Publish Year: 2016 Title: Sphalerite Inclusions in Namibian Demantoid Abstract: Figure 1. A brownish orange sphalerite inclusion in Namibian demantoid with a spheroidal diopside aggregate along its upper left side. Based on its morphology, the rhombohedral crystal on the upper right could be a calcite inclusion. Photomicrograph by Aaron Palke; field of view 0.72 mm.

The inclusion scene of skarn-related demantoid garnets from Namibia and Madagascar is dramatically different from that of serpentinite-hosted demantoid found in the classic locality of the Russian Urals. Reported inclusions in Namibian demantoid include diopside, wollastonite, quartz, calcite, fluid inclusions, and sphalerite (F. Koller et al., “The demantoid garnets of the Green Dragon mine (Tubussi, Erongo Region, Namibia),” Joint 5th Mineral Sciences in the Carpathians Conference and 3rd Central-European Mineralogical Conference, April 19–21, Miskolc, Hungary, 2012). Demantoid from Madagascar is reported to contain inclusions of diopside, wollastonite, fluid inclusions, and growth tubes (F. Pezzotta et al., “Demantoid and topazolite from Antetezambato, northern Madagascar: Review and new data,” Spring 2011 G&G, pp. 2–14). There has been little photomicrographic documentation of these inclusion suites, however.

In this contribution we document relatively rare sphalerite inclusions in a Namibian demantoid crystal. Figure 1 shows a translucent brownish orange sphalerite inclusion with a spheroidal diopside aggregate adhering to it (both identified by Raman spectroscopy). While a clear Raman signal could not be obtained on a nearby crystal, its rhombohedral morphology leads the author to speculate that it is a calcite inclusion. The two sphalerite inclusions seen in figure 2 are larger, so their color is a much darker orangy brown. The oblique fiber-optic illumination used in this photo highlights the highly lustrous surface of these sphalerite inclusions. Further photomicrographic documentation of the inclusion suites in demantoid from Namibia and Madagascar may help to identify inclusion scenes unique to these skarn deposits.

Figure 2. Oblique fiber-optic light illuminates the surface luster of these sphalerite crystals within a Namibian demantoid. Photomicrograph by Aaron Palke; field of view 0.84 mm. @topic:1


Publish Year: 2013 Title: Imitation Larimar Abstract: Figure 1. This 3.91 ct ceramic imitation of Larimar (left) is shown with Larimar from the Dominican Republic. Photo by Lore Kiefert.

Pectolite is a mineral of the wollastonite group with the chemical formula NaCa2Si3O8(OH). It has an RI of 1.599–1.628, with a typical spot RI reading of about 1.60 and a specific gravity of 2.81. The light blue variety of this mineral, known by the trade name “Larimar,” has only been reported from the Dominican Republic (R.E. Woodruff and E. Fritsch, “Blue pectolite from the Dominican Republic,” Winter 1989 G&G, pp. 216–225; figure 1).
We recently acquired a 3.91 ct drop-shaped cabochon, purchased in India as a Larimar imitation, that consisted of a ceramic material (figure 1). According to the vendor, the material was manufactured in China. Close microscopic examination showed white gas bubbles and blue color concentration (figure 2).

Figure 2. Microscopic observation reveals dark blue color concentrations
and whitish gas bubbles. Photomicrograph by Lore Kiefert; magnified 40×.
The cabochon’s spot RI reading of 1.53 and SG of 1.87 were distinctly lower than the values for Larimar. Semi-quantitative EDXRF chemical analysis gave a composition of 95% Al2O3 and 4% SiO2, with traces of SO3, K2O, CaO, Sc2O3, Cr2O3, Fe2O3, and Ga2O3. In contrast, the average composition of pectolite consists of 54.23% SiO2, 33.74% CaO, 9.32% Na2O, and 2.71% H2O.
Although the imitation material does indeed resemble Larimar, standard gemological tests such as microscopy, RI, and SG should be sufficient to distinguish it. @topic:1


Publish Year: 2018 Title: A Cat’s-Eye Rock Consisting of Jadeite and Amphibole Abstract: Figure 1. This 1.42 ct translucent variegated green bead displays a distinct chatoyant band on the darker green side (left). No chatoyancy was observed on the lighter green side (right). Photos by Tony Leung.
The Hong Kong laboratory recently examined a translucent variegated green bead exhibiting chatoyancy (figure 1). The 1.42 ct bead, measuring approximately 5.62 mm in diameter, displayed two different shades of green on opposite sides. A distinct cat’s-eye band was readily visible across the darker green region with fiber-optic illumination, whereas no chatoyancy was observed in the lighter green region on the reverse side.

Figure 2. Left: Parallel fibrous amphibole crystals were the cause of chatoyancy in this green bead; field of view 11.34 mm. Right: Tight interlocking grains were visible in the lighter green jadeite region; field of view 3.80 mm. Both observed with fiber-optic illumination. Photomicrographs by Bona Hiu Yan Chow.
Microscopic observation revealed that the darker green side consisted of parallel fibrous crystals (figure 2, left). Light reflecting off these oriented crystals produced a chatoyant band perpendicular to the length of the crystals. On the lighter green side, tight interlocking grains were observed (figure 2, right). Raman spectroscopy detected the presence of richterite, an amphibole with the general formula Na2CaMg5Si8O22(OH)2, in the darker green region and jadeite in the lighter green region.
While it is not unusual to encounter a rock consisting of jadeite and amphibole (G. Shi, “Mineralogy of jadeitite and related rocks from Myanmar: a review with new data,” European Journal of Mineralogy, Vol. 24, No. 2, 2012, pp. 345–370), it is fascinating to see such a rock being fashioned into an attractive variegated green bead exhibiting chatoyancy. @topic:9


Publish Year: 2017 Title: Quarterly Crystal: Molybdenite Phantoms in Quartz Abstract: Figure 1. Weighing 378.73 (left) and 294.05 ct (right), these two quartz crystals contain phantoms composed of an abundance of dark silvery gray to black hexagonal inclusions. Photo by Kevin Schumacher.

Quartz is the most abundant mineral found in the earth’s crust. When it forms as solid single crystals, it can serve as a transparent and durable host for a wide variety of mineral inclusions. The two crystals seen in figure 1 came from collector Terry Szenics (Massapequa, New York), who found them in 2004 as part of a very small discovery at the Confianza mine in the Coquimbo region of Chile.

At a glance, the inclusions in the two crystals looked as though they might be hematite, a common iron oxide. However, laser Raman microspectrometry identified them as molybdenite (figure 2), a hexagonal molybdenum sulfide and a much more unusual inclusion than hematite. The inclusions were situated in the quartz crystals in the form of phantoms that developed through the deposition of the molybdenite on the surface of the quartz. The host then continued to grow, enveloping the molybdenite as inclusion planes tracing the form of the original quartz host.

Figure 2. The hexagonal crystals in this phantom plane in quartz were identified through Raman analysis as molybdenite. Photomicrograph by Nathan Renfro; field of view 7.19 mm. @topic:1


Publish Year: 2017 Title: Negative Crystals in Sapphires Abstract: Figure 1. A beautiful iridescent rosette pattern made up of flattened negative crystals appears around the primary negative crystals when illuminated by oblique fiber-optic lighting. Photomicrograph by Victoria Raynaud; field of view 1.07 mm.

	Negative crystals, or cavities within a crystal, and fluid inclusions occur in almost every mineral. They are generally too small to notice without high magnification, but these modest features hold great beauty and scientific value. These microscopic features are valuable to understanding the growth of continents, the rise of mountains, and the formation of gems. The following photos show beautiful examples of such inclusions in sapphires from the Baw Mar mining area in Mogok, Myanmar. Some of these fluid inclusions are arranged in a “rosette” pattern consisting of a large flattened negative crystal surrounded by smaller ones. This structure is always seen perpendicular to the c-axis (figure 1). The larger primary inclusions like those seen in figure 2 are characterized by their high relief and may display triangular growth markings as well as beautiful iridescence under oblique fiber-optic illumination. Other negative crystals associated with healed fissures are observed in random orientation. The smaller, more delicate fluid inclusions in these structures have a smoother outline, while the fingerprints themselves are often associated with the primary negative crystals.

	Figure 2. These two large primary fluid inclusions containing a black solid phase are associated with fingerprints that have a variable orientation. The photo was taken along the c-axis in darkfield illumination. Photomicrograph by Victoria Raynaud; field of view 1.07 mm.

	The multiphase inclusion in figure 3 contains a gas, a liquid, and at least one solid. When the specimen was gently heated by the microscope’s well light, the gas and the liquid homogenized. Raman spectroscopy identified the gas phase as pure CO2 and the opaque solid as marcasite. Using the same method, we also identified diaspore fibers, seen as faint lines in the inclusions, and a miniscule siderite crystal. Although fluid inclusions are common in most blue sapphires, the examples from Baw Mar reveal these fascinating inclusions in an appealing way.

	Figure 3. Left: A large fluid inclusion containing a CO2 gas bubble and a marcasite crystal. The primary inclusion is surrounded by smaller inclusions that make up a healed fissure. Right: When the sample was gently heated, the gas bubble disappeared as the gas and liquid homogenized. The sample is illuminated using diffused backlighting. Photomicrographs by Victoria Raynaud; field of view 1.20 mm.

	These photos were taken as part of a research project to document the blue sapphires from the Baw Mar mine. The complete report of this study can be found at https://www.gia.edu/gia-news-research/blue-sapphires-baw-mar-mine-mogok-myanmar. @topic:3


Publish Year: 2016 Title: Metallic Chromium Inclusions in Industrial By-Product Ruby Abstract: Figure 1. Photomicrograph of a petrographic thin section of ruby (purplish red)-diaoyudaoite (grayish green) slag, shown in transmitted light. From Sorokina et al. (2010).

	Technogenic corundum contained in metallurgical slag represents a potentially unique source of gem material. Since the 1950s, slags have been studied for their secondary uses. Their mineralogical and petrographic attributes have been documented, but to date there have been virtually no studies from a gemological standpoint.

