carlsbad laboratory five samples (figure 1) for scientific examination.
Colombian sapphires occur in a variety of colors, such as blue, pink, and violet, and there have been past reports of color-change sapphire from this deposit. The five samples consisted of a 0.41 ct pink faceted pear, a 0.92 ct color-change (blue to violet) faceted oval, a 1.66 ct pink rough, a 2.26 ct blue faceted octagon, and a 3.65 ct blue rough. All five had gemological characteristics consistent with corundum. They exhibited a refractive index of 1.762 to 1.770 and a specific gravity of around 4. Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) was performed to identify their chemical compositions. A high concentration of Fe ranging from 1515 to 1749 ppma suggested a magmatic source. Infrared spectroscopy showed no indications of treatment.

Figure 2. Zircon crystals scattered throughout angular milky clouds were more prominent in these sapphires compared to other high-Fe sapphires. Photomicrograph by Jessa Rizzo; field of view 4.7 mm.
The internal features (figure 2) were color zoning, particle clouds, angular milky clouds, and twinning. The sapphires contained transparent colorless and red crystals that showed no sign of heat treatment. Using Raman spectroscopy, the inclusions were identified as unaltered zircon and rutile crystals, consistent with the inclusions reported in Keller et al. (1985). Sapphires transported to the surface by hot magma tend to show characteristics similar to those of artificially heated sapphires, such as tension fractures around crystals and altered fingerprints. The suite of inclusions in these high-temperature-formed sapphires confirmed that no heat treatment was performed.
These stones provided useful data for ongoing origin determination studies. Although Colombian sapphires are rare, they are on the market, and the deposit continues to show great promise. Source: GIA @topic:1


Title: Rainy Lakeside City in Peridot Abstract: Blade-like magnetite inclusions developed from a healed fracture in a 2.08 ct Burmese peridot resemble a rainy lakeside city. Photomicrograph by Makoto Miura; field of view 1.06 mm.
Inclusions in gemstones provide useful information regarding their geological origin. A 2.08 ct Burmese peridot containing unique black blade-like inclusions developed from healed fractures (fingerprints), as shown in the figure above. Raman spectroscopy identified these blade-like inclusions as magnetite. Tiny raindrop-like magnetite lamellae were also observed throughout the stone. Such inclusions in Burmese peridot sometimes create four-rayed asterism. According to previous studies, the presence of magnetite lamellae suggests the oxidation or dehydration of olivine by geological processes. This image resembles a rainy lakeside city landscape. Source: GIA @topic:1


Title: Opal from West Java, Indonesia Abstract: Figure 1. These cabochons, weighing 6.94 ct and 3.79 ct, were among the Indonesian opals at Rare Earth’s AGTA booth. Photo by Robison McMurtry.

At the AGTA show, Rare Earth Mining Co. (Trumbull, Connecticut) displayed an unexpected material: Indonesian opal reportedly from West Java. Two cabochons (figure 1) yielded a refractive index of 1.45 and a specific gravity of 2.13, consistent with opal. Energy-dispersive X-ray fluorescence (EDXRF) analysis revealed the presence of copper.

According to Rare Earth’s Curt Heher, the material was first seen in the spring of 2017. While the opal comes in a wide range of colors, including browns and blues, the greenish blues were of particular interest. Rare Earth displayed cabochons where this was the primary hue, with the accessory colors distributed in an aesthetically pleasing manner. Source: GIA @topic:12


Title: Coated Kornerupine Beads Abstract: Figure 1. These three kornerupine beads (0.95–1.38 ct) were found to have a metallic coating. Photo by Robison McMurtry.

Three dark brown faceted beads with an unusual metallic luster were recently submitted to the Carlsbad laboratory for identification service (figure 1). The three beads ranged from 0.95 ct to 1.38 ct. Standard gemological properties revealed an RI of approximately 1.668–1.680, consistent with kornerupine. The hydrostatic SG ranged from 3.01 to 3.19. This is slightly lower than expected for kornerupine, but can be explained by air trapped in the drill holes. Raman spectroscopy confirmed that the stones were kornerupine.

All three beads exhibited a high metallic luster with silver and bronze coloration, which is not typical for kornerupine. Under microscopic examination with reflected lighting, the surfaces showed spotty luster, consistent with a surface coating (figure 2). Further evidence of coating was visible along the facet junctions, where the coating was worn away.

