Title: Flame-Fusion Synthetic Ruby Boule with Flux Synthetic Ruby Overgrowth Abstract: Synthetic rubies with both curved growth and flux-type inclusions in a single stone occasionally appear in the trade. Often these are flame-fusion synthetics that have been quench-crackled and flux-healed to produce a more “natural” appearance. In other instances, flame-fusion material may be used as a seed for flux corundum overgrowth. If the seed crystal is not removed during cutting, it becomes part of the faceted synthetic gemstone (R.E. Kane, “A preliminary report on the new Lechleitner synthetic ruby and synthetic blue sapphire,” Spring 1985 G&G, pp. 35–39).

The Carlsbad laboratory recently examined a 249.78 ct transparent to semi-transparent rough red crystal (figure 1). Standard gemological testing using a handheld spectroscope revealed a typical ruby spectrum. Observed with a dichroscope, the rough crystal displayed medium orange red to purplish red pleochroism and fluoresced strong red to long-wave UV and medium red to short-wave UV. All of these properties were consistent with ruby.

Figure 1. This 73.69-mm-long synthetic ruby crystal is composed of a flame-fusion synthetic ruby boule core with a flux synthetic ruby overgrowth. Photo by Nathan Renfro.

Figure 2. Subtle curved striae (right arrow) and fingerprint-like flux residue (left arrow) are indicative of both flame-fusion and flux growth. Photomicrograph by Nathan Renfro; image width 6.94 mm.
Microscopic examination using brightfield illumination revealed both curved striae and flux fingerprint patterns (figure 2). Careful examination of one end of the rough crystal showed a noticeable boundary between a flame-fusion core and a flux-grown overgrowth. Part of the core had not been covered by the flux overgrowth (again, see figure 1). The flux fingerprint inclusion penetrated just a few millimeters into the crystal and was only visible in the flux overgrowth (again, see figure 2). What appears to be a pronounced dark grayish reaction zone at the interface of flame-fusion and flux growth was observed (figure 3). The reaction zone likely indicates slight structural and chemical variations between the flame-fusion core and the flux overgrowth. When a new crystal is grown on top of an old crystal, the new growth starts on an irregular surface that was created when the old surface was melted back slightly at the melt temperature. When growth starts on an irregular surface, it creates a non-perfect crystal lattice match between the original seed and new overgrowth. This growth boundary face will disrupt the regularity of the structure of the growth crystal and contribute to the presence of the reaction zone (Schmetzer et al., “Flux-grown synthetic alexandrites from Creative Crystals Inc.,” 2012, Journal of Gemmology, Vol. 33, No. 1–4, pp. 49–81). In areas where the structural and chemical difference was not very distinct, the reaction zone was partially visible as dark grayish color patches (figure 4). The reaction zone looked grayish because the red bodycolor of the ruby masked what is probably a blue color zone caused by Ti-Fe pairs, a well-known defect that causes blue color in corundum (Summer 1991 Lab Notes, p. 112). The blue zone is along the interface of the flame-fusion core and flux overgrowth.

Figure 3. A dark grayish reaction zone was observed between the flame-fusion core and the flux overgrowth. Photomicrograph by Nathan Renfro; image width 15.67 mm.

Figure 4. Also observed was a partial reaction zone between the flame-fusion core and the flux overgrowth. Photomicrograph by Nathan Renfro; image width 5.85 mm.
Advanced testing on the rough crystal using energy-dispersive X-ray fluorescence (EDXRF) analysis revealed traces of Ca, Ti, and Cr in the areas both with and without flux overgrowth; Mo was only detected in areas with the flux overgrowth. The concentration of Fe was below the detection limit of EDXRF. This result is consistent with the chemical element differences between flame-fusion and flux synthetics (S. Muhlmeister et al., “Separating natural and synthetic rubies on the basis of trace-element chemistry,” Summer 1998 G&G, pp. 80–101).

This synthetic ruby specimen is unusual in that regions originating from the two growth methods occur in the same crystal, with the half of the split boule seed crystal composing the bulk of the entire specimen. While flux overgrowth on flame-fusion seed crystals has been previously reported (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 2, Opinion Verlag, Basel, Switzerland, 2005, p. 352), this type of material is rarely seen in GIA’s laboratory, and this example was particularly unusual due to its large size. Source: GIA @topic:3


Title: Letters: More on Orange Luminescence in Corundum Abstract: We have read with great interest the Winter 2021 article entitled “Blue sapphires from Mogok, Myanmar: A gemological review,” by Wasura Soonthorntantikul et al. (pp. 292–317). The authors conducted a fairly complete bibliographical review and a qualitative characterization using gemological, spectroscopic, and chemical techniques, improving our knowledge of Mogok’s rare and renowned blue sapphires. In the process, the authors associate the 640 nm emission band of orange luminescence with “trapped hole chromophores,” quoting Hughes et al. (2017), that section of the book being based on Segura’s gemology dissertation at the University of Nantes (Segura, 2013). We wish to add further details regarding orange luminescence in corundum, from Mogok and elsewhere. In particular, we recently conducted a rather extensive study of this luminescence, making it possible to describe in further detail the defect(s) involved.
Dr. Soonthorntantikul and her associates state that “the remainder displayed zoned orange fluorescence (with very weak or no red fluorescence) in near-colorless to light blue color zones,” as seen in their figure 12. For Mogok, orange luminescence has also been described in the yellow zone of a blue sapphire (Ho et al., 2018, pp. 128–129). Actually, for all sapphires worldwide, orange luminescence is absent from blue zones and may be found only in near-colorless or yellow domains. This behavior can be explained for all corundum. Indeed, the blue color is related to the Fe-Ti charge transfer, and thus blue zones contain iron, also as Fe3+, as can be seen in their UV-visible absorption spectrum (see figure 26 of Soonthorntantikul et al.). In blue zones, the O2–-Fe3+ charge transfer absorbs the ultraviolet range, taking away the source of energy necessary to induce luminescence. Thus, it acts as a luminescence quencher for orange and red emissions.

A schematic of the F2 center, believed to be responsible for the orange luminescence in corundum (Vigier et al., 2021a,b). Two adjacent AlO6 octahedra in the corundum (α-Al2O3) structure are represented here. Two oxygen vacancies are present (noted with two “e–” each, for the two electrons). X2+ stands for a divalent cation, most likely Mg2+.
Regarding the nature of the defect involved with orange fluorescence, the locution “trapped hole chromophore” does not describe the atomic structure in which the hole is trapped. Our team proposes a more complete description deduced from the careful characterization of a collection of nearly 100 orange-luminescing corundum (Vigier et al., 2021a,b). Based on luminescence excitation spectra and other arguments, the orange luminescence has been related to a color center or defect including two oxygen vacancies. An oxygen vacancy is a missing oxygen atom in the lattice (see above), which can be created by chemical means during growth or induced by irradiation after growth, for example. Such a defect is called an F-center, or even VO°° (Kröger-Vink notation) in the physics community. An oxygen vacancy may contain zero, one, or two unpaired electrons. Thus, when there are two vacancies from two oxygens, each containing two electrons, four electrons are electrically compensated in the corundum structure by the presence of two divalent cations (see also Emmett et al., 2003). This double defect is an F2 center, compensated by two divalent ions such as Mg2+, Be2+, and rarely Mn2+ (again, see above). The concentration of such defects is not known but may be very small (of the order of parts per million or less), as luminescence is a very efficient way to detect defects. The chemical results presented in Soonthorntantikul et al. (2021) explicit that there are always traces of magnesium, which is consistent with this proposed structure.
Furthermore, concerning the relation between orange luminescence and infrared absorption, the authors state: “We noted that the studied sapphires exhibiting the 3161 cm–1 IR feature frequently show orange zoned fluorescence…” This is true for Mogok samples and—in our experience—for some metamorphic yellow sapphires (generally from Sri Lanka). However, for other corundum (natural, synthetic, or treated), we did not note any correlation of the 3161 cm–1 band with orange luminescence.
We hope these additional scientific details will be helpful to better understand the little-studied orange luminescence in sapphire and will nicely complement the work of Dr. Soonthorntantikul and her colleagues.
Maxence Vigier and Emmanuel Fritsch
University of Nantes
CNRS, Institut des Matériaux Jean Rouxel, IMN
Nantes, France
REPLY
We truly appreciate the letter from Maxence Vigier and Dr. Emmanuel Fritsch for the detailed information on defects for orange luminescence in corundum and also for sharing their experience with this feature. Their letter is very helpful and improved our knowledge on this luminescence. We noted the feature in a few samples but did not further explore this, since it would have taken us outside the scope of the article.
Wasura Soonthorntantikul, Ungkhana Atikarnsakul, and Wim Vertriest
GIA, Bangkok Source: GIA @topic:3


Title: Resin Imitation Ivory with a Pseudo “Engine-Turned” Structure Abstract: Figure 1. Left: Material A, 24.40 mm in diameter and sold under the name “Arvorin Plus,” shows parallel linear striations along its length and unorganized perpendicular striations along the horizontal plane. Right: Material B, 18.93 mm in diameter and marketed as “Resin-Ivory+S,” exhibits parallel linear striations along its length and perpendicular striations with an average angle of 90° along its horizontal plane. Photo by Dylan Hand.

Resin materials marketed as imitation ivory were recently acquired by a GIA gemologist. Material A, marketed under the name “Arvorin Plus,” was purchased from a billiard store. Material B, sold as “Resin-Ivory+S,” was purchased from a guitar store. These are manufactured as rods that can be purchased in a variety of lengths. Both show fine parallel linear striations along their length and a distinct pattern reminiscent of Schreger lines, commonly referred to as an “engine-turned” effect, when viewed across their horizontal plane (figure 1). These are also characteristics seen in genuine elephant and mammoth ivory.
The resin materials were found to have nearly identical gemological properties. Both had a Mohs hardness around 2, indented when pressed firmly with a pointer probe, and melted rapidly when touched with a hot point. They also had a spot refractive index reading of 1.57, a hydrostatic specific gravity of 1.24, and were inert to long-wave and short-wave ultraviolet light. Raman spectroscopy further confirmed their identity as a polymer substance.

Figure 2. Left: Elephant ivory with Schreger lines intersecting at an average angle of 109°; field of view 19.27 mm. GIA Collection no. 4287. Right: Mammoth ivory with Schreger lines intersecting at an average angle of 69°; field of view 19.27 mm. Part of GIA Collection no. 19267, donated in 1995 by Richard Marcus of Mammoth Enterprises, Inc. Photos by Dylan Hand and Britni LeCroy.
Genuine elephant and mammoth ivory typically show a refractive index of 1.540, a specific gravity between 1.70 and 2.00, and weak white to blue fluorescence under both long-wave and short-wave UV. Ivory’s most distinguishing characteristic is a display of Schreger lines (“engine turning”), an inherent growth property that is visible when specimens are cut perpendicular to the length of the tusk. These Schreger lines create unique angles that distinguish between mammoth and elephant species. When concave angles that open to the inner area of the tusk are measured, mammoth ivory will show an average angle of less than 90°, while elephant ivory will show an average angle greater than 90°. Figure 2 shows elephant and mammoth specimens oriented with their concave angles opening to the inner area of the tusk. Their Schreger lines intersect at average angles of 109° and 69°, respectively. These can be compared to materials A and B. While material A did show perpendicular striations along the horizontal plane, the angles were not particularly organized or consistently measurable. However, material B had “engine-turned” striations at an average angle of 90° along this same plane.

