Title: Heat Treatment Effects on the Behavior of the 3161 cm–1 Feature in Low-Iron Metamorphic Yellow Sapphire Abstract: Figure 1. Plot of FTIR peak height at 3161 cm–1 of representative yellow sapphires from Sri Lanka (above) and Madagascar (bottom), before and after heating at different temperatures between 500° and 1050°C for six hours.
Heating is the most common treatment to improve the color and/or clarity of corundum. Untreated natural yellow sapphires from metamorphic deposits often have low color saturation; therefore, heat treatment is typically performed to intensify the yellow coloration. However, the chemical composition of the stones, the heating temperatures employed, the duration of the treatment process, as well as the composition of the furnace atmosphere—reducing or oxidizing—are also important factors that influence the color alteration (K. Nassau, “Heat treating ruby and sapphire: Technical aspects,” Fall 1981 G&G, pp. 121–131; J.L. Emmett et al., “Treatments,” in R.W. Hughes, Ed., Ruby & Sapphire: A Gemologist’s Guide, 2017, pp. 197–247).
The identification of heat treatment in a yellow sapphire is challenging for gemologists. Apart from visible inclusion changes, Fourier-transform infrared (FTIR) absorption spectra are one of the few remaining clues to identify the treatment of low iron content metamorphic yellow sapphires. These sapphires as formed are acceptor dominated when [Mg2+] > [Ti4+] + [Si4+] with the charge compensation being accomplished totally or partially by hydrogen (H+) (E.V. Dubinsky et al., “A quantitative description of the causes of color in corundum,” Spring 2020 G&G, pp. 2–28). In corundum, H+ forms a bond with oxygen creating OH–. It is the OH– that is responsible for the broad peak at 3161 cm–1 (and the series of peaks at 3161, 3242, and 3355 cm–1) when associated with Mg2+ (C.P. Smith et al., “Infrared spectra of gem corundum,” Fall 2006 G&G, pp. 92–93). However, the origin of the 3161 cm–1 peak is not well understood. The article by N. Fukatsu et al. (“Incorporation of hydrogen into magnesium-doped α-alumina,” Solid State Ionics, Vol. 162, 2003, pp. 147–159) showed that when OH– is incorporated into Mg2+-doped synthetic sapphire, the 3161 cm–1 peak was not present but a broad band appeared in the 3000 cm–1 region. If the hydrogen is eliminated either in nature or in the laboratory, the trapped hole (h•) forms to provide charge compensation. The trapped hole pairs with Fe3+, creating a trapped-hole-Fe3+ (h•-Fe3+) pair, which is a very strong yellow chromophore in corundum. In this report, the authors aim to study the effects of heat treatment in changing the 3161 cm–1 feature and creating the yellow coloration.
Twelve yellow sapphires reportedly from Sri Lanka and Madagascar that initially displayed a weak to strong 3161 cm–1 peak or a 3161 cm–1 series in FTIR were selected for heat treatment in an oxidizing atmosphere (air) at 500°, 700°, 900°, and 1050°C for a fixed duration of six hours at each temperature. For a final step, some stones were heated at 1550°C in pure oxygen to assure the complete elimination of hydrogen. The samples were fabricated as optical wafers with at least two polished surfaces perpendicular and/or parallel to the c-axis. The samples possess a sufficiently large and clean area to get high-quality FTIR spectra. After each heat treatment step, FTIR spectra were collected at the same position for each sample by fixing it in an identical position in the sample holder.
Heat treatment can cause the H+ to move to different sites by diffusion or at sufficiently high temperatures to diffuse completely out of the sample. The diffusion coefficient of hydrogen in corundum is exponentially dependent on temperature. After heat treatments at 500°C and 700°C, the intensities of 3161 cm–1 peaks and the color appearance of the stones were essentially unaltered. Thus, there is little outward diffusion for a sample of this size. However, heating at 900°C and above for six hours in air will begin to diffuse the hydrogen out of the lattice. As the hydrogen begins to diffuse out, trapped holes form and pair with Fe3+ to maintain charge compensation, increasing the yellow coloration.
At the same time, the amplitude of the 3161 cm–1 feature will decrease proportionally. The test at 1550°C for six hours was conducted in pure oxygen to eliminate any possibility of the water vapor in air contributing hydrogen. With this last step, the outward diffusion of all the hydrogen in the stone was complete, eliminating OH– peaks in FTIR spectra and maximizing the yellow trapped-hole coloration.
Figure 1 shows these heating processes as applied to stones from Sri Lanka with a strong 3161 cm–1 feature and to some of the stones from Madagascar with a weak 3161 cm–1 feature. As expected, both types exhibited a similar diffusion reduction in the initial hydrogen content with temperature and time. The coloration of some of the Madagascar stones was zoned, with areas colored by the h•-Fe3+ pair, by h•-Fe3+ plus Fe3+, and some by Fe3+ only, depending on the distributions of Fe3+ and h•-Fe3+ in the stone. Usually, the zones in which h•-Fe3+ is dominant will increase yellow coloration with high-temperature heat treatment by removing the hydrogen, whereas the areas with Fe3+ alone are rarely strongly zoned.

