Title: Recrystallization of Baddeleyite as an Indicator of PHT (“HPHT”) Treatment in Sapphire Abstract: Figure 1. This 7.11 ct oval blue sapphire, measuring 11.66 × 10.44 × 7.38 mm, exhibits eye-visible white mineral inclusions. Photo by Yizhi Zhao.

PHT (“HPHT”) treatment in sapphire has been a controversial topic the last few years. Recently, Guild Gem Laboratories in Shenzhen received a 7.11 ct blue sapphire (figure 1) for identification. The refractive index of 1.762–1.770 and hydrostatic specific gravity of 4.00 confirmed the stone’s identity. It was inert under long-wave and short-wave UV. Microscopic examination revealed several distinct features, such as diffuse color bands and melted white solid mineral inclusions surrounded by discoid fractures, indicating that this stone had undergone thermal enhancement (figure 2).

Figure 2. Blurred blue color zoning and melted white solid mineral inclusions surrounded by discoid fractures. Photomicrograph by Yujie Gao; field of view 5.26 mm.

Figure 3. FTIR spectra of conventionally heated sapphire and the HPHT sapphire in figure 1. The latter showed distinct bands centered around 3042 cm–1, accompanied by peaks at 2627, 2412, 2349, 2319, and 2096 cm–1.
Further UV-Vis spectroscopic testing specified a metamorphic geological origin, while energy-dispersive X-ray fluorescence (EDXRF) analysis revealed low Fe content around 400–600 ppm. FTIR spectra (figure 3) showed a distinct 3309 cm–1 series at 3181 and 3373 cm–1, consistent with heated metamorphic sapphire. We also noticed a broad band centered at 3042 cm–1, accompanied by peaks at 2627, 2412, 2349, 2319, and 2096 cm–1. According to previous reports (S.-K. Kim et al., “Gem Notes: HPHT-treated blue sapphire: An update,” Journal of Gemmology, Vol. 35, No. 3, 2016, pp. 208–210; A. Peretti et al., “Identification and characteristics of PHT (‘HPHT’) - treated sapphires – An update of the GRS research progress,” 2018, http://gemresearch.ch/hpht-update), the ~3042 cm–1 series band is diagnostic of sapphire treated by a high-pressure, high-temperature process.

Figure 4. Discoid fractures were oriented in almost the same direction within the sapphire host. Photomicrograph by Yujie Gao; field of view 2.28 mm.
As shown in figure 4, the mineral inclusions melted and solidified within the surrounding discoid fractures, exhibiting a dendritic appearance. Micro-Raman spectra analysis on the white mineral and recrystallized dendritic inclusions using 473 nm laser excitation produced some interesting results. The white melted minerals and the recrystallized inclusion showed almost the same peaks in the region of 1000–100 cm–1, suggesting that they were the same mineral. Peaks at 641, 560, 541, 475, 334, and 221 cm–1 and a characteristic doublet at 188/178 cm–1 matched with the Raman spectrum for baddeleyite (a rare zirconium oxide mineral), according to the RRUFF database, as shown in figure 5.

Figure 5. Raman spectra of the white mineral and dendritic inclusion both matched with baddeleyite (ZrO2).
Zircon (ZrSiO4) is known as a common inclusion in sapphires, which may undergo solid state thermal dissociation to zirconia and silica at extreme conditions such as high temperature and/or high pressure as follows:

ZrSiO4 (zircon) → ZrO2 (baddeleyite) + SiO2

Baddeleyite, a monoclinic polymorph of zirconia, forms at relatively high pressure (up to about 7 GPa). W. Wang et al. (“The effects of heat treatment on zircon inclusions in Madagascar sapphires,” Summer 2006 G&G, pp. 134–150) confirmed the existence of baddeleyite with zircon in heated blue sapphire by detecting a 188/178 cm–1 Raman doublet of baddeleyite in melted zircon after heating at around 1400–1700°C and normal pressure. The results of Wang et al. (2006) suggest that when using conventional heating techniques, only a small fraction of zircon transforms into baddeleyite, while most of the zircon inclusions keep their crystalline structure intact without any phase transformation. Based on our Raman testing, however, no zircon was found in this 7.11 ct sapphire, and spectra of both the white mineral at the center and the recrystallized minerals in the fracture were consistent with baddeleyite.
Additionally, we also noticed several fractures filled with baddeleyite in a uniform orientation (again, see figure 4). Using a polariscope and a conoscope under a microscope, we confirmed that these fractures occurred along the basal plane (0001) of the sapphire.
One question is whether these flat fractures already existed from parting before treatment (which is commonly encountered in sapphire) or formed during treatment. It is known that parting may occur along the basal plane of sapphire under certain situations, such as twinning or exsolution of inclusions. Neither distinct twinning nor exsolved inclusions were found, and almost all of the fractures were fully filled, leaving no empty space within them. Thus, we believe that these fractures could have been triggered by treatment. The proposed occurrence and healing process of these fractures are illustrated in figure 6.

Figure 6. The occurrence and healing process of discoid fractures in the sapphire during treatment. A: Zircon inclusions and blue color bands in the sapphire. B: Under high pressure and high temperature, progressive decomposition of zircon results in the formation of baddeleyite and flat fractures. C: Baddeleyite penetrates into the discoid and fills the fracture with no space left. D: Baddeleyite recrystallizes in a dendritic pattern shown by the red line. Illustrations by Xueying Sun.
In conclusion, we can appropriately speculate that PHT (“HPHT”) treatment might cause flat fractures along the basal plane and facilitate the transformation from zircon to baddeleyite. The high baddeleyite content in heated sapphire may serve as a good indicator of PHT (“HPHT”) treatment. Further experiments are needed to support this argument. Source: GIA @topic:3


Title: Quarterly Crystal: Quartz and Lazulite Abstract: Figure 1. Recovered from Canada’s Yukon Territory, these doubly terminated parallel-growth quartz crystals are decorated with deep blue crystals of lazulite. This specimen weighs 76.19 ct and measures 36.12 × 22.24 × 16.95 mm. Photo by Kevin Schumacher.

	Before a gemstone is fashioned by a lapidary, it enters the gem trade in its natural state, in a form generally referred to as “rough” or “gem rough.” Not all rough is gem quality, nor is most so-called rough appropriate for fine mineral collections. Only a very special piece of rough is suitable for gem use or fits the visual definition of a fine mineral specimen. When such crystals are encountered it then becomes a difficult decision, often financially based, whether to leave them in a natural state or fashion them into polished gems.

	Our new “Quarterly Crystal” section of the Micro-World column will feature very attractive inclusion-bearing minerals that could also be fashioned by a skilled lapidary into a gem or a polished inclusion study block. The quartz and lazulite specimen shown in figure 1 is one such mineral.

	These parallel-growth, doubly terminated glassy quartz crystals were recovered from Rapid Creek in the Dawson mining district of Canada’s Yukon Territory. While this is a nearly perfect mineral specimen, hosting swarms of deep blue lazulite crystals both on the surface and within (figure 2), it also makes a remarkable piece for any inclusionist’s collection. Since this is a very uncommon mineral association from the locality, whether to polish it is a difficult decision. Fortunately, this dilemma can often be avoided with a simple trick: A small drop of mineral oil placed on the surface serves as a temporary window through which the inclusions may be observed and photographed.

Figure 2. Inclusions of lazulite in this Canadian quartz were photographed using a partial immersion technique. A drop of mineral oil was placed on the surface to create a temporary window into the interior. Photomicrograph by Nathan Renfro; field of view 4.45 mm. Source: GIA @topic:1


Title: Peter J. Dunn (1942–2017) Abstract: Distinguished mineralogist and author Pete Dunn died November 8 at the age of 74. He is best known for the 134 new mineral descriptions he wrote over the course of his long career.

Dr. Dunn received his master’s degree and PhD in mineralogy/geology from the University of Delaware in Newark. Before joining the Smithsonian Institution’s National Museum of Natural History in 1972, he served in the U.S. Air Force and worked at Boston University as a curator in the geology department. In addition to characterizing new minerals, Dr. Dunn published a nine-volume monograph and more than 70 papers on the Franklin–Sterling Hill mining district in New Jersey in a number of scientific publications. In 1987, a member of the clinopyroxene subgroup from the Franklin mining district was named “petedunnite” in his honor. A prolific contributor to G&G throughout the 1970s, Dr. Dunn served on the journal’s editorial review board from its inception in 1981 until 1987. Upon his retirement from the National Museum of Natural History in 2008, he volunteered at the museum’s information desk until his death. Source: GIA @topic:7


Title: GIA Lab Reports on Low-Temperature Heat Treatment of Mozambique Ruby Abstract: Drawing on extensive experience with traditional and modern methods, many Sri Lankan “burners” have become adept at low-temperature heat treatment of ruby from Mozambique. Photo by Vincent Pardieu/GIA.

                      Since 2009, Mozambique has become the world’s leading source of commercial and gem-quality ruby. While many gems from this country are subject to “conventional” high-temperature heating (1300oC, or 2,372oF), rumors have been circulating within the gem trade that many rubies might be treated in Sri Lanka at much lower temperatures. With red to pink corundum, low-temperature treatment aims to remove any blue color component from the gem and enhance the resulting color.

Over the last 30 years, Sri Lankan burners have refined locally produced furnaces—including the Lakmini—and gained extensive heat treatment expertise. The top practitioners in that country now rival those in Thailand, especially where low-temperature heating of corundum is concerned.

In early 2015, as a result of trade concerns, GIA researchers undertook two sessions of experimental low-temperature heat treatment of Mozambique ruby, one conducted in collaboration with burners in Sri Lanka and the other in Bangkok. For the latter, the temperatures reached ranged from approximately 550o to 750oC (1,022o to 1,382oF). The researchers confirmed that treatment caused a noticeable decrease of the blue color component in many samples.

These experiments aimed to determine whether low-temperature heating produced any detectable alterations to the treated gems’ inclusions, IR spectra, or chemical composition. The results appear in a study titled “‘Low-Temperature’ Heat Treatment of Mozambique Ruby - Results Report.”

Using high magnification and fiber-optic lighting, GIA researchers were able to show that many—though not all—inclusions were affected by low-temperature heating. In many cases, fractures appeared around crystals, with larger crystals the most affected. Mica, feldspar, and chalcopyrite inclusions showed the most alteration, with amphibole crystals showing the least. Fractures lined with limonite or iron staining might also appear darker after low-temperature heating.

Treatment caused modest but observable changes in peaks detected by FTIR spectroscopy at 3309 and 3161 cm-1. Trace-element analysis using LA-ICP-MS showed no significant change after treatment.