Figure 2. Diffused reflected light exposed spotty luster on the surface of one of the tested
stones, indicating the presence of a coating. Photomicrograph by Amy Neurauter; field of
view 2.17 mm.
Energy-dispersive X-ray fluorescence (EDXRF) chemical analysis detected large amounts of Mg, Al, and Si, consistent with kornerupine. EDXRF also revealed the presence of copper. The authors could not find documentation of naturally occurring copper in kornerupine, so this element may have been used to create the metallic coating. This is the first time the GIA laboratory has seen coated kornerupine. Source: GIA @topic:12


Title: Gemstone Irradiation and Radioactivity Abstract: With the increasing use of radiation to color enhance gemstones, the issue of radioactivity has become a source of concern for gemologists worldwide. This article examines the basic characteristics of radiation and radioactivity, the sources of radiation in the earth and in the laboratory, the radiation treatment of gemstones in particular, and the detection and measurement of radiation. Also included is a discussion of potential health hazards and current government regulations regarding gemstone radioactivity. Source: GIA @topic:1


Title: Ruby and Sapphire from the Southern Ural Mountains, Russia Abstract: Primary occurrences of ruby, pink sapphire, sapphires of other colors, and spinel have been found in marbles in the Ural Mountains. This article describes one occurrence, at Kootchinskoye, in the southern Urals, as a model for others in the Ural Mountains. Study of Kootchinskoye also gives some guidelines for predicting other ruby deposits. Although at present, there is no commercial production in this area, it appears to have significant potential. Source: GIA @topic:1


Title: Reactor-Irradiated Green Topaz Abstract: Examination of samples of faceted "Ocean green" topaz reveals that this material has been irradiated in a nuclear reactor. An earlier reactor-irradiation experiment suggests that temperature conditions during the irradiation of this material may be higher than those used to produce typical "London-blue" topaz. Like such reactor-irradiated blue topaz, this material may be radioactive. In addition, the green color is not stable to direct sunlight. Source: GIA @topic:1


Title: Hydrothermally Grown Synthetic Aquamarine Manufactured in Novosibirsk, USSR Abstract: Physical, chemical, spectroscopic, and microscopic characteristics of a sample of hydrothermally grown synthetic aquamarine from the USSR are presented. Physical and spectroscopic data are correlated with the chemical composition of the synthetic beryl to establish cause of color. Diagnostic criteria to separate natural from synthetic aquamarine are given, and the growth conditions of this synthetic blue beryl are discussed. This is the first description of synthetic aquamarine in the English gemological literature. Source: GIA @topic:3


Title: Induced Fingerprints Abstract: Over the past few years, numerous Verneuil-type (flame fusion) synthetic sapphires and rubies with somewhat natural-appearing induced fingerprint inclusions have surfaced in the trade. This article reports the results of a series of experiments conducted to explain the phenomenon of induced fingerprints and how they are produced in gemstones generally and in flame-fusion synthetic corundum specifically. Source: GIA @topic:3


Title: A New Classification for Red-To-Violet Garnets Abstract: The recent article by Manson and Stockton on the classification of red-to-violet garnets should be welcomed by all gemologists. With this work, the Gemological Institute of America has opened the subject for review and revision. The following article presents an overall view of previous red-to-violet garnet classification schemes and proposes a new one that is well within the capabilities of every gemologist. Source: GIA @topic:3


Title: A Cubic Zirconia Refractometer Abstract: With the development by C. D. West of practical high refractive-index liquids, the major barrier to extending the range and durability of the refractometer has been the need for an isotropic substance with an index of refraction higher than that of the glass commonly used. On the basis of the author's experiments with a cubic zirconia refractometer, CZ - with its relatively low cost, high refractive index and hardness - shows great promise for meeting this need. Source: GIA @topic:3


Title: New Tourmaline Pockets in San Diego County’s Pala District Abstract: Figure 1. A 16.96 ct emerald-cut green tourmaline from rough found near a new pocket at the Tourmaline King mine. Photo by Robert Weldon; courtesy of Pala International.
At the AGTA show, Bill and Carl Larson (Pala International, Fallbrook, California) shared details about new pockets uncovered at the Tourmaline King mine. The first was discovered in January 2022—the first major find at the mine in more than a hundred years, and the first in Southern California since the “Big Kahuna” pocket at the Oceanview mine in 2010. “We’ve hit off and on three or four pockets, some of which are very good,” Bill said.