Figure 2. Sri Lankan sample no. 2801 showing a 3161 cm−1 series (red) in FTIR with initially light yellow color, then altered to 3000 cm−1 broad band series (blue) with a bit stronger yellow zone after heating at 900°C for six hours. Finally, the broad bands disappeared (green) and a much stronger yellow coloration was generated at 1550°C, thickness 3.748 mm, 190 ± 41 ppma Fe.
Interestingly, a characteristic peak at 3161 cm–1 in certain Sri Lankan samples could be occasionally transformed to the broadband series in 3000 cm–1 region with a broad band at 2625 cm–1 when heated at 900°C and above in air, as presented in figure 2. Previously, the 3000 cm–1 broad band series has been reported as indicative of heat treatment observed in Punsiri-type heated blue sapphires (G. DuToit et al., “Beryllium treated blue sapphires: Continuing market observations and update including the emergence of larger size stones,” GIA Research News, 2009, https://www.gia.edu/gia-news-research-nr62609) and could be observed in unheated high-Fe yellow sapphires from basalt-hosted deposits, such as Thailand and Australia (Fall 2016 GNI, pp. 325–327). However, the 3000 cm–1 broad band series could also be found in heat-treated Sri Lanka yellow sapphires, as seen from this study.
In summary, heat treatment was carried out in an oxidizing atmosphere to increase the trapped-hole color centers and deepen the yellow coloration. Sri Lankan samples colored mainly by the h•-Fe3+ pair can produce stronger yellow coloration by heat treatment, but only at high temperatures (900°C and above). The heating temperature at 900°C starts to change the 3161 cm–1 peak/series in FTIR and the color appearance in metamorphic yellow sapphires. It may well be that heating for a much longer time at 900°C would more completely diffuse out the hydrogen. The amplitude of the 3161 cm–1 peak is insignificantly altered when heated at low temperature (below 700°C) but can be greatly reduced when heated at 900°C and above, and sometimes converted to the 3000 cm–1 broadband series, and then it disappears at much higher heating temperature. Although the 3000 cm–1 broadband series might not be indicative of heat treatment in basalt-related yellow sapphires, it is able to indicate heat treatment in Sri Lankan yellow sapphires. Careful consideration should be exercised when using FTIR to identify heat treatment in corundum. Source: GIA @topic:3


Title: Gemfields Inaugural Rough Ruby Auction in Singapore Abstract: Gemfields held its first Mozambique rough ruby auction in Singapore, where buyers from around the world came to bid on parcels. Photo by Andrew Lucas, ©GIA.

                      When you travel the world researching the industry, from time to time you experience a moment that you realize could be historic. This was the case in Singapore, where the first Gemfields rough ruby auction was held, with material from the Montepuez ruby deposit in Mozambique. While watching the buyers go through the lots offered for bidding, while at the same time observing the auction’s expert organization, we knew we might be witnessing the dawn of a change in the way the ruby industry does business.

The inaugural Mozambique ruby auction in Singapore has the potential to alter how rubies change hands in the market. Photo by Vincent Pardieu, ©GIA.
The auction marks a turning point in the way rubies are coming into the market. For the past 20 years, the Mong Hsu deposit in Myanmar (formerly Burma) was the world’s main source of rubies. Today, most of the rubies found in gem markets in Thailand (the global hub for ruby trading, processing, and cutting) come from the Montepuez area in Mozambique. Since the 2009 discovery of ruby deposits there, Montepuez has emerged as the world’s most active ruby mining area—though the stones that have reached the market thus far have all been mined illegally and smuggled out of Mozambique.

Now, for the first time, the legal owners of the mining license in Montepuez have introduced their product into the marketplace at auction. This development has stirred up excitement (leavened with some fear) in both Thailand and India, signaling as it does a seismic shift in the way rubies will enter the market. This groundbreaking event took place between June 12 and June 17, 2014. It was held in Singapore, considered one of the world's easiest countries for doing business. The source of the rough was Montepuez Ruby Mining Limitada. Gemfields had proposed acquiring a 75 percent interest in this deposit on June 8, 2011, and completion of the acquisition was announced on February 27, 2012. A 25-year mining license was issued at that time. Bulk sampling began in November 2012. By March 3, 2014, the mine had produced 8.2 million carats of ruby and other corundum. As of the auction date, Gemfields’s total expenditures at the Montepuez mine had reached US$34 million, including costs of acquiring the mining rights.