Figure 3. Three ivory imitations carved for this study. The tusk (52.23 ct) and the cabochon on the right (35.37 ct) were created from material A. The cabochon on the left (14.67 ct) was created from material B. Photo and lapidary by Dylan Hand.
Cabochons were cut from both types of resin, and the form of a small elephant tusk was carved out of material A (figure 3). The resins’ low hardness allowed them to be quickly ground down for shaping, while their high toughness prevented any chipping or fracturing even on small details. The resins each consist of two components with slightly different hardness, which produces the engine-turned pattern. One difficulty is that when attempting to shape a smooth surface, the darker and lighter areas erode at different speeds, creating an uneven texture. This effect is minimized, though, at the prepolishing stage of the carving. The low melting point of the ivory imitations posed an added challenge during the polishing process. When attempting to polish with a compound applied to a felt wheel, the resins can melt and deform relatively quickly.
Elephant ivory was first regulated under the Endangered Species Act in 1976, with more recent laws creating a near-total ban on its import and export. Laws regarding mammoth ivory vary by state. Ivory imitations are now commonly used in their place for furniture and musical instrument inlays, jewelry, and various accessories. Both resins are purportedly composed of spun polyester and are being produced in China. Source: GIA @topic:13


Title: Star Beryl Abstract: Figure 1. Left: Black beryl beads displaying six-rayed stars. Right: Black beryl beads displaying twelve-rayed stars. Photos by Tinh Xuan Nguyen.
Asterism is not a common phenomenon in beryl species, but it has previously been reported in emerald and aquamarine (K. Schmetzer et al., “Asterism in beryl, aquamarine and emerald – an update,” Journal of Gemmology, Vol. 29, No. 2, 2004, pp. 65–71; Fall 2015 Gem News International, pp. 334–335). Recently, the author observed several star black beryl bead bracelets purchased from a Chinese e-commerce platform. For this report, four beads with noticeable asterism were collected for testing. The material was called “Devil Blue” aquamarine. The beads ranged from 9.11 to 9.47 mm in diameter and displayed a star phenomenon.
Of the four beads, two had six-rayed stars with arms intersecting at 60° angles (figure 1, left) and two had twelve-rayed stars with two sets of six-rayed stars located in the same concentric point but with different orientations—the two stars were offset by approximately 10° (figure 1, right). Gemological testing of the beads provided the following characteristics: a hydrostatic specific gravity varying from 2.67 to 2.73, a spot refractive index of 1.57, an inert reaction under long-wave and short-wave UV, and no diagnostic absorption spectrum. These properties were consistent with beryl. Raman analysis confirmed the material was beryl.

Figure 2. The observed asterism was due to oriented iridescent needle inclusions. Several dark intersecting lines with lower relief are from the hexagonal growth structure of beryl. Photomicrograph by Tinh Xuan Nguyen; field of view 0.5 mm.

Figure 3. Multiple parting planes, illustrated by parallel lines lying perpendicular to the c-axis, represent the differing concentrations of oriented needle inclusions occurring during growth. Photomicrograph by Tinh Xuan Nguyen; field of view 0.5 mm.
Under the microscope, we observed numerous needle inclusions oriented perpendicular to the c -axis and parallel to the three a-axes, which caused the asterism (figure 2). Moreover, the needles were concentrated as layers, forming multiple parting planes (figure 3) parallel to the basal pinacoid plane in all beads. This parting, combined with the presence of twelve-rayed stars, suggested that the growth orientation of this beryl was changing during the growth process. Additionally, the samples also showed an intersecting structure (figure 2) with angles of 120°/60° that resembled part of the hexagonal growth structure previously observed on the pinacoid of an aquamarine (Spring 2022 G&G Micro-World, pp. 70–71). This structure highlights that the asterism is oriented perpendicular to the c -axis, allowing the easy determination of this direction in translucent to opaque beryl. Source: GIA @topic:3


Title: Windmills in Rare Mineral Sphalerite Abstract: A group of windmill-like inclusions with orange color concentrations observed in sphalerite. Photomicrograph by Ungkhana Atikarnsakul; field of view 3.1 mm.

Sphalerite is a rare gem mineral that crystallizes in the cubic crystal system and consists largely of zinc sulfide formed with variable iron, with the chemical formula of (Zn,Fe)S. Its color is usually yellow, brown, red, or gray to gray-black with high dispersion and high adamantine luster. The author recently examined a high-quality faceted orange sphalerite weighing 47.56 ct that revealed three-ray structures reminiscent of windmills with each propeller arm separated by 120°. Additionally, the orange color was concentrated in the immediate region of the three radial arms of each propeller-like structure (see above). Other typical internal characteristics of sphalerite such as strong angular internal growth with orange color zoning, particulate clouds, tiny crystals, and fingerprints, were also observed. This distinctive structure resembling windmills is the first such feature the author has encountered in sphalerite. Source: GIA @topic:2


Title: Unusual Inclusions in Natural Emerald from Chivor Abstract: Tubular three-phase inclusions with albite (Ab) at each end in a natural Colombian emerald. These inclusions are oriented parallel to the c-axis of the crystal. Photomicrograph by Javier Toloza; field of view 0.95 mm.
Nailhead inclusions are commonly associated with hydrothermal synthetic emeralds and occasionally found in flux-grown emeralds as well (G. Choudhary and C. Golecha, “A study of nail-head spicule inclusions in natural gemstones,” Fall 2007 G&G, pp. 228–235; N. Renfro et al., “Inclusions in natural, synthetic, and treated emerald,” Winter 2016 G&G, pp. 402–403). Interestingly, similar inclusions have also been observed in natural emeralds. These inclusions occur when a tiny particle or platelet of a foreign substance becomes trapped within the host mineral during crystal growth. As the crystal continues growing, a conical void develops behind the particle, which typically captures various forms of matter, including liquids and gases (Choudhary and Golecha, 2007).
While examining a 1.40 ct rough Colombian emerald sourced from the Chivor district in Boyacá, the authors encountered growth blockage inclusions resembling nailhead inclusions. Unlike the jagged shape typical in Colombian emeralds, these three-phase inclusions exhibited a tubular form and were oriented parallel to the c-axis of the crystal. Using Raman spectroscopy, euhedral albite crystals were identified at both ends of the inclusion (see above), suggesting a strong interaction between the mineralizing fluids and the host rock, where the fluids may have dissolved albite from the rock and become enriched with its constituents. This could be due to previous alteration processes within the host rock resulting in the replacement of preexisting minerals by albite, known as albitites (A. Cheilletz and G. Giuliani, “The genesis of Colombian emeralds: A restatement,” Mineralium Deposita, Vol. 31, No. 5, 1996, pp. 359–364). Source: GIA @topic:3


Title: Quarterly Crystal: Topaz with Phlogopite Abstract: Figure 1. This 216.56 ct topaz crystal is from Dusso, Pakistan. Photo by Diego Sanchez.

This issue’s quarterly crystal is a gem-quality very light pinkish brown topaz (figure 1) from the Dusso mine in Pakistan. The transparent singly terminated topaz crystal measures 30.52 × 29.84 × 27.89 mm and weighs 216.56 ct. It hosts a prominent 6 mm long dark brownish orange phlogopite mica booklet that shows strong brownish orange and yellow dichroism as well as lamellar cleavage planes (figure 2).

Figure 2. This prominent 6 mm crystal of phlogopite mica is hosted by the Pakistani topaz. Photomicrograph by Nathan Renfro; field of view 9.09 mm.
A tiny cluster of dark brownish red manganotantalite and colorless albite inclusions are also present. Small near-colorless and transparent mica and feldspar inclusions are randomly scattered throughout the crystal. This suite of inclusions strongly suggests that a complex granitic pegmatite was the parent rock type of this topaz. Source: GIA @topic:2


Title: Rubies and Sapphires from Winza, Central Tanzania Abstract: Since late 2007, rubies and sapphires have been mined by hand methods from both eluvial and primary deposits at Winza in central Tanzania. The gem corundum is related to “dikes” of amphibolitic rocks that belong to the Paleoproterozoic Usagaran Belt. Based on crystal morphology, Winza corundum is subdivided into two types: prismatic-tabular-rhombohedral and dipyramidal. In general, medium red and dark (orangy) red top-quality rubies are rhombohedral. Pinkish red and purplish red rubies, as well as pink, purple, and blue (often strongly color zoned) sapphires are, for the most part, dipyramidal. The top-quality rubies are characterized by a distinct assemblage of long tube-, fiber-, needle-, or hair-like inclusions containing an orange-brown material (most likely limonite). The lower-quality material generally contains a larger amount of solid inclusions (mostly amphibole crystals), fissures, and growth features. Unique to corundum from this locality are bluish violet color zones oriented parallel to the prism and basal pinacoid, and occasionally also parallel to rhombohedral and dipyramidal faces. The relatively high Fe content of Winza rubies separates them from most other natural and almost all synthetic counterparts.

	DATA DEPOSITORY

Corrected UV-Vis-NIR Absorption Spectra
Mining Photos
Photomicrographs
Stone Photos
Transit Photos
Washing Photos
	Submitted by Brendan M. Laurs
	Winter, 2008 Source: GIA @topic:1


Title: Unusual Composite Ruby Rough Abstract: Figure 1. The 14.77 ct composite ruby rough was partially polished on opposite sides where natural ruby slabs were pasted to a synthetic ruby crystal. Notice the hexagonal zoning on the polished surface. Photo by Meenakshi Chauhan; magnified 15×.

ABSTRACT
The Indian Gemological Institute – Gem Testing Laboratory recently examined an unusual 14.77 ct specimen that resembled ruby rough. Initial gemological testing (RI, hydrostatic SG, optical properties, visible spectrum, and infrared spectroscopic analysis) was consistent with ruby.

The rough was partially polished on two opposite sides, where hexagonal growth zoning was easily visible with the unaided eye (figure 1). Several striations and grooves were visible on the side of the rough.

The pattern and nature of these grooves raised suspicion about the rough’s origin. Closer examination under magnification revealed that hexagonal zoning and fine silk on the partially polished surfaces were confined to a depth of approximately 1.5 mm. Two thin slabs of about 1.5 mm each appeared to be attached to the two opposite ends of the rough. No other inclusions were found under magnification. We did observe a slight difference in the color of the thin layer and the main body. The thin slabs were purplish red, while the main body was pinkish red. Since the hexagonal zoning was within the thin slabs and the physical properties were consistent with ruby, we concluded that they were natural ruby slabs. The natural ruby slabs were pasted with a glue that made them appear orangy in transmitted light, and trapped gas bubbles were also observed in the junction plane (figure 2). The two natural slabs were polished to show the hexagonal zoning, while the rest of the rough was kept coarse to restrict views of the interior. Fine triangular grooves were engraved on the rough’s surface to imitate the natural growth markings of ruby.