Figure 2. Rubellite tourmaline rough (440 g) from one of the Tourmaline King mine’s new pockets. Photo by Robert Weldon; courtesy of Pala International.
The Larsons showed us several stones, including a 16.96 ct emerald-cut green tourmaline (figure 1) from rough found near the first pocket in 2022. Bill said the green tourmaline is relatively uncommon for the Pala District. “The green has actually been transparent enough to facet,” Carl added. “That’s been the best material so far.” The new pockets have also produced about 3 kg of fine-color rubellite rough (figure 2).
The Tourmaline King mine’s main tunnel produced eight tons during San Diego County’s massive output of tourmaline in the early nineteenth century, which also involved the Pala District’s Tourmaline Queen, Pala Chief, and Stewart mines, as well as Mesa Grande’s Himalaya mine. (There was a resurgence of mining at Pala in the 1970s.)
Around 1920, mine owner R.M. Wilke and his crew installed a new tunnel below the main one. “They hit this very dangerous zone right before they hit the pegmatite,” Bill said. Here they encountered a shear zone that caused a roof collapse. Wilke abandoned mining efforts around 1922.
Pala International’s mining partner, San Diego Mining Company, reclaimed the tunnel several years ago and began extending it in 2019. “They got to the dangerous area, and then they backed up about 10 meters and went around and hit the pegmatite,” Bill said. “Now they’re in from the front to the back, where we’re hitting tourmaline.”
Carl recalled his initial look at the first new pocket. “Kiel Snyder stopped me and said, ‘Everyone else gave up here,’” he said. “He just believed in it and kept going. Then they hit a small pocket—nothing of note, but something that said, ‘There are stones here.’ I think they called that the ‘Never Give Up’ pocket. Within 10, 15 feet, they hit that first pocket.”
The crystals were large and well formed, and the miners uncovered a very large terminated quartz crystal, a collector specimen. Carl said the crystals in this pocket lack the rubellite color and are not typical of the mine, making them inadequate for cutting and cabbing. But in January of 2023, they discovered a pocket of beautifully colored red rubellite, too included for faceting but suitable for cabbing and carving. “We’re hoping that we’ll hit some more gemmy transparent material,” he said.
“It’s really exciting to have an active mine in Southern California because of its rich history,” Carl said. “At the turn of the century we were hitting a lot, and then it was vacant for so long. So to have some energy coming in with new material is exciting.” Source: GIA @topic:1


Title: Rubies from a New Deposit in Zahamena National Park, Madagascar Abstract: Figure 1. Rough rubies from Zahamena National Park with a combination of good shape, transparency, and attractive color. Photo by Vincent Pardieu/GIA.

	In July 2015, news circulated through the trade about a ruby discovery south of Andilamena, near Lake Alotra (figure 1). Photos of clean, attractive stones of over 10 carats were shared on social media by Malagasy and Sri Lankan gem merchants. Several thousand unlicensed miners quickly descended on the area, creating serious conservation concerns as the new deposit was located inside Zahamena National Park. In August 2015, the Malagasy government sent soldiers to close the mining site. But because the area is very remote, they could not maintain their presence longer than a month. As soon as the soldiers departed, the miners returned in numbers.

	Gem-quality rubies and sapphires are not unknown in northeastern Madagascar: They were first found in 2000, east of Andilamena and west of Vatomandry (Summer 2001 GNI, pp. 147–149). These discoveries were followed by a blue sapphire deposit near Andrebabe, a few kilometers south of Andilamena, in 2002 (www.ruby-sapphire.com/madagascar_ruby_
	sapphire.htm). Ruby mining was limited until 2004, when demand for the heavily fractured material from Andilamena dramatically increased with the advent of the lead-glass filling treatment developed in Thailand between 2001 and 2004. Visiting the deposit in June and September 2005, author VP could see that more than 10,000 miners were living and working in the jungle (www.rwwise.com/madagascar1.html). In 2011 and 2012, two new discoveries occurred in the region. The first was a pink and blue sapphire deposit near Mandraka village, north of Toamasina. In 2012, a deposit was discovered east of Didy (www.giathai.net/pdf/Didy_Madagascar_US.pdf). That deposit produced some large, clean, and attractive rubies and blue sapphires. More discoveries followed—near Bemainty, north of Didy, for instance—but either the gems were ordinary or the rush was short-lived. In 2015, a new blue sapphire rush occurred near Andrebabe in February, followed by a ruby discovery near Ambodivoangy village in July (http://lotusgemology.com/index.php/library/articles/322-blood-red-rubies-from-madagascar-lotus-gemology).