The bulk sampling by Gemfields of the Montepuez ruby deposit produced parcels of rough for auction that covered a wide range of qualities and sizes. This parcel contained 6,820 grams of untreated ruby rough. Photo by Vincent Pardieu, ©GIA.

	Gemfields
Gemfields (GEM) is a publicly traded company listed on the AIM market of the London Stock Exchange, where it is a constituent of the AIM50 index. In July 2008, the company acquired a 75 percent interest in the Kagem mine in Zambia, one of the world’s principal emerald-producing mines. In July 2009, Gemfields held its first rough emerald auction. Since then, the company has held 15 auctions of rough emeralds from its Kagem mine as well as two auctions of emeralds from other sources. Its total revenue for all emerald auctions to date is US$282 million. All together, sales for the financial year ending June 30, 2014, including emerald rough as well as ruby rough from the June auction, exceeded US$143 million.

Gemfields also owns other mining interests, including 50 percent of the Kariba amethyst mine in Zambia and licenses in Madagascar for ruby, sapphire, and emerald deposits. Gemfields acquired the Fabergé luxury jewelry brand in January 2013, giving the company a position in the luxury colored gemstone market.

	Covering the Auction
At the auction, the GIA team examined and evaluated several ruby lots offered for sale. We also interviewed Gemfields staff directly involved in the grading and creation of the lots and in setting up and operating the auction, as well as more than two dozen auction attendees.

The GIA team spent many hours examining the parcels of ruby available at the auction. Vincent Pardieu is evaluating a rough ruby parcel with Assistant Product Manager for Montepuez Ruby Mining Philippe Ressigeac. Photo by Andrew Lucas, ©GIA.
As a result of their emerald auctions, Gemfields is very experienced in auctioning rough gemstones, so the actual viewing and buying process was no mystery to most of the buyers. Gemfields followed the auction process as previously, refined over the years by inviting attendee feedback. Even some attendees who were new to the Gemfields system had an idea of what to expect at this auction.

GIA’s Andrew Lucas (left) consults with Gemfields Product Director Adrian Banks. Photo by Vincent Pardieu, ©GIA.
About 60 different companies attended, mainly from Thailand and India, but Gemfields also invited firms from the United States, Germany, France, and Switzerland. Most of the buyers were interested in how the lots were graded and arranged. The overwhelming feedback we received was that Gemfields did a very good job, considering this was the first time they had graded rough ruby parcels. All the buyers we spoke with felt the grading and lot organization were good, and most were very pleased. While some buyers would have made some changes to the organization of the lots, they all said any such changes would have been to suit their own business models. They felt the organization of the lots was fair for both the buyers and Gemfields’s interests.

Buyers spent considerable time grading and evaluating the rough ruby parcels at each booth before placing their bids. Photo by Vincent Pardieu, ©GIA.
At the Montepuez deposit, Gemfields recovers both primary and secondary ruby rough and uses two grading criteria, one for each type of deposit. Generally, the material from the secondary deposit is cleaner than that from the primary deposit. Gemfields said it took an average of two weeks to sort a lot of high-quality ruby rough, and six weeks for low-quality ruby rough. Gemfields grades rough by color, clarity, size, and shape. The Montepuez deposit produces ruby rough of all qualities for all market sectors: premium stones fine enough to be faceted without treatment, rough material to be heated with or without flux, and rough material to be treated with lead glass.

	Comparing Singapore and Myanmar Auctions
A few of the buyers interviewed also regularly attend rough ruby auctions in Myanmar. It was interesting to hear them compare the two auction systems and how the differences affected their buying. They all said the Gemfields auction featured more sophisticated grading criteria, and the lots were better organized by size and quality. Far more lots were offered there than at the Myanmar auctions, and they were broken down into narrower categories of detailed size and quality ranges.

Unlike Singapore, the Myanmar auction allows bids to be placed on one lot at a time. The results are declared before bids have to be submitted for the next lot. This allows buyers to know if they were successful on the first lot before bidding on the next lot, and so on. At the Gemfields auction, buyers had to submit bids for any lots they were interested in ahead of time. This meant buyers had to place bids on lots knowing that they might exceed their available capital if they were successful on most of their bids.