Figure 2. In transmitted light, the natural ruby slab appeared orangy due to the adhesive. Trapped gas bubbles are seen in the junction plane. Photo by Meenakshi Chauhan; magnified 30×.
Under magnification, a small cluster of gas bubbles was visible through one of the smooth grooves on the specimen’s main body, evidence of synthetic origin. Several fractures were also present in the rough, probably an attempt to imitate fingerprint inclusions. Under short-wave UV, the natural slabs fluoresced red while the synthetic ruby rough showed a strong chalky fluorescence (figure 3). Chalky fluorescence was further evidence of the rough’s synthetic origin.

Figure 3. Under short-wave UV light, the synthetic ruby portion of composite rough fluoresced chalky while the natural ruby slabs fluoresced red. Photo by Meenakshi Chauhan.
Cut and polished composites are regularly encountered, but a composite where synthetic rough is fashioned to imitate natural gem material poses a more significant challenge. Source: GIA @topic:3


Title: Plastic Amber Imitation in a Rosary Abstract: Figure 1. Left: The rosary shows yellow to yellowish brown color in daylight-equivalent lighting (left). Right: The rosary under long-wave UV. The amber shows a moderate to strong chalky greenish blue and yellow reaction, but the plastic appears brown. Photos by Nazar Ahmed Ambalathveettil.

Dubai Central Laboratory (DCL) receives almost all types of ambers, natural and treated (e.g. heated, dyed, reconstructed) as well as amber imitations for identification. Amber rosaries (prayer beads) are increasingly popular in Middle East countries, especially the United Arab Emirates and Arabian Gulf countries.

Recently DCL received a rosary for amber identification. The yellow and yellowish brown color, structure, and size of the 102 beads were identical (figure 1, left). At first glance, even with a well-trained eye, this rosary could easily be misidentified as exclusively natural amber. Testing revealed that the rosary was strung with 71 heat-treated amber beads and 31 Bakelite plastic beads.

Spot refractive indices (RIs) of the amber beads were 1.53; observation between crossed polarization of most beads revealed anomalous double refraction with strained colors. Stress spangles and brown thread-like substances are the most noticeable inclusions in these beads; these features are commonly seen in heat-treated amber. The spot RIs of the plastic beads were around 1.64. Aggregate and anomalous double refraction reaction was observed under the polariscope and gas bubbles and swirl marks were the main inclusions.

The most interesting aspect of the specimen was its reaction under long-wave UV. The amber showed moderate to strong chalky greenish blue and yellow fluorescence, but the plastic appeared brown (figure 1, right).This reaction was very useful for differentiating between the two materials.

To confirm the identity of each material, we analyzed their infrared spectra with attenuated total reflectance (ATR) mode (figure 2). Spectrum A displayed main peaks at 1716.4 and 1161.1 cm–1, consistent with amber. The main peaks of Spectrum B were at 1650.8, 1600.7, and 1218.8 cm–1. After comparison with spectrum A and the spectra of other plastics, spectrum B confirmed the spot RI’s identification of this sample as Bakelite plastic.

Figure 2. IR spectra of the two specimens, with ATR method applied. Spectrum A
represents natural amber, with typical peaks at 1716.4 and 1161.1 cm–1. Spectrum B’s
main peaks at 1650.8, 1600.7, and 1218.8 cm–1 indicate that it is Bakelite plastic.
This rosary is an excellent example of the importance of testing and disclosure, because even an experienced person could not differentiate between the amber and Bakelite beads with the unaided eye. Source: GIA @topic:13


Title: An In-Depth Gemological Study of Blue Sapphires from the Baw Mar Mine (Mogok, Myanmar) Abstract: Rough and faceted blue sapphires from the Baw Mar mine in Mogok, Myanmar. Photo by Vincent Pardieu/GIA.

Myanmar (formerly Burma) is one of the world’s oldest sources of fine corundum. Over the last decade, the Baw Mar mine increased its production providing the market with a large number of fine blue sapphires. These sapphires have slightly different properties from the classic Mogok sapphires, but have not been studied in great depth.

Researchers from GIA’s Bangkok laboratory analyzed 64 sapphire samples collected during field expeditions to Baw Mar. They investigated gemological properties, inclusion scenes, spectroscopic features, and trace element chemical composition. Results from their study and field observations from the mining area appear in a new article titled “An In-Depth Gemological Study of Blue Sapphires from the Baw Mar Mine (Mogok, Myanmar).”

The sapphires were mined in different parts of the mine and showed different properties. The most striking difference is the color. Sapphires from the northern part of the mine showed a medium-to-dark blue color, while those from the southern area are generally lighter in tone. Trace element concentrations were measured and compared with those from other metamorphic blue sapphire sources such as Sri Lanka and Madagascar. Source: GIA @topic:3


Title: Chromophore Behaviors (Including the 880 nm Absorption Band) in an Irradiated Pink Sapphire Abstract: Figure 1. Color-calibrated photo of a 0.664 ct pink sapphire from Madagascar before and after irradiation, and after fade test using fiber-optic light for 6 hours. Path length/thickness: 1.514 mm. Photos by Sasithorn Engniwat.
Irradiation is a known process for enhancing color in corundum, particularly yellow and pink sapphire. Recently, some rubies and pink sapphires with bluish tint were reportedly treated with radiation (“LMHC makes progress on laboratory report harmonisation, discussed current challenges in detection of corundum treatments,” LMHC press release, March 14, 2023). However, chromophore behaviors in irradiated ruby/pink sapphire have not been fully investigated. This report shows preliminary results of an experiment involving irradiated pink sapphire. An untreated Madagascar pink sapphire with a blue modifier (figure 1) was fabricated as an optical wafer with two polished faces perpendicular to the c-axis for ultraviolet/visible/near-infrared (UV-Vis-NIR) spectroscopic study. Trace element chemistry was analyzed in the UV-Vis-NIR measurement area using laser ablation−inductively coupled plasma−mass spectrometry. This information can be used to link the visual color and the color-causing trace elements listed in figure 1.

Figure 2. Polarized UV-Vis-NIR spectra comparisons of the pink sapphire before and after irradiation with a gamma irradiation dose of 500 kGy. The difference spectrum revealed a significant increase in trapped hole paired with Cr3+ and the 880 nm band in the irradiated pink sapphire.
The spectrum of the untreated sample displayed broad absorption bands at ~400 and ~560 nm together with weak peaks at ~470 and at 693 nm, demonstrating that the Cr3+ chromophore was responsible for the pink color (blue line in figure 2; see E.V. Dubinsky et al., “A quantitative description of the causes of color in corundum,” Spring 2020 G&G, pp. 2–28). This sample also showed a weak broad band at around 580 nm related to Fe2+-Ti4+ pairs, which produced a blue color, modifying the pink color from Cr3+ to purple-pink. Weak Fe3+-related absorption features were also observed, represented by a broad band at ~330 nm and narrow peaks at 377, 388, and 450 nm. The iron-related chromophore only causes significant yellow color at relatively high iron concentrations (greater than ~1000 ppma) due to Fe3+ chromophores’ weak color strength.
For our radiation experiment, the sample was treated with a gamma irradiation dose of 500 kGy at the Irradiation Center at the Thailand Institute of Nuclear Technology (public organization). After irradiation, the pink sapphire changed to a padparadscha-like coloration in which the subtle blue color was partially removed (figure 1). The UV-Vis-NIR spectrum after irradiation showed a significant increase in absorption intensities at wavelengths shorter than ~560 nm or longer than ~660 nm (red line in figure 2). To observe changes in chromophore behavior caused by irradiation, the spectrum after irradiation was subtracted from the pretreatment spectrum. The difference spectrum (green line in figure 2) revealed that this acceptor-dominated corundum with an atomic concentration of magnesium greater than the sum of titanium and silicon concentrations created a strong absorption feature below ~560 nm to the UV region, which matches well with the trapped hole associated with the Cr3+ spectrum for causing orange coloration (Dubinsky et al., 2020). Using the absorption cross section information provided in Dubinsky et al. (2020), the concentration of trapped hole-Cr3+ chromophores induced by irradiation was approximately 0.8 ppma in the sample. This chromophore had very high color strength, and therefore a noticeable color change could be observed with only a tiny concentration of the trapped hole paired with Cr3+ created after treatment. The Fe2+-Ti4+ chromophore also reduced by approximately 0.7 ppma in the treated sample, resulting in less blue color modification. This slight lightening in blue color after irradiation is possibly due to the change in oxidation state of iron (which would reduce the number of Fe2+-Ti4+ pairs). In addition, the creation of orange color (trapped hole-Cr3+) masked a certain portion of remaining blue color after treatment, as blue and orange are complementary colors. The change in UV-Vis-NIR spectrum corresponded with the change in color appearance caused by irradiation.
When studying absorption features in the UV-Vis-NIR spectrum of corundum, a broad band centered at around 880 nm in the red to near-infrared region is typically associated with basalt-related blue sapphire (e.g., A.C. Palke et al., “Geographic origin determination of blue sapphire,” Winter 2019 G&G, pp. 536–579). This band has little or no impact on color. In addition to basalt-related blue sapphires that are exposed to heat naturally, the 880 nm band can be induced in the spectrum of a metamorphic-type sapphire that has been heat treated, such as heated Madagascar sapphire (E.B. Hughes and R. Perkins, “Madagascar sapphire: Low-temperature heat treatment experiments,” Summer 2019 G&G, pp. 184–197) or heated Rock Creek sapphire (J.L. Emmett and T.R. Douthit, “Heat treating the sapphires of Rock Creek, Montana,” Winter 1993 G&G, pp. 250–272). This feature can also be found in Mozambican ruby after heat treatment (S. Saeseaw et al., “Update on “low-temperature” heat treatment of Mozambican ruby: A focus on inclusions and FTIR spectroscopy,” GIA Research News, April 30, 2018). The origin of this band is not fully understood but may be related to iron clusters.

Figure 3. Polarized UV-Vis-NIR spectra comparisons of the pink sapphire after irradiation with a gamma irradiation dose of 500 kGy and after the fade test. The difference spectrum between after irradiation and after fade test obviously shows the reduction in the trapped hole paired with Cr3+ chromophore when exposed to intense light for several hours.
The 880 nm band was absent in the UV-Vis-NIR spectrum of this sample before treatment. Interestingly, this pink sapphire developed the 880 nm band after irradiation, with a significant intensity around 1.2 cm–1. Color stability testing is usually performed in gem laboratories for yellow to padparadscha sapphires that may contain unstable color centers (e.g., A.C. Palke et al., “An update on sapphires with unstable color,” GIA Research News, December 12, 2022; Summer 2022 GNI, pp. 259–260). After the color stability test (figures 1 and 3), the orange coloration introduced by irradiation faded away after exposure to intense incandescent light due to the dissociation of the trapped hole paired with Cr3+, whereas the 880 nm band remained. This preliminary observation suggests that the 880 nm band can be produced by an irradiation process, and this feature could provide some interesting evidence of treatment, either heat or irradiation, in pink sapphires and rubies. However, further studies would be needed to understand the development of the 880 nm absorption band. Source: GIA @topic:3


Title: Maine Pegmatite Workshop Abstract: Figure 1. Workshop attendees at the Havey Quarry, which has produced some of the finest Maine elbaite tourmalines. The mine was originally opened in 1902 and worked for feldspar. This view shows the Havey pegmatite body, with three pockets visible. Photo by Duncan Pay/GIA.