	X-ray powder diffraction analysis (XRD) was performed on two slag samples taken from the waste products of chromium ore processing by thermite reaction at a refinery located in Russia’s Ural Mountains. These specimens showed the presence of corundum (α-Al2O3), the rare phase diaoyudaoite NaAl11O17, and a spinel-group mineral. For the spinel-group mineral, electron microprobe analysis (EPMA) indicated significant amounts of Mg, Cr, and Al. As seen in figure 1, the corundum contains transparent purplish red crystals up to 2.5 cm in length embedded in a diaoyudaoite matrix. The crystals may be elongated and prismatic, irregularly formed, or rounded. Gemological testing including refractometry, specific gravity measurements, and reaction under short-wave (254 nm) and long-wave (365 nm) UV. The UV reaction (figure 2, left) was consistent with natural and synthetic ruby (for in-depth analytical procedures and results, see E.S. Sorokina et. al., “On the question of technogenic ruby in the slags of Cr-V production,” Mine Surveying and Using of Mineral Resources, Vol. 2, 2010, pp. 33–35, in Russian). Microscopic examination of the samples showed features such as gas bubbles and irregular growth lines, both of which are inconsistent with natural corundum. Most significant was the presence of a metallic-phase chromium that appeared in several forms, such as needles, dendrites, and rounded or irregularly formed black solid inclusions with metallic luster. The metallic chromium was most frequently observed along the ruby parting planes (figure 2, right); it is an inclusion that has never been detected in naturally occurring corundum or in any synthetic analogues.

	Figure 2. Left: Intense red photoluminescence typical of ruby observed under long-wave UV; field of view 8.34 mm. Right: Strongly reflecting rounded and irregularly shaped metallic chromium inclusions within the technogenic ruby, surrounded by greenish gray diaoyudaoite matrix. Shown in reflected light; field of view 0.288 mm. Photomicrographs by Elena S. Sorokina.

	Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) and EPMA showed high Cr content (4.3–7.7 wt.%), most likely linked to the capture of micron-sized metallic chromium inclusions during the measuring process. We also found 135–270 ppmw of Mg, 30–70 ppmw of Ti, and 5–10 ppmw of V. Fe, Ga, Ni, Pb, and Pt were found to be below detection limit by both methods. This was the first time LA-ICP-MS had been applied to technogenic ruby.

	The identification of metallic-phase chromium inclusions, coupled with trace-element chemistry, will serve to separate these ruby slag materials from natural and other artificial analogues. @topic:3


Publish Year: 2023 Title: Special Hair-Like Inclusions in Quartz Abstract: Figure 1. “Rabbit hair” quartz samples with different colors. Photos by Shuqian Rui.
“Rabbit hair” quartz is a commercial variety of quartz with special inclusions. These inclusions resemble rabbit fur and are shorter and thinner than the typical rutile, tourmaline, or other acicular inclusions found in sagenitic quartz. To explore their internal features, nine rabbit hair quartz samples were classified according to the color of their inclusions (figure 1): red (R1–R4), yellow (Y1 and Y2), and white (W1–W3). The white rabbit hair quartz is rarer than the other colors.

Figure 2. A: Fibrous inclusions in red rabbit hair quartz (sample R1). B: Needle-like inclusions in yellow rabbit hair quartz (sample Y2). C: The tubular inclusions in white rabbit hair quartz (sample W1). Photomicrographs by Shuqian Rui; fields of view 0.71 mm (A), 0.91 mm (B), and 1.26 mm (C).
Microscopic observation shows slight variation between the different colors of these hair-like inclusions. In the red rabbit hair quartz, massive curved red fibers are distributed evenly. They are mostly brownish red and less than 1 mm in length (figure 2A). The bright yellow needle-like inclusions are distributed regularly but with some localized disorder. Some of the disordered parts form divergent bundles (figure 2B). The white inclusions seem to be hollow tubes, measuring approximately 1–2 mm (figure 2C).
Raman analysis identified the inclusions in samples W1, R1, and Y2. The hollow tubes in sample W1 with peaks at 208, 266, 355, 405, 465, 810, and 1083 cm–1 are the characteristic peaks of quartz. The fibrous red inclusions in sample R1 with peaks at 246, 295, 412, 612, and 1319 cm–1 are hematite. The yellow inclusions in sample Y2 with peaks at 305, 394, and 694 cm–1 are goethite.

Figure 3. The secondary electron images of the oblique section of the hollow tubes, outlined in yellow (sample W1). Images by Jinyu Zheng.
The freshly exposed surface of sample W1 was observed by scanning electron microscope (SEM). Figure 3 shows the secondary electron images; the pits are oblique sections of exposed hollow tubular inclusions (left), and the morphology of parallel sections of hollow tubes can be observed as grooves (right). In the pits, SEM with energy-dispersive spectrometry indicated that the main composition was SiO2, and no other impurity minerals filled into the hollow.
Fibrous hematite inclusions present in this study are rare in quartz, and their formation is likely related to the growth conditions (I. Sunagawa, Crystals: Growth, Morphology and Perfection, Cambridge University Press, Cambridge, 2005, p. 61). White hollow tubular inclusions might be the corroded product of hydrothermal fluids or weathering. In these processes, mineral inclusions were etched away, leaving the hollow tube with its original shape (Winter 2007 GNI, p. 370–373). However, the origin of yellow rabbit hair quartz still needs further research. @topic:1


Publish Year: 2022 Title: Grossular with Strong Red Fluorescence Abstract: Figure 1. The 9.63 ct pink grossular garnet reportedly from Mogok (A) fluoresced very strong red under long-wave UV (B) and weak chalky red under short-wave UV radiation (C). Photos by Qian Zhang.
The authors recently encountered a pink garnet rough reportedly from Mogok, Myanmar. The garnet was characterized by a light pink color in daylight, and it showed unusual strong red fluorescence under long-wave ultraviolet radiation and a weak chalky red reaction under short-wave UV (figure 1). A previously published report on grossular garnet showed similar fluorescence under long-wave UV, but the short-wave UV reaction was very different (M.S. Krzemnicki, “Pink grossular garnet from Mogok,” Facette, No. 26, 2020, pp. 26).

Raman spectroscopy identified the garnet as grossular. Electron probe microanalysis determined that the composition was consistent with that of nearly pure grossular with major elements of calcium, aluminum, and silicon (Ca3.114Al2.003Si2.883O12), and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) testing revealed trace elements of titanium, vanadium, manganese, and others (table 1). The pink coloration was due to two weak bands between 470 and 600 nm in the UV/visible absorption spectrum; Geiger et al. (1999) suggested they are related to Mn3+ (C.A. Geiger et al., “Raspberry-red grossular from Sierra de Cruces Range, Coahuila, Mexico,” European Journal of Mineralogy, Vol. 11, No. 6, 1999, pp. 1109–1113).

Figure 2. The photoluminescence spectrum collected on the grossular using 325 nm excitation at 300 K.
A photoluminescence spectrum recorded with 325 nm laser excitation displayed a strong narrow band at 604 nm accompanied by some weaker bands at 583, 595, 617, 631, 645, and 660 nm (figure 2). Gaft et al. (2013, 2022) published two papers about the luminescence of grossular (M. Gaft et al., “Laser-induced time resolved luminescence of natural grossular Ca3Al2(SiO4)3,” Journal of Luminescence, Vol. 137, 2013, pp. 43–53; M. Gaft et al., “Zero-phonon Mn2+ luminescence in natural grossular Ca3Al2(SiO4)3,” Journal of Luminescence, Vol. 248, 2022, article no. 119001). Our result is consistent with their 2022 result. They proposed that such luminescence emission may be related to the presence of Mn2+.

Figure 3. The 3D contour map of the pink grossular’s fluorescence spectrum. The stacked excitation spectra are not scaled or shifted for clarity.
In order to describe the pink grossular fluorescence features in detail, 3D fluorescence spectral data (i.e., excitation-emission mapping or EEM) was collected at room temperature using a Jasco FP-8500 fluorescence spectrometer (figure 3). The excitation wavelengths varied from 350 to 630 nm, with a step size of 1 nm and an excitation bandwidth of 5 nm. The emission spectra were collected from 400 to 680 nm, with the bandwidth set to 2.5 nm and a data interval of 0.1 nm, showing five obvious emission wavelengths at 604, 617, 631, 645, and 660 nm and their corresponding optimal excitation wavelength at 388 nm.
To our knowledge, this is the first time a detailed fluorescence analysis of pink grossular has been documented. @topic:1


Publish Year: 2022 Title: Synthetic Sapphire with Rose Channels Abstract: Figure 1. A 15.84 ct light purplish blue synthetic sapphire measuring 15.35 × 14.05 × 8.25 mm. Photo by U. Hennebois.
The Laboratoire Français de Gemmologie (LFG) received a 15.84 ct light purplish blue corundum for identification (figure 1). Under the microscope, clouds of bubbles similar to those seen in synthetic corundum were observed (figure 2), along with twinning planes and hollow channels known as Rose channels (figures 2 and 3). The Rose channels, which are always found at the intersection of twin lamellae, were crystallographically oriented along the edges of the rhombohedral faces and formed angles of about 90° (again, see figure 2); these features are normally seen in natural corundum (F. Notari et al., “‘Boehmite needles’ in corundum are Rose channels,” Fall 2018 G&G, p. 257).

Figure 2. Clouds of bubbles, Rose channels, and twinning planes in the synthetic corundum under crossed polarizers. Photomicrograph by U. Hennebois; field of view 3 mm.

Figure 3. Clouds of bubbles, Rose channels, and twinning planes in the synthetic corundum. Photomicrograph by U. Hennebois; field of view 10 mm.
Rose channels and twinning lamellae are common in natural corundum but seldom reported in synthetic corundum, including one instance in a Ramaura flux synthetic ruby (E. Fritsch et al., “Are boehmite needles in corundum Rose channels?” Geophysical Research Abstracts, Vol. 20, EGU2018-19493, 2018). This is because the twinning lamellae is most often formed via deformation twinning and results from post-growth events; thus, it is frequently observed in natural samples.