The Gemfields auction offered 32 tables in white booths, with daylight and torches available for examining rough ruby parcels. Buyers waited at tables for their turn to examine their chosen parcels. Photo by Andrew Lucas, ©GIA.

	Auction Logistics
The Gemfields auction offered 32 tables with similar natural lighting conditions and a total of 62 rough ruby lots. Buyers had a schedule book listing the bid schedules available at each table. When a table was free, interested buyers would sit and go through the lots in the bid schedule at that table. Each auction book page listed bid schedule, table number, disclosure of any treatment, numbered lots included in that bid schedule, Gemfields grade, gram weight or millimeter size range, number of pieces and total weight for that lot, and total number of pieces and total weight for the entire bid schedule. There were also sections in the book for buyers to list their own graded price per gram and total price in US$ for each lot in the bid schedule, as well as the price they would bid for the entire schedule. At the bottom of each page was a space for the company name, bidder’s name, bid amount in US$, and the amount again to be written in words. Buyers submitted bids by filling out and signing the page.

The parcel labeled “schedule-C at table 2” was composed of five pieces of fine-grade untreated ruby rough. Each weighed over 4 grams, for a total of 22.93 grams. Photo by Vincent Pardieu, ©GIA.
The lots were clearly created to attract existing ruby dealers with treatment expertise as well as new ruby buyers. Some lots were already treated. The treatments included lead-glass filling for lower-end material, as well as heating with borax for flux-assisted healed fissures. These lots were meant for manufacturers without expertise in ruby treatment. The same types of material were offered in untreated lots for those who preferred to do their own treatment. There were also higher-end lots of untreated material.

Some of the parcels of rough ruby had already been enhanced. This lot was heated with borax to enhance color and heal fissures. This gave buyers the option to bid on already-enhanced parcels or on similar but untreated material. Photo by Andrew Lucas, ©GIA.

	Outcome
Overall, the auction was a resounding success. Fifty-five companies placed bids, a record number for any Gemfields auction. Fifty-seven of the 62 offered lots were sold, a total of 91 percent by value and 90 percent by weight. Out of the 2.03 million carats of rough ruby offered, 1.83 million carats were sold. The total revenue generated was US$33.5 million. The total expenditure by Gemfields into the Montepuez mine was US$34 million by the time of the auction.

Auction buyers were satisfied. The Gemfields crew seems to have set reasonable reserve prices on the lots, and failure to reach the reserve price was not an issue. Gemfields seemed very open to feedback from the buyers on the auction process and the grading of lots for sale. Gemfields expects to narrow the invited companies down from 55 to somewhere in the 30s. They will use auction results to determine which companies to invite back on an ongoing basis. The next ruby auction is expected to take place before the end of 2014.

	The auction workbook, with bid schedule pages, proved very useful to auction
	attendees for viewing and evaluating lots and placing bids.

Table 1. Auction Results Summary

Auction Results (Ruby and Corundum)

June '14 Auction

					Dates

					12-17 June 2014

					Location

					Singapore

					Type

					Rough ruby and corundum

					Carats offered)

					2.03 million

					Carats sold

					1.82 million

					No. of companies placing bids

					55

					No. of lots offered

					62

					No. of lots sold

					57

					Percentage of lots sold

					92%

					Percentage of lots sold by weight

					90%

					Percentage of lts sold by market value

					91%

					Total sales realized at auction

					US$33.5 million

					Average per carat sales value

					US$18.43/carat

	Conclusion
The colored stone industry has been moving toward companies with greater investments in mining and more vertical integration through the value chain. Although most global colored stone production still comes from artisanal and small-scale mining, larger companies with deep pockets are now strategically positioning themselves. Gemfields’s first Mozambique ruby auction follows their successful emerald auctions in establishing an organized and transparent process for rough colored gemstones to reach the market.

The Gemfields staff worked closely with GIA team members to ensure that the story of this first Mozambique ruby auction was shared. Photo by Vincent Pardieu, ©GIA.
With the success of these auctions, it’s very possible the trend will spread. Governments of gemstone-producing countries may see the benefits of a transparent system for legally obtaining their fair royalties in exchange for their countries’ rich gemstone resources. These factors can promote transparency in gemstone marketing, in a world where scrutiny is intensifying. Source: GIA @topic:7