	From September 23 to October 6, 2015, a GIA field expedition team collected samples at the mines. After three days of walking in the jungle, the team was able to visit the new mining sites (figure 2), located about four hours’ walking distance from Ambodivoangy. There they witnessed some illegal ruby mining activity by artisanal miners at two different sites, located in a valley at 17°37'60''S 48°52'19''E and along a creek in a forested area at 17°38'26''S 48°52'38''E. They confirmed that the deposit was indeed located inside Zahamena National Park. Approximately 500 people were seen at the lower mining site, while about the same number worked in the forest along a stream where ruby-rich gravels were collected (figure 3).

Figure 2. A young Malagasy miner searches for rubies in Zahamena with simple homemade tools: a pierced plastic oil can used as a sieve and an empty water bottle to store his gems. Photo by Vincent Pardieu/GIA.

Figure 3. Artisanal Malagasy ruby miners wash gem-rich gravels in the stream that runs through the jungle of the Zahamena National Park. Photo by Vincent Pardieu/GIA.

	The local trading center was in Andrebakely, with mainly Malagasy buyers, while foreign buyers (typically from Sri Lanka) waited for local miners and businessmen at Tanambe and Andilamena. In both towns, more than 20 Sri Lankan buying offices were visible, mostly in houses with painted signs for the different companies.

	The new deposit is located about halfway between the old ruby deposit in the jungle east of Andilamena (discovered in 2000) and the rush that occurred at Didy in 2012 (www.giathai.net/pdf/Didy_Madagascar_US.pdf). The rubies from Zahamena share obvious similarities with those from Andilamena, such as their inclusions (mainly zircon and rutile crystals associated with rutile needles) and trace-element composition. Therefore, it is likely that these deposits are related, and a huge ruby and sapphire deposit could be hidden under the jungle in northeastern Madagascar.

	Back at GIA’s Bangkok lab in October 2015, the samples were fabricated and data was collected from them; a more extensive study is in progress. At this point it is interesting to note that the rubies from the Zahamena deposit have a very similar aspect to those from amphibole-related African deposits such as Montepuez in Mozambique, Chimwadzulu in Malawi, and Winza in Tanzania. Their iron content is indeed much higher than that of the marble-type rubies mined in Myanmar, Vietnam, Afghanistan, or Tajikistan. The shape of the crystals is generally tabular but not as flat as what is commonly found in Mozambique, meaning that faceted stones with good proportions can be produced. The new material is on average more included than the ruby from Montepuez. But ultimately the limiting factor for this deposit is its location inside Zahamena National Park, where gem mining is illegal. Source: GIA @topic:1


Title: Unique Metal Sulfide Inclusion in “Bing Piao” Red Agate from Liangshan, China Abstract: Figure 1. The cabochon on the left is a normal “Bing Piao” red agate measuring 12.50 × 19.60 × 10.11 mm. The bead on the right, approximately 11.80 mm in diameter, is a special type of “Bing Piao” red agate. Photo by Su Xu.

Over the past decade, with the discovery of “Nanhong” agate ore deposits in Sichuan Province, a significant amount of this material has been mined in Meigu County, located in the northeast of Liangshan Yi Autonomous Prefecture. Commercial gem mines in Meigu County are located in three main areas, including Jiu Kou, Wa Xi, and Lian He. Field observations show that the ore body is found either in the interlayer fissures and cavities of Permian Emeishan basalt crystallized from siliceous hydrothermal fluid or as conglomerates of the Permian Leping Formation.
Previous reports found that “Nanhong” agate is colored by natural hematite inclusions. Moreover, these agates are divided into five major categories, including “Bing Piao” (a Chinese term that refers to their inclusions “floating on ice”). This type of agate (see figure 1, left) is colorless and contains red hematite particles distributed in attractive patterns.
Recently, a special type of “Bing Piao” red agate called “black grass” agate by merchants appeared in the market at Liangshan. A bead of this material (figure 1, right) was obtained for examination at the National Gold-Silver Gem & Jewelry Quality Supervision & Inspection Center (Sichuan).