This study confirms that gemological laboratories have the capability to detect low-temperature treatment in rubies from Mozambique, especially with careful observation of inclusions and certain peaks in IR spectra. Source: GIA @topic:3


Title: Introduction to Analyzing Internal Growth Structures: Identification of the Negative d Plane in Natural Ruby Abstract: Growth-structure analysis has become increasingly important as a gemological tool for locality classification and distinguishing between natural and synthetic gemstones. This article presents the methods and instruments needed to analyze the internal growth structures of corundum. As an application of this testing procedure, the negative rhombohedral d (0112) plane is documented as part of the crystal habit in a small number of natural rubies—both as a subordinate form and, for the first time in natural rubies, as a dominant crystal form. Until recently, this crystal face was primarily associated with flux-grown synthetic rubies and sapphires. Source: GIA @topic:3


Title: Books: The Collector's Guide to the Minerals of New York State Abstract: By Steven C. Chamberlain and George W. Robinson, 96 pp., softcover, illus., publ. by Schiffer Publishing, Ltd, Atglen, PA 2013. US$19.99.

              From the outset, authors Steven Chamberlain and George Robinson acknowledge that their goal was not a field guide, but rather a guide for mineral specimen appreciation. On the whole, it succeeds in this aim, and is worth its moderate price for those cultivating an interest in minerals of the Empire State.

In the introduction, the first of four chapters, Chamberlain and Robinson provide a brief positioning of the mineral sources of New York State. While there are no localities as important as Mont Saint-Hilaire in nearby Canada or Franklin, New Jersey, but it is of note that (starting with warwickite in 1838) twelve new mineral species have been discovered in New York. Some have become world-famous for their beauty, like the Herkimer diamonds, which could soon be designated as the official state mineral.

The authors devote an entire page to the important collections and collectors of New York minerals since the early 19th century, but only one page of text (plus ten references) to the geology of New York State. The other pages of this sub-section contain beautiful photos, though most do not contribute much to the illustration of the subject. The most important geological takeaway is that almost all mineralogically interesting occurrences are found in either sedimentary or crystalline rocks and in fractures within these rocks.

The following chapters are devoted to the description of the mineral occurrences. In contrast to conventional field guides, which are usually organized geographically, this book groups the localities according to the geology of the host rocks: occurrences in sedimentary rocks, in crystalline rocks, and in fractures. This is perhaps the most unique feature of the book. The description of each locality discusses the same aspects: its significance to specimen mineralogy, its location and history, its geological setting and origin, and the relevance of the minerals to collectors. Each chapter ends with a listing of similar occurrences (with GPS coordinates) and references.

As both authors are recognized as specialists in New York minerals, these chapters are a treasure trove of information, especially as they attached importance to include the latest research results and modern mineral nomenclature (e.g., the brown tourmaline from Bush Farm has now been identified as fluoruvite).

The authors claim that the guide’s organization is “a new approach that brings coherence to relationships among similar localities.” This seems plausible and is certainly true to some extent, as the relations between similar occurrences become more visible. My overall impression, however, is that the advantages of this approach do not reach as far as the authors probably hoped.

Apart from minor criticisms (What is the interest of the lengthy enumeration of collections and collectors? Shouldn’t the part on geology be elaborated a little more, especially as the basic approach of the book is based on it?) one question immediately comes to mind: Can the minerals of an entire state be adequately described in just 96 pages, a quarter of which is filled with (admittedly beautiful) color photos? Obviously, the authors recognized this and chose to limit themselves to the most important occurrences: While this book is too incomplete to serve as a field guide or to act as a comprehensive local mineralogy text, its merit lies in the attempt at a new approach, the well-written and up-to-date text and the sheer beauty of the photos. Source: GIA @topic:7


Title: Quarterly Crystal: Etching on Laurentthomasite Abstract: Figure 1. This deeply etched 11.24 mm laurentthomasite crystal from Madagascar displayed a rich greenish blue color. The orange color patches are epigenetic limonitic residue. Photo by Annie Haynes; courtesy of Arkfeld Minerals.
The micro-world of gems and minerals involves the study of not only fluid and solid inclusions but also any significant surface features caused by growth and/or etching. When a rough crystal is fashioned into a gemstone, most if not all surface features of any importance are removed during the lapidary process. So when we encounter an interesting gem crystal, we always take the opportunity to examine the natural surfaces for any interesting evidence of growth or dissolution.
With that in mind, we recently studied a rough-surfaced etched hexagonal crystal of laurentthomasite (figure 1) from Madagascar that measured 11.24 × 9.76 × 4.32 mm and weighed 3.71 ct. Laurentthomasite, with the chemical formula Mg2K(Be2Al)Si12O30, is a relatively recent mineral approved in 2019 by the International Mineralogical Association (IMA) as a new species in the milarite (osumilite) group. It was named after French mineral dealer Laurent Thomas.
The rough surface of the laurentthomasite prevented the application of standard gemological testing. With magnification, however, we were able to observe a uniaxial optic figure from the crystal in polarized light. As expected, the dichroism displayed was a greenish blue down the optic axis direction and greenish yellow perpendicular to the c-axis. Under UV radiation, the crystal’s reaction was inert.

Figure 2. Some of the dissolution features observed on the etched surface of the laurentthomasite crystal were reminiscent of decorative hexagonal tiles, as seen using differential interference contrast (left) and diffuse transmitted light (right). Photomicrographs by Nathan Renfro; field of view 1.44 mm.
Examination of the surface using differential interference contrast microscopy showed an abundance of hexagonal etch features, some with a rather dramatic architecture. Reflecting the hexagonal symmetry of the laurentthomasite, as shown in figure 2, these dissolution features were targeted for photomicrography. Source: GIA @topic:2


Title: Update on Spectroscopy of “Gold Sheen” Sapphires Abstract: Figure 1. These 14 sapphires, weighing up to 97.69 ct each, displayed a golden sheen effect and in some cases six-rayed asterism. They possessed sufficiently large inclusion-free areas to enable good-quality spectra.

Sapphires displaying a golden sheen, known in the trade as “gold sheen” or “Zawadi” sapphires, entered the gem market in late 2009. These sapphires are mined in eastern Kenya (T.N. Bui et al., “From exsolution to ‘gold sheen’: A new variety of corundum,” Journal of Gemmology, Vol. 34, No. 8, 2015, pp. 678–691). They contain dense needles and platelets of hematite/ilmenite inclusions, which are responsible for producing a golden shimmer on the surface.

Recently, GIA’s laboratory in Bangkok received 14 gold sheen sapphires of various shapes and cuts. The samples had yellow and green to blue bodycolor, were transparent to translucent, and weighed 1.06 to 97.69 ct (figure 1). Their physical properties and inclusions were similar to those of gold sheen sapphires described in Bui et al. (2015): an RI of 1.762–1.772, a birefringence of 0.008–0.009, a hydrostatic SG of 3.98–4.01, an inert reaction to long- and short-wave UV radiation, and an abundance of hematite/ilmenite platelets. Since the samples had some transparent windows, UV-Vis-NIR spectra were analyzed.

The UV-Vis-NIR spectra all displayed strong Fe-related absorption features at 377, 388, and 450 nm. Samples with a yellow bodycolor showed mainly the three Fe features, whereas the green to blue sapphires revealed a band centered at around 580 nm that is related to Fe2+-Ti4+ intervalence charge transfer, in addition to the three strong Fe features (figure 2). LA-ICP-MS analysis on inclusion-free areas showed high Fe ranging from 2550 to 3260 ppma, 2 to 8 ppma Mg, 4 to 11 ppma Ti, 30 to 45 ppma Ga, and 0.2 to 0.7 ppma V. For the green to blue samples, Ga/Mg overlapped, varying from 5 to 30. Samples with a yellow bodycolor varied from 4 to 11. Other trace elements including Zr, Nb, Ta, W, Th, and U were also detected but in insignificant quantities. It is notable that Mg and Ti concentrations were comparable in the yellow samples (all Ti4+ charges compensate Mg2+, leaving no Ti4+ to interact with Fe2+), whereas Ti concentrations were significantly higher than Mg concentrations in the green to blue sapphires resulting in some Ti4+ forming Fe2+-Ti4+ pairs (J.L. Emmett et al., “Beryllium diffusion of ruby and sapphire,” Summer 2003 G&G, pp. 84–135). The chemical and UV-Vis-NIR spectroscopic features corresponded with the bodycolors of these sapphires. In addition, FTIR spectra of the gold sheen sapphires generally showed diagnostic features of AlO(OH), consistent with either boehmite or diaspore; kaolinite; and gibbsite.

Figure 2. The UV-Vis-NIR spectrum of a gold sheen sapphire with yellow bodycolor
revealed strong Fe-related absorption features at 377, 388, and 450 nm. The spectra
of green to blue samples revealed an additional Fe2+- Ti4+ intervalence charge-transfer
band centered at around 580 nm. These samples were not specifically aligned to the
c-axis. Source: GIA @topic:3


Title: Quarterly Crystal: “Ball Bearing” in Quartz Abstract: Figure 1. This doubly terminated scepter quartz crystal from Sichuan, China, weighs 200.28 ct and measures 75.03 mm in length. Photo by Diego Sanchez.
Quartz crystals with three-phase fluid inclusions from the Jinkouhe mine in the Sichuan Province of China have been sold for many years at gem and mineral shows such as those held annually in Tucson, Arizona. Unfortunately, many of those crystals are damaged due to the mining methods used and the packing together of numerous crystals for transport. Good terminations on those crystals are few and far between, and the edges are generally chipped, while the broad flat crystal faces are often scratched and abraded.
So it was with high interest that we examined the relatively large doubly terminated scepter rock crystal quartz shown in figure 1. At 200.28 ct and measuring 75.03 × 21.76 × 17.98, this crystal was much larger than most others from the Jinkouhe mine. It was preserved in its own cotton-lined box, and as shown in figure 1, essentially undamaged.

Figure 2. Nomarski differential interference contrast revealed light etching on the prism faces of the quartz crystal. Photomicrograph by Nathan Renfro; field of view 0.72 mm.

Figure 3. In this image, the silver-gray bubble can be seen at the right side of the liquid-filled void. The coating gives it the appearance of a small ball bearing. Photomicrograph by Nathan Renfro; field of view 7.42 mm.