              The 2015 Maine pegmatite workshop took place at the Poland mining camp, May 29–June 6. As readers know, many important colored gemstones including tourmaline, beryl, topaz, garnet, quartz, and spodumene are mined worldwide from pegmatites, and these rocks are the source for most fine gem crystals. Maine pegmatites have been mined for many decades (some back as far as the 1820s) and are renowned for their fine tourmaline, beryl, and quartz crystals. The workshop’s website is at pegworkshop.com.

The workshop is conducted by Dr. William “Skip” Simmons, Dr. Karen Webber, and Alexander Falster—all formerly of the University of New Orleans—and Ray Sprague, a local pegmatite miner. Simmons, Weber, and Falster were the core of the university’s mineralogy, petrology, and pegmatology (“MP2”) research group. Following the closure of the university’s mineralogy department, they relocated to the new Maine Mineral and Gem Museum in Bethel (www.mainemineralgemmuseum.org).

The workshop has taken place annually since 2001. The 2015 workshop had a total of 26 attendees, including six undergraduate mineralogy students from University of New Orleans, one postgraduate mineralogy student from the University of the Basque Country (Bilbao, Spain), a well-known mineral dealer, a variety of mineral collectors, and interested members of the public.

The workshop is structured with morning presentations and lectures, followed by excursions to mines and quarries in the afternoon. Given the breadth of participants (rockhounds from mineral clubs, undergraduate and graduate geology students, mineral dealers, gemologists, and PhD-level researchers), the content varied from introductory to quite complex—and sometimes contentious— topics, such as pegmatite genesis (fractional crystallization from granite vs. anatexis) and crystallization time. In particular, the relationship of pegmatites to tectonic settings was well explored, as was the current consensus on cooling time and the formation of large crystals. Nonetheless, the presenters did an excellent job and encouraged plenty of debate. Some of the best questions came from the mineral collectors in the group, many of whom have visited these quarries repeatedly.

The selection of field excursions (figures 1 and 2) varies from year to year and is dependent on which mines are available or being worked at the time. This year’s destinations included the following quarries: Western Mount Apatite, Tamminen, Waisanen, Bennett, Orchard, Havey, Mount Mica, and Emmons. Around noon each day, participants would caravan in a stream of cars to the “quarry du jour.” The workshop organizers enjoy excellent relationships with local mine owners, dependent on the good conduct of the attendees.

Figure 2. Colorful mineralogy at the Havey quarry. Pink and green tourmaline, clevelandite, lepidolite, and “salmon”-colored feldspar all indicate the presence of a nearby pocket. Photo by Duncan Pay/GIA.
At each quarry, Simmons or Falster explained pegmatite mineralogy and miners Frank Perham or Ray Sprague outlined current or past mining history at the site. The remainder of the time could be spent mineral collecting, which was a focus for a good portion of the group. Those interested in more depth could talk with members of the MP2 research group about the exposures, or with Perham and Sprague about the practice of mining pegmatites. Indeed, this is the workshop’s strong suit: The theory from the morning presentations is applied to real rocks in the afternoon.

Besides the quarries, workshop attendees also visited the new Maine Mineral and Gem Museum in Bethel. There they could see the progress of the exhibits and view the MP2 research group’s laboratory in the basement, which includes an electron microprobe, scanning electron microscope, X-ray diffraction equipment, and other advanced instrumentation.

Following an evening lecture on pegmatite mineralogy complemented by numerous hand specimens, the opening session kicked off with a general introduction to pegmatites, the earth’s chemistry, and phase equilibria. Throughout the week, the presentations delivered by Simmons, Webber, and Falster built on the basics to cover the relationship of granites to pegmatites, magmatic differentiation, pegmatite classification, magma genesis, and the influence of tectonic setting. Some of the more complex topics covered included crystallization dynamics, such as the influence of volatiles and fluxes (water, lithium, fluorine, boron, and phosphorous), pegmatite textures, aplites (“line rocks”), pocket formation and indicators, and regional and internal zonation of pegmatites.

Besides these instructional sessions, workshop attendees were also treated to a variety of other presentations, including:

Myles Fetch (Maine Mineral and Gem Museum, Bethel) described the garnet line in Oxford County pegmatites. He explained that the garnet line marks the lower edge of the pegmatite’s productive zone. It might swell upward close to a pocket, serving as an important indicator.

Dr. Encar Roda-Robles (University of the Basque Country and a member of the MP2 pegmatite research group) presented on pegmatites from the Iberian Massif and the central Maine belt, covering the differentiation of granitic melts vs. anatexis. Dr. Roda-Robles also delivered a talk on tourmaline, mica, and garnet as sensitive indicators of pegmatite evolution in the Berry-Havey pegmatite. This last talk was very relevant, as the afternoon’s field trip was to this quarry.

Idoia Garante-Olave (University of the Basque Country) delivered a presentation on mineralogy and geochemistry of micas from the Tres Arroyos pegmatite field in Badajoz, Spain.

Frank Perham, a noted Maine pegmatite miner, reminisced on the remarkable Newry tourmaline discovery, which produced an estimated $30 million worth of gem and specimen-grade tourmaline crystals in 1972. Perham also delivered a talk on Maine feldspar mining.

Dr. Skip Simmons presented previous work on the chemistry and a calculation of volume, by mineral, for the Mt. Mica pegmatite. The volume of tourmaline was estimated at 1%.

Jim Nizamoff (a mineralogist with Omya AG and former University of New Orleans research associate) and mineral collector Don Dallaire discussed the pegmatite mineralogy of the Conway and Osceola granites from the White Mountains of New Hampshire.

Ray Sprague (pegmatite workshop organizer and miner) presented on the mineralogy of specimens from the Emmons pegmatite in preparation for the all-day visit to that quarry. Source: GIA @topic:1


Title: Faceting Large Gemstones Abstract: The quest for the largest permeates all societies and disciplines. With the advent of new machinery and techniques, size records for faceted gemstones are falling constantly.  Currently, a 22,898-ct yellow topaz holds the record for weight and a 19,548-ct citrine holds the record for size. This article discusses some of the more important gemstone giants, and describes the specialized equipment and techniques developed to cut and polish them. Source: GIA @topic:7


Title: Heated Purplish Pink Sapphire from Ilakaka (Madagascar) with Colored Monazite Inclusions Abstract: Figure 1. A 3.02 ct heated purplish pink sapphire measuring 9.57 × 7.74 × 4.55 mm. Photo by Ugo Hennebois.
The Laboratoire Français de Gemmologie (LFG) received a 3.02 ct purplish pink sapphire (figure 1) for identification. Under the microscope, zircon and monazite inclusions (figure 2) along with tubes (figure 3) were observed. This inclusion scene was characteristic of similarly colored sapphires from Ilakaka, Madagascar (W. Wang et al., “The effects of heat treatment on zircon inclusions in Madagascar sapphires,” Summer 2006 G&G, pp. 134–150; S. Saeseaw et al., “Low-temperature heat treatment of pink sapphires from Ilakaka, Madagascar,” Winter 2020 G&G, pp. 448–457). No indication of heating was observed. Moreover, the monazite inclusions were orange-brown. It was previously observed that monazite inclusions in pink sapphires turn colorless when heated above 600°C (see again Saeseaw et al., 2020).

Figure 2. A series of colorless zircon inclusions and orange-brown monazite inclusions in the heated purplish pink sapphire. Photomicrograph by Ugo Hennebois; field of view 1.5 mm.

Figure 3. Unaltered tubes in the heated purplish pink sapphire. Photomicrograph by Ugo Hennebois; field of view 2 mm.
Using Raman spectroscopy, the full width at half maximum (FWHM) of the band around 1010 cm–1 due to anti-symmetric stretching vibration SiO4 in the zircon structure and the band around 975 cm–1 due to PO4 stretching vibration in the monazite structure can decrease during heating of pink sapphires from Ilakaka (Wang et al., 2006; Saeseaw et al., 2020). The zircon and monazite inclusions were analyzed using a Raman Renishaw inVia spectrometer, with a 514 nm diode-pumped solid-state (DPSS) laser, with about 10 mW laser power on the sample, 50× long working distance objective lens, confocal mode (100 microns entrance slit), 1800 lines/mm grating, and about 1.5 cm–1 spectral resolution. The FWHM of the most intense band of seven monazite inclusions at around 975 cm–1 ranged from 12.7 to 14.2 cm–1, and those of 10 zircon inclusions at around 1010 cm–1 ranged from 6.4 to 7.8 cm–1. Both appeared to be sharper and less variable compared to FWHM in unheated pink sapphires, which present zircon inclusions with FWHM of the main band from 7.1 to 21.7 cm–1 and monazite inclusions with FWHM of the main band from 14.2 to 18.4 cm–1 (Saeseaw et al., 2020; M. Krzemnicki et al., “Zircon inclusions in unheated pink sapphires from Ilakaka, Madagascar: A Raman spectroscopic study,” Proceedings of the Online International Gemmological Conference, 2021, pp. 21–23; S. Karampelas et al., “Détection du traitement thermique à basse température des corindons,” Revue de Gemmologie a.f.g., No. 217, 2022, pp. 4–5).
Unpolarized Fourier-transform infrared spectra in different directions were collected using a Thermo Fisher Magna-IR560 with 4 cm–1 spectral resolution and 500 scans using a diffuse reflectance accessory as beam condenser. The sample presented a band at 3309 cm–1 and a less intense band at 3232 cm–1, which in pink sapphire is considered an indication of heating (Saeseaw et al., 2020). These bands are linked to different forms of titanium associated with hydroxyl defects in corundum (E. Balan, “Theoretical infrared spectra of OH defects in corundum (α-Al2O3),” European Journal of Mineralogy, Vol. 32, No. 5, 2020, pp. 457–467).
In line with previous experiments showing that monazite inclusions can keep their color after heating to 600°C (Saeseaw et al., 2020), the presence of colored monazite inclusions alone cannot serve as evidence that a pink sapphire from Ilakaka is unheated. On the other hand, the presence of colorless monazite inclusions in pink sapphires from Ilakaka could be considered an indication of heat treatment. Source: GIA @topic:3


Title: A New Phantom Quartz Imitation: Laser-Engraved Rock Crystal Abstract: Figure 1. The “phantom quartz” pendant was later confirmed to be natural quartz with three-dimensional laser engraving. Photo by Shu-Hong Lin.