Title: Complex Fluid Inclusion in Topaz Abstract: This complex fluid inclusion in topaz is composed of minute solid crystals, an aqueous liquid, and an immiscible CO2 fluid. When cooled below 31.5°C, the CO2 is in a liquid state with a vapor bubble trapped in the CO2 liquid (left). When gently warmed, the CO2 vapor bubble shrinks (center) until it ultimately disappears (right) as the CO2 is homogenized into a single phase. Photomicrographs by Nathan Renfro; field of view 1.93 mm.
A blue topaz recently examined by the authors contained an interesting and complex fluid-filled negative crystal that revealed some remarkable behavior when cooled down. The contents of this three-phase fluid inclusion were very small solid phases, and carbon dioxide fluid trapped within an aqueous immiscible liquid, which has been previously documented (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 2, Opinio Verlag, Basel, Switzerland, 2005, p. 731). When the stone was cooled below approximately 31.5°C, the carbon dioxide fluid turned into liquid and gaseous states consisting of a multitude of tiny vapor bubbles nucleating and coalescing into a single larger bubble of gaseous CO2 within the liquid CO2 (see the video). This type of complex inclusion results in a CO2 vapor bubble trapped within a liquid CO2 bubble that is trapped within an aqueous, immiscible liquid (see above, left). If the stone is warmed above 31.5°C, the liquid and gaseous CO2 phases are homogenized into a single-phase fluid, causing the vapor bubble to shrink (see above, center) and ultimately disappear (see above, right). Similar behavior of CO2 trapped in negative crystals has been previously documented in sapphire (Spring 2016 G&G Micro-World, pp. 78–79). The extraordinary behavior of this fluid inclusion in topaz is a delight for any gemologist.

	Fluid Inclusion in Topaz Source: GIA @topic:3


Title: Trapiche-Like Ruby from the Batakundi Mine, Kashmir Abstract: Each leg of the trapiche-like structure in this ruby from the Batakundi mine in Kashmir is aligned perpendicular to hexagonal growth. The center of the star consists of a hexagonal group of colorless feldspar crystals and black graphite platelets. Black rutile crystals with associated comet tails are seen near the core of the trapiche-like pattern. Photomicrograph by Patcharee Wongrawang; field of view 4.80 mm.

Recently, the author examined a 5.26 ct faceted transparent oval ruby that showed a well-formed fixed six-rayed pattern under the table of the stone. Chemical analysis and gemological observation of internal features determined the origin of this stone to be the Batakundi mining area of Kashmir.
The six rays were oriented perpendicular to the sides of the hexagonal growth structure (see above). Each arm consisted of numerous minute particles mixed with needle-like inclusions and small thin films. The center of the star contained a group of colorless and black mineral inclusions that were identified by Raman spectroscopy as feldspar and graphite. Near the core, two black crystals with high luster were identified by Raman spectroscopy as rutile. They were also associated with a string of fine particles spreading out to form a comet tail pattern.
The pattern of this ruby from the Batakundi mine resembles that of a trapiche-type sapphire from Tasmania (Winter 2016 GNI, pp. 430–431). Trapiche-like minerals are quite different from true trapiche rubies, which have six arms that run from a core to the six corners of the hexagonal growth structure and show clear boundaries of six crystallographic sectors. The most renowned of the true trapiche ruby can be found in certain areas such as Mong Hsu, Myanmar (G. Giuliani and I. Pignatelli, “‘Trapiche’ vs ‘trapiche-like’ textures in minerals,” InColor, Vol. 31, 2016, pp. 45–46).
Although trapiche-like corundum specimens are not unheard of, it is unusual to find them well developed in high-quality ruby. This trapiche-like ruby from the Batakundi area shows a beautiful inclusion scene of a fixed six-rayed star standing out against the pleasing bodycolor and transparency. Source: GIA @topic:3


Title: Large Laboratory-Grown Star Ruby and Sapphire Abstract: Figure 1. A 4,759 ct synthetic star ruby and a 467.2 ct synthetic star sapphire were submitted to GIA’s Tokyo lab. Photo by Shunsuke Nagai.

The Tokyo lab received for a Quality Assurance report two unusually large loose stones with asterism. One was a 4,759 ct red sphere (figure 1, left) with a diameter of approximately 76.96 mm, and the other a 467.2 ct blue cabochon measuring approximately 52.04 × 42.29 × 20.89 mm (figure 1, right).

Figure 2. Asterism seen on the surface and irregular grain boundaries (Plato striations). Photomicrograph by Masumi Saito; field of view 11.4 mm.
These stones both had a spot refractive index of 1.77 and were doubly refractive with a uniaxial interference figure. The red sphere displayed a ruby spectrum with a handheld spectroscope. Microscopic observation showed curved bands of gas bubbles, cottony structure on the surface, and Plato striations (figure 2), providing proof of a laboratory-grown star ruby. The cottony structure indicates the possibility of diffusion treatment. The blue cabochon displayed a faint blue sapphire spectrum with the handheld spectroscope. It had a mottled blue color in diffused light (figure 3). Apparently it was a titanium-diffused colorless synthetic sapphire polished to produce asterism. As a result of polishing, the blue color is concentrated on the flat bottom and mottled on the curved top. This is visible when viewed from the side. Microscopic observation showed curved bands of gas bubbles, proof of laboratory growth.