Figure 4. The metallic-looking bubble has floated toward the left end of the fluid inclusion chamber. Photomicrograph by Nathan Renfro; field of view 7.42 mm.
Microscopic examination of the crystal revealed light etching on the prism faces (figure 2), which was highlighted using Nomarski differential interference contrast. Internally there were several primary fluid inclusions, with typical black organic compounds as the solid phase. One fluid inclusion in particular contained a gas bubble (figure 3) that moved freely across the entire length of the void (figure 4). The bubble was coated with a metallic-looking substance that gave it the appearance of a small stainless steel ball bearing. We could not identify the coating but suspect that it was an organic compound. Source: GIA @topic:2


Title: Strong Fluorescence in B-Jade Impregnated with Wax Abstract: Figure 1. Left: The wax-impregnated jadeite jade bangle submitted for identification. Right: The bangle exhibited strong bluish fluorescence under long-wave UV radiation. Photos by Lai Tai-An Gem Lab.
Fine-quality jadeite jade is known for its high value in the market. “A,” “B,” and “C” jade are classifications applied to jadeite that relate to various states of enhancement. However, many in the market may not understand the real meaning of the terms. A-jade shows no indications of having undergone modification through the impregnation with colorless or near-colorless wax, resin, or any other agent. When the material has been treated through bleaching and the impregnation with colorless or near-colorless wax, resin, or any other agent, it is described as B-jade. When it shows indications of having fissures or fractures filled with a color agent, it is defined as C-jade. B and C areas may exist in the same specimen; this is described as B+C-jade. A bangle submitted to the Lai Tai-An Gem Laboratory (figure 1, left) illustrates the common misconception that B jade is only impregnated by resin. In fact, wax-impregnated jadeite jade is also defined as B-jade.
The client who submitted the bangle believed it was resin-impregnated jadeite owing to its suspiciously strong fluorescence reaction. The item possessed an uneven green and white color with a greasy luster and weighed 277.14 ct. It measured approximately 76 mm with a thickness of 9–10 mm. A refractive index (RI) reading of 1.66 was obtained from five random spots on the bangle, and a specific gravity (SG) of 3.34 was also recorded. The most interesting feature was an unusually strong reaction under long-wave UV (figure 1, right), indicating it was probably treated and should be examined with more care. This material was determined to be jadeite jade when subsequently tested by Fourier-transform infrared (FTIR) spectroscopy, but the FTIR results also revealed some features other than the jadeite-related peaks.

Figure 2. Microscopic observation revealed obvious acid etching marks, coarse pits, and cobweb-like surface fissures. Photo by Lai Tai-An Gem Lab; field of view 4.6 mm.
FTIR analysis confirmed that the jadeite bangle was heavily impregnated with wax. The absorption peaks at 2850, 2920, and 2965 cm–1 differed from those expected in resin-impregnated material—which usually exhibits peaks at 3061 and 3040 cm–1—and they were intense and sharp enough to indicate that a significant quantity of wax had been applied. Microscopic examination revealed obvious acid etching marks, coarse pits, and cobweb-like surface fissures (figure 2). Wax residues were also found within pits and fissures when poked. Additional unseen wax was apparently within the structure according to the wax pattern revealed by FTIR analysis, typical for wax-impregnated B-type jadeite, which clearly explains the strong reaction under long-wave UV.
While the term B-jade is meant to be applied to wax- and/or resin-impregnated material (Laboratory Manual Harmonisation Committee Information Sheet #11, http://www.lmhc-gemology.org/pdfs/IS11_20111215.pdf), many traders misleadingly describe B-type jadeite jade as resin-impregnated only. This leads the unsuspecting buyer to believe that wax-impregnated jadeite jade is A-jade. This case clearly shows that those dealing in jadeite should be aware of the differences between resin- and wax-impregnated materials, even though both are considered B-jade, and understand that confusion may arise if items are not carefully checked. Source: GIA @topic:13


Title: Quench-Crackled Blue Synthetic Spinel Abstract: Figure 1. A 9.75 ct synthetic spinel, seen in GIA’s Bangkok lab, was proven to be treated by the quench-crackling method. Photo by Nuttapol Kitdee.

	Recently, GIA’s Bangkok laboratory examined an interesting 9.75 ct blue oval mixed cut (figure 1). Standard gemological properties included an RI of 1.728, with strong anomalous double refraction using the polariscope. The sample’s Chelsea filter reaction exhibited a strong red transmission, and absorption bands at 540, 580, and 635 nm were seen in the handheld spectroscope. The specimen fluoresced strong red under long-wave UV radiation and strong bluish white under short-wave UV. These properties are diagnostic features of cobalt blue synthetic spinel grown by the Verneuil (flame-fusion) process.

	Microscopic observation revealed tiny strings of gas bubbles and strong irregular graining, with many reflective fractures on one side of the sample (figure 2). The specimen appeared to have been heated and thermally shocked. This method, known as quench-crackling, typically involves the use of a dye to create a preferable color, but not in this specimen. While DiamondView imaging showed clear fractures similar to those found in quench-crackled treated material (figure 3), a PL spectrum of Cr3+ shifted from 685 to 689 nm was consistent with synthetic spinel (S. Saeseaw et al., “Distinguishing heated spinels from unheated natural spinels and from synthetic spinels,” GIA Research News, April 2009).

Figure 2. These reflective fractures were seen in the blue synthetic spinel. Photomicrograph by Charuwan Khowpong; field of view 2.5 mm.

Figure 3. DiamondView imaging of the synthetic spinel showed fractures typical of quench-crackled material. Photo by Charuwan Khowpong.

	Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) was utilized for a trace element analysis. The results displayed high amounts of Co (up to 167 ppma), along with 1137 ppma Ti and 337 ppma Cr. Zn was found with a maximum of 6 ppma, and Ga was below the detection limit. This specimen contained higher amounts of Ti and Co than those previously reported in S. Saeseaw et al. (“Cobalt diffusion of natural spinel: A report describing a new treatment on the gem market,” GIA Research News, June 2015). We concluded that a quench-crackling technique was used to make the synthetic spinel appear more like a natural spinel. In such cases, standard gemological properties are useful for accurate identification. Source: GIA @topic:3


Title: Three-Rayed Asterism in Quartz Abstract: Figure 1. Asterism with a three-rayed star seen on a quartz cabochon (sample B) in reflected light with fiber-optic illumination. Photo by Martin P. Steinbach.
Asterism is a well-known (if not the most familiar) optical phenomenon observed in numerous gem species. In transparent or translucent gemstones, a series of parallel inclusions consisting of tiny needles or channels produces a distinct light band by a complex process of scattering and reflection of light. If the gemstone is cut as a cabochon, the light band, which is oriented perpendicular to the needle or channel axis, generally produces a sharp light line on the surface of the gemstone, an effect known as chatoyancy. If several series of parallel inclusions are present, we observe several intersecting light bands producing asterism. The number of rays in a star depends on the number of intersecting light bands. For example, two intersecting light bands produce four-rayed stars, three intersecting light bands produce six-rayed stars, and so on.
A single star is observed if all needles or channels are oriented parallel to a single plane. If the inclusions are found in different planes, we might observe several stars on the surface of a cabochon or sphere (K. Schmetzer et al., “Dual-color double stars in ruby, sapphire, and quartz: Cause and historical account,” Summer 2015 G&G, pp. 112–143). This effect can be due to the symmetry of the host, which causes several series of non-planar needles (e.g., in cubic spinel or garnet). Multi-asterism is also produced by several series of needles that are independent of each other, as in quartz or beryl (K. Schmetzer and M. Glas, “Multi-star quartzes from Sri Lanka,” Journal of Gemmology, Vol. 28, No. 6, 2003, pp. 321–332). A combination of these two variants is observed in garnet. All different variants may be designated as a “network of stars.”
The present contribution describes three-rayed asterism, a phenomenon that does not really fit into the generally accepted knowledge about the formation of asterism and multi-asterism. This variant of asterism in quartz is a rare optical phenomenon mentioned briefly by Gübelin and Koivula (Photoatlas of Inclusions in Gemstones, Volume 2, 2005, Opinio-Verlag, Basel, Switzerland, p. 548) and by Steinbach (Asterism: Gems with a Star, 2016, MPS Publishing and Media, Idar-Oberstein, Germany, pp. 649–651). Hainschwang (Fall 2007 GNI, pp. 261–262) observed two three-rayed stars on quartz cabochons with chlorite inclusions. The two stars had one ray in common and were observed upon rotation of the cabochon, with one of the three-rayed stars observed at another end of the ray that is shared by both stars. Hainschwang assumed that the optical phenomenon was caused by the chlorite inclusions, but the formation mechanism is not completely understood.

Our observation is based on the examination of four star quartz samples, which came from the private collection of one of the authors (MPS). The quartz cabochons were purchased at various gem and mineral fairs and were said by the vendors to originate from Brazil; further details on locality are unknown. The properties of the cabochons are summarized in table 1.
Upon first view, the samples showed broad light bands forming a three-rayed star, with all branches of the star originating from a center (figure 1). The single branches of the three-rayed stars move along the surface of the cabochons after rotation of the stone or a change of the position of the light source or the observer. So far, this observation is consistent with the features of light bands generally observed in asteriated gemstones. But in “normal” gemstones (e.g., star rubies or star sapphires), we see three intersecting light bands forming a six-rayed star.

Figure 2. Upon rotation of sample A, the center of a three-rayed star moves to the girdle and another center of a three-rayed star comes into sight (D); upon further rotation, this star is also moved. The sequence A to F shows the optical phenomenon described. Photos by Karl Schmetzer; reflected light, fiber-optic illumination.
Surprisingly, upon rotation of the cabochons it was detected that the samples did not show a single three-rayed star but a multi-star network. Rotating each quartz cabochon in a direction in which it was possible to follow one of the light bands on the cabochon’s surface, at some point this branch of the star ended in another center of a three-rayed star. Repeating this procedure, another center of a three-rayed star was occasionally detected, unless the branches of the three-rayed star ended at the girdle (figure 2).

Figure 3. Schematic representation of the multi-star network observed on the four quartz cabochons (samples A–D in table 1). The red lines represent the light bands observed on the surface upon various rotations. The patterns in A and B were observed on the round cabochons; sample C was an oval cabochon, while sample D was an irregularly shaped cabochon. The direction of the c-axis for the three transparent samples is also indicated.
Figure 3 shows a schematic representation of the multi-star networks observed in the four samples. It must be underscored that the different patterns drawn represent lines on curved domes of the different cabochons. If the branches of the stars are in a position close to the girdle, some lines that appear almost straight in the middle of the cabochon will appear more or less curved. So far, due to the different orientations of the cabochons and the different shapes, each sample represents only part of a full star network that would be seen on the surface of a complete sphere.

Figure 4. Fibrous inclusions in a quartz cabochon from Brazil showing three-rayed asterism. Photomicrograph by Karl Schmetzer; immersion, field of view 7.6 mm.
All the samples revealed a dense pattern of needle-like to fibrous inclusions (figure 4) typically described as rutile (J. Hyršl and G. Niedermayr, Magic World: Inclusions in Quartz, 2003, Bode Verlag, Haltern, Germany, pp. 82–139). However, these inclusions are mostly bent or curved, and no series of parallel needles or channels were seen under the magnification of a gemological microscope (up to 100×). It is uncertain how these curved rutile inclusions, sometimes described as “fibers” or “hairs,” contribute to the phenomenal pattern observed.
The mechanism responsible for the observed multi-star network is unknown; it could be caused by structural features or inclusions. However, quartzes with similar rutile inclusion patterns from Brazil (as shown in figure 4) and elsewhere generally do not show three-rayed asterism or the type of three-rayed asterism network described here. It is possible to create a single three-dimensional network by a combination of the variants seen in figure 3, A–D. But this would be highly speculative, since we cannot (based on the samples available) prove that all variants seen so far contribute to one single pattern. Source: GIA @topic:3


Title: Alums Named 2013 JCK Rising Stars Abstract: GIA alums, from left, Jason Dow, Patrick and Mary Kay Mohs, and Cornelia Goldsmith, are JCK’s 2013 Rising Stars. Photos provided by Jason Dow, Patrick Mohs Jewelry and Cornelia Goldsmith.