Phantom quartz generally refers to a rock crystal with inclusions of prismatic or pyramidal growth zonation, which represents early crystal faces covered by minerals, such as clinochlore, clay minerals, limonite, or fuchsite. Recently, a new type of phantom quartz imitation has appeared in the market, most of which is sold in the form of beads, pendants, or crystal spheres. A package of these imitation phantom quartz products was sent to the Taiwan Union Lab of Gem Research (TULAB) for identification services (figure 1).
These samples submitted as phantom quartz had a powdery white growth zonation in the form of a hexagonal pyramid. The host crystal was confirmed to be natural quartz by infrared absorption spectroscopy. The samples had an abnormal appearance for phantom quartz, of which the internal growth zonation was composed of regular and oriented small cracks (figure 2). Similar inclusions are often found in crafts made of glass or synthetic quartz engraved with a laser. According to the client, one of these samples had fractures along the ridgeline of the apparent pseudo-hexagonal pyramid (figure 3), which were possibly self-propagated due to the internal stress from the oriented small cracks.

Figure 2. The internal growth zonation was composed of a regular network of small crack clusters around a central black point, presumably due to laser impact. Photomicrograph by Yu-Ho Li; field of view 2.14 mm.

Figure 3. Left to right: A schematic diagram, a bottom view, and a top view of an imitation phantom crystal. The six fractures (red dashed lines) along the ridgeline of the pseudo-hexagonal pyramid in this imitation phantom quartz sphere were reportedly formed without any external force or heat treatment. The diameter of this sphere is 17.68 mm. Photos by Shu-Hong Lin.
In a true phantom, the axial direction of the host crystal is identical to that of the phantom crystal inside; however, the interference images through a polariscope revealed that the c-axis direction of these phantom quartz products was mostly inconsistent with what appeared to be their internal growth zonation (figure 4). In consideration of the morphological characteristics of inclusions as well as the interference images, these phantoms are imitations made of natural “rock crystal” with artificial growth zonation produced by laser engraving, irrespective of the crystallographic orientation of the host crystal.

Figure 4. Crossed polarizers revealed that the bull’s eye, indicating the optic axis, was nearly perpendicular to the axis of the engraved “phantom.” Photo by Shu-Hong Lin.
Although internal laser engraving can imitate the appearance of a phantom quartz inclusion, such products can be easily identified through a microscope and a polariscope. More controversially, the internal stress generated by the regular and oriented cracks seems to reduce the toughness of the host crystal; therefore, consumers should be aware of the risk of such imitations. Source: GIA @topic:2


Title: Blue Dravite-Uvite Tourmaline from Koksha Valley, Afghanistan Abstract: Figure 1. This specimen of dark blue tourmaline on micaceous matrix, from the Koksha Valley of Badakhshan Province in Afghanistan, measures 28 × 25 × 17 mm. Photo by Kevin Schmacher.

	Tourmaline is popular among gem and mineral enthusiasts for its extensive variety of colors. Blue, one of the most sought-after hues, is usually encountered as elbaite, a sodium- and lithium-containing species with the chemical formula Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH). While it has been reported that very limited quantities of dark blue tourmaline crystals are being mined in Afghanistan’s Koksha Valley, we have found that this material appears to be a hybrid species of dravite-uvite tourmaline (figure 1).

	Around a dozen blue crystals in pale green and brown micaceous matrix first surfaced in the gem markets of Peshawar, Pakistan, in late 2009, as confirmed by two sources (S. Khan and P. Slootweg, pers. comms., 2016). These crystals, reportedly from Badakhshan Province’s Koksha Valley, were subsequently assumed to be a member of the tourmaline group based on their ditrigonal pyramidal habit. Since that time, only very small batches of these crystals have turned up; interestingly, a few of these specimens have been associated with sapphire in the same matrix (P. Slootweg, pers. comm., 2016). In 2010, while examining sapphire rough believed to be from a deposit near the Koksha Valley, GIA’s Bangkok laboratory identified bluish green crystals present in some matrix specimens of sapphire as dravite tourmaline (Spring 2011 Lab Notes, pp. 53–54). While the Koksha Valley is most famous for extensive deposits of high-quality lapis lazuli near Sar-e-Sang, sapphire mining takes place near the village of Hazrat Saeed, 25 km north of Sar-e-Sang along the Koksha River (T.P. Moore and R.W.M. Woodside, “The Sar-e-Sang lapis mine,” Mineralogical Record, Vol. 45, No. 3, 2014, pp. 280–336). The sapphire at Hazrat Saeed is recovered from mica-rich gneiss, and it appears that these green and blue tourmalines were uncovered as a by-product of sapphire mining operations.

	Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) was used to analyze the chemical composition of the dark blue tourmaline seen in figure 1. Three spots were measured and plotted (figure 2). Two of the spots showed that the tourmaline contained dravite; the third revealed the presence of uvite (D.J. Henry et al., “Nomenclature of the tourmaline-supergroup minerals,” American Mineralogist, Vol. 96, No. 5–6, 2011, pp. 895–913). Dravite, NaMg3Al6(Si6O18)(BO3)3(OH)3OH, is a sodium- and magnesium-rich tourmaline typically encountered in brown, yellow, black, and rarely as intense green. Uvite, Ca(Mg3)MgAl5(Si6O18)(BO3)3(OH)3(F/OH), is a calcium- and magnesium-rich tourmaline that is often brown, green, or deep red. Our analysis suggests that this blue tourmaline specimen is composed of a mixture of dravite and uvite. While fibrous blue dravite has been reported in the Czech Republic (M. Novak, “Blue dravite as an indicator of fluid composition during subsolidus replacement processes in Li-poor granitic pegmatites in the Moldanubicum, Czech Republic,” Journal of the Czech Geological Society, Vol. 43, No. 1–2, 1998, pp. 24–30), this is the first large single-crystal blue dravite-uvite tourmaline the authors have encountered.

	Figure 2. Left: Three laser spots were plotted in the ternary system for the primary tourmaline groups based on the dominant occupancy of the X site. Center: Two blue laser spots that belong to the alkali primary tourmaline group were further plotted in the ternary dravite-schorl-elbaite subsystem. Right: One orange laser spot that belongs to the calcic primary tourmaline group was further plotted in the ternary liddicoatite-feruvite-uvite subsystem. These findings show a range of composition consistent with the dravite-uvite series. Source: GIA @topic:2


Title: Hollandite in Amethyst Abstract: Hollandite crystals inside a natural amethyst from Bahia, Brazil. Photomicrograph by Liviano Soprani; field of view 2.20 mm.
We are used to seeing groups of dark hollandite crystals that resemble sea urchins, but this time Mother Nature offered up a completely different and evocative vision. Crystals of hollandite, with the chemical formula Ba(Mn4+6Mn3+2)O16, were observed inside a 15.00 ct amethyst cabochon. The arrangement of the acicular crystals created a shape resembling ears of barley (see above), making this photomicrograph look more like a botanical image. It was taken in darkfield illumination and oblique fiber-optic illumination with the use of image stacking. To obtain a good focus, the author took multiple photos on different focal planes and then used specific software to reconstruct the image—in this case, 67 stacked images. Source: GIA @topic:2


Title: Suspended Crystal in Red Spinel Abstract: A crystal inclusion in red spinel shown in darkfield illumination (left) and fiber-optic lighting (right). Photomicrographs by Isabelle Corvin; field of view 1.78 mm.
The sharp outline of a tabular included crystal in a 0.44 ct red spinel (see above) appeared suspended when viewed with darkfield illumination. Under fiber-optic lighting, the body of the crystal darkened and displayed a flash of rainbow colors caused by thin-film interference between the host spinel and the inclusion.
Not all included crystals display such drastically different appearances with different light sources. This particular well-formed crystal was the only notable inclusion in the red spinel. The surprising “rainbow” effect made it stand out from other crystal inclusions observed in similar material. Source: GIA @topic:3


Title: Tourmaline in Emerald Abstract: Prismatic black tourmaline in a Zambian emerald. Photomicrograph by Virginia Schneider; field of view 1.76 mm.
The author recently examined a 3.80 ct emerald with well-formed black, opaque prismatic crystals (see above). The surface-reaching crystals were identified as tourmaline through the use of Raman spectroscopy. While tourmaline crystals are relatively uncommon inclusions, they have been documented in emeralds from Zambia, Pakistan, Russia, and Ethiopia, all of which are schist-hosted deposits. Laser ablation–inductively coupled plasma–mass spectrometry chemical analysis combined with inclusion observation revealed this emerald to be of Zambian origin. Source: GIA @topic:2


Title: Large Stellate Dislocation in Spinel Abstract: Stellate dislocations decorate the interior of a greenish blue spinel believed to be from Vietnam. Photomicrograph by Ezgi Kiyak; field of view 4.79 mm.
The author recently examined a 4.49 ct greenish blue spinel exhibiting a prominent stellate inclusion characterized by a network of needle-like dislocations clustered in a six-rayed star pattern (see above). The inclusion was large enough to be readily observed without magnification.
Star-like needles have been previously documented in spinel originating from Vietnam. These findings contribute to our understanding of spinel and its origins, providing valuable information for gemologists. This is one of the most remarkable stellate inclusions the author has observed in a spinel. Source: GIA @topic:3


Title: “Electromagnetic Wave” Inclusion in Mong Hsu Ruby Abstract: An electromagnetic wave-like pattern of whitish dust in Mong Hsu ruby. Photomicrograph by Narint Jaisanit; field of view 1.70 mm.
Recently the author examined a vivid red 1.18 ct cushion-cut ruby. This ruby contained several inclusions, such as distinctive hexagonal zoning with a blue core, a cloud of snowflake-like particles, and ladder-like particles. These inclusions combined with chemical analysis indicated a geographic origin of Mong Hsu, Myanmar. Interestingly, fiber-optic illumination revealed an electromagnetic wave-like pattern of particles (see above). Although whitish particles are common in Mong Hsu rubies, this electromagnetic wave pattern is truly unique. Source: GIA @topic:3


Title: Vietnamese Skyline Abstract: Hogbomite-filled dislocations in a Vietnamese spinel. Photo by Wimon Manorotkul; vertical field of view 4 mm.
In the red spinel from Vietnam’s Luc Yen district in the figure above, layers of iridescent needles stretch skyward like a futuristic skyline from a science fiction novel. Such hogbomite-filled dislocations are a common sight in red, pink, and blue spinel from Vietnam. According to Gübelin and Koivula (Photoatlas of Inclusions in Gemstones, Volume 2, Opinio Verlag, Basel, Switzerland, 2005), hogbomite (Mg,Fe)2(Al,Ti)5O10 is found in spinel via isomorphous replacement. Source: GIA @topic:3


Title: Demantoid from Val Malenco, Italy: Review and Update Abstract: New data are presented for demantoid from Val Malenco, Italy, as obtained by classical gemological methods, electron microprobe and LA-ICP-MS chemical analyses, and UV-Vis-NIR and mid-IR spectroscopy. The results confirmed that these garnets are almost pure andradite (≥98 mol%, RI>1.81, SG = 3.81–3.88). All 18 samples studied contained “horsetail” inclusions, which are characteristic of a serpentinite geologic origin. Fe and Cr control the coloration of demantoid, though color variations in these samples were mainly correlated to Cr content. Source: GIA @topic:2


Title: Nail-Head Spicule in a Russian Emerald Abstract: Figure 1. A 1.86 ct transparent green pear mixed-cut emerald. Photo by Diego Sanchez.
Recently, a 1.86 ct transparent green pear mixed cut (figure 1) was submitted for identification to the Carlsbad laboratory. Initial testing produced the following results: refractive index values of 1.582–1.590, birefringence of 0.008, doubly refractive, and a hydrostatic specific gravity of 2.73. The long-wave UV reaction was red with a blue fluorescence in surface-reaching fractures from the clarity enhancement. These results were consistent with natural emerald. Trace element chemistry of the host emerald collected via laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) matched well with GIA’s Russian emerald chemistry reference data.