Figure 2. These antennae-like inclusions consist of dot-like black minerals, coupled with red inclusions. Photomicrograph by Xiaoping Shi; field of view 9.00 mm.
Gemological properties of the semitransparent bead, including its RI of 1.54 and hydrostatic SG of 2.65, suggested agate; this was confirmed by FTIR spectroscopy. Magnification revealed tiny red inclusions that were identified as hematite by Raman spectra (peaks at 225, 244, 291, 410, 610, and 1320 cm–1) using a 785 nm laser. In addition to these attractive red forms made of hematite, the bead hosted many unusual black mineral particles displaying various shapes such as blades, planar clusters, and the like (figure 2). When viewed with reflected light, microscopic observations of their opaque, anhedral form and metallic luster suggested the particles were likely an iron sulfide. A Raman spectrum obtained from a surface-reaching black particle showed two major peaks at 342 and 377 cm–1, matching well with pyrite, according to the RRUFF database (reference spectrum R100166), as shown in figure 3.

Figure 3. The black particle was identified as pyrite based on comparison with Raman reference spectra from the RRUFF database. Spectra are offset vertically for clarity.
To obtain confirmation, the bead was polished down to a plate to perform chemical analysis and phase identification of the black particles using a scanning electron microscope in combination with an energy-dispersive spectrometer (SEM-EDS) equipped with an electron backscatter diffraction (EBSD) detector. Qualitative analysis revealed the expected major elements of Fe, As, and S, along with minor Si, likely from the agate host. This was consistent with pyrite composition. The EBSD analyses indicated a cubic structure, and a search of the NIST Structural Database using Aztec software revealed a match for pyrite (FeS2).
Except for Liangshan, such distinctive black minerals of various forms have not been found in other “Bing Piao” red agate deposits. The pyrite particles, as inclusions that are unique to “Bing Piao” red agate from Liangshan, may therefore be considered reliable indicators of origin. Further gemological studies on these inclusions are required to construct the database for origin determination. Source: GIA @topic:12


Title: Distinguishing Between Natural and Synthetic Green Chrysoberyl Abstract: K. Schmetzer, M.S. Krzemnicki, T. Hainschwang, and H.-J. Bernhardt. “Natural and synthetic vanadium-bearing chrysoberyl,” Journal of Gemmology, Vol. 33, No. 7–8, 2013, pp. 223–238. These photos show natural chrysoberyl from Tanzania (left) and synthetic green chrysoberyl crystals manufactured by the Kyocera Corporation of Japan. Photos courtesy of Karl Schmetzer.

              Bright mint-green chrysoberyl emerged from Tunduru, Tanzania, in the mid-1990s. This material, which owes its color to V3+ substituting for Al3+ in the chrysoberyl lattice, does not exhibit the green-red color change of the alexandrite variety of chrysoberyl (colored by Cr3+). Prior to the introduction of these goods into the marketplace, manufacturers in both Japan and Russia demonstrated that vanadium-containing chrysoberyl could be grown using the Czochralski technique. Only after the popularity of natural mint-green chrysoberyl did the production of gem-quality synthetic material begin, however. That was when Kyocera of Japan (and to a much lesser extent the Russian company Tairus) developed V-bearing synthetic alexandrite to mimic the crystals coming from Tanzania.

Natural mint-green chrysoberyl, much of it extremely clean, is also found in Ilakaka, Madagascar; Sri Lanka; and Mogok, Myanmar. Prior to this study, there had been very little investigation into either natural or synthetic V-bearing chrysoberyl. The authors compare the optical characteristics and trace element composition of the Kyocera synthetic material with natural specimens from all four regions to help distinguish between the various sources. Additionally, they evaluate the impact of V3+, Cr3+, and Fe3+ on color and absorption characteristics.

The Kyocera synthetic chrysoberyl, most similar in appearance to the Tunduru material, almost exclusively contained the chromophore V3+ (approximately 0.1 wt.% V2O3), with little to no Ti4+, Cr3+, or Fe3+ present. Natural green chrysoberyl had much more variable amounts of these cations, with Tunduru specimens containing 0.04–0.30 wt.% V2O3, 0.004–0.040 wt.% Cr2O3, 0.001–0.110 wt.% TiO2, and 0.08- 0.32 wt.% Fe2O3. The Ilakaka material, some of which appeared more yellow than the Tunduru chrysoberyl, had similar levels of V2O3, was nearly Cr2O3 free, and had lower levels of TiO2. In some cases, the samples showed significantly more Fe2O3, with levels as high as 0.55 wt.%. Sri Lankan material, which was more yellowish green than the other studied samples, had substantially more Fe2O3 (0.47 – 0.90 wt.%), with generally less V2O3 and similar Cr2O3 contents as compared to Tunduru material. The Mogok chrysoberyl, which was an intense bluish green, had essentially no iron but high levels of both V2O3 and Cr2O3, at 0.38 and 0.24 wt.%, respectively. The Mogok material also demonstrates the strongest pleochroism, with observed colors ranging from grayish violet to yellowish green to intense blue-green. Additionally, gallium was detected in all of the natural chrysoberyl and none of the synthetics. Tin is also found in much of the natural green chrysoberyl but not in the synthetic form.