Figure 4. DiamondView imaging revealed curved growth lines characteristic of synthetic Verneuil corundum. Image by A. Herreweghe; field of view 10 mm.
The sample was inert under long-wave UV and presented strong blue luminescence under short-wave UV. No gallium was detected with energy dispersive X-ray fluorescence, which further confirms that this corundum was synthetic (S. Muhlmeister et al., “Separating natural and synthetic rubies on the basis of trace-element chemistry,” Summer 1998 G&G, pp. 80–101). DiamondView imaging showed curved growth lines, characteristic of Verneuil flame-fusion synthetic corundum (figure 4). Rose channels in corundum were linked in the past with boehmite needles and the characteristic absorptions in the 1500–4000 cm–1 region (Notari et al., 2018); however, no absorptions were observed in this region of the FTIR spectrum.
Although by far most common in natural corundum, the presence of Rose channels and twinning planes in synthetic corundum serves as evidence that these features alone cannot be used to confirm natural origin. @topic:3


Publish Year: 2022 Title: Social Media Success for Black Opal Direct Abstract: Figure 1. Black Opal Direct’s YouTube channel helped dramatically increase sales during the last two years.
At the GJX show, Justin Thomas (New South Wales, Australia) told us about Black Opal Direct’s success on social media during the pandemic, his efforts to share opal knowledge, and a black opal with a special story. Founded in 1961 by Thomas’s father, Jurgen, and owned and operated by Thomas and his wife, Ruth, Black Opal Direct specializes in black opal from Lightning Ridge.
Thomas said most of their customers come from YouTube and Instagram. In the last three years, their YouTube subscriber count has increased from 30,000 to 170,000. He said views fluctuate between 500,000 and 3 million a month, averaging about a million. This led to a tripling of sales over the last two years, though their business has now returned to normal. “It was a dream run,” Thomas said. “I believe those days are over.” He acknowledged that they have been fortunate in a time when many businesses around the world failed due to the pandemic. Without YouTube, he said, they would have weathered the last two years but would not be doing nearly as well.
Black Opal Direct began selling on eBay more than a decade ago. They determined that a million people per month were searching the Internet for the word “opal.” Within a few months of starting to sell rough on eBay, sales were strong; then they built their website and brought their eBay customers to it. Thomas created a YouTube channel (figure 1) around the same time as the eBay store, but it was only three years ago that he started posting videos more frequently.
“As the channel grew, it started to morph into more entertainment videos, showing them how fun it is to cut an opal, and my funny side, so they can see my personality,” he said. “I think in social media you have to show a lot more and a little bit of vulnerability. If you can connect in that way, in the heartstrings way, people will trust you a lot more and are much more likely to buy from you.”
Thomas believes his videos are helping the whole industry because he does not push sales. “I don’t even give the link to my website very often,” he said. “It’s all about the love of opal, how to cut it, how to mine it. It also helps the world understand opal.”
According to Thomas, the opal industry is very secretive, and he is probably the first person to share so openly through social media how to cut opal. He said many had thanked him at the show, saying they learned how to cut opal from his videos and in some cases quit their jobs to go into the opal business. “I think it’s awesome to be able to share that abundance,” he said.
Thomas learned to cut opal from his father, who moved to Australia from East Germany in the ‘60s and began mining in Lightning Ridge. Jurgen Thomas’s tools included a pick, shovel, and candle. When he began cutting, he used a manual Singer sewing machine that he converted by adding a corundum grinding wheel. “He’s passed away now, and all that knowledge is only with me,” Justin Thomas said. Despite the positive response of those learning from his videos, he said, many cutters are unhappy because he’s giving away prized secrets. “That knowledge—if that’s gone with my dad, and it goes with me, and my son never takes it up, it’s wasted,” he said. “Why let it go?”
Thomas emphasizes the quality of social media followers over the number. “Even if you’ve got a hundred followers, they could be a hundred genuine followers because they genuinely like you,” he said. “Say up to five percent of those people may buy. You grow from that.”
When Thomas cuts a highly valuable opal from rough on camera, he often does a dance. “They love it,” he said. “There’s always a comment before they watch a video: ‘I hope this one gets a dance!’” He has also been testing TikTok. “I always make jokes so they can see that I’m human, I’m personable, I can make an idiot of myself. I thought TikTok could be a good place for me to concentrate on those parts of my videos. I had a lot of followers quickly, who want to see me dancing.”
Some competitors have tried to copy him—unsuccessfully, according to Thomas, because “their heart’s not in it.” Some also criticize his style. “I get lots of people saying ‘You’re an idiot’ or ‘You’re a clown’ or ‘Why are you dancing?’ Water off a duck’s back. I try to focus on all the people that love me.”
After years of working out of their home, the Thomases recently purchased a warehouse and built a cutting workshop there. Thomas said their subscribers have loved watching the small business grow. “I love this industry so much and I love what I do so much that it’s addictive,” he said. “Giving more and more to the subscribers and to my followers, going to the next level. So watch this space.”
Thomas showed us a 10.65 ct black opal (figure 2), which he calls “the ultimate black opal.” Its vivid colors, patterns, and strong play-of-color make it extraordinary. One of his father’s friends, who mined with him at Lightning Ridge in the ‘60s, brought it to Thomas two years ago after finding it almost directly under the shed his father lived in back then.

Figure 2. A 10.65 ct black opal found in Lightning Ridge by one of Jurgen Thomas’s friends, at a location almost directly under where Jurgen lived nearly 60 years ago. Shown in diffused (left) and direct (right) lighting. Photos by Robert Weldon; courtesy of Black Opal Direct. @topic:9


Publish Year: 2022 Title: Mercury Free Mining Pilot Program Abstract: Figure 1. Gold and dense black sands in a traditional wooden batea, shown by a Colombian miner at Oro Verde. Typically, mercury is used to separate the two materials. Photo courtesy of Toby Pomeroy.
In late 2021, Mercury Free Mining (MFM), the Alliance for Responsible Mining (ARM), and GIA joined with Peruvian artisanal and small-scale gold miners (ASGM) to launch a new program intended to find alternatives to mercury in gold mining. The partners are bound in recognizing the reliance on artisanal and small-scale gold mining to produce major quantities of an extremely valuable commodity. This situation unfortunately perpetuates the leading cause of anthropogenic mercury pollution. The pilot program aims to proactively develop mercury alternatives in two gold mines, increasing their sustainability, building a traceable ASGM gold supply, and acting as a major leap in the MFM research team’s understanding of how we can ultimately eradicate mercury in gold mining.
Mercury Free Mining, the program lead, is a nonprofit organization founded by Toby Pomeroy, a lifelong goldsmith, jeweler, and passionate advocate for responsible sourcing. Founded in 2019 with the mission of eradicating mercury, MFM has been building a community of jewelers supporting efforts to provide the nearly 20 million ASGM with efficient and nontoxic mercury alternatives where presently unavailable.
MFM’s research and deployment team, led by the author, a geometallurgist, fosters novel sociotechnical solutions to address the issues facing ASGM with a focus on finding suitable mercury alternatives. This is a challenge. Gold is nonreactive to most chemicals (mercury being one of the only exceptions) and coincides with dense black sands that are difficult to mechanically separate (figure 1). The team’s methodologies rely upon the miners’ desire to maximize earnings by recovering more gold from the raw ores while also minimizing harmful social, health, and environmental side effects. Currently, reliable information about implementing mercury alternatives that are more effective and less harmful is scarce. Without this, miners have no choice but to rely upon a multi-generational neurotoxin in order to earn an income (figure 2).

Figure 2. In this photo from November 2020, Kenyan miners in Kakamega County press amalgam in a pan to remove excess water. Amalgam is a mixture of mercury and gold produced by adding mercury to concentrated gold ores. This method puts miners in direct contact with mercury, a potent neurotoxin that can be absorbed through the skin. Photo courtesy of Ruth Epwoka.
GIA granted $50,000 to jumpstart the pilot. Since then, MFM has collaborated with ARM engineers and Peruvian miners to collect representative mineral samples for use in testing a suite of innovative gold concentrators. MFM is partnering with six mineral processing experts to evaluate their respective technologies based on key performance indicators such as throughput, gold recovery, and concentration ratio. Spread across three continents, the testing will evaluate a large swath of potential mercury alternatives, helping to gather critical information on how different processors are suited for various gold ores (figure 3). This stage of the project will draw from advanced engineering and science to perform thorough analyses in an accurate and timely manner.

Figure 3. Miners wash the gold ores and use a sluice to collect gold within the slurry. Sluices are one of the most common tools used in artisanal and small-scale mining to concentrate gold. This simple configuration can capture ~20–70% of gold based on ore type, water flow, feed rate, and other specifications geometallurgists determine through research. Photo courtesy of Ruth Epwoka.
Following the testing, the results will be holistically synthesized by the MFM research team with respect to the many complexities of the miners’ unique situations. This will include a mercury comparison to understand the true viability for the miners to adopt an alternative. Stakeholder discussions will then determine whether the miners ultimately decide to adopt one of the mercury-free technologies. If so, the team will help implement the transition to mercury-free methods and conduct observational research to better define the impact on the health of miners and their communities.
The completion of this pilot program in 2022 will mark a turning point in MFM’s ability to minimize the global impacts of mercury by having a tested and verified framework that can translate to additional mercury elimination projects as MFM expands. Following the pilot, the MFM team will publicly release the first report documenting the research process and results in complete detail. This and future reports can be used freely by miners and organizations to enhance the ability to safely source gold. For those interested in learning more, collaborating, or using these methods elsewhere, please contact the author. @topic:11


Publish Year: 2021 Title: Biogenic Carbon in Pink Corundum from Southern West Greenland Abstract: Figure 1. Field relationship of aluminum-rich metasedimentary rocks with ultramafic rocks at the Maniitsoq pink corundum occurrence in Greenland. Corundum is found along the boundary between these two rock types. Photo by Kristoffer Szilas.
Some of the oldest ruby is found in the southern part of West Greenland. Although the most famous locality is the Aappaluttoq deposit—where corundum is hosted by igneous rocks (N. Keulen et al., “Formation, origin and geographic typing of corundum (ruby and pink sapphire) from the Fiskenæsset complex, Greenland,” Lithos, Vol. 366–367, 2020, article no. 105536)—several smaller occurrences are found throughout the region. A number of these smaller occurrences are hosted by metamorphosed sedimentary rocks that were tectonically interleaved with ultramafic rocks (figure 1). Fluid-assisted movement of silica from the metasedimentary rocks to the ultramafic rocks and reverse movement of minor amounts of chromium during metamorphism have been proposed to cause the chemical conditions necessary for ruby growth.