                      Four GIA alums have been named “Rising Stars” for the 2013 JCK Las Vegas Show. Each will exhibit their work in the JCK Design Center at the Mandalay Bay Resort & Casino May 31 through June 3. The JCK Rising Star program identifies emerging artists and highlights their designs to buyers at the show.

“We’re so excited and proud that four of our graduates have been selected as this year’s JCK Rising Stars,” said Bev Hori, vice president of Education and chief learning officer for GIA. "This is a great opportunity for them to showcase their design aesthetics and craftsmanship to some of the industry’s most influential buyers.”

Jason Dow channels his heritage in jewelry designs that integrate ancient Asian motifs with modern and Western concepts.
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Cornelia Goldsmith’s designs reflect her enduring love of natural, organic forms that blend ancient and new world sentiments.
Read More

Mary Kay and Patrick Mohs of Patrick Mohs Jewelry find inspiration for their designs in nature.
Read More Source: GIA @topic:11


Title: Synthetic Rock Crystal Quartz Cluster with Natural-Looking Inclusions Abstract: Figure 1. The cluster specimen weighing 1114 g and measuring 119 × 126 mm. Photo by Lai Tai-An Gem Lab.
A client recently submitted for identification the piece shown in figure 1, assuming it to be a natural mineral specimen. It weighed 1114 g, measured 119 × 126 mm, and contained colorless transparent to semitransparent crystals. Eye-visible inclusions as well as numerous tiny crystals and some minute powdered material were seen around the cluster’s base.

Figure 2. Magnification revealed obvious fluid and two-phase inclusions within the crystals. Photomicrograph by Lai Tai-An Gem Lab; field of view 4.60 mm.

Figure 3. A peak at 3584 cm–1 in the FTIR spectrum proved the rock crystal quartz specimen was synthetic (red). In contrast, a natural quartz reference sample analyzed by our lab exhibits peaks at 3378, 3482, and 3595 cm–1 (black) that were absent in the sample.
Standard gemological testing yielded a refractive index of 1.542–1.555, a specific gravity of 2.65, and inert reactions under long- and short-wave UV radiation, properties consistent with quartz. Microscopic examination revealed obvious fluid and two-phase inclusions (figure 2). Examination by Fourier-transform infrared (FTIR) spectroscopy showed an absorbance region in the 400–1600 cm–1 range, also consistent with quartz, and Raman spectroscopy confirmed the identification. However, the most important data came from the FTIR analysis in transmission mode in the 1000–6000 cm–1 range. A characteristic peak of synthetic quartz at 3584 cm–1 (figure 3) was observed, while peaks consistent with natural quartz (3378, 3482, and 3595 cm–1) were not detected. Similar spectra were collected from the other crystals in the group, confirming a synthetic origin (S. Karampelas et al., “Infrared spectroscopy of natural vs. synthetic amethyst: An update,” Fall 2011 G&G, pp. 196–201; Winter 2015 Lab Notes, pp. 439–440).

Figure 4. Natural quartz’s horizontal prismatic striations, relative to the c-axis (left, reference sample), were instead diagonal in the synthetic quartz cluster studied (right). Because striations can be faked, they should not be considered diagnostic. Photos by Lai Tai-An Gem Lab.
Synthetic quartz crystal clusters are not new to the market, but as the use of synthetic quartz has increased, such crystal specimens have become available on numerous online shopping platforms. Surprisingly, most of them are sold as “natural quartz clusters.” One of the common trade methods for separating natural and synthetic quartz clusters is to observe the striations on the prism faces. In natural quartz, the striations form horizontally (perpendicular to the c-axis), while synthetic quartz typically displays diagonal or triangular striations (figure 4) (Winter 2016 G&G Micro-World, pp. 425–426). This method may aid in identification but should not be considered diagnostic, since the striations can be faked.
When synthetic quartz clusters are fashioned into polished products, the potential of misidentifying them as “natural quartz” increases significantly, especially with inexperienced consumers and small-scale labs lacking analytical equipment. In such cases, the inclusion scene is almost identical to that observed in natural quartz, and the helpful prismatic face growth lines disappear. Therefore, members of the trade should be cautious when handling synthetic quartz, although the crystal clusters may be somewhat easier to identify. Source: GIA @topic:2


Title: Trapiche-Type Emeralds from Pakistan Abstract: Growth pattern observed in a trapiche-type emerald from Swat, Pakistan. The slice shows two colorless cores and two intermediate lighter green zones surrounded by a more intense green rim. Viewed perpendicular to the c-axis, in air (left) and immersion (right); diameter of the sample from 4.6 to 4.8 mm. Photos by Karl Schmetzer.
Numerous gem materials have been designated “trapiche” in the trade and in various publications. They generally describe a pattern consisting of a fixed non-transparent star in a transparent matrix, with the arms of the six-rayed star radiating from a central point or from a central core to the rim of the crystal. Only a limited number of mineral species show a clear trapiche pattern within crystal slices (i.e., a pattern with a clear separation of the crystal into distinct growth sectors). The boundaries of these growth sectors, running from the center to the edges between external prism or pyramidal faces, are normally sharp and contain mineral or fluid inclusions, separating different parts within the rim. These sector boundaries are also described as the arms of the fixed six-rayed star. The most prominent gem minerals showing a distinct trapiche pattern are Colombian emeralds and rubies from Myanmar.
Another group of gem materials is characterized by several areas of increased transparency and translucency that surround a central point or central core according to the symmetry of the host. The two types of areas are characterized by different concentrations of inclusions, which are trapped within specific parts of symmetry-equivalent growth sectors of the host. The arms of the fixed star are perpendicular to the external crystal faces. The most prominent gem materials of this second group are blue basaltic sapphires from different sources, but similar patterns also have been described for other gem varieties such as aquamarine from Namibia. This second group of crystals is designated “trapiche-type,” and the emeralds from Pakistan described in this entry belong to this group of gem materials.
Trapiche-type emeralds originating from the Swat mining region in Pakistan have recently been described by Y. Gao et al. (Fall 2019 Gem News International, pp. 441–442) and H. Guo et al. (“Inclusion and trace element characteristics of emeralds from Swat Valley, Pakistan,” pp. 336–355 of this issue). The samples showed an interesting growth pattern and color zoning with a colorless core, a lighter green intermediate zone, and a more intense green rim. The inclusions forming the trapiche-type pattern were restricted to the lighter green intermediate growth zone.
Recently, the author received six slices of similar material, reportedly from Swat, from the gem collector S. Hanken of Waldkraiburg, Germany; the samples had been purchased in 2020 from the U.S. gem trade. One of these samples, which were all cut perpendicular to the c-axis of the emerald crystals, showed an interesting growth pattern. The emerald slice measured from 4.6 to 4.8 mm (distances between different prism faces) with a thickness of 1.9 mm (see above). The sample revealed two colorless beryl cores of almost equal size. One of these colorless cores was surrounded by a large light green intermediate zone, which also contained the inclusions forming the trapiche-type pattern. The second core was surrounded by a lighter green intermediate zone, which was much smaller. Encompassing these two intermediate zones were intense green hexagonal growth boundaries with growth planes parallel to the external prism faces.
This intense green growth boundary surrounds both light green intermediate growth zones. Subsequent to this intense green boundary, an intense green outer rim without trapiche-type inclusions but with additional growth planes parallel to the prism faces was present.
As already described by Gao et al., the emerald was grown in three distinct steps with a colorless beryl core, a light green intermediate zone, and an intense green rim. All growth steps were separated by sharp boundaries, with a thin growth layer between the intermediate zone and the rim, which showed the most intense green coloration observed in the sample. The emerald formed with two cores, with a subsequent growth step, in which both parts were still separated from each other. Only in the last growth step, in which the intense green rim was formed, were the two parts of the final emerald crystal in contact with each other. Source: GIA @topic:3


Title: Opal Description Abstract: "The Path of Enlightenment" necklace contains 180 magnificent opals from Lightning Ridge, Australia, a famous opal producing area. - Courtesy Cody Opal

                      Opal is the product of seasonal rains that drenched dry ground in regions such as Australia’s semi-desert “outback.” The showers soaked deep into ancient underground rock, carrying dissolved silica (a compound of silicon and oxygen) downward.

During dry periods, much of the water evaporated, leaving solid deposits of silica in the cracks and between the layers of underground sedimentary rock. The silica deposits formed opal.

How Opal Forms
Opal is known for its unique display of flashing rainbow colors called play-of-color. There are two broad classes of opal: precious and common. Precious opal displays play-of-color, common opal does not.

Play-of-color occurs in precious opal because it’s made up of sub-microscopic spheres stacked in a grid-like pattern—like layers of Ping-Pong balls in a box. As the lightwaves travel between the spheres, the waves diffract, or bend. As they bend, they break up into the colors of the rainbow, called spectral colors. Play-of-color is the result.

	This black opal exhibits exceptional play-of-color. - Courtesy Cody Opal
The color you see varies with the sizes of the spheres. Spheres that are approximately 0.1 micron (one ten-millionth of a meter) in diameter produce violet. Spheres about 0.2 microns in size produce red.  Sizes in between produce the remaining rainbow colors.

	This fine-quality light opal is from Mintabie, South Australia. Almost all of its spectral colors are visible from a variety of viewing angles. - Courtesy Cody Opal
Although experts divide gem opals into many different categories, five of the main types are:

		White or light opal: Translucent to semitranslucent, with play-of-color against a white or light gray background color, called bodycolor.

		Black opal: Translucent to opaque, with play-of-color against a black or other dark background.

		Fire opal: Transparent to translucent, with brown, yellow, orange, or red bodycolor. This material—which often doesn’t show play-of-color—is also known as “Mexican opal.”

		Boulder opal: Translucent to opaque, with play-of-color against a light to dark background. Fragments of the surrounding rock, called matrix, become part of the finished gem.

		Crystal or water opal: Transparent to semitransparent, with a clear background. This type shows exceptional play-of-color.

	This exceptional light opal is from South Australia’s Coober Pedy opal fields. - Courtesy Cody Opal

	The rough specimen is a thin seam of boulder opal on sandstone host rock. The 3.47-carat boulder opal tablet was cut from a similar piece of rough. Source: GIA @topic:12


Title: New Deposit of Black Opal from Ethiopia Abstract: ABSTRACT
Opal was first discovered in Ethiopia in the early 1990s. Specimens from Mezezo in the historical Shewa province consist of nodules of a reddish brown volcanic rock with orange, reddish brown, or “chocolate” brown precious opal inside. The next major discovery occurred in 2008, when white precious opal was found in the province of Wollo near Wegel Tena, about 550 km north of Addis Ababa (F. Mazzero et al., “Nouveau gisement ďopales ďEthiopie dans la Province du Welo: Premières informations,” Revue de Gemmologie a.f.g., No. 167, pp. 4–5). This deposit still produces large amounts of white and crystal precious opal and occasionally some black material (Winter 2011 Lab Notes, pp. 312–313).