Spectroscopically, the positions of the absorption maxima and the intensity ratios for the V3+ absorption bands were found to be consistent between synthetic and natural material containing little to no Cr3+. Features attributable to Cr3+ and Fe3+ were detectable in the corresponding natural spectra. Finally, the authors show that with the proximity of the Cr3+ and V3+ bands in chrysoberyl, separate bands for the two cations are not visible. Instead, a shift of the ν1 band to shorter wavelengths was observed with increasing Cr3+ content. Visually, much of the material was inclusion free, but all natural samples contained growth patterns not observed in the Kyocera synthetics. Source: GIA @topic:3


Title: Neptunite Inclusion in Benitoite Abstract: This faceted benitoite contains a small reddish brown inclusion of neptunite that was identified by Raman spectroscopy. Photomicrograph by Nathan Renfro; field of view 1.20 mm. Courtesy of Michael Jakubowski.

The authors recently examined a round, slightly zoned blue and near-colorless faceted benitoite that contained an interesting inclusion. Microscopic observation revealed a well-formed euhedral semitransparent reddish brown crystal surrounded by fine short needles and fluid fingerprints (see above). Because of the color and structure of the inclusion, both neptunite and joaquinite were considered as the possible identity. In benitoite, these minerals are often found in association and may have a similar color to the inclusion observed in this particular example. One method of separating neptunite from joaquinite is pleochroism. A yellow-orange, orange, and deep red pleochroism is consistent with neptunite, while light yellow and colorless pleochroism is consistent with joaquinite (webmineral.com). This inclusion showed a reddish orange to red pleochroism that was more consistent with neptunite. Raman analysis confirmed the host crystal was benitoite and the orangy red inclusion was neptunite, which has been previously documented (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Vol. 1, 5th ed., 2008, Opinio-Verlag Publishers, Basel, Switzerland, p. 416).
Benitoite is a barium titanium silicate (BaTiSi3O9). This rare gem is found primarily in San Benito County, California, though it also occurs in other locations worldwide. Neptunite’s chemical formula is KNa2Li(Fe2+,Mn)2Ti2Si8O24, and it also occurs in San Benito County. Neptunite is found in association with other minerals in New Mexico, Greenland, and Canada, to name just a few (W.L. Roberts et al., Encyclopedia of Minerals, 2nd ed., 1990, Van Nostrand Reinhold, New York, pp. 603–604). The gem-quality benitoite material comes from the Benitoite Gem mine and the Junnila Claim (B. Laurs et al., “Benitoite from the New Idria District, San Benito County, California,” Fall 1997 G&G, pp. 166–187). This faceted benitoite contains one of the best examples of neptunite in benitoite seen by the authors. Source: GIA @topic:2


Title: Native Copper Inclusions in Indonesian Purple Chalcedony Abstract: This purple chalcedony from Indonesia contained interesting inclusions of native copper. Photomicrograph by Nathan Renfro; field of view 5.74 mm.

As a gem material, chalcedony can contain an array of interesting structures and mineral inclusions. This was particularly evident in one example recently examined by the authors. Purchased by author SC from gemstone dealer John Garsow (John E. Garsow Gems & Minerals, Murrieta, California), this vibrant purple chalcedony reportedly from Indonesia contained several small clusters of what appeared to be native copper (see above). This suspicion was confirmed by energy-dispersive X-ray fluorescence (EDXRF) testing. While the origin of the purple color is not clear, it certainly does not appear to be related to copper. In purple areas that were devoid of copper inclusions, no copper was detected by EDXRF. We did detect iron, which may be related to the purple color.
While native copper inclusions have been previously reported in chalcedony (B.M. Laurs and N.D. Renfro, “Chrysocolla chalcedony with native copper inclusions,” Journal of Gemmology, Vol. 36, No. 2, 2018, p. 92), this is the first time the authors have examined purple chalcedony from Indonesia with native copper inclusions. Source: GIA @topic:12