Figure 2. Pink corundum from the Maniitsoq locality containing a macroscopic inclusion of graphite. Photo by Kristoffer Szilas.
Pink corundum from these smaller occurrences contains various types of mineral inclusions, most notably rutile and graphite (figure 2). Two recent studies investigated these rocks with the goals of dating the absolute timing of corundum growth, understanding the corundum formation mechanisms, and determining the origin of graphite (V. van Hinsberg et al., “The corundum conundrum: Constraining the compositions of fluids involved in ruby formation in metamorphic melanges of ultramafic and aluminous rocks,” Chemical Geology, Vol. 571, 2021, article no. 120180; C. Yakymchuk et al., “Corundum (ruby) growth during the final assembly of the Archean North Atlantic Craton, southern West Greenland,” Ore Geology Reviews, Vol. 138, 2021, article no. 104417). Samples were collected from an occurrence near the town of Maniitsoq and from a second occurrence on Storø Island to the northeast of Greenland’s capital, Nuuk.
Rutile inclusions are about 2.5 billion years old at both localities, based on uranium–lead geochronology. However, the pink corundum may be slightly older than this, given that the isotopic clock in rutile may only start sometime on the post-growth cooling history. Nevertheless, this constrains the timing of corundum growth during the final stabilization of the continental crust in the region.
This research also analyzed the carbon isotope composition of graphite to determine its origin. In general, biogenic activity modifies carbon isotopes; living organisms preferentially incorporate the lighter isotope (12C) compared with the heavier isotope (13C). Graphite from the Storø Island location was very enriched in the lighter isotope and was interpreted as a bona fide organic signature, which suggests that the graphitic carbon was originally part of a living organism. Graphite from the Maniitsoq pink corundum locality was less enriched in the lighter carbon isotope, but the isotope signature was still most consistent with a biogenic origin. Although the presence of carbon of biogenic origin is not surprising given the sedimentary nature of the host rocks, the research team modeled the chemical conditions necessary for corundum growth and suggested that the presence of graphite created the conditions in the rocks that facilitated corundum formation at the imposed depths and temperatures of metamorphism.
Although the recognition of biogenic carbon in the form of graphite in pink corundum occurrences is based on a limited number of samples, future work should be able to determine how widespread this association is in southern West Greenland. In addition, in situ analysis of carbon in graphite inclusions using secondary ion mass spectrometry would help further test the hypothesis of a biogenic origin of graphite in 2.5 billion-year-old pink corundum. @topic:2


Publish Year: 2015 Title: Demantoid Garnet with Giant Fluid Inclusion Abstract: Figure 1. The demantoid crystal from Madagascar contains a giant two-phase fluid inclusion. The photomicrograph shows the FI cavity with its bubble trapped by the garnet. The bubble’s diameter is around 2 mm. Photo by Michel Cathelineau.

Since 2009 the Antetezambato demantoid garnet deposit, near Ambanja, in the Ambato peninsula of northern Madagascar, has yielded a huge quantity of rough gem material. This skarn-related deposit continues to produce fine crystals for the international market in a wide range of colors (F. Pezzotta et al., “Demantoid and topazolite from Antetezambato, northern Madagascar: Review and new data,” Spring 2011 G&G, pp. 2–14). Mineralogical curiosities were also found, such as demantoid garnet fossil pseudomorphs of gastropod and coral (Winter 2013 GNI, pp. 257–258; J. Raoul et al., “Pseudomorphose de fossiles en andradite ‘démantoïde’ à Antetezambato, Madagascar,” le Règne Minéral, Vol. 123, 2015, pp. 21–26). An andradite crystal (figure 1) hosting a giant two-phase (liquid + vapor) fluid inclusion (FI) was extracted from the mangrove swamps and is now the property of M. J. Raoul.

The greenish gem crystal, measuring 1.5 × 0.6 cm (figure 2A), exhibits some faces that follow a more dodecahedral habit {110} while others are more trapezoidal {110}. Micro-Raman spectroscopy clearly showed the four main peaks of andradite at 352, 371, 515, and 874 cm–1 (figure 3, top). The bubble of the FI cavity is visible to the naked eye and moves when the sample is turned, similar to some giant FI in quartz. The demantoid garnet was investigated by X-ray computed tomography (CT) scanning to reveal its 3D interior morphology. Images were made with a Phoenix Nanotom S scanner using a resolution of 7.59 μm/voxel and an X-ray tube on nanofocus tension of 115 kV. The calculation of all the phases was computed by VGStudio software, and the volumes of the respective phases are the sums of voxels. The 3D tomography images show a unique fluid inclusion cavity (figure 2B) with a morphology like a negative crystal with polygonal outlines parallel to the faces of the host garnet crystal (figures 2C, D). All the criteria define a primary two-phase FI. The total volume of the garnet is 896.1 mm3, of which 6.2 vol.% is occupied by the FI cavity. The volume of the liquid phase is 52.16 mm3 and the volume of the vapor phase is 3.52 mm3, which corresponds to a liquid/vapor ratio of 6.75%.

Figure 2. 3-D tomography images of the demantoid and the giant fluid inclusion cavity. Top left: Morphology of the crystal. Top right: Tomographic section of the crystal showing the morphology of the fluid inclusion cavity. Bottom left: The internal view of the cavity showing the gas bubble. Bottom right: The cavity displays a negative crystal morphology with polygonal outlines parallel to the faces of the host garnet crystal, as well as the bubble phase (blue).

Figure 3. The micro-Raman spectra of the Antetezambato demantoid garnet in the
170–1200 cm–1 range (top) and the 2750–4000 cm–1 range (bottom).
The Raman spectrometry data show that the fluid is free of CO2, CH4, H2S, and N2: the FI is a primary two-phase aqueous FI (liquid + vapor). The salinity of the aqueous FI was determined by analyzing the Raman spectrum of H2O based on the weakening of the hydrogen bond by chloride. A deformation of the OH stretching vibration band of water appears in the range between 2900 and 3700 cm–1 (figure 3, bottom). Even if the cationic composition of the natural FI differs from pure sodium, the experimental approach yields the salinity of any inclusion accurately if NaCl is the main species (M.-C. Caumon et al., “Fused-silica capillary capsules (FSCCs) as reference synthetic aqueous fluid inclusions to determine chlorinity by Raman spectroscopy,” European Journal of Mineralogy, Vol. 25, No. 4, 2014, pp. 755–763). Under these conditions the calculated salinity for the demantoid garnet FI is about 8 wt.% equivalent NaCl.

The gem garnet mineralization of Antetezambato is described as a skarn-type deposit related to Upper Mesozoic to Cenozoic magmatism affecting the limestones of the Mesozoic Isalo Group (again, see Pezzotta et al., 2011). Similar demantoid-bearing skarns are described in the Ampasindava Peninsula at Ambohimirahavavy, 50 km west of Ambanja (G. Estrade et al., “REE and HFSE mineralization in peralkaline granites of the Ambohimirahavavy alkaline complex, Ampasindava peninsula, Madagascar,” Journal of African Earth Sciences, Vol. 94, 2014, pp. 141–155). The skarns of the Ambohimirahavavy alkaline granitioid complex are host to rare-metal mineralization. Peralkaline dykes intruded (at 24.2 ± 0.6 Ma) the limestone of the Isalo groups (G. Estrade et al., “Unusual evolution of silica-under- and -oversaturated alkaline rocks in the Cenozoic Ambohimirahavavy Complex (Madagascar): Mineralogical and geochemical evidence,” Lithos, Vol. 206–207, 2014, pp. 361–383) and developed a bi-metasomatic skarn. The metasomatic zone was formed at the contact with the calcareous rocks by calc-silicate rocks (exo-skarn zone) with diopside, garnet andradite (demantoid variety), calcite, apatite, phlogopite, fluorite, and wollastonite. At the contact of the granite (endo-skarn zone), the associated minerals are quartz, albite, aegirine-augite, and calcite (G. Estrade, “Le complexe cénozoïque alcalin d’Ambohimirahavavy à Madagascar: origine, évolution et minéralisations en métaux rares,” PhD thesis, Paul Sabatier University, Toulouse, France, 2014, 299 pp.) Exo-skarn paragenesis is also found as inclusions in the demantoid of Antetezambato, such as fluorine-(arsenic)-bearing apatite, fluorite, calcite, wollastonite, fluorine-bearing vesuvianite, diopside, calcite, and quartz (W. Barrois et al., “Caractéristiques minéralogique et chimique des grenats démantoides de Bagh Borj (Iran) et d’Antetezambato (Madagascar): conséquences géologiques. 2ème partie, Études minéralogique et chimique,” Revue de Gemmologie a.f.g., Vol. 183, 2013, pp. 10–15, in French).

Fluid inclusions were observed in all the minerals of the exo- and endo-skarns of the Ambohimirahavavy alkaline complex, but they were too small in the garnet for microthermometric studies. In quartz, calcite, and diopside, three types of primary aqueous FI, free of CO2, CH4, H2S, and N2, were characterized (see Estrade’s PhD thesis). The main FI type (liquid + vapor) consists of 20 to 40 vol.% vapor, and homogenizes to liquid between 255 and 375°C for quartz, and 350 to 370°C for diopside, with a wide range of salinity between 0.5 and 25 wt.% equivalent NaCl. There is also a vapor-rich (V) FI and a halite-bearing FI (liquid + vapor + halite). The giant liquid-rich FI (liquid + vapor) trapped by the demantoid of Antetezambato has a salinity of 8 wt.% equivalent NaCl that falls within the salinity range of the (liquid + vapor) FI type found for all the minerals from the Ambohimirahavavy skarn.

Such chemical and salinity similarities of the fluids between the two settings confirm that the Antetezambato deposit is associated with a skarn deposit linked to the intrusion of Oligocene alkaline magmatism. In the Ambohimirahavavy deposit, fluid inclusions in garnet are too small to be studied by microthermometry. The giant inclusion trapped in the demantoid from Antetezambato testifies to the presence of cavities favorable for fluid inclusion studies and proves that the parental fluid of demantoid garnet was aqueous.

Demantoid at Ambato peninsula is linked to the presence of alkaline magmas intruding limestones of the Isalo group. These garnets are Cr-free but contain Al (Barrois et al., 2013). The source of aluminum and iron is the alkaline magma (syenite, nepheline syenite, and alkaline granite), while calcium originated from the limestone. The fluorine and phosphorus-bearing inclusions trapped by the andradite from both occurrences were carried by the alkaline magma, which was rich in fluorine, phosphorus, and rare earth elements. In the future, primary skarn-type demantoid-bearing deposits in northwestern Madagascar at the contact between alkaline granite dykes and limestone from the Isalo Group should be prospected for this material. @topic:1


Publish Year: - Title: Mozambique Copper Bearing Tourmaline Mine Abstract: Moussa KonateBC Gemas do Brazil and Mozambique Gems

Interview with Moussa Konate, BC Gemas do Brazil and Mozambique Gems
For some time, Brazil was considered the sole legitimate source of the electric-blue tourmaline known as Paraíba. As a result, Mr. Konate and his company met considerable resistance when they first started mining similar material in Mozambique.

The market soon accepted his copper-bearing Paraíba tourmaline because, he says, it became about the quality rather than the name.

Every day, miners dig out the ore and bring the material to the washing plant, where they currently wash about 11 16-ton truckloads per day, up from 6 to 7 at the beginning. Mr. Konate’s stated goal is to increase production to 30 truckloads daily. The mine, which started up in 2006, yields about 1 to 2 kg (about 2 to 4 lbs.) of good-quality tourmaline a month, mostly in 1 to 5 gram (under .20 ounce) sizes, but up to 200 grams (7 ounces) in some rare cases.