Figure 3. Mottled blue patterns were observed in the synthetic sapphire against transmitted illumination through a diffuser plate. Photo by Shunsuke Nagai.
As Schmetzer et al. summarized (“Dual-color double stars in ruby, sapphire, and quartz: Cause and historical account,” Summer 2015 G&G, pp. 112–143), the Czochralski pulling technique can produce large crystals. These crystals have a uniform distribution of color and titanium-bearing precipitates compared to other growth methods, and they can be cut from any part of the crystal, regardless of size. Therefore, this laboratory-grown star ruby was most likely produced by the pulling technique. Also, this specimen was too large to have been produced by flame fusion. Detailed information on these two items is not available, but they are probably similar products.
Synthetic star corundum is not rare, but these were among the largest laboratory-grown star rubies and star sapphires submitted to the GIA laboratory. Source: GIA @topic:3


Title: Dyed Green Marble Imitating Jadeite Abstract: Figure 1. This was claimed to be a high-quality piece of jadeite jade mounted in a yellow metal pendant. The oval cabochon measured 39.8 × 29.8 mm, exhibited a homogenous green color, and on first impression appeared to resemble jadeite. Photo by Lai Tai-An Gem Lab.

              A client of the Lai-Tai An Gem Lab in Taipei recently submitted for identification what was claimed to be a piece of fine jadeite mounted in a yellow metal pendant (figure 1). The oval cabochon measured 39.8 × 29.8 mm and exhibited a homogenous green color. At first glance, it bore a strong resemblance to jadeite. While dyes, polymer treatments, or a combination of the two are commonly applied to jadeite—and dyed green quartzite is sometimes used to imitate green jadeite and other materials such as glass and plastic—this piece proved to be dyed green marble with calcite as the main mineral. This was the first time dyed marble had been represented to us as jadeite.

Although marble is fairly abundant, calcite’s low hardness and easily visible cleavages do not make it a viable substitute for jadeite. Yet it does lend itself well to carving. Chinese merchants often sell untreated carved marble by the trade names “Hanbai jade” or “Afghanistan jade,” or even offer such material as “antique jade.” Jade, pronounced “yu” in Chinese, is a general term that typically applies to aggregates of minerals. Marble in the Chinese jewelry market is frequently fashioned into bangles and carved pendants, and some may subsequently be dyed or partially dyed to imitate jadeite jade. Although it was impossible to calculate the SG of this mounted specimen, calcite’s RI of 1.65 overlaps with jadeite jade’s, leading to the possible misidentification of such material (J.M. Hobbs, “The jade enigma,” Spring 1982 G&G, pp. 3–19).

	Figure 2. Raman peaks at around 1084, 712, 275, and 145 cm–1 were consistent with calcite.
The identification was determined using Raman and FTIR spectroscopy. The sample showed Raman peaks at around 1084, 712, 275, and 145 cm–1 (figure 2), with IR peaks at around 1445 and 878 cm–1. Microscopic observation revealed a network of dyed grain boundaries (figure 3). The dye treatment was confirmed with the spectroscope, where a single broad band typical of some green dyes was clearly evident in the red-orange region. Long-wave UV did not offer any distinction. Although destructive tests are always avoided, the client allowed us to gently scratch the surface with a metal pointer, which confirmed the material’s low hardness. This submission reinforces the need to consider all types of material when dealing with items resembling jadeite.

Figure 3. Microscopic observation revealed a network of dyed grain boundaries. Photo by Lai Tai-An Gem Lab; magnified 50×. Source: GIA @topic:13


Title: Green Opal Displaying Aventurescence Abstract: Figure 1. Opal with unusual aventurescence, seen with fiber-optic lighting. Photo by Diego Sanchez.

Recently the Carlsbad laboratory received a variegated dark green and blue partially polished rough stone for identification services. The stone measured 23.64 × 20.13 × 15.52 mm and weighed 23.74 ct (figure 1). A vitreous to waxy luster and bright yellow inclusions were observed.
Standard gemological testing revealed a refractive index spot reading of 1.43 and a specific gravity of 2.15 obtained hydrostatically. These properties were consistent with opal. During microscopic analysis, fine hazy clouds and turbidity were seen within the structure, as well as a reddish brown portion with iron staining. Although no play-of-color was observed, an unusual aventurescence was seen in several areas with fiber-optic lighting while rotating the stone. This unusual phenomenon was caused by the scattering of light from the small, eye-visible yellow inclusions (figure 2). These inclusions were later confirmed by Raman spectroscopy as pyrite.