Figure 2. Nail-head spicule in the natural emerald from figure 1. Photomicrograph by Nathan Renfro; field of view 2.01 mm.
While the identification of any gem requires further testing with a variety of instruments, in most cases the stone’s natural or synthetic origin can be determined conclusively by features seen under magnification. Nail-head spicules are typically associated with synthetic hydrothermal (and occasionally flux-grown) emerald and synthetic quartz, but they are also occasionally found in natural gems such as beryl, sapphire, spinel, tourmaline, and quartz (G. Choudhary and C. Golecha, “A study of nail-head spicule inclusions in natural gemstones,” Fall 2007 G&G, pp. 228–235; K. Schmetzer et al., “Multicomponent inclusions in Nacken synthetic emeralds,” Journal of Gemmology, Vol. 26, No. 8, 1999, pp. 487–500). Nail-head spicules are wedge-shaped two-phase (liquid and gas) inclusions capped by crystals that act as growth obstacles (figure 2). During growth of the host crystal, a small crystal or platelet is deposited on its surface. As the crystal continues to grow past the inclusion, a tapered void is created, which traps the hydrothermal growth medium such that, upon cooling, it becomes two phases consisting of liquid and a gas bubble (Choudhary and Golecha, 2007). Source: GIA @topic:3


Title: Skull Carved of Meteorite Abstract: A skull carved from the Gibeon meteorite, which landed in Namibia in prehistoric times. The brown line is a tridymite inclusion. Exhibited by Nature’s Geometry at the 2022 AGTA show in Tucson. Photo by Robert Weldon; courtesy of Lee Downey.
At the AGTA show, Nature’s Geometry (Tucson) had on display a life-sized skull carved of meteorite (see above). The skull, “Gaia,” was a collaboration between Lee Downey of Artifactual Studios (Tucson and Bali, Indonesia) and Balinese artist Ida Bagus Alit. It was carved from two pieces of the Gibeon iron meteorite, which landed in prehistoric times after bursting into pieces upon coming through the atmosphere. Its fragments are scattered over a large area in Namibia. Based on radiometric dating, the meteorite is estimated to be around four billion years old. Long before Westerners documented it in the early 1800s, the Nama people used pieces of it as weapons and tools.
Downey and Alit worked on the carving from March 2015 to January 2020 in the workshop Downey shares with Ratu Pedanda Manuaba, a high priest of Bali. In Balinese culture, meteorites are seen as powerful, and meteorite iron is used to make traditional keris (daggers) for ceremonial use.
The Gibeon meteorite’s makeup is about 90% iron and 8% nickel, with small amounts of cobalt and phosphorus. Downey said the material is somewhat soft and sticky. The critical aspects were maintaining the proportions and watching for potential imperfections in the material. “Cracks and pockets of odd space junk can pop up,” he said. “Luckily Gaia was basically flawless. She was difficult but forgiving.”
The work was done using hacksaws, steel grinders, and rotary carving setups. Protective gear was required when using cutting burrs because the tiny shards coming off the skull were “like little razor blades flying around.” Based on models of the human skull, a sphere-shaped piece of the meteorite was carved for the upper cranium and a block for the jaw, which is articulated and removable. Roughly 159 lbs. (72 kg) of material were cut and ground away to form the 39 lb. (18 kg) skull. After carving, the skull was fully polished to a chrome-like finish.
The final step was etching with a weak acid to reveal the meteorite’s fine octahedrite structure, visible in the pattern on the skull’s surface. The pattern, known as a Widmanstätten pattern or Thomson structure, is composed of interwoven bands of kamacite and taenite (iron-nickel alloys) and develops over millions of years of very slow cooling. It is revealed only through cutting, polishing, and etching.
The brown line on top of the skull is an inclusion of tridymite, a silica polymorph. Tridymite is also found on Earth, the moon, and Mars, and in planet-forming disks of dust and gas around stars.
Downey has previously described the human skull as “undeniably sure to register emotions in all of us. It has all the fear of death, the reminder of being alive, and the possibility of something greater in store…out there in the mysterious beyond.”
“The intense gravity of this extraterrestrial metal is itself a mystery of life,” he said. “Four billion years old and counting, the long travel to arrive on Earth, the rare beauty of the crystal patterns that can only form in the vacuum of space. The symmetry of the entire tale is beyond human comprehension.” Source: GIA @topic:2


Title: Tourmaline Inclusion in Russian Alexandrite Abstract: The longest inclusion in this photomicrograph of a Russian alexandrite was conclusively identified as tourmaline. This tourmaline inclusion exhibits a well-formed prismatic/rod-like crystal shape. Darkfield illumination. Photomicrograph by Jonathan Muyal; field of view 1.44 mm.

Alexandrite is the color-change variety of the mineral chrysoberyl. The most coveted alexandrite exhibits a luscious green to greenish blue color in daylight and a warm raspberry red in incandescent light. This phenomenal color change is caused by the presence of trace Cr3+ substituting for Al3+ in the chrysoberyl crystal structure. Alexandrite was originally found in the Ural Mountains of Russia in the early nineteenth century and was named in honor of Czar Alexander II.
GIA recently examined several Russian alexandrite rough specimens. These were reportedly from the Tokovaya mining area in the Ural Mountains, located a few kilometers away from the city of Yekaterinburg. Closer microscopic examination revealed a brown, transparent, well-formed prismatic crystal inclusion with triangular termination, indicating it might belong to the trigonal crystal system (see above).
The inclusion proved to be doubly refractive when viewed between crossed polarizers. Raman microspectrometry analysis conclusively identified the inclusion as tourmaline. In order to validate the Raman results and further identify the tourmaline species, laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) was used to obtain the chemistry of the inclusion (Z. Sun et al., “A new method for determining gem tourmaline species by LA-ICP-MS,” Spring 2019 G&G, pp. 2–17). It was classified as dravite, a sodium- and magnesium-rich tourmaline species. The trace element chemistry of the host alexandrite matched well with GIA’s Russian alexandrite chemistry reference data.
Inclusions in alexandrite from various localities have been reported (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Vol. 1, ABC Edition, Zurich, 1986, pp. 265–267; Vol. 3, Opinio Publishers, Basel, Switzerland, 2008, pp. 372–405). However, tourmaline in an alexandrite host is rare.
Alexandrite is traditionally popular for its beautiful color-change phenomenon rather than its inclusion scenes. The fine tourmaline crystal inclusion in this Russian alexandrite makes it an unusual collector’s gem specimen. Source: GIA @topic:2


Title: Unusual Short-Wave UV Reaction in Synthetic Blue Spinel Abstract: Figure 1. This 1.44 ct synthetic spinel was grown by the Verneuil process but displayed the short-wave UV reaction of a flux-grown sample. Photo by Pragati Verma.

ABSTRACT
The Indian Gemological Institute – Gem Testing Laboratory recently examined a 1.44 ct blue oval mixed cut specimen (figure 1). Standard gemological testing revealed the following properties: RI—1.728; hydrostatic SG—3.64; strong anomalous double refraction under the polariscope; Chelsea filter reaction—strong red; and red transmission in fiber-optic light. The sample showed general absorption bands between 535–550, 560–590, and 615–635 nm in the handheld spectroscope. Microscopic examination with a fiber-optic light source revealed shiny dotted inclusions that were scattered and created a wavy pattern; in some areas, the dotted inclusions were arranged in a series (figure 2). This wavy pattern has not been reported in natural spinel. The author has seen this pattern in some Verneuil synthetic spinel. There is a possibility that these inclusions might be very minute gas bubbles or unmelted feed powder.

Figure 2. Series of dotted inclusions were seen in some areas of the synthetic spinel. The dots were so concentrated that it was difficult to distinguish them individually. Photomicrograph by Pragati Verma; magnified 25×.
These properties—higher RI, higher SG, red Chelsea filter reaction, anomalous double refraction, and absorption spectrum features—are diagnostic features of cobalt-doped synthetic blue spinel grown by the Verneuil (flame-fusion) process (M. O’ Donoghue, Synthetic, Imitation & Treated Gemstones, Butterworth-Heinemann, Oxford, UK, 1997, p. 153).

When tested with UV, this synthetic spinel had an unusual reaction. Under both long- and short-wave UV, the sample showed red fluorescence (figure 3). This was an unexpected short-wave UV reaction for Verneuil-grown blue synthetic spinel, which generally shows a mottled blue to bluish white reaction. This kind of fluorescence was observed in synthetic blue spinel grown by a flux method (S. Muhlmeister et al., “Flux-grown synthetic red and blue spinels from Russia,” Summer 1993 G&G, pp. 81–98).

Figure 3. The synthetic spinel displayed red fluorescence under short-wave UV. Photo by Pragati Verma. Source: GIA @topic:3


Title: Azurite Through the Ages: Millennia of Mining Have Not Depleted Its Sources Abstract: Azurite, a copper carbonate mineral, is a common secondary mineral. The host is usually a volcanic rock. Collector’s azurite crystals mostly came from Chessy in France (the oldest mine since mid-1800s), Morenci and Bisbee in Arizona, Tsumeb in Namibia, and Touissit in Morocco. The increasing copper price in the first decade of the 21st century lead to reopening of old known copper mines. Well-crystallized azurite specimens have been recently mined in China, Morocco and Mexico.

The quality of well-crystallized samples from a decade-old Milpillas mine in Mexico could be compared to these collector’s samples. Azurite crystals (e.g., the Electric Blue from the Milpillas mine) show dark, blue color with high luster, and they are usually 1–2 inches long prisms or blocky crystals up to 4 inches long. They were gradually pseudomorphed into malachite in high oxidizing environment. Thus, malachite was found more abundant than azurite. Sometimes, thin layer of azurite can be deposited atop malachite as the final layer. The light to dark green, melachite pseudomorphs from the Milpillas mine are mostly blocky crystals, and ranged from one to ten inches in size. The Milpillas mine also produced emerald-green bronchantites, a hydrous copper sulfate, of one-two inches long needle-like crystals on a rhyolite matrix. Free copper ions of bronchantite absorb all wave lengths except green, causing bright green color.

Abstracted by Kyaw Soe Moe Source: GIA @topic:12


Title: Quartz Windows in Chalcedony Abstract: Figure 1. Measuring 52.56 × 36.71 × 2.88 mm, this half-moon-shaped chalcedony plate contains more than a dozen hexagonal quartz windows. Photo by Kevin Schumacher.