In 2013, yet another source was discovered in Wollo, at the Stayish mine near the town of Gashena (figure 1). This discovery has yielded mostly dark and black opal, along with some white and crystal opal. Although it is only now being reported, the deposit has been actively producing since 2013. It is set in a distinct opal-bearing layer in a mountainous area at an altitude of around 3,000 meters. It lies approximately 700 km northeast of Addis Ababa, more than 100 km from the historic town of Lalibela by road, and about 30 km north of the white opal deposit.

Figure 1. The Stayish black opal mine, active since 2013, is located in the Wollo province of northern Ethiopia.
Like the white opal, the black opal is found at the contact zone between the volcanic rock series and the underlying clay-rich layer (figure 2). The layer is one in a sequence of repeating volcanic ash and ignimbrite layers. Field observations at different locations show that the opal-bearing layer is contained in a single stratum extending for tens and even hundreds of kilometers along the mountain belt. The opal-bearing clay layer is about 60 cm thick and contains opal of various quality and color. The black opal is retrieved from flat tunnels up to 15–20 meters long that are dug horizontally into the mountain slope by local villagers. The material generally comes in nodules and chunks 2–5 cm long, but 10 cm pieces have also been retrieved from this deposit (figure 3).

Figure 2. While acidic ash layers occur repeatedly within the stratigraphic sequence at Stayish, precious black opal occurs only in this stratum. Photo by Pierre Hardy.

Figure 3. Pieces of black opal from the Stayish mine are usually 2–5 cm in diameter (bottom), though some may reach 10 cm in length (top). Photo by Tewodros Sintayehu.
The specimens are usually very dark, reminiscent of dyed or smoke-treated opal except that the surface does not show any staining in surface pits or fissures (figure 4). The stones also display a dark, even color all the way through and are sometimes layered with dark gray common opal. This separates it from sugar-acid treated opal (Winter 2011 GNI, pp. 333–334), where the darker color is confined to a more or less thick surface layer.

Figure 4. This microscopic image of an Ethiopian black opal with surface scratches shows none of the black staining seen in smoke-treated or dyed opal. Some grayish non-precious opal material can be observed between the color patches. Photo by Hpone-Phyo Kan-Nyunt.
Initial X-ray fluorescence analyses showed barium (Ba) values ranging from below detection limit for one deposit with more crystal-like opal to 1000 ppmw for another deposit with more dense and grayish material. The two deposits are on adjacent sides of the same mountain. The wide range of Ba values confirmed the volcano-sedimentary character of the black opals, as previously described for white opals from Wegel Tena (B. Rondeau et al., “Play-of-color opal from Wegel Tena, Wollo Province, Ethiopia,” Summer 2010 G&G, pp. 90–105).

Preliminary studies with Fourier-transform infrared (FTIR) spectrometry did not give conclusive results due to the relatively opaque character of our samples. Raman spectra showed very strong carbon peaks, though these alone do not allow a reliable distinction between treated opal from Wegel Tena and natural-color black opal from the Stayish mine. Careful microscopic observation should reveal the natural character of opal from this new deposit, and further studies are in progress. Source: GIA @topic:12


Title: Natural Sapphire with Trapiche Pattern Inclusions Abstract: The regular hexagonal inclusions consisted of six independent units, resembling a trapiche pattern. Photomicrograph and illustration by Yizhi Zhao; field of view 1.70 mm.
A blue gemstone pendant was recently submitted to Guild Gem Laboratories for identification. Standard gemological testing identified it as a sapphire, with a refractive index of 1.762–1.770 and birefringence of 0.008. Fourier-transform infrared (FTIR) spectroscopy combined with microscopic observation confirmed it was a natural sapphire. The UV-Vis spectrum indicated a basalt-related origin owing to relatively high iron content. The FTIR transmitted spectrum also revealed a 3309 series with peaks at 3366, 3309, 3232, and 3185 cm–1, which are commonly seen in basalt-related sapphire.
Microscopic observation showed several colorless crystals and fluid inclusions under reflective and transmitted light. Using a fiber-optic light, we also observed very interesting scenes of whitish clouds (see above) consisting of arrays of hexagonal particles. These particles seemed to be flat and parallel to each other. A distinct uniaxial interference pattern was observed when viewing perpendicular to these particles under the polariscope equipped with a conoscope, which proved that they were parallel to the basal plane (0001) crystalline face of corundum. Further observations revealed that each particle possessed six nearly identical triangular sectors, divided by six arms with hexagonal symmetry. Based on our microscopic observation and estimation, the diameters of the hexagons ranged from approximately 0.06 to 0.13 mm. This pattern was very similar to the trapiche structure seen in some sapphire, ruby, and emerald.
The depth of the inclusions prohibited Raman spectroscopy testing, but we will monitor this phenomenon in other samples for further study in the future. Source: GIA @topic:3


Title: Aquamarine from a New Primary Deposit in Mexico Abstract: Figure 1. Aquamarine was recently discovered in San Luis Potosí State in north-central Mexico. Here the aquamarine is shown in association with muscovite and quartz. The approximate size of the visible aquamarine crystal is 12.04 × 5.68 × 4.57 mm. Photo by M. Ostrooumov.

Scientists still have not adequately surveyed Mexico from a mineralogical or gemological point of view. But recent finds of amazonite, jadeite, topazolite, demantoid, and labradorite demonstrate the importance of systematic research of the Mexican subsoil, which may lead to the discovery of other gemstones and gem localities (M. Ostrooumov, “Gemstones from Mexico—A review,” Summer 2011 G&G, p. 141).

Recently, the author discovered transparent blue crystals with hexagonal-prismatic habit in a granitic pluton in the hills of Guadalcázar municipality, San Luis Potosí State, in north-central Mexico. These crystals, the largest of which measured 12.04 × 5.68 × 4.57 mm, were embedded in a single quartz vein in association with muscovite (figure 1). All observed aquamarine crystals were generally characterized by a lighter blue tone, lacking visible inclusions. The samples were submitted for identification at the Institute of Earth Sciences at the University of Michoacan in Morelia, Mexico.

Standard gemological testing yielded the following properties: refractive index (RI)—no=1.582−1.587 and ne=1.575−1.580; pleochroism—strong blue and near-colorless; birefringence—0.007, with a uniaxial negative optic sign; hydrostatic specific gravity (SG)—2.70−2.71; fluorescence—inert to both long- and short-wave UV radiation. These properties suggested beryl, which we later confirmed with UV-Vis-NIR and infrared reflection spectroscopy and Raman microprobe.

UV-Vis-NIR spectroscopy showed absorption bands at 428, 452, 575, 630, and 805–815 nm. Narrow, weak absorption lines at 428 and 452 nm are attributed to the spin-forbidden transition of six-coordinated Fe3+. A broad intense band at 575 nm and a much weaker line at 630 nm, which are responsible for the aquamarine color, are assigned to an Fe2+-O-Fe3+ intervalence charge transfer transition (A.S. Marfunin, Advanced Mineralogy, Vol. 2, Springer-Verlag, Berlin, 1995, pp. 113−114). Finally, an intense broad band at approximately 805–815 nm is attributed to spin-allowed transitions of Fe2+.

Infrared reflection spectroscopy and Raman microprobe are methods of “fingerprinting,” and a combination of these techniques permits the user to identify a wide range of mineralogical, gemological, and archaeological objects (M. Ostrooumov, “Infrared reflection spectrometry analysis as a non-destructive method of characterizing minerals and stone materials in geoarchaeological and archaeometric applications,” Geoarchaeology, Vol. 24, No. 5, 2009, pp. 619−637).

Figure 2. Infrared reflection spectra and Raman microprobe results of the samples
confirm their aquamarine identity. The IR spectrum at the top is from the {1010} orientation,
while the middle spectrum shows the {0001} orientation. The bottom plot shows the
unoriented Raman microprobe results, with principal peaks at 322, 396, 447, 528, 684,
773, 916, 1011, and 1068 cm–1.
This study confirmed that the crystals belonged to the beryl group (http://rruff.info). The infrared reflection spectra were obtained on oriented crystal faces {0001} and {1010} in order to take into account the effect of orientation (figure 2, top and middle). These results indicate the presence of the typical Be-O band vibrations at 743–807 cm–1 and 1215–1276 cm–1. The infrared absorption spectra showed the presence of hydroxyl groups with a prominent band at 3450 cm−1 and a secondary band at about 3558 cm−1 due to the fundamental OH stretching vibration of water molecules, as well as the water-bending vibration at approximately 1630 cm−1. The Raman microprobe spectra (figure 2, bottom) showed excellent agreement with a reference spectrum for aquamarine from Ilmen, Russia, in the author’s FT-Raman database (http://www.mineralog.net). The Raman spectra of aquamarine in the water range from 3700 to 3500 cm−1 using 532 nm excitation wavelength showed two Raman bands at 3608 and 3598 cm−1 with different intensities. Water molecules in the channels are classified as type I or type II according to their orientation to the beryl structure. The Raman band at 3608 cm−1 is assigned to the vibration of type I water, and the Raman band at 3598 cm−1 is ascribed to the vibration of type II water molecules. UV-Vis-NIR, infrared reflection, and Raman microprobe techniques, as well as standard gemological testing, confirmed the discovery of aquamarine in the Guadalcázar granitoid deposits of San Luis Potosí State.

The recent discovery of in situ aquamarine in Mexico has renewed interest in the geology and mineralogy of gem deposits in that country. More discoveries are anticipated with further exploration in the region. Source: GIA @topic:2


Title: Pyritized Triceratops Fossils from South Dakota Abstract: Figure 1. Triceratops fossils recovered from the Hell Creek Formation in South Dakota. Photo by SD Gem & Fossil.
In recent years, the Hell Creek Formation spanning the Dakotas, Montana, and Wyoming has been extensively studied by paleontologists. This rock formation is home to fossils of various vertebrates, including dinosaurs such as Tyrannosaurus rex and triceratops. The author, an amateur paleontologist, recently unearthed a new dinosaur fossil site on privately owned land in Perkins County, on the northern edge of South Dakota.