Since starting operations, his company has explored barely 2 hectares (5 acres) of their 300-hectare (740-acre) claim, leaving plenty of area still unexplored. The company’s license is in effect until 2036.

Mr. Konate’s company is also exploring for aquamarine in the mine’s northern region. They’ve had some success, finding scattered pieces of cabochon material, but they’re still looking for the pocket that will lead them to maximum yield. As he says with a smile, “Then we can invite you guys to come and see us take out 100 kilos (220 lbs) of pure aquamarine.” @topic:9


Publish Year: 2013 Title: Petrochemical Characteristics and Genesic Significance of Luodian Jade from Guizhou Abstract: Luodian jade is a new nephrite variety discovered in 2009 at Luodian County in China’s Guizhou province. The nephrite formed within the metasomatic zone between the Varisian gabbro and calc-silicate. Geochemistry and petrology studies of both the white and greenish white varieties indicate  98% and 95% tremolite, respectively. Tremolite has an ideal chemical formula of Ca2(Mg, Fe)5[Si4O11]2(OH)2, with Mg and Fe substituting for each other to form a solid solution series. Al can also substitute for a small amount of Mg and Fe, while Na, K, and Mn can substitute for Ca and Mg. Chondrite-normalized REE (rare earth element) patterns of the nephrite and the host rock are very similar with enrichment of LREE (light rare earth elements). The concentration of REE is lower in the nephrite than that in the host rock. The La/Yb ratio is also much higher in nephrite, which indicates a higher differentiation of REE in nephrite. Compared to the greenish and greenish white nephrite, the white variety is more evolved. This tells us that the nephrite deposit formed in two stages. Ca/Mg is higher in the greenish and greenish white varieties, meaning they were formed when Mg was unsaturated in the fluid; the white variety formed when Ca and Mg were both saturated. The substitution of trace-element V and Cr into the crystal lattice is closely related to the saturation of Mg in fluid. V and Cr are also the chromophores of the greenish and greenish white varieties. Nephrite formation is caused by metasomatism during the interaction with thermal fluid brought by the intrusive gabbro and the limestone. Limestone provided Ca and Mg, while the fluid brought Si, K, Na, and Al. @topic:9


Publish Year: 2013 Title: Paramagnetic Hole Centres in Natural Zircon and Zircon Colouration Abstract: This article explores atomic defect centers (color centers) of natural zircon from three localities: North Carolina, the Massif Central in southern France, and the Ural Mountains of Russia. The origin of zircon coloration is little discussed in the spectroscopic literature. This study further explores paramagnetic properties and optical absorption, and also suggests additional constraints in the nature of some color centers occurring in natural zircon.

Electron paramagnetic resonance (EPR) and optical absorption spectroscopy are used on a heterogeneous sample group of 11 small untreated zircon crystals. The findings indicate an obvious correlation between color and certain paramagnetic defect centers in the crystal structure. But the EPR studies also show that the presence of tetragonal centers of trivalent rare-earth elements and niobium is not directly related to any specific zircon coloration.

The paper discusses the highly technical EPR spectral indications for electron and hole defect centers (e.g., angular dependencies and crystal axes, principal g-values), as well as the intricate substitutional charge patterns that reflect the isomorphism of zircon.

The optical absorption spectra in samples from the United States and France (colorless through pinkish to reddish and brownish) show similar spectra with two broad bands at 340–350 and 510–515 nm. The Russian samples (colorless through yellowish-brownish) show a more complicated spectra of three dominant bands at 320, 390, and 420 nm, plus a weak band at 510.

The results confirm that these two common color series subdivisions are meaningful.

Abstracted by Edward R. Blomgren @topic:3


Publish Year: 2013 Title: Major Crocoite Discoveries at the Adelaide Mine, Tasmania Abstract: Crocoite, first discovered in the Urals in 1766, was named crocoise in 1832. Its attractive orange-red hue and adamantine to vitreous luster make it one of the most pursued mineral collector specimens. Tasmania, located southeast of mainland Australia, has long been famous for its outstanding crocoite specimens, and nearly all commercial specimens come from the Red Lead and Adelaide mines.

The mines lie within a four-square-kilometer area. Cambrian intrusions of serpentinite within the Precambrian and slightly younger metasedimentary rocks provided the Cr needed to form crocoite. During the Devonian, metal-rich granitic intrusions provided hydrothermal fluids along the extensive shear zones to alter much of the serpentinite to a peculiar rock called listwanite and precipitate pods with veins of Pb-bearing minerals. Since crocoite is more stable than other Pb-bearing minerals at low pH levels, it predominated in these mines. Crocoite was common in the gossan, but open pockets yielded the best samples.

The earliest discovery of crocoite in Tasmania dates back to 1891. Over the last 120 years, it has been mined intermittently at several localities. Until the 1970s, many of the high-quality specimens were either destroyed or used for industrial applications. In 1970, “crocoite king” Frank Mihajlowits leased the Adelaide mine and began a string of major discoveries. Among these was a watercourse discovered in 1990 that was worked on for 14 years and yielded thousands of superb specimens.

In 2004, Mihajlowits sold the mine to Adam Wright’s newly established Adelaide Mining Company, which continues to work the deposit. A major new pocket of crocoite found in 2012 was of great excitement to mineral collectors. The opening of this watercourse is about one meter wide and two meters tall. Crocoite crystals of various lengths protrude at different angles to each other. This discovery is called the “Red River find,” and the watercourse has been broken into from below with no end to the channel found as yet. Many of these superb specimens were exhibited at the 2012 Tucson show.

Abstracted by Tao Hsu @topic:2


Publish Year: 2022 Title: Hydrothermal Synthetic Ruby Abstract: Figure 1. Photos of the hydrothermal synthetic ruby in daylight and short-wave UV light. Photos by Diego Sanchez.
Hydrothermal synthetic ruby was first introduced to the market in the 1960s (A. Peretti and C.P. Smith, “An in-depth look at Russia’s hydrothermal synthetic rubies,” JewelSiam, April-May 1993, pp. 96–102). The hydrothermal process is very slow and requires high heat and very high pressure (400–600°C, 5,000–30,000 psi), mimicking the conditions deep in the earth that result in the formation of natural ruby. In this method, the corundum seed plates are suspended inside the growth chamber and nutrients are placed in the bottom. Slowly the nutrients dissolve and form a solution which deposits new synthetic corundum growth onto the seed crystal. The size of the synthetic crystal depends on the size of the seed, amount of nutrient solution, and time.
The Carlsbad laboratory recently received a 4.55 ct transparent cushion-cut hydrothermal synthetic ruby for an identification report (figure 1). This type of laboratory-grown ruby is seldom submitted to the laboratory today, though they were more prevalent in the 1980s. Gemological testing yielded an RI of 1.761–1.769 and a specific gravity of 3.99. Its fluorescence reaction was strong red to long-wave and medium red to short-wave UV radiation, and its pleochroism was orangy red to purplish red. These properties are typical of most rubies, natural or laboratory grown.
Chemical analysis was done by EDXRF and showed a high amount of chromium (1550 ppma), low iron (153 ppma), titanium (25.5 ppma), no gallium, and very low vanadium (2.24 ppma), which matches the synthetic corundum chemistry.

Figure 2. The chevron growth structure observed in the hydrothermal synthetic ruby. Photomicrograph by Shiva Sohrabi; field of view 4.79 mm.
Magnification showed characteristic internal features of hydrothermal synthetic corundum such as subparallel striations and angular/zigzag (chevron) graining using a standard gemological microscope in conjunction with fiber-optic light or diffused light (figure 2).

Figure 3. The DiamondView image of the chevron growth pattern in the hydrothermal synthetic ruby. Photomicrograph by Shiva Sohrabi; field of view 8.63 mm.
The baseline-corrected spectra showed very strong water peaks in the region between 3200 and 3600 cm–1, which is strongly indicative of hydrothermal synthetic origin. (The instrument was baseline corrected to remove the water signal from the atmosphere as well as having the sample chamber purged with dry air to minimize the detection of water from the atmosphere.) Luminescence images in an ultra-short-wave UV radiation DiamondView showed an interesting chevron growth pattern as well with red fluorescence, further confirming hydrothermal synthetic origin (figure 3).
While hydrothermal synthetic rubies are not as common in the gem trade today, it is helpful to review the distinctive features and characteristics that make them identifiable. @topic:3


Publish Year: 2019 Title: Intergrown Emerald Specimen from Chivor Abstract: Figure 1. An emerald crystal inclusion measuring ~2.67 × 2.71 × 5.43 mm is found inside this large emerald specimen (18.35 × 10.69 × 9.79 mm) from Colombia’s Chivor mine. Photo by John Jairo Zamora.

Colombia’s Chivor emerald mines are located in the eastern zone of the Eastern Cordillera range of the Andes Mountains. Chivor translates to “green and rich land” in Chibcha, the language of the indigenous people who were already mining emerald more than 500 years ago, before the arrival of the Spanish conquistadors (D. Fortaleché et al., “The Colombian emerald industry: Winds of change,” Fall 2017 G&G, pp. 332–358). Chivor emeralds exhibit a bright green color with a tint of blue; they have relatively high clarity and fewer inclusions than emeralds found in Colombia’s western belt.
The authors recently examined a rough emerald crystal specimen (figure 1), measuring 18.35 × 10.69 × 9.79 mm, reportedly from Chivor. This crystal weighed 3.22 g (16.10 ct) and had a prismatic hexagonal crystal shape. Standard gemological examination confirmed the gemstone to be emerald, and ultraviolet/visible/near-infrared (UV-Vis-NIR) spectroscopy showed a classic Colombian emerald absorption spectrum. The crystal’s color was typical of Chivor emeralds, a medium dark green showing a blue tint. The emerald, which hosted jagged three-phase inclusions that are typically observed in Colombian material, showed no signs of clarity enhancement.