	We recently examined a 55.08 ct polished half-moon-shaped plate of white and brownish yellow chalcedony from Madagascar that was fashioned by Falk Burger (Hard Works, Tucson, Arizona). As can be seen in figure 1, more than a dozen hexagonal windows of transparent colorless quartz accentuated by thin frames of brownish yellow chalcedony are randomly scattered throughout the host. In this specimen the quartz crystals would be considered protogenetic inclusions since the chalcedony formed around the preexisting crystals. The quartz crystals are all twinned on the Brazil law, and the c-axes of the quartz windows are all aligned in parallel fashion. As a result, when the chalcedony plate is examined between crossed polarizing filters, the transparent windows all display their twinning through the presence of colorful stellate patterns (figure 2) that vary in appearance as the plate is rotated or moved about in the polarized light field (see video at http://www.gia.edu/gems-gemology/quartz-window-chalcedony).

	Figure 2. When viewed between crossed polars, Brazil-law twinning in the quartz windows is revealed as stellate patterns (left). As the analyzer is rotated, different colors are revealed along the twinning (right). Photomicrographs by Nathan Renfro; field of view 19.01 mm. Source: GIA @topic:2


Title: Applications of Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry (LA-ICP-MS) To Gemology Abstract: Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) is an important technique for quantitative chemical analysis. The authors have applied this minimally destructive technique to gemology to take advantage of its high spatial resolution, rapid and direct analysis of gemstones (whether loose or mounted), and precise measurement of a wide range of elements—even in ultra-trace amounts. This article summarizes LA-ICP-MS principles and describes the successful application of this technique to detecting beryllium diffusion treatment in corundum and identifying the geographic origin of emeralds. LA-ICP-MS is significantly less expensive than SIMS and more sensitive than LIBS, which is the least costly of the three instruments. Source: GIA @topic:3


Title: Andradite in Andradite Abstract: Figure 1. This 16.79 ct Japanese andradite garnet exhibits a very unusual rhomb-shaped “hot spot” below the surface of one crystal face. Photo by Kevin Schumacher.

Recently we had the opportunity to examine a dramatic iridescent andradite fashioned by Falk Burger (Hard Works, Tucson, Arizona) from a crystal originating from the Tenkawa area of Nara Prefecture in Japan. Known as “rainbow” andradite, this material was previously reported in Gems & Gemology (T. Hainschwang and F. Notari, “The cause of iridescence in rainbow andradite from Nara, Japan,” Winter 2006, pp. 248–258). The specimen was unique for its genesis and optical phenomenon.

Weighing 16.79 ct and measuring 15.41 × 13.86 × 10.49 mm, the andradite was very large for its species and locality, but size was not what made it special. As shown in figure 1, close examination of one of the polished crystal faces revealed a bright reddish orange “hot spot” in the center, caused by an iridescent inclusion of andradite with a different crystallographic orientation than its host. As seen in figure 2, the inclusion’s different orientation caused the iridescence of the rhomb-shaped “hot spot” to appear and disappear as the light source was passed over the crystal’s surface. To see the iridescence from both the host and inclusion at the same time, two light sources from opposite directions must be used due to the different crystallographic orientation of the host and inclusion. This elusive optical phenomenon made this Japanese andradite crystal extremely interesting for any aspiring inclusionist.

Figure 2. Using two oblique fiber-optic light sources from opposing directions, the iridescent surface of the host crystal and inclusion can be seen at the same time (center). Viewed with only one fiber-optic light, the iridescence on either the host or the inclusion alone can be seen because of their different crystallographic orientations. Photomicrographs by Nathan Renfro; field of view 5.11 mm. Source: GIA @topic:3


Title: Apatite Cluster in Orthoclase Feldspar Abstract: Figure 1. Located just left of center, a large apatite crystal cluster is visible directly below the table facet of this 7.20 ct orthoclase feldspar (the inclusion is also reflected numerous times by the pavilion facets). Photo by Kevin Schumacher.

	A yellow orthoclase feldspar (figure 1) recently examined by these authors was of particular interest, not only for its size and clarity but also for the unusual cut. The 7.20 ct oval had a wide table facet that dramatically framed a large eye-visible crystal cluster just below its surface. The potassium-rich orthoclase host was identified using traditional gemological testing and confirmed by Raman microspectrometry, which also identified the inclusion as apatite (figure 2).

	Figure 2. A tiny crystal next to this large cluster of prismatic hexagonal apatite crystals resembles a space shuttle approaching a space station. The image was taken using darkfield illumination. Photomicrograph by Jonathan Muyal; field of view 4.79 mm.

	This relatively large apatite cluster was composed of hexagonal elongated prismatic crystals, a morphology typical of the mineral. They also proved to be opaque and exhibited evidence of a certain degree of softness by their slightly corroded crystal faces (again, see figure 2). Several small tension stress cracks were observed surrounding the inclusion. The altered appearance suggests that these apatite crystals are protogenetic inclusions that were present in the growth environment before the orthoclase began to form.

	Apatite, a common phosphate mineral, has been described in the literature as a crystal inclusion in various gem materials and as randomly scattered “jackstraw” needles in yellow orthoclase from Madagascar (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 2, Opinio Verlag, Basel, Switzerland, 2005). This specimen’s morphology and size make it an aesthetically pleasing example of apatite as a crystal inclusion in orthoclase, and therefore an interesting collector’s gemstone. Source: GIA @topic:2


Title: Forsterite in a Purple Tanzanian Spinel Abstract: Figure 1. This faceted purple spinel, weighing 0.51 ct and measuring 5.20 × 4.17 × 3.10 mm, was reportedly from Tanzania. Photo by Jinlin Wu.
Purple/violet spinel from Tanzania is popular in the gem market today. Recently, author JW encountered an oval-shaped purple gemstone reportedly from Tanzania (figure 1). Its refractive index of 1.714 and hydrostatic specific gravity of 3.59 indicated spinel. Its ultraviolet/visible/near-infrared (UV-Vis-NIR) absorption spectrum was characterized by a series of absorption bands centered at 555 nm and several iron-related small bands centered at around 371, 385, 461, and 478 nm, as well as an extremely weak band at ~625 nm for Co2+ (figure 2). This absorption profile revealed that iron (Fe2+ and Fe3+) was the main coloring element (P.M. Belley and A.C. Palke, “Purple gem spinel from Vietnam and Afghanistan: Comparison of trace element chemistry, cause of color, and inclusions,” Fall 2021 G&G, pp. 228–238).

Figure 2. The UV-Vis-NIR spectrum of the spinel sample shows absorption peaks mainly related to Fe2+ and Fe3+.
Energy-dispersive X-ray fluorescence analysis was performed to determine the sample’s trace element concentration, which showed 10950 ppmw iron, 963 ppmw zinc, 52 ppmw chromium, 94 ppmw vanadium, and 9 ppmw cobalt. These results were similar to the chemical features of representative purple Tanzanian spinel: extremely high iron content, medium zinc content, and low chromium and vanadium contents (G. Giuliani et al., “Pink and red spinels in marble: Trace elements, oxygen isotopes, and sources,” Canadian Mineralogist, Vol. 55, No. 4, 2017, pp. 743–761).

Figure 3. A colorless subhedral forsterite (Fo) inclusion and a dolomite (Dol) inclusion with an unknown dark material attached. Photomicrograph by Jinlin Wu; field of view 0.66 mm.

Figure 4. Oriented short needles in the spinel. Photomicrograph by Jinlin Wu; field of view 1.10 mm.
Microscopic observation revealed a colorless subhedral mineral, a dolomite with an unknown dark material attached (figure 3), and oriented short needles (figure 4). Raman spectroscopy identified the colorless mineral as forsterite. According to the RRUFF database (B. Lafuente et al., https://rruff.info/about/downloads/HMC1-30.pdf), peaks at 822, 855, 918, and 963 cm−1 were consistent with the main peaks of forsterite (figure 5).

Figure 5. Comparison of Raman spectra of the colorless mineral and forsterite in the RRUFF database. Peaks in the inclusion spectrum at 312, 405, 664, and 766 cm–1 are from the host spinel. Spectra are offset vertically for clarity.
As a rock-forming mineral, forsterite (Mg2SiO4) itself is common, especially in marble-hosted spinel. However, it is rarely observed in Tanzanian spinel and has been reported only once to our knowledge (E. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 2, Opinio Publishers, Basel, Switzerland, 2005, 829 pp.).
In Tanzania, the primary deposits of spinel occur in marbles and calc-silicate rocks that belong to the Neoproterozoic metamorphic Mozambique Belt (G. Giuliani et al., “Les gisements de rubis et de spinelle rouge de la Ceinture Métamorphique Néoprotérozoıque Mozambicaine,” Revue de Gemmologie, Vol. 192, 2015, pp. 11–18). Under high-temperature conditions, spinel and forsterite are both stable mineral phases in marbles (Giuliani et al., 2017). Spinel is found in marble or impure marble associated with calcite, dolomite, forsterite, clinohumite, and phlogopite in deposits in Myanmar and Vietnam. Thus, forsterite is commonly seen as an inclusion in spinel from these sources (G. Giuliani et al., “Pink and red gem spinels in marble and placers,” InColor, No. 43, 2019, pp. 14–28).
It was noteworthy to see forsterite in the Tanzanian sample. This finding could indicate a similar formation environment between spinel in Tanzanian deposits and those in Myanmar and Vietnam. Source: GIA @topic:2


Title: Chemical Analysis of Zircon Abstract: Figure 1. The five zircon samples used in this study, ranging in size from 0.56–21.92 ct, were analyzed for radioactive degradation of their crystal structure.

Radioactive elements such as thorium and uranium existed at higher concentrations during earlier ages of the earth; crystal formations from these periods were therefore more susceptible to acquiring higher concentrations of these materials. Zircon has a particular affinity for attracting rare earth elements such as uranium and thorium into its crystal structure due to similarities in the three elements’ cation sizes, which allows U and Th to substitute for Zr in the crystal lattice, and other bonding properties such as coordination, electronegativity, and cation change. The isotopes break down through radioactive decay, releasing harmful doses of radiation to the host crystal. This destroys the crystal structure of zircon until it is nearly amorphous, in a process called metamictization (J.A. Woodhead, “The metamictization of zircon: Radiation dose-dependent structural characteristics,” American Mineralogist, Vol. 76, 1991, pp. 74–82).

In gemology, zircon is categorized by the degree of radioactive degradation that has taken place. Highly degraded material with little to no crystal structure remaining is termed “low” or “metamict” zircon. “High” zircon is crystalline and nearly unaffected by radiation, while “intermediate” zircon is semi-crystalline, between the amorphicity of low zircon and the ordered crystalline structure of high zircon.

Five zircon samples were analyzed in this study based on their apparent crystallinity (figure 1). Raman spectroscopy shows the degradation of the crystal structure from its original structure, which can be illustrated by comparing it to zircon that has not been affected by radiation (figure 2). Infrared spectra (figure 3) also show differences between the low and high zircons, as the former displays peak broadening and baseline irregularities.

Figure 2. Raman analysis of samples 2 and 4, illustrating the difference between “low”
and “high” zircons. Low zircon displaying amorphicity by peak loss and broadening.