Figure 2. The cut and polished piece of pyritized triceratops fossil on the left weighs 50.5 ct and measures 41.28 × 22.23 mm. The piece on the right weighs 22.5 ct and measures 31.75 × 15.88 mm. Photos by SD Gem & Fossil.
Although multiple creatures are being uncovered at the site, closer examination of these fossils recovered revealed that they were from triceratops (figure 1). In addition, the fossils contained pyrite, an iron sulfide also known as “fool’s gold” that forms in sedimentary rocks, giving the fossils a striking metallic appearance. This discovery of pyrite inspired the author to cut and polish the fossils into pieces for collectors to display (figure 2). Sixteen pieces have been cut so far.
Only water was used for cutting, to avoid dust inhalation and to keep the specimens from turning black. A cerium oxide polishing compound was used for the finish, followed by a drying process. The pieces were then treated with an epoxy adhesive to prevent pyrite decay.
The newfound dinosaur site in the Hell Creek Formation of South Dakota holds the promise of unveiling more treasures from the past. As the author’s team and others dive deeper into the site, they hope to uncover additional fossils, providing insight into the long-lost world of dinosaurs. Source: GIA @topic:12


Title: Quarterly Crystal: Dravite in Fluorapatite Abstract: Figure 1. Dark yellowish to brownish green needle-like inclusions dominate the interior of this 21.36 ct Portuguese fluorapatite on siderite matrix. Photo by Adriana Robinson.
Growing from an angular matrix plate of brown siderite, a doubly terminated hexagonal crystal weighing 21.36 ct with a very light purplish blue color (figure 1) was identified as fluorapatite by Raman analysis. As the photo shows, the semitransparent crystal clearly hosts a number of randomly arranged, eye-visible, translucent acicular inclusions. The fluorapatite thumbnail specimen, from the Panasqueira mine in the Castelo Branco district of Covilhã, Portugal, was acquired by author JIK from the collection of Dr. Vasco Trancoso at auction in June 2023. When the specimen was examined microscopically, the acicular morphology and dark yellowish to brownish green bodycolor of the inclusions, as well as their behavior in polarized light, suggested they might be tourmaline. Laser Raman microspectrometry was able to pinpoint their identity as dravite (figure 2), a member of the tourmaline group.

Figure 2. Raman analysis was used to identify the acicular inclusions in the fluorapatite host crystal as dravite tourmaline. Photomicrograph by Nathan Renfro; field of view 7.37 mm. Source: GIA @topic:2


Title: Quarterly Crystal: Geocronite in Fluorite Abstract: Figure 1. This 29.60 × 23.84 × 18.35 mm cluster of well-formed isometric fluorite and monoclinic geocronite crystals was recently discovered at the Milpo mine in Peru. Photo by Annie Haynes.
A tight crystal cluster of bright apple-green fluorite and opaque silvery gray geocronite, Pb14(Sb,As)6S23, was recently examined for this edition of Quarterly Crystal. The specimen shown in figure 1 measured 29.60 × 23.84 × 18.35 mm, and the fluorite portion played host to several small, well-formed monoclinic crystals, all situated near the surface. The crystals appeared to be geocronite, a very rare sulfide containing lead, antimony, and arsenic.

Figure 2. A combination of optical microscopy and Raman analysis identified the opaque silvery gray monoclinic inclusions as the very rare sulfide geocronite. Photomicrograph by Nathan Renfro; field of view 2.39 mm.
The specimen was obtained from Luciana Barbosa of Barbosa Minerals (Asheville, North Carolina). It came from a recent discovery at the Milpo mine in the Atacocha mining district of Pasco Province, Peru. The Milpo mine is known to produce fluorite crystals with inclusions of various sulfides. Since the fluorite and geocronite are intimately intergrown, the opaque silvery gray bodycolor of the inclusions in the fluorite, together with their monoclinic appearance shown in figure 2, strongly suggested geocronite.
The next logical step was laser Raman microspectrometry. Using this technique, we conclusively identified the inclusions as geocronite, thereby confirming our suspicions. It should be noted that, to the authors’ knowledge, this is the first time geocronite has been identified as an inclusion in any mineral. Source: GIA @topic:2


Title: Clinochlore and Muscovite in Quartz from Colorado Abstract: Figure 1. This quartz crystal cluster from Larimer County, Colorado, contains numerous bluish green and white spherical inclusions on phantom growth planes. Photo by Annie Haynes; courtesy of Nico Jackson.
Recently the author encountered a parcel of quartz with phantom layers consisting of beautiful bluish green and white spheres (figure 1). Raman analysis identified the green spheres as clinochlore (figure 2), Mg5Al(AlSi3O10)(OH)8, a member of the chlorite group. Many of the white orbs appeared to be secondarily altered, presumably by fluids entering through fractures in the quartz host, though some showed no clear evidence of alteration. Raman analysis of one of the unaltered white spheres identified it as muscovite, KAl2(AlSi3O10)(OH)2. Minute dark brown to black spheres were also present and visually consistent with hematite, but that could not be confirmed by Raman analysis.

Figure 2. These bluish green spheres in the quartz crystal were identified as clinochlore, and the white spheres were identified as muscovite. Photomicrograph by Nathan Renfro; field of view 4.23 mm.
This material is from Larimer County, Colorado, where it was collected in 2020 by Nico Jackson. So far, three pockets of material have been discovered, with a total production of about 10 kg. While chlorite-group minerals are relatively common inclusions in quartz, the soft texture and greenish blue color of these clinochlore spheres are less common in the author’s experience. These green clinochlore spheres with contrasting white muscovite spheres are a striking addition to the possible minerals seen in the micro-world of quartz. Source: GIA @topic:2


Title: Quarterly Crystal: Panasqueira Quartz Abstract: Figure 1. Weighing 751.95 ct, this parallel cluster of two quartz crystals contains a directional phantom plane composed of numerous green to near-colorless hexagonal inclusions. Photo by Adriana Gudino.
With its relatively high hardness and high degree of transparency, colorless rock crystal quartz is the perfect host for an abundance of fluid and mineral inclusions. As a common crustal mineral, it sometimes forms as solid single crystals and crystal clusters.

Figure 2. The translucent green-colored crystals along the phantom plane in the Portuguese quartz were identified as fluorapatite by Raman analysis. Photomicrograph by Nathan Renfro; field of view 12.47 mm.
This issue’s Quarterly Crystal, a 751.95 ct double crystal measuring 110.54 × 50.30 × 24.82 mm from Minas da Panasqueira in Portugal (figure 1), comes from the personal collection of Jordi Fabre of Fabre Minerals in Barcelona. Examination of the two parallel quartz crystals revealed numerous colorless to green, transparent to translucent euhedral inclusions, identified by Raman analysis as fluorapatite (figure 2). Some of these fluorapatite inclusions surrounded a much larger dark brownish orange protruding crystal confirmed as cassiterite (figure 3).

Figure 3. Using Raman microspectrometry, this single protruding dark brownish orange crystal was identified as cassiterite. Photomicrograph by Nathan Renfro; field of view 13.64 mm.
The colorless to green fluorapatite crystals show directional deposition and are along a phantom plane, situated only on one side of the quartz specimen. This suggests that they are syngenetic with the quartz host.
Quartz is relatively common at the Panasqueira mine. This “floater” quartz crystal group, which is recrystallized at its base, is an excellent host for the numerous inclusions of fluorapatite and the solitary cassiterite crystal. Source: GIA @topic:2


Title: Quarterly Crystal: Cinnabar in Fluorite Abstract: Figure 1. Several bright red to dark red well-formed trigonal crystals of cinnabar highlight the interior of the fluorite crystals in this fluorite and calcite cluster from Spain. Photo by Diego Sanchez.
This issue’s Quarterly Crystal deals with a 362.09 ct crystal cluster of fluorite and calcite recently examined by the authors. The 55.79 × 42.80 × 38.63 mm specimen was colorless and transparent to translucent and played host to several small bright red to dark red well-formed trigonal crystals, visible in figure 1. These crystals were all situated on the same growth plane in the fluorite portion.

Figure 2. A combination of optical microscopy and Raman analysis served to identify the trigonal inclusions as the mercury sulfide cinnabar. Photomicrograph by Nathan Renfro; field of view 2.35 mm.
The fluorite and calcite specimen was obtained from Jordi Fabre of Fabre Minerals in Barcelona. It is from the Emilio mine in the Caravia mining area in the Asturias region of northwestern Spain. The Emilio mine is known to produce fluorite crystals with inclusions of various sulfides, including cinnabar. Therefore, the pure red bodycolor of these inclusions, together with the trigonal symmetry shown in figure 2, strongly suggested they were cinnabar. Using Raman microspectrometry, we were able to identify the inclusions as cinnabar, thereby confirming our initial impression. Source: GIA @topic:2


Title: Willemite in Topaz Abstract: Figure 1. This 21.36 × 14.94 × 9.44 mm custom-cut study block of topaz from Jos, Nigeria, is host to several interesting inclusions. Photo by Diego Sanchez.
The authors recently had the opportunity to examine a 28.61 ct transparent freeform custom-cut study block of colorless topaz (figure 1) from Jos in Plateau State, Nigeria, that hosted a very large forest green inclusion of chlorite with an intricate stepped surface structure.

Figure 2. Transparent colorless willemite crystals appear to be tumbling down the slope of a large chlorite inclusion in a Nigerian topaz. Photomicrograph by Nathan Renfro; field of view 4.02 mm.
Magnification showed that the chlorite inclusion was partially rimmed by transparent near-colorless crystals (figure 2) identified by laser Raman microspectrometry as willemite (Zn2SiO4), a trigonal zinc silicate.
The willemite crystals in this topaz fluoresced bright yellow-green to short-wave ultraviolet radiation, giving the chlorite a partial fluorescent halo. This is the only known example of the mineral willemite as inclusions in topaz from any locality.
In addition to the willemite, bright bluish green patches of color on the chlorite might be the microcline feldspar amazonite, but Raman analysis could not identify them. There were also some tiny rounded opaque inclusions with metallic luster that resembled metal sulfides. Bright red epigenetic hematite was found in one surface-reaching cleavage crack, and a few tiny transparent brownish yellow high-relief crystals of sphalerite were also present with the willemite. Source: GIA @topic:2


Title: Monazite (?) in Quartz Abstract: Figure 1. This 10.54 ct rock crystal quartz is host to a transparent yellow mineral inclusion. Photo by Annie Haynes.

We recently examined an interesting 10.54 ct transparent, colorless, square modified step cut with a slightly convex table facet (figure 1). The faceted rock crystal quartz host, measuring 11.82 × 11.77 × 9.57 mm, is from Itinga in Minas Gerais, Brazil, and came to us from Luciana Barbosa at the Gemological Center in Asheville, North Carolina.

Figure 2. The transparent yellow monazite (?) inclusion in the rock crystal quartz and the stress cracks immediately surrounding it are both clearly visible in this image. Photomicrograph by Nathan Renfro; field of view 4.86 mm.
The gem played host to an eye-visible transparent yellow crystal located near its center, which was visible from several directions. On examination with a gemological microscope, we observed a transparent yellow angular crystal of what appeared to be monazite, with a skirt of small stress cracks, suspended in the quartz (figure 2).
Laser Raman microspectrometry was not able to identify the inclusion because it was too deep in the host; all it returned were quartz peaks. Energy-dispersive X-ray fluorescence (EDXRF) also failed to produce hints of unusual chemistry on the inclusion. After several attempts at Raman and EDXRF, we realized that destructive analysis would be needed to clearly identify the yellow crystal, but destructive analysis was not possible.