Figure 2. Left: A well-formed emerald inclusion, showing a hexagonal prismatic shape with pyramidal termination. Right: The view from below shows a perfect hexagonal crystal outline. Photomicrographs by John Jairo Zamora; field of view 12 mm.
The emerald specimen hosted a large, unique inclusion of emerald almost perpendicular to the c-axis, measuring approximately 2.67 × 2.71 × 5.43 mm. The inclusion’s identity was confirmed by Raman spectroscopy. The inclusion exhibited a well-formed hexagonal prismatic shape with pyramid-like termination (figure 2). Although intergrowth emerald crystals have been described and documented in the literature several times (G. Grundmann and G. Giuliani, “Emeralds of the world,” in G. Giuliani et al., Eds., Emeralds of the World, extraLapis English, No. 2, 2002, pp. 24–35; I. Sunagawa, Crystals: Growth, Morphology and Perfection, Cambridge University Press, 2005, pp. 127–149), it is always a spectacular feature to observe, making this emerald rough crystal from Chivor with an emerald crystal inclusion a unique collector’s specimen. @topic:1


Publish Year: 2016 Title: Inclusions in Burmese Amber Abstract: Figure 1. This Tropidogyne flower is still attached to its stem and has a small flea-like bug near its right side, as seen with darkfield and fiber-optic illumination. Photomicrograph by Victoria Raynaud; field of view 5.97 mm.

	Burmese amber has been well documented in the paleontological literature, but is overshadowed in the gemological community by material from the Dominican Republic and the Baltic area. Despite the armed conflict in the Hukawng Valley, possibly the world’s largest tiger reserve, accessibility has improved and amber production has steadily increased since 2014. As a result, more Burmese amber is reaching the marketplace. We have observed rising interest in the Bangkok, China, and Hong Kong markets, with specimens containing large inclusions of flora and fauna in great demand and commanding high prices. The samples presented here (figures 1–3) were acquired during a January 2016 field expedition to the Hukawng Valley and are now part of the GIA research collection.

Figure 2. This spider is surrounded by small air bubbles and plant debris. It is very easy to resolve fine details, such as individual hairs and different sets of eyes. The sample is illuminated with a combination of diffuse brightfield and fiber-optic light. Photomicrograph by Victoria Raynaud; field of view 7.20 mm.

	Figure 3. Left: The delicate features of this fly, particularly its wings, are surrounded by gas bubbles and trichomes (hair-like structures that grow on plants). Right: This image demonstrates the excellent preservation qualities of amber, as evidenced by the detailed structure of the fly’s eye. Photomicrographs by Victoria Raynaud; field of view 4.80 mm (left) and 0.86 mm (right). Brightfield and fiber-optic illumination.

	These amber specimens are interesting because they potentially preserve evidence from biological environments of 80 to 100 million years ago (G. Shi et al., “Age constraint on Burmese amber based on U–Pb dating of zircons,” Cretaceous Research, Vol. 37, 2012, pp. 155–163, www.sciencedirect.com/science/article/pii/S0195667112000535). They are significantly older than amber from the Dominican Republic, estimated at 25–40 million years old) and the Baltic region, which are about 25–28 million years old (D. Penney, Biodiversity of Fossils in Amber from the Major World Deposits, Siri Scientific Press, Manchester, United Kingdom, 2010). @topic:8


Publish Year: 2014 Title: Colombian Emerald Mining:Will the Giant Awaken? Abstract: R. Ringsrud. “Peñas Blancas: An Historic Colombian Emerald Mine,” The Journal of Gemmology, Vol. 33, No. 7–8, 2013, pp. 187–199. Photo courtesy of Edward Boehm.

              Emerald is the green variety of the mineral beryl, colored by chromium and vanadium. These trace elements are normally concentrated in quite different parts of the Earth’s crust, and only complicated geological processes enabled these contrasting elements to find each other and to crystallize into one of the most beautiful gemstones.

Colombian emeralds are mined from two belts within a mountain range known as the Eastern Cordillera. The western zone hosts, from north to south, the Peñas Blancas, Cosquez, La Pita, Muzo, and Yacopi mining regions; the eastern zone hosts the Chivor (Somondoco) and Gachala mines. These mines are located in the state of Boyacá, and access is difficult.

Colombian emeralds formed through a hydrothermal-sedimentary process. The geochemical processes for both the western and eastern zones are basically the same. The emeralds occur in organic rich shales and limestones. The fractures in the shales allowed hydrothermal fluids to infiltrate and deposit emerald and other accompanying minerals. This deposition occurred in several episodes involving heat and sometimes violent pulses of pressure. Fluid inclusions of the solutions from which the emeralds were formed became trapped during the crystallization process. These fluid inclusions represent a geological “fingerprint.”

Peñas Blancas emeralds are slightly bluish green, with little color zoning and a velvety appearance. One unique characteristic of the rough material is called “cascocho,” which refers to the crystals’ tendency to have pits and cavities due to secondary chemical etching. The abundance of quartz as a vein mineral differentiates Peñas Blancas from other emerald mines in the area.

Trapiche emeralds are perhaps the rarest and most memorable of “pattern” gems. Trapiche is the Spanish word for a spoked wheel used to grind sugar cane, which bears a striking resemblance to the pattern in these emeralds. Two distinct growth regimes are responsible for the formation. First, the central tapered core grows under hydrothermal conditions. Then, growth conditions change and both emerald and albite are formed. The hexagonal prism faces of the core maintain their uniform growth, producing pure emerald, while areas growing from the edges between prism faces do not and are filled with albite. This results in six sectors of clear emerald, and six of predominantly albite and minor emerald. Trapiche emeralds are cut into cabochons to display the beautiful spoke-like star. In the 1960s and 1970s, many large trapiches from Peñas Blancas found their way into collections all over the world.

Colombian emeralds are among the world’s finest in terms of quality. The Andean nation is still one of the main emerald producing countries, alongside Brazil and Zambia. A lack of investment and mechanization at aging mines led to a decline after easily accessible gems became scarce. Heavy overgrowth has inhibited geologic exploration, and prospecting has been hindered by remoteness, steep topography, and a difficult social climate. A sound government policy along with investment and thorough prospecting could tap the full potential of the Colombian emerald deposits. @topic:9


Publish Year: - Title: Paramagnetic Hole Centres in Natural Zircon and Zircon Colouration Abstract: This article explores atomic defect centers (color centers) of natural zircon from three localities (North Carolina, the Massif Central in the south of France, and the Ural Mountains of Russia). The origin of zircon coloration is little discussed in the spectroscopic literature. This study further explores paramagnetic properties and optical absorption, and also suggests additional constraints in the nature of some of the color centers occurring in natural zircon.

Electron paramagnetic resonance (EPR, an absorption technique using magnetic fields to measure transition energies in atomic defect centers) and optical absorption spectroscopy are used on a heterogeneous sample group of eleven small untreated zircon crystals. The findings indicate an obvious correlation between colors and certain paramagnetic defect centers in the crystal structure. However, the EPR studies also show that the presence of tetragonal centers of trivalent rare-earth elements and niobium is not directly related to any specific zircon coloration.

The paper discusses the highly technical EPR spectral indications for electron and hole defect centers (e.g., angular dependencies and crystal axes; principal g-values, etc.), as well as the intricate substitutional charge patterns which reflect the isomorphism of zircon.

The optical absorption spectra in samples from the US and France (from colorless through pinkish to reddish and brownish) show one type of spectra, two broad bands, 340–350 nm and 510–515 nm. The Russian samples (from colorless through yellowish-brownish) are different, showing a more complicated spectra of three dominant bands at 320, 390, and 420 nm and a weak band at 510.

The results confirm that the subdivision of these two common color series is meaningful.

Abstracted by Edward R. Blomgren @topic:3


Publish Year: 2024 Title: Brazilian Watermelon Tourmaline with Iris Effect Abstract: These 18 × 18 × 4 mm watermelon tourmaline slices (17.82 ct on the left and 17.17 ct on the right) display an exceptional iris effect. Photo by Jeffrey Scovil.
The watermelon tourmaline slices shown in the figure above are remarkable for their mesmerizing iris effect. Unearthed from the famed Cruzeiro mine in the Brazilian state of Minas Gerais more than seven years ago, they were precisely cut to unveil their rainbow spectrum. Each slice, measuring 18 × 18 × 4 mm, radiates an alluring interplay of colors attributed to the iris effect, a phenomenon created by subtle internal fractures within the gemstone. This rare flawlessly matched pair weighed 34.99 carats total, conjuring the enchantment of fiery Australian opals. @topic:9


Publish Year: 2024 Title: “Cyber” Butterfly Abstract: The rectilinear zigzag-patterned fingerprint and the negative crystal in the center are reminiscent of a beautiful “cyber” butterfly trapped in this 2.56 ct purple sapphire. Photomicrograph by Yuxiao Li; field of view 2.60 mm.
The author recently examined a 2.56 ct purple octagonal step-cut sapphire. This sapphire contained a negative crystal with a sharp rectilinear zigzag-patterned fingerprint, providing strong evidence that no heat treatment took place. Under fiber-optic illumination, the fingerprint displayed vibrant colors due to thin-film interference. The combination of the fingerprint and negative crystal created an image reminiscent of a digital butterfly (see above). Both the negative crystal and the unique fingerprint were caused by the natural healing of a surface-reaching fracture in the sapphire host. The healed areas parallel to the c-axis displayed rectangular outlines, resulting in the “cyber” appearance of the wings. @topic:3


Publish Year: 2023 Title: Fissure with Moiré Pattern in Spinel Abstract: A precipitation of an unidentified mineral in a fissure of a purple spinel creates this highly intricate moiré pattern. A combination of oblique fiber-optic and darkfield illumination was used. Photomicrograph by Tyler Smith; field of view 2.90 mm.
Surface-reaching fissures commonly host precipitates of epigenetic minerals, as was the case with a 4.22 ct purple spinel recently examined by the author. “Islands” of unidentified birefringent inclusions occupied a near-planar fissure. These inclusions were inert to Raman spectroscopy. Delicate depositions radiating from these islands interacted to create a complex moiré pattern (see above). Moiré patterns, named after their resemblance to a type of fabric, form when parallel or concentric lines overlap. It is unclear whether the islands formed first and were partially dissolved in a secondary event, or if they formed simultaneously with the spinel. Although moiré patterns have been observed in partially healed fluid fingerprints and surface-reaching fissures, it is rare to see them expressed in such a spectacular form. @topic:3


Publish Year: 2023 Title: Night Sky in Yellow Sapphire Abstract: This scene of an iron stain and numerous curved lines showing rainbow colors in a fracture resembles a scene from the night sky viewed through a telescope rather than a microscope. Photomicrograph by Charuwan Khowpong; field of view 2.85 mm.
Fractures are usually not desired in gemstones, but in some cases they provide a great subject for photomicrography. When a 2.49 ct yellow sapphire from Ilakaka, Madagascar, was examined with a fiber-optic light, the scene in the figure above was revealed. It is reminiscent of a long-exposure photograph of a star-filled sky with an extraterrestrial object floating in it. In reality, this is a globular iron stain in a large fracture, but the spotted iron staining evokes a faraway planet. The colorful curved lines are conchoidal patterns in the fracture. The combination of features makes the image seem as if viewed through a telescope rather than a microscope.
Illumination is very important for capturing the iridescence effect. Only if a strong fiber-optic light is used at the correct angle relative to the fracture will the colorful curved lines be highlighted. @topic:3