Figure 3. FTIR spectra of the zircon samples. The metamict zircons, samples 1 and 2,
display an undefined baseline and broader bands than the high zircons.
Trace-element analysis of high and low/intermediate zircon using LA-ICP-MS illustrated variations in concentrations of several elements, including thorium, uranium, and lead. While uranium and thorium are easily incorporated into the crystal structure, the same is not true for lead, which can only appear in zircon as the byproduct of the radioactive decay chains of thorium and uranium. Due to this property, scientists have been able to accurately date zircons and Earth’s age using isotope ratio analysis by comparing the lead to uranium (238U/206Pb) and lead to thorium (232Th/208Pb) ratios. These results showed the low zircon samples to be far older than the high zircon. Isotopic elemental analysis using LA-ICP-MS (table 1) determined that the low zircon was approximately a billion years old. This is far older than the high zircon samples, which were determined to be approximately 100 million years old. The higher content of radioactive elements earlier in Earth’s formation, along with the longer period of time for metamictization to occur, contributed to the structures of the low zircons.

TABLE 1. Isotopic elemental analysis of zircon using LA-ICP-MS.

Sample
Weight
206Pb
208Pb
232Pb
238U

Greenish yellow "low" zircon
16.32 ct
848.40
54.53
237.10
4529.00

Greenish yellow "low" zircon
21.92 ct
636.67
24.67
603.00
2083.33

Greenish blue "high" zircon
10.14 ct
bdl*
bdl*
51.83
73.17

Near-colorless "high" zircon
0.56 ct
0.81
0.63
200.00
210.17

Blue "high" zircon
1.96 ct
0.12
0.19
85.02
99.98

Trace-element analysis combined with spectroscopy can also detect treatments in zircon. Heat treatment, which is commonly performed on all types of zircon for color modification, can reestablish the crystal structure that was originally destroyed by natural processes. Zircon crystals with high lead content must have experienced a considerable amount of radiation exposure, leading to their lower crystalline order. High-lead zircon samples that show an ordered crystalline structure could have initially been low or intermediate and heat treated to restore the crystal structure. By correlating the trace-element chemistry with other analytical tools such as Raman spectroscopy, it may be possible to determine heat treatment of some types of zircons.

Nearly all blue and near-colorless zircons have undergone heat treatment, as these colors are rarely found in nature; the majority of zircon rough is brown. The blue color of zircon is theorized to come from the chromophore U4+ cations, depending on how the uranium cations interact within the crystal structure. “Electric” blue zircon’s color is typically produced by heating the stone to 1000°C in a reducing environment, while near-colorless material is produced at about the same temperature in an oxidizing environment. Heat treatment of zircons that have not had significant radiation damage can restore the crystallinity at the temperatures used for color modification treatments. Although very metamict zircons must undergo higher temperatures and longer duration of heating to restore a degree of crystallinity, these zircons will never achieve the electric blue color. It is difficult to even produce gem-quality material from this material. Zircon with poor crystallinity has more variation in polycrystalline grain orientation, bond length, element location, and bonding, as well as varying amorphicity. Knowledge of zircon’s chemistry can facilitate the identification of treatments and growth conditions, and can be applied to determine various correlations pertaining to color and origin. Source: GIA @topic:3


Title: FTIR Identification of Carbon Dioxide Fluids in Sapphire Abstract: Figure 1. Various negative crystals in pink sapphire from Sri Lanka (A, enlarged in B) and fingerprints in blue sapphire from Myanmar (C, enlarged in D). Image B shows bubbles in flat negative crystals, and the center negative crystal in D has a bubble. Photomicrographs by Momo Matsumura (A and B) and Shunsuke Nagai (C and D); fields of view 4.05 mm (A), 8.15 mm (B), 8.47 mm (C), and 1.71 mm (D).
Carbon dioxide is well known as a trapped fluid in negative crystals in sapphire. From room temperature to cooler temperatures, the negative crystals change from a single supercritical fluid phase to two phases of gas and liquid. This feature is fascinating to observe under the microscope (e.g., Spring 2016 G&G Micro-World, pp. 78–79). These fluid inclusions are considered proof that a sapphire has not undergone thermal treatment (e.g., J.I. Koivula, “Carbon dioxide fluid inclusions as proof of natural-colored corundum,” Fall 1986 G&G, pp. 152–155).
However, the Summer 2020 issue of G&G reported on a sapphire heated with pressure that contained a carbon dioxide gas bubble even after treatment (Summer 2020 Lab Notes, pp. 287–288). Most previous reports about carbon dioxide fluid inclusions were based on microscopic observation, but this one addressed the presence of carbon dioxide fluid using Fourier-transform infrared (FTIR) spectroscopy.

Figure 2. FTIR spectra of the two sapphires from figure 1 indicate dense carbon dioxide–assigned peaks from 2000 to 4000 cm–1 and 4500 to 5500 cm–1. The two peaks at 3601 and 3705 cm–1 are easily mistaken for kaolinite peaks at 3619 and 3698 cm–1.

Figure 1 shows two sapphires from Sri Lanka and Myanmar with fluid inclusions of primary and secondary negative crystals. FTIR spectra of these two sapphires are presented in figure 2. The two peaks at 3601 and 3705 cm–1 are easily confused with kaolinite-related peaks at 3619 and 3698 cm–1. All of the spectra show several peaks assigned to dense carbon dioxide vibration and combination overtone bands. The 2342 cm–1 peak is C=O asymmetric stretching vibration ν3. The 3601 and 3705 cm–1 peaks are 2ν2 + ν3 and ν1 + ν3 first Fermi resonance, respectively. The 4838, 4967, and 5088 cm–1 peaks are 4ν2 + ν3, ν1 + 2ν2 + ν3, and 2ν1 + ν3 second Fermi resonance peaks, respectively, where ν1 is a symmetric stretching and ν2 is a doubly degenerate bending (table 1). Those peaks generally present double absorption bands, P- and R-contour, under atmospheric pressure and temperature due to the rotational transitions that occur for the stretching band, as seen in the bottom spectrum of figure 2. The double peaks change to a single peak, increasing the carbon dioxide fluid density by more than ~0.4 g/cm3 (M. Buback et al., “Near infrared absorption of pure carbon dioxide up to 3100 bar and 500 K. I. Wavenumber range 3200 cm–1 to 5600 cm–1,” Zeitschrift für Naturforschung A, Vol. 41, 1986, pp. 505–511; A. Oancea et al., “Laboratory infrared reflection spectrum of carbon dioxide clathrate hydrates for astrophysical remote sensing applications,” Icarus, Vol. 221, No. 2, 2012, pp. 900–910).

Figure 3. Raman spectrum of carbon dioxide showing the Fermi diad (or doublet) from a negative crystal inclusion in a sapphire.
In order to prove the high density of carbon dioxide fluids, this author used micro-Raman spectroscopy. Raman spectra of carbon dioxide in fluid inclusions show a Fermi diad (or doublet) (figure 3), which is useful in estimating carbon dioxide fluid pressure and density in negative crystals (e.g., J. Yamamoto et al., “Paleo-Moho depth determined from the pressure of CO2 fluid inclusions: Raman spectroscopic barometry of mantle- and crust-derived rocks,” Earth and Planetary Science Letters, Vol. 253, 2007, pp. 369–377; H.M. Lamadrid et al., “Reassessment of the Raman CO2 densimeter,” Chemical Geology, Vol. 450, 2016, pp. 201–222). Using the equations reported by Lamadrid et al. (2016), carbon dioxide fluid densities in sapphires measured by FTIR spectra were estimated at 0.54–0.74 g/cm3. This density is consistent with the results derived from FTIR spectra in figure 2.
According to the Summer 2020 Lab Notes entry, sapphire with heat and pressure showed a strong broad peak at 3047 cm–1 with C=O asymmetric stretching vibration ν3 at 2342 cm–1 and no other peaks at wavenumbers higher than 3600 cm–1. The Raman spectra also revealed a carbon dioxide Fermi diad (N. Ng-Pooresatien, pers. comm., 2023), and the density was estimated at 0.11–0.18 g/cm3, which is about one-fifth lower. The existence of carbon dioxide bubbles in a negative crystal is therefore no longer definitive proof of the absence of thermal treatment. This study also showed that FTIR analysis is a useful method for detecting the high density of carbon dioxide fluid in sapphire, and resulting FTIR peaks above 3600 cm–1 could indicate the absence of heat treatment. Source: GIA @topic:3


Title: Pressed Amber Imitation for “Root Amber” Abstract: Figure 1. This bracelet containing 12 mm beads was submitted as “root amber.” Photo by Tsung-Ying Yang.
Root amber, a commercial variety of burmite (amber from northern Myanmar), is popular in the Taiwanese market. As the name suggests, root amber resembles tree roots and usually has a dark brown to light yellow color with creamy swirls caused by the mixing of fine calcite particles and resin during the sedimentation of the amber (Y. Wang, Amber Gemology, China University of Geosciences Press, Beijing, 2018, p. 244).

Figure 2. Pressed amber imitations and natural root amber. Under white light, the pressed amber (A) appeared less homogeneous than natural root amber (C). Granular structure of the pressed amber (B) revealed under long-wave ultraviolet light, whereas natural root amber showed relatively even fluorescence (D) under the same long-wave UV lighting. Photomicrographs by Kai-Yun Huang; field of view 4.23 mm.
Recently, a bracelet was submitted to Taiwan Union Lab of Gem Research (TULAB) as root amber (figure 1). This bracelet consisted of a string of dark brown beads with light yellow creamy swirls. The refractive index of these beads was about 1.54 by spot reading, which was consistent with the RI of amber, and the beads showed uneven medium blue to faint yellow fluorescence under long-wave UV light. Microscopic observation of the beads revealed slight differences from natural root amber. First, the yellow swirls appeared to have a coarse texture rather than smooth. Second, the brown regions seemed to show a vaguely granular structure. The beads were further investigated under a microscope with long-wave UV illumination and compared with those of natural root amber. The results of fluorescence microscopy revealed that these regions did, in fact, show a granular structure with particle sizes ranging from tens to hundreds of microns, while the natural root amber appeared relatively fine-grained and homogeneous under the same lighting (figure 2). Raman spectroscopic analysis and comparison with both the RRUFF database and the internal amber references compiled by TULAB confirmed that these beads were made of amber and calcite particles (figure 3). Previous studies also pointed out that the strongest peaks at 1645 and 1450 cm–1 may respectively be assigned to ν(C=C) and δ(CH2) modes in fossil resin (R.H. Brody et al., “A study of amber and copal samples using FT-Raman spectroscopy,” Spectrochimica Acta Part A, Vol. 57, No. 6, 2001, pp. 1325–1338). To summarize, the amber bracelet should be defined as an imitation—specifically, a pressed amber mixed with calcite powder during the manufacturing process.

Figure 3. Raman spectra comparisons between the spectrum of the bead, amber reference (TULAB), and that of calcite from the RRUFF database suggested that the bead consisted of calcite and amber. The peaks at 1645 and 1450 cm–1 may be assigned respectively to ν(C=C) and δ(CH2) modes in fossil resin. The stacked spectra are baseline-corrected and normalized.
Although pressed amber has long existed in the trade, the addition of calcite powder made this sample a better imitation of natural root amber and more difficult to distinguish by standard gemological testing. The best identification method for such an imitation is observation with fluorescence microscopy. Source: GIA @topic:13