Figure 3. The monazite (?) inclusion shows its birefringent (anisotropic) nature with bright interference colors in polarized light. Photomicrograph by Nathan Renfro; field of view 3.06 mm.
As a result, we turned to optical mineralogy and the crystal habit shown by the well-formed inclusion. Morphologically, the inclusion looked like monazite crystals we have encountered in the past, and it appeared to be monoclinic. The yellow color also suggested monazite. The inclusion showed its birefringent (anisotropic) nature with bright interference colors in polarized light (figure 3). A small condensing lens was used to pull a partial biaxial interference figure from the inclusion. The crystal had weak pleochroism, and a Becke line test showed that the inclusion had a higher refractive index than the surrounding host quartz. All of these findings could lead to its identification as monazite. But there is still a nagging uncertainty, so we are left with “monazite (?).” Source: GIA @topic:2


Title: Grossular Garnet Crystals in Demantoid Garnet Abstract: Figure 1. A cluster of transparent octahedral crystals observed in a yellowish green demantoid garnet. Photomicrograph by Ungkhana Atikarnsakul; field of view 1.2 mm.

Demantoid, the green variety of andradite garnet, is a rare gemstone. It typically possesses high dispersion and diamond-like luster, which is often partly masked by the green and yellow-green bodycolors. Variations in the color of demantoid garnet are generally caused by traces of chromium (Cr3+), ferric iron (Fe3+), Fe2+-Ti4+ intervalence charge transfer, and Fe2+-Fe3+ interactions (G. Giuliani et al., “Gem andradite garnet deposits demantoid variety,” InColor, No. 36, Summer 2017, pp. 28–39).
Recently, GIA’s Bangkok laboratory received a 4.47 ct yellowish green gemstone for identification. Standard gemological testing, including a refractive index over the limits of the refractometer and a specific gravity of 3.86, and Raman spectroscopy identified it as demantoid garnet. Microscopic examination revealed strong internal graining, fingerprints, and particles mixed with short needles. Interestingly, it also exhibited transparent octahedral crystals at the crown (figure 1). Some of them reached the surface and had a different luster from the host material. Close examination showed that the crystals contained two different luster areas, which also distinguished them from the host demantoid (figures 2 and 3).

Figure 2. Some of the transparent octahedral crystals reached the surface of the demantoid. Photomicrograph by Ungkhana Atikarnsakul; field of view 2.0 mm.

Figure 3. LA-ICP-MS was performed on three different areas: the host demantoid (spot 1), the outer area of the included crystal (spot 2), and the inner area of the included crystal (spot 3). The blue dashed line shows the separation between the demantoid area and the outer area of the inclusion. The yellow dashed line separates the outer and inner areas of the inclusion. Photomicrograph by Ungkhana Atikarnsakul; field of view 1.0 mm.
Raman spectroscopy was performed on the three different areas to identify the materials. The Raman spectra of the two areas of the crystals were similar to that of the host, matching with andradite garnet. Garnet species typically possess similar physical properties and crystal forms, but differ in chemical composition. For example, andradite is a calcium-iron garnet with the formula Ca3Fe2(SiO4)3, whereas grossular is a calcium-aluminum garnet with the formula Ca3Al2(SiO4)3. Those two garnet species are in the same isomorphous series and therefore have the same general chemical formula, but differ only in containing Fe or Al. Due to their similar Raman spectra, chemical analysis is better suited to separate the species of garnet.
In this case, laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) was used to compare the chemical composition of the demantoid against that of the surface-reaching inclusions. Spot 1 was on the host material, spot 2 on the outer area of the crystal inclusion, and spot 3 on the inner area of the crystal (figure 3).

Surprisingly, the three spot areas exhibited different chemical compositions, especially between the host demantoid area and the inner area of the crystal. This indicated that the crystal inclusion was from a garnet species other than andradite. Table 1 shows the chemical composition of the three spot areas, provided first in parts per million by weight (ppmw) units, followed by wt.% oxides of elements, and then as recalculated cations normalized to 12 oxygen atoms. Spot 1 (the demantoid) contained significantly more Fe than Al, whereas spots 2 and 3 of the crystal inclusion contained both elements. Spot 2 contained a higher concentration of Fe than Al, and the calculation showed a mix of two garnet species. It is possible that the detection area partly included the host material. Spot 3 contained a higher Al concentration than Fe (a 75.36% match with grossular).
Many types of solid inclusions are found in demantoid garnet, such as chromite, apatite, and diopside. From the results obtained here, it is interesting that solid inclusions of a different garnet species—grossular, in this case—can also be trapped in demantoid. Source: GIA @topic:3


Title: The Year of Mineralogy at the Perot Museum Abstract: Figure 1. The Year of Mineralogy at the Perot Museum of Nature and Science in Dallas features 10 cases filled with fascinating samples demonstrating the importance of the mineral world around us. Photo courtesy of the Perot Museum of Nature and Science.
2022 is the International Mineralogical Association’s designated year for celebrating the history, development, and role of mineralogy, with a goal of promoting public interest in mineral studies. The association aims to emphasize mineralogy’s critical role in technology and society and to highlight the future of mineralogy through the exploration of new and environmentally conscious methods for extracting the minerals used today. To help carry out this mission, the Perot Museum of Nature and Science in Dallas has created the Year of Mineralogy exhibit (figure 1) in the Lyda Hill Gems and Minerals Hall (https://www.perotmuseum.org/exhibits/halls/lyda-hill-gems-and-minerals-hall/).

Figure 2. This striking example of lapis lazuli, a rock composed of minerals including lazurite, pyrite, and calcite, is on display in the exhibit. From the Sar-e-Sang mine in the Kokcha River area of Badakhshan Province, Afghanistan. Photo courtesy of the Perot Museum of Nature and Science; specimen courtesy of Keith and Diane Brownlee.
With more than 5,700 minerals identified to date, and more added each year, there is no shortage of specimens to display. Each of the exhibit’s 10 cases educates visitors with spectacular examples to illustrate various mineral properties. The first case defines what a mineral is, showing specimens such as lapis lazuli and lazurite (figure 2). Chemical composition and crystal structure are explained in the second case, while the remainder are dedicated to the various properties of minerals, including hardness, tenacity, streak, luster (figure 3), and color.

Figure 3. The resinous appearance of this sphalerite specimen highlights the mineral property of luster. From the Picos de Europa Mountains, Asturias, Spain. Photo courtesy of the Perot Museum of Nature and Science; specimen courtesy of Gail and Jim Spann.
“By understanding mineral characteristics, like hardness, magnetism, and specific gravity, we are able to find solutions to many modern industrial problems and improve our overall well-being,” said Kimberly Vagner, director of gems and minerals at the Perot Museum.
On display until April 24, 2023, the exhibit is an opportunity for all ages to acquire a deeper understanding of the mineral world around us. Can’t make it to Dallas before April 24? Follow the museum’s Lyda Hill Gems and Minerals Hall on Instagram for posts highlighting some of the magnificent minerals on display. Source: GIA @topic:1


Title: Gota de Aceite in a Zambian Emerald Abstract: A muted gota de aceite effect, with epigenetic ilmenite, in an emerald from Zambia. Photo by Nathan Renfro; field of view 1.26 mm.

Gota de aceite (Spanish for “drop of oil”), a rare phenomenon that occurs in the finest emeralds, is typically associated with Colombian origin (R. Ringsrud, “Gota de aceite: Nomenclature for the finest Colombian emeralds,” Fall 2008 G&G, pp. 242–245). The phenomenon creates a roiled effect caused by irregularity in the emerald’s internal crystal structure. During the gemstone’s crystallization the growth conditions are altered, giving rise to rapid columnar growth. When looking down the emerald’s c-axis, the outline of the columns can be seen. This sometimes has the appearance of drops of oil, giving rise to the name. The columns typically have a slightly different trace element composition from that of the host emerald. This heterogeneity in trace element chemistry will cause a minor change in the refractive index of the columns, allowing the structure to be visible.

The Carlsbad laboratory recently received a 2.10 ct emerald for origin determination. The stone had blocky multiphase inclusions and ilmenite scattered throughout, along with mica platelets and a very subtle blue flash effect associated with some small feathers. At a certain angle, a muted gota de aceite effect was also visible (see above). The UV-Vis spectrum shows a distinct Fe2+ broad band at approximately 900 nm. Inductively coupled plasma–mass spectrometry (ICP-MS) confirmed the stone’s relatively high iron content and indicated a chemical composition consistent with Zambian origin.

The gota de aceite seen in this Zambian emerald was not exactly the same as the phenomenon found in Colombian emeralds. Dendritic ilmenite, an iron-rich mineral, was fully enclosed in the columnar structure. We believe the epigenetic ilmenite exsolved the increased iron content, as Zambian emeralds contain a larger amount of iron than their Colombian counterparts (J.C. Zwaan et al., “Emeralds from the Kafubu area, Zambia,” Summer 2005 G&G, pp. 116–148).

Until now, gota de aceite has only been documented in Colombian emeralds and has been an aid in origin determination. Still, this is not the first time that an inclusion indicative of a particular origin has been found elsewhere. Jagged three-phase inclusions, traditionally seen in Colombian emeralds, have also been documented in emeralds from certain mines in Afghanistan, China, and Zambia (S. Saeseaw et al., “Three-phase inclusions in emerald and their impact on origin determination,” Summer 2014 G&G, pp. 114–132). This emerald shows that inclusions may not always provide conclusive proof of origin, but they can still provide useful information. Source: GIA @topic:3


Title: Aquamarine from Pakistan Abstract: Figure 1. Map of the Gilgit-Baltistan region in northern Pakistan showing the main aquamarine deposits of the Hunza, Braldu, and Shigar Valleys.
In recent decades, a steady supply of aquamarine has come from northern Pakistan, an increasingly important mining locality. The aquamarine was mined mostly from the Gilgit-Baltistan region, including the Shigar Valley, as well as the Hunza and Braldu Valleys (figure 1). The aquamarine occurs in zoned pegmatites formed by hydrothermal fluids in the cavities or veins (M.H. Agheem et al., “Shigar Valley gemstones, their chemical composition and origin, Skardu, Gilgit-Baltistan, Pakistan,” Arabian Journal of Geosciences, Vol. 7, No. 9, 2014, pp. 3801–3814).

Figure 2. The aquamarine crystal on feldspar from the Shigar Valley in Pakistan measures 17 cm tall. Photo by Joe Budd, courtesy of Arkenstone.
Most aquamarines from northern Pakistan show a long hexagonal prism habit and can reach up to a dozen centimeters in length (figure 2). Albite, muscovite, and tourmaline (schorl) are commonly associated as matrix, and most of these are collected as mineral specimens. Parts of them are gem quality and suitable for jewelry use.

Aquamarine samples from the Shigar Valley were obtained from local merchants who deal with Pakistani material. The samples displayed colors ranging from pale greenish blue and pale blue to nearly colorless, with a translucent to transparent appearance. The samples measured 1–2 cm in length and 0.5–1 cm in diameter. To explore the gemological and other properties of these samples, six of them (figure 3) were investigated by standard gemological methods as well as spectroscopic and chemical analyses at China University of Geosciences (Wuhan).