Figure 2. Scattered inclusions in the green opal were identified by Raman spectroscopy as pyrite. Photomicrograph by Nathan Renfro; field of view 1.79 mm.
LA-ICP-MS analysis was performed on the sample to investigate which chromophore was responsible for its green color. The results showed that the stone contained approximately 3540 ppma Fe. No other chromophoric trace elements were measured in significant quantities, indicating that iron was most likely the cause of the green color. UV-Vis-NIR spectra were collected and used to quantitatively calculate the color of this material (figures 3 and 4, table 1). In figure 3, a broad absorption band centered at about 741 nm produces the green color of the opal. This absorption band is likely related to octahedral Fe2+. Previous publications have shown that iron can produce green color in quartz due to an absorption band centered at 741 nm relating to interstitial Fe2+ (L.B. Hebert and G.R. Rossman, “Greenish quartz from the Thunder Bay amethyst mine panorama (TBAMP), Thunder Bay, Ontario, Canada,” Canadian Mineralogist, Vol. 46, No. 1, 2008, pp. 111–124). Octahedral Fe2+ can strongly absorb red, orange, and some portion of yellow light of the visible spectrum to produce a transmission window in the yellowish green region. In this case, a transmission window around 570 nm results in the green color in the iron opal (solid line in figure 3). The presence of some additional Fe3+ cannot be ruled out and may contribute to the rise in absorption at shorter wavelengths into the UV region.

Figure 3. The spectra of the two types of opal were measured and renormalized for comparison with each other with similar lightness (see corresponding color panels in table 1). The solid line represents iron opal. The broad absorption band centered at 741 nm is likely caused by interstitial Fe2+. The dashed line represents chromium opal. The smaller absorption band centered at around 600 nm is caused mainly by Cr3+.
Another type of green opal colored by Cr3+ (Winter 2020 Lab Notes, pp. 520–521) was compared with the iron-colored opal (solid line in figure 3). Cr3+ produces a smaller absorption band centered at about 600 nm, leading to a transmission window in the green region around 540 nm that causes a less yellow and more pure green color (figure 3).
The two color panels calculated from the two spectra were also plotted in the CIE L*a*b* 1976 color circle seen in figure 4. This allows for a more accurate comparison between the two color panels using quantitative colorimetric data. In the plot, the hue angle of the iron opal is smaller than chromium opal, resulting in a more yellowish green hue. The chroma of the iron opal is larger than that of a chromium opal with similar lightness, resulting in a more saturated color.

Figure 4. Color panels corresponding to the two spectra were plotted in the CIE L*a*b* 1976 color circle. The color of the iron opal, looking more yellowish and saturated, has a smaller hue angle and larger chroma than the color of the more greenish and less saturated chromium opal. Both calculated color panels have similar lightness for comparison (table 1).

This green common opal is a clear example of iron contributing to the yellowish green color, in contrast to the more pure green color due to the chromium in the opal previously documented with a slightly grayish green color. Both the yellowish green color and pyrite inclusions are consistent with an iron-rich environment. The pyrite inclusions also add a unique display of aventurescence not typically seen in common opal. Source: GIA @topic:12


Title: Radial Limonite in Sapphire Abstract: Radial limonite within a surface-reaching fracture of a violet sapphire shows bright interference colors when viewed under diffused reflected light. Photomicrograph by Nathan Renfro; field of view 1.44 mm.
Limonite, a composite of hydrated iron oxide minerals, is an inclusion commonly seen in corundum, usually as a thin yellow veil of epigenetic deposits within surface-reaching fractures. A unique example of this material is shown in the figure above, where limonite precipitated into a small fracture and formed in a radial fashion. When viewed under diffused reflected light, the inclusion displayed bright interference colors. The inclusion stands in sharp contrast to the violet sapphire host. As a composite of hydrated iron oxide minerals, the limonite’s yellow color is a strong indication that the stone has not been heat treated, as this would cause the yellow limonite to alter into red hematite (J.I. Koivula, “Useful visual clue indicating corundum heat treatment,” Fall 2013 G&G, pp. 160–161). This example demonstrates that even the most common of inclusions can occasionally materialize as something remarkable. Source: GIA @topic:3