Publish Year: 2022 Title: Stellate Zircon in a Paraíba Tourmaline Abstract: Zircon needles in a stellate formation observed in a 1.17 ct blue-green Paraíba tourmaline. Photomicrograph by Nicole Ahline; field of view 2.18 mm.
While examining a 1.17 ct blue-green Paraíba tourmaline with a fiber-optic light, the author observed a remarkable set of stellate inclusions (see above). The striking suite consisted of one larger cluster with scattered smaller needles trailing behind it. Reflective lighting revealed needles breaking the surface with a different luster from the host tourmaline. Raman spectroscopy identified the needles as zircon.
Tourmalines form in a pegmatite environment and contain inclusions that reflect this type of growth, most notably fluid inclusions, transparent crystals, and tubular inclusions. Zircon has been observed in tourmaline as prismatic or rounded crystals. The zircons in this 1.17 ct Paraíba tourmaline were atypical as they were needles and in a stellate formation. This type of zircon morphology has been previously documented in morganite (Winter 2013 Lab Notes, pp. 253–254), but stellate inclusions, specifically those composed of zircon, are a rather unique find. The stellates in this Paraíba tourmaline make the gemstone quite unusual. @topic:1


Publish Year: 2022 Title: Blue Apatite in Tanzanian Garnet Abstract: Blue apatite crystals are beautifully framed by prominent rutile needles in a garnet from Tanzania. Photomicrograph by E. Billie Hughes; field of view 3.5 mm.
In the micro-world, it can be challenging to identify inclusions based on sight alone, as many minerals can have a similar appearance. Occasionally, though, some inclusions have characteristic features that can aid in their identification.
Recently this author had the opportunity to observe a pyrope-spessartine garnet, reportedly from Lindi Province, Tanzania, that contained blue crystal inclusions ensconced among intersecting needles (see above). Analysis with micro-Raman spectroscopy identified the inclusions as apatite. Apatites are known for their bright blue hues, and these inclusions offered an attractive example.
While this sample hails from Tanzania, blue apatite has previously been reported as an inclusion in garnet from Madagascar (Winter 2020 G&G Micro-World, p. 526). These inclusions’ distinctive appearance may help gemologists recognize the material in other samples, but further analysis should be performed to identify them definitively. @topic:1


Publish Year: 2021 Title: Exquisite Opal Strand Abstract: This spectacular opal strand displayed unusually bright, vibrant play-of-color across all 28 beads. Photo by Angelica Sanchez.
The Carlsbad laboratory recently received for identification a strand of 28 graduated round gray beads displaying spectacular play-of-color (see above). At the time of inspection, the strand weighed 115.5 grams total. Standard gemological properties were consistent with opal. All 28 beads had a spot RI reading of approximately 1.39 and fluoresced very weak yellow under short-wave UV and weak yellow to long-wave UV. No indications of dye, color treatment, clarity enhancement, or coating were present. All of the beads showed a natural play-of-color phenomenon under microscopic examination. A single drop of water was placed on the surface of each bead and observed under direct transmitted light in brightfield mode in the microscope. Each bead absorbed the water, revealing them to be porous. Therefore, it was concluded that all 28 beads were natural hydrophane opal with natural color. Crazing was not observed in any of them.
Hydrophane opals are porous enough to absorb water, which can cause a change in appearance and a temporary increase in weight. It is therefore not advisable to immerse them in water (Fall 2013 Lab Notes, pp. 175–176).
This opal strand was remarkable due to the unusually bright and vibrant spectral play-of-color seen evenly across all 28 beads. Play-of-color in precious opal is caused by light interacting with stacked submicroscopic silica spheres. Light waves bend as they pass between these spheres, causing the light to diffract into the spectral colors of the rainbow. The resulting color is determined by the size of the spheres. For example, approximately 0.1 micron spheres produce a violet color and approximately 0.2 micron spheres display a red color (https://www.gia.edu/opal-description). @topic:13


Publish Year: 2016 Title: A Halo in a Sri Lankan Taaffeite Abstract: Figure 1. This 0.57 ct taaffeite from Sri Lanka measures 5.63 × 4.00 × 3.21 mm. Photo by Elise A. Skalwold.

	The lovely chromium-bearing purplish red taaffeite from Sri Lanka seen in figure 1 is home to a swarm of included crystals, but one is particularly intriguing. Due to this crystal’s depth and minute size, it cannot be conclusively identified without destructive testing. But its opaque black appearance leads us to believe it is either thorianite or uraninite. The latter is a uranium-rich mineral formerly known as pitchblende and reported to exist in taaffeites from this locality (see E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 3, Opinio Verlag, Basel, Switzerland, 2008, pp. 649–650).

	The strong alpha emissions from such mineral inclusions may lead to stress fractures in the host mineral. Unlike gamma and beta particles, alpha particles are massive and can cause considerable destruction in their path. In this case, it appears the gem has escaped fracturing: the effect is manifested as a concentric two-tiered halo surrounding the black crystal (figure 2). Its three-dimensional bulge-like appearance may be interpreted as radiation-induced distortions in the taaffeite’s crystal structure. These distortions also locally changed the taaffeite’s color, transparency, and refractive index and resulted in other strain features.

Figure 2. In the taaffeite, a radiation-induced two-tiered halo surrounds a minute black crystal; the outer tier is subtle. The haloed crystal is most likely thorianite or uraninite, while numerous colorless zircon and apatite crystals are also present. Photomicrograph by John Koivula; field of view 0.75 mm.

	While the colorless inclusions display reflective surfaces in oblique light from the right, the haloed black inclusion does not. Instead there is a reflection-like scattering of light from the halo surrounding it. We suggest that this is due to a gradational difference in the taaffeite host’s refractive index farther from the black crystal as light is scattered off of the disrupted region. An everyday example of this comes from observing the sun before it rises above the horizon, an optical phenomenon that would not occur without the gradational refractive index of the atmosphere bending the light. The refractive index of the atmosphere decreases with altitude. Because light rays are bent toward the higher refractive index, we may surmise that the inclusion’s halo has a lower refractive index than the rest of the taaffeite host. To support this explanation, in-depth exploration of the geometry of the halo’s refractive index will be needed.

	In the early days of radioactivity studies by scientists such as G.H. Henderson (in a series of five papers published between 1934 and 1939), these inclusions were known as “pleochroic halos.” Although this term may be misleading, the halos’ appearance is partially the result of localized changes in optical properties in the vicinity of the inclusion. Such inclusions are also relevant in determining the age of the planet by studying the characteristics and effects of radioactive guests in various minerals. @topic:1


Publish Year: 2017 Title: Quarterly Crystal: Shattuckite in Quartz Abstract: Figure 1. Measuring 41.27 mm and weighing 164.63 ct, this quartz crystal cluster contains a phantom composed of an abundance of deep blue radial concretions of shattuckite, forming a rich blue felted mat. Photo by Kevin Schumacher.
For our “Quarterly Crystal” in the Micro-World column, we are always searching for unusual crystal specimens that contain interesting mineral inclusions and other micro-features worthy of description. This quarter’s offering is an intergrown cluster of quartz crystals that play host to a rich blue deposition of the orthorhombic copper silicate mineral shattuckite, which typically forms aggregates of spherulitic to circular masses composed of acicular crystals (figure 1). The 41.27 mm long quartz crystal grouping (figure 2) came from the Kandesei mine in the Kunene region of Namibia and was acquired from Jordi Fabre (Fabre Minerals, Barcelona).

Figure 2. As an inclusion in quartz, shattuckite typically forms aggregates of circular to spherulitic masses composed of acicular crystals. Photomicrograph by Nathan Renfro; field of view 3.55 mm.
The inclusions were situated in the quartz crystals in the form of phantoms that developed through the deposition of the shattuckite on the surface. Laser Raman microspectrometry identified the phantom layers as shattuckite. As the quartz continued to grow, the shattuckite was captured as inclusion phantom planes tracing the form of the original quartz host.

Named for the type locality—the Shattuck mine in Bisbee, Arizona—shattuckite is a medium to deep blue mineral with a silky luster. A secondary mineral in oxidized copper deposits, shattuckite is often found together with ajoite, chrysocolla, and malachite, in addition to quartz. @topic:1


Publish Year: 2013 Title: Scheelite and Hübnerite Inclusions in Quartz from China Abstract: Figure 1. Quartz with scheelite and hübnerite inclusions from China, 2.3 cm wide, in daylight (left) and under short-wave UV light (right). Photos by Jaroslav Hyršl.

              Scheelite, a very popular mineral among collectors, is very rarely found as an inclusion in quartz (J. Hyršl and G. Niedermayr, Magic World: Inclusions in Quartz, Bode Verlag, Haltern, Germany, 2003, p. 147). One such quartz specimen, measuring 4.5 cm high and with very high luster (figure 1, left), was collected in 2010 from the famous tungsten deposit at Yaogangxian in Hunan Province, China.

	Figure 2. Two scheelite crystals in quartz, image width 2 mm. Photomicrograph by Jaroslav Hyršl.
The specimen contained about 25 small pseudo-octahedral crystals up to 2 mm with an adamantine luster. Most of the crystals were black, but some were colorless. Under long-wave UV light, both crystal types are inert;  under short-wave UV light, the colorless crystals showed a strong bluish fluorescence, indicating scheelite (figure 1, right). Nevertheless, the black crystals were not fluorescent and their edges were red-brown, a typical color for Mn-rich members of the wolframite group, (Fe, Mn)WO4. Raman testing (by Prof. Albert Gilg, Technical University of Munich) identified colorless crystals as scheelite (figure 2) and black crystals as the mineral hübnerite (figure 3), with the strongest peak at 877 cm–1. Their pseudo-octahedral form confirmed their origin as a pseudomorph after scheelite.