Figure 3. Six rough and two faceted aquamarines from Shigar Valley. The rough samples range from about 5 to 10 ct. The round brilliant cut weighs 3.82 ct, the square cut 7.91 ct. Photo by Yang Hu.
The following gemological properties were recorded: refractive index (RI)—no = 1.574–1.580, ne = 1.569–1.575; birefringence—0.005–0.006; specific gravity (SG)—2.60–2.72; UV fluorescence—weak bluish white to both long- and short-wave UV. The moderate to weak dichroism observed was a relatively saturated blue or greenish blue along the e-ray and very pale blue, greenish blue, or near-colorless along the o-ray.

Microscopic observation revealed abundant 20–300 µm inclusions, either two-phase (fluid, gas) or three-phase (one or two types of fluid, solid, gas) with various shapes. The irregularly shaped multiphase inclusions often gathered together to form a complex “fingerprint” network distributed along healed fissure planes (figure 4, top row). In addition, two-phase inclusions with elongated shapes parallel to the c-axis, and with hexagonal outer profiles perpendicular to the c-axis, were consistent with the crystalline symmetry of beryl (figure 4, bottom row).

Figure 4. Multiphase inclusions in aquamarines from Shigar Valley. Top: Abundant two-phase and multiphase inclusions with irregular shape showing complex “fingerprint” networks. Bottom left: An elongated two-phase inclusion parallel to the c-axis. Bottom right: The same inclusion (shown in the bottom left image) viewed down the c-axis, presenting a perfect circular gas bubble and hexagonal outer profile consistent with the crystalline symmetry of beryl. Photomicrographs by Yang Hu.
These two kinds of multiphase inclusions formed by different crystallization processes. When the beryl crystallized out of a hydrothermal fluid, some of the fluid was trapped. With dropping temperature during mineralization, beryl was re-deposited and a gaseous phase was released from the fluid, gradually forming single multiphase inclusions whose shape conformed to beryl’s hexagonal symmetry. But the formation of multiphase “fingerprint-like” inclusions with irregular shape occurred later. Fluid was embedded in the fracture of the beryl crystal. Due to the solution and re-deposition of beryl from fluid on the fracture surfaces, a small amount of liquid and released gas were gathered and closed off, just like “fingerprint” or dendritic growth networks along healed fissure planes. For a detailed description of these processes, please refer to E. Roedder, “Ancient fluids in crystals,” Scientific American, Vol. 207, No. 4, 1962, pp. 38–47.

Large amounts of multiphase inclusions could lead to a misty, translucent, and uneven appearance, such as the aquamarine crystal in figure 2, with a misty translucence toward the bedrock end. Generally, these characteristics can also be seen in aquamarine from other deposits in Brazil, the United States, South Africa, and China (D. Belakovskiy et al., Beryl and Its Color Varieties: Aquamarine, Heliodor, Morganite, Goshenite, Emerald, and Red Beryl, Lapis International LLC, East Hampton, Connecticut, 2005).

Multiphase and mineral inclusions were identified by Raman spectroscopy with 532 nm laser excitation. The gaseous phase was identified as a mixture of CO2 and a small amount of methane (CH4), and the fluid inclusion consisted of water with dissolved CO2 or liquid CO2. Solid phases inside the multiphase inclusions were identified as solid sulfur and orpiment. Along with columnar tourmaline, white albite, and flaky muscovite, other mineral inclusions such as orange-red almandine, brown tantalite, and yellow argentojarosite [AgFe3(SO4)2(OH)6] were identified by Raman.

Chemical analysis on aquamarine samples by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) showed the following ranges for alkali elements: Li 70–1240 ppmw, Na 830–3970 ppmw, K 54–453 ppmw, Rb 10–64 ppmw, and Cs 310–3220 ppmw. The amount of total alkali content including Li, Na, K, Rb, and Cs ranged from 1296 to 6033 ppmw. As alkali ions (mainly for Na) were associated with “type II” water molecules in structural channels (D.L. Wood and K. Nassau, “The characterization of beryl and emerald by visible and infrared absorption spectroscopy,” American Mineralogist, Vol. 53, No. 5, 1968, pp. 777–800), the relatively low Na content was in agreement with the low peak intensity of “type II” H2O revealed by Raman and IR spectroscopy. The low concentration of alkali content and lack of “type II” water in our aquamarine samples were similar to that in aquamarine from Italy and Vietnam (R. Bocchio et al., “Aquamarine from the Masino-Bregaglia Massif, Central Alps, Italy,” Fall 2009 G&G, pp. 204–207; L.T.-T. Huong et al., “Aquamarine from the Thuong Xuan District, Thanh Hoa Province, Vietnam,” Spring 2011 G&G, pp. 42–48). The chromophore Fe, responsible for blue color, was the richest among all transition elements between 1350 and 5080 ppmw; the samples showed the typical iron absorption at 375, 425, 620, and 820 nm in UV-Vis-NIR spectra. Transition elements V and Mn were present at 1–33 ppmw and 17–56 ppmw, respectively, and the bluish white fluorescence mentioned above may originate from Mn2+ or VO4 centers (M. Gaft et al., Modern Luminescence Spectroscopy of Minerals and Materials, 2005, Springer Berlin, pp. 97–99). Chemical and spectral characteristic suggested the Pakistani samples were low-alkali aquamarine colored by Fe ions rather than irradiation (i.e., Maxixe beryl). Source: GIA @topic:3


Title: Multi-Color-Zoned Quartz from Brazil Abstract: Cabochons of strongly zoned Brazilian quartz, measuring up to 4 cm long. The five described zones are numbered. Photo by Jaroslav Hyršl.

Quartz very often crystallizes in zones during formation, when chemical or physical conditions change. An interesting example of strong zoning caused by variable iron content came recently from Bahia State in Brazil. No rough specimens were seen by the author, but several dozen flat cabochons up to about 4 cm long (see above) were available for study.

The quartz crystallized in five stages, each with a different type of iron. If there is any Fe in the original solution, it acts as a chromophore and produces citrine or amethyst; a higher Fe content will cause separate iron minerals to form. The oldest generation (1) is represented by parallel crystals of yellow citrine with small amethyst sectors, which can be described as ametrine. Their surface was covered by a thin quartz layer (2) with tiny goethite needles. The next generation (3) was a red layer, consistently about 3 mm thick, with fine agate-like zoning. The color was probably caused by very finely dispersed hematite, an identification based on typical color and microgranular texture. The next zone (4) was rich in pyrite, which formed fibers perpendicular to the older red layer, but pyrite can also form in this layer as tiny cubic crystals. After crystallization of the pyrite, the last pale purple amethyst layer (5) was filled with bundles of brown goethite needles up to about 3 mm, which also grew perpendicular to the original surface.

The inclusions in these attractive specimens can explain their complicated formation, with iron found in quartz structure (amethyst and citrine), in sulfide (pyrite), or in oxide (goethite and hematite). Source: GIA @topic:2


Title: Trapiche-like Amethyst from Brazil Abstract: Figure 1. Left to right: 16.73 ct, 14.50 ct, 17.03 ct, and 27.75 ct trapiche-like amethysts. The four cabochons were cut with the base perpendicular to the c-axis (optic axis). Photo by Diego Sanchez.

Minerals such as corundum, beryl, tourmaline, and quartz, which belong to either the trigonal or the hexagonal crystal system, can show a trapiche-like texture with a hexagonal core and six extended arms when viewed down the c-axis. Four trapiche-like amethyst cabochons (figure 1) were submitted to GIA’s Carlsbad laboratory by L. Allen Brown (All That Glitters, Methuen, Massachusetts) for scientific examination. Each was characterized by a hexagonal black core and six brownish arms with pale purple color zoning in between. Magnification revealed that the black core was composed of dense metallic dendritic inclusions (figure 2, left). The brown color of the arms was caused by numerous tufts of tiny inclusions (figure 2, right), some of which resembled either brushes or bullets.
Raman spectra were collected with a Renishaw inVia Raman microscope system. The confocal capabilities of the system allowed inclusions beneath the surface to be analyzed. The black core was identified as an FeS2 (iron sulfide) mineral, likely pyrite. The brownish tiny inclusions in arms could not be identified but were likely goethite (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Vol. 2, Opinio Verlag, Basel, Switzerland, p. 558) based on appearance and occurrence in quartz matrix.

Figure 2. Left: Metallic dendritic inclusions compose the hexagonal black core in the amethysts; field of view 19.27 mm. Right: Brownish and yellowish brush-like and bullet-like fibrous inclusions in the trapiche-like arms; field of view 2.34 mm. Photomicrographs by Jonathan Muyal.
The texture of trapiche-like amethysts is often caused only by the distribution of color-inducing elements (K. Schmetzer and B. Williams, “Gem-quality amethyst from Rwanda: Optical and microscopic properties,” Journal of Gemmology, Vol. 36, No. 1, 2018, pp. 26–36). The fact that the texture was caused by two sets of distinctly colored inclusions makes these four gemstones unique. Source: GIA @topic:2


Title: Striving for Timeliness and Synergy Abstract: We hope you enjoy the Fall 2013 Gems & Gemology. For this issue, we present two fascinating papers from European authors, one on Moroccan agate and one on columnar growth patterns in natural opal from Ethiopia. This second paper outlines a persuasive model of formation for the distinctive “digit” patterns characteristic of some gems from this source.

We also feature articles from GIA authors on diverse topics ranging from a practical indication of heat treatment to Oregon sunstone to our lead article on the Museum of London’s fabulous Cheapside Hoard.

In August, GIA’s Robert Weldon received an invitation to view this astonishing collection, lost for almost 300 years until a chance discovery in 1912 during a demolition near London’s famous St. Paul’s Cathedral.

As it was such a rare opportunity—this cache of jewels represents both a tantalizing window into trade patterns of the 1600s and a great story in itself—we accepted the invitation and traveled to the UK to document it. This trip also gave the impetus to produce an article in time for the Fall 2013 G&G, which will coincide with the very first major exhibition of the jewels. In other words, we had an opportunity to be timely and produce what we hope will be the definitive paper on this extraordinary collection. In London, GIA was able to record video interviews with the museum’s staff and a tour of the hoard, which we will make available on our website.

In this issue, we’re also introducing a new article category to G&G: the field report, which chronicles a GIA expedition to a gem-producing or processing area and may even stand as a statement of intent for future lines of research and publication. Field reports will also serve as anchors on the GIA website for video and images acquired on these trips. Our first field report documents three sunstone feldspar occurrences in Oregon. Readers will find slideshows plus videos of mining processes and interviews with miners at www.gia.edu/gems-gemology. This rich media allows us to offer a far more comprehensive and engaging picture of a topic than we’ve been able to in the past.

This synergy with the GIA website gives us the ability to quickly post articles and news stories online rather than waiting three months for the next print issue. And we can provide supporting resources for our regular print articles that enrich the user experience. We trust we’ve been able to deliver this with the Fall issue and invite you to explore the associated online media for the Cheapside Hoard and Oregon sunstone articles.

Let me also take this opportunity to thank all the authors who have submitted manuscripts to G&G for review. We truly value your contributions.

Duncan Pay
Editor-in-Chief Source: GIA @topic:9