	Figure 3. This group of scheelite crystals in quartz was partially replaced by hübnerite.  Photomicrographs by Jaroslav Hyršl; image width 3 mm. @topic:1


Publish Year: 2022 Title: Characteristics of Amber with Irradiation Treatment Abstract: Figure 1. A: Rough amber material after irradiation treatment. B: Irradiated amber products with dendritic inclusions. C: Irradiated amber pendants without root-like inclusions and irradiated amber with a red-white alternating pattern (far right). D: The current irradiated amber products have much more natural color. Photos by Yamei Wang.
The organic gem amber is particularly popular in China, Europe, the Middle East, and South Asia. With strong demand for rarer colors, some enterprises use electron accelerator–charged particles or 60Co gamma-ray radiation to irradiate amber and enhance its color from light yellow to orange-yellow and orange-red.
As early as 2012, foreign suppliers tried to introduce irradiation-treated amber into the Chinese market. Due to the booming demand for natural golden and beeswax amber in the Chinese market, amber manufacturers had little interest in the irradiated products. After the market cooled in late 2015, irradiated amber emerged as a new variety (figure 1). Some irradiated amber (containing microstructure defects in the original material before treatment) was accompanied by dendritic inclusions with color enhancement or change (figure 1B). The amber materials used for irradiation treatment were selected from Baltic amber. After irradiation, the red color was usually internally uniform when the weathered skin was polished. Due to differences in original bodycolor and flow pattern, the irradiated amber with the superimposed red color can be red, orange-red, orange-yellow, or yellow-brown, or have a red-white alternating pattern (figure 1C, far right). Early irradiated amber from the end of 2015 was easy to identify due to the presence of dendritic inclusions. Recently, the generation of dendritic inclusions has been suppressed and the quality of the samples has improved (figure 1C). The dendritic inclusions are basically inhibited, and the irradiated amber will not produce them as long as there are no cracks or defects on the surface that can be broken down by the irradiation source. Moreover, the enhanced color via irradiation treatment is much more natural (figure 1D).

Figure 2. A: The irradiation treatment of amber via an IBA Rhodotron TT200 accelerator. B: The color improvement of sample 1 at different irradiation doses: before irradiation (B-1) and after irradiation doses of 10 kGy (B-2), 150 kGy (B-3), and 200 kGy (B-4). C: Color enhancement and annealing of sample 2 with different irradiation doses: before irradiation (C-1) and after irradiation doses of 10 kGy (C-2), 170 kGy (C-3), and 200 kGy (C-5). C-4 shows discoloration after heat treatment (10 minutes, 100°C) after cutting. Photos by Yamei Wang.
The authors selected 13 Baltic rough amber samples for irradiation treatment via an IBA Rhodotron TT200 electron accelerator to investigate the effects of different irradiation doses on the color enhancement of amber  (figure 2A), considering that the utilization of high-energy gamma-ray could change its color into red, possibly accompanied by the introduction of dendritic inclusions.
Since the irradiated amber on the market consists of Baltic amber, 12 of the 13 sample groups were Baltic amber (including transparent, translucent, and opaque yellow polished double-sided wafers and round beads), and one group was Burmese amber. The irradiation dose ranged from 10 to 200 kGy (1 kGy = 1000 J/kg), accumulated multiple times, and the samples began to display a red color at 150 kGy. When the irradiation dose reached 200 kGy, the samples turned obvious red, and the irradiation effect showed most clearly. The color changes of representative samples (1 and 2) under different radiation doses were selected; only sample 1 with surface cracks produced dendritic inclusions. When the irradiation dose exceeded 200 kGy, the samples turned varying degrees of red (figure 2B); sample 2 most clearly showed the effect (figure 2C).

Figure 3. Various appearances of the dendritic inclusions. Photomicrographs by Yamei Wang.
The dendritic inclusions are triggered by microstructure defects (physically weak points) and extend like microfractures (figure 3). The roots usually start from the micro defects of amber and form a structural deterioration zone with microcracks. Under the high-energy electron beam, the microcracks in the degradation zone expand rapidly and connect to form a submicroscopic “tree.” The continuous development of the submicroscopic tree forms the root-like whisker region with a macro fractal structure. The growth of dendrites can be regarded as a random growth process of fractal clusters composed of discontinuous microcracks.

Figure 4. Discoloration of irradiated amber. A: Two irradiated round beads cut into halves (top). Bottom left: the half bead heated in an oven at 90°C for 10 minutes fades to yellow; on the bottom right, the internal color is uniform after irradiation. B: Heating the bead in the pressure furnace restores the original color but does not heal the root pattern. C: The irradiated color gradually fades after natural storage for 12 months. D: The color of irradiated amber becomes uneven after natural fading. E: Red spots appear at weak points of the dendrites. F: Red dots remain at the site of irradiation. Photos by Yamei Wang.
If the irradiated amber undergoes heat treatment at 100ºC for 10 minutes in an oven, its original color will be restored (figure 4A and figure 1, C-4); the treated color can also fade and return to its original yellow after heating in a pressure furnace. But once the dendritic inclusion is formed, it is irreversible (figure 4B). After about a year in a natural environment, the induced color from irradiation will automatically fade (figure 4C). Along with a significant reduction in brightness, the color will no longer be uniform (figure 4D) and color spots will appear (figure 4E). Even the original irradiation points are clearly displayed as color spots after fading (figure 4F), indicating that the irradiated color is not stable.

Figure 5. A: The UV-Vis-NIR spectra of natural and irradiated Baltic amber. B: The fluorescence characteristics of irradiated amber under a 365 nm UV lamp. Sample C-2 with a small irradiation dose of 10 kGy; sample C-4 shows discoloration after heat treatment at 100°C for 10 minutes. Photo by Yamei Wang.
Some irradiated ambers with bright color and high transparency that lack the dendritic inclusions can be distinguished using a conventional 365 nm ultraviolet lamp, but the treatment of lighter-colored amber is not as easy to distinguish. The non-irradiated natural Baltic amber showed a strong absorption peak at 521 nm. The irradiated Baltic amber (orange-red) showed three characteristic peaks at 535, 578, and 728 nm (figure 5A). Dendritic inclusions are common in the earlier versions of irradiated amber. In addition, as the irradiation dose increases, the fluorescence intensity of the amber weakens. Under the 365 nm UV lamp, irradiated amber (samples C-3 and C-5 with irradiation doses higher than 150 kGy) has weaker fluorescence intensity than natural amber. Furthermore, the weaker florescence is superimposed on the darker bodycolor of orange-red (C-3, C-5). The fluorescence of amber with heat treatment (C-4) is the same as that of unirradiated natural sample (C-1). @topic:10


Publish Year: 2016 Title: Synthetic Quartz: A Designer Inclusion Specimen Abstract: Figure 1. A 50 × 27 × 13 mm synthetic quartz crystal in which almandine and pyrope garnets introduced during the growth process created a suite of inclusions in the lower right of the specimen within the same plane as an elongated liquid and gas two-phase inclusion. The six vertical prism faces and angled rhombohedral faces help orient the crystal and mirror those of natural quartz, but their unnatural surface features immediately give away the synthetic origin. In the foreground are approximately 2.5 mm water-worn pyrope crystals (left) and 1.5–2.0 mm dodecahedral almandine crystals (right) similar to those used as inclusions; the almandines were extracted from the schist matrix specimen shown in the background. Photo by Elise A. Skalwold.

	As interest in gem and mineral inclusions grows, the value of inclusion specimens has increased as well. This has led to the relatively recent trend of simulated inclusion specimens being offered in the marketplace (see E.A. Skalwold, “Evolution of the inclusion illusion,” InColor, Summer 2016, pp. 22–23). To the best of this author’s knowledge, the synthesis of a quartz host with inclusions—or for that matter, any type of synthetic crystal—for the express purpose of creating a collectable inclusion specimen has not yet been reported and therefore presents a very interesting project to pursue.

	Natural quartz plays host to a wide variety of inclusions, including several types of colorful garnets that often lend an aesthetic contrast to this already fascinating mineral. The author retained the services of a synthetic quartz manufacturer who refined and implemented her plan for growing four small specimens: one with pyrope garnets, one with almandine garnets, one with both types, and one without added garnets as control. The chosen garnets are brightly colored despite their tiny size and so fit with the desire to keep the finished quartz crystals small, given the long and expensive growth period required for the hydrothermal process.

	Using a five-meter-tall industrial high-pressure autoclave, several runs were completed over a four-month period. Prior to the second run, the garnets were introduced into holes bored into the quartz. A few of the garnets were thus successfully captured and incorporated within the host as the second run continued. The nutrient solution for the quartz growth consisted of approximately 10 wt.% of Na2CO3 in pure water, with many trace elements originating from the milky vein Arkansas quartz used as the silica source. To produce the desired crystal morphology, a seed with “c-a” cut was used to initiate growth vertically along the c-axis and elongation along the a-axis. Rather than being hung by wires in the autoclave, the growing crystals sit on a shelf, and hence there is no wire in the finished specimen. The growth temperature was approximately 350°C in a pressurized environment of 700-plus bars.

	When the autoclave was opened at the end of four months, four crystals of approximately the same size emerged intact, one of which is described here as representative of the entire set (figure 1). Along with “breadcrumb” inclusions familiar to gemologists, the suite of captured garnets was surrounded by unidentified white masses and radiating cracks. Quartz’s structure can be thought of as an open yet distorted framework of silicon and oxygen atoms. Because these bonds have angles that change rapidly with temperature, the volume of quartz changes rapidly with change in temperature—much more rapidly than the rather closely packed atoms in garnet. So it is not surprising that as the specimens cooled, the quartz shrank faster than the garnets, causing the quartz to fracture (figure 2). Having formed previous to the growth of the quartz that later captured them, these garnets would be considered “protogenetic” inclusions. Some liquid and gas originating from the autoclave’s environment was also captured as a two-phase inclusion running perpendicular to the c-axis of the quartz. The glassy prism faces of the crystals display characteristic diagonal striations, unlike the prism faces of natural quartz, which have horizontal striations (i.e., perpendicular to the c-axis). Originally, one of the four crystals was intended to be cut into a cabochon to illustrate a classic “rough and cut” suite, but it would have been a shame to sacrifice even one of these pristine and arguably unique synthetic quartz inclusion specimen simulants. Therefore, they will remain as they are in the author’s collection—as her own “designer inclusion specimens.”

	Figure 2. Amid a storm of breadcrumb inclusions, two orangy red almandines and two larger red pyropes caused tension cracks to form in the quartz upon cooling. Portions of a two-phase liquid and gas inclusion running nearly the length of the crystal are indicated by the large bubbles seen at the left and right edges of the image. The guest quartz crystal (part of a multiphase inclusion at right), along with the white masses accompanying the garnets, are remnants from the nutrient environment in which the quartz crystal grew. Transmitted and oblique fiber-optic light. Photo by Elise A. Skalwold; field of view 13 mm. @topic:1