Title: Extraterrestrial-Like Inclusion in Mozambique Ruby Abstract: An extraterrestrial-like inclusion with iridescent color observed in a Mozambique ruby using fiber-optic illumination. Photomicrograph by Nattapat Karava; field of view 6.3 mm.
A 3.03 ct stone submitted to GIA’s Bangkok laboratory was identified as a ruby from Mozambique with no indication of heating. Microscopic examination revealed a hypnotizing inclusion that resembled an extraterrestrial standing among specks of nebulae and waving its hand (see above). It had a large head and very thin legs, with two outstretched hands. This large, eye-visible inclusion was a colorless crystal among the particulate clouds. It showed iridescent color using fiber-optic illumination and was identified by Raman analysis as mica. Mica inclusions in Mozambique rubies usually have a pseudohexagonal shape with fringes (small expansion fractures) and can be found with a rosette pattern around them (“Rubies from the Montepuez area [Mozambique],” GIA Research News, 2013). This is another example of pareidolia observed in gems, the tendency to interpret an inclusion as some other object. Source: GIA @topic:3


Title: A Remarkable 16.71 ct Transparent Orange-Yellow Sodalite Abstract: A 16.71 ct transparent orange-yellow oval sodalite measuring 17.61 × 15.74 × 12.88 mm. Photo by Lhapsin Nillapat.
GIA’s Bangkok laboratory recently examined the 16.71 ct transparent orange-yellow faceted oval shown in the figure above. Standard gemological testing revealed the stone to be singly refractive with a refractive index of 1.484 and a hydrostatic specific gravity of 2.28. The stone showed strong orange fluorescence under long-wave ultraviolet light and weak orange with chalky white fluorescence under short-wave UV. Microscopic examination revealed internal features such as a fingerprint-like plane of two-phase fluid inclusions and numerous tiny transparent crystals. Raman spectroscopy analysis using 514 nm laser excitation showed several distinct peaks at 263, 294, 464, 969, 986, and 1058 cm–1, which are characteristic features of sodalite (B. Lafuente et al., 2015, http://rruff.info/about/downloads/HMC1-30.pdf). Energy-dispersive X-ray fluorescence also identified the main chemical composition as sodium, aluminum, silicon, and chlorine, consistent with sodalite, which falls into the feldspathoid mineral group Na8(Al6Si6O24)Cl2.
Sodalite is typically a semitransparent to opaque blue stone with calcite veining resembling lapis lazuli. However, it can occasionally exhibit other colors. The orange-yellow variety of sodalite is rare, and its color may be related to the presence of sulfide ions (F. Seel, “Sulfur in artwork: Lapis lazuli and ultramarine pigments,” Studies in Inorganic Chemistry, Vol. 5, 1984, pp. 67–89). Ultraviolet/visible spectroscopy showed an absorption band centered at approximately 480 nm, likely caused by heavy radioactive elements creating an unstable color center substituting for Cl– in a tetrahedron of Na+ ions (H. Annerstein and A. Hassib, “Blue sodalite,” Canadian Mineralogist, Vol. 17, 1979, pp. 39–46; P.S. Pizani et al., “Color centers in sodalite,” American Mineralogist, Vol. 70, 1985, pp. 1186–1192). This sodalite is exceptional for its color, transparency, and 16.71 ct size. To the author’s knowledge, this is GIA’s first encounter with a large faceted orange-yellow sodalite. Source: GIA @topic:2


Title: Opals Revisited Abstract: Figure 1. The untouched opal specimen displays the yellow coating caused by years of storage in silicone oil. Photo by Ted Grussing.

In the 1980s, the author and his wife, Corky, acquired large quantities of Virgin Valley “wet” opal specimens displayed in glass domes with water and other specimens immersed in silicone oil. The domes had black rubber stoppers on the bottom. The mine representative had put them in water and silicone oil to enhance their beauty, since wetting the surface gives the illusion of a polished gem specimen.
Opal is a hydrated amorphous silica, and those with a high water content tend to craze and crack if left to dry. If a specimen is inclined to craze or crack, placing it in a liquid does not stabilize it or heal the cracks within, but it does delay the “day of reckoning” when the opal eventually deteriorates.
The specimens displayed in the domes with water began forming deposits, and within months the water became cloudy and the domes were crusted with precipitate from dissolved minerals. Those in silicone oil fared better, but eventually they too deteriorated, with the silicone oil taking on a yellow cast from the black rubber stoppers, which appeared to coat the opals with a yellow crust (figure 1).
After years of changing the water and silicone oil, the cleaning and repackaging eventually became very time-consuming. The author removed all the wet specimens from their domes, cleaned and wrapped them in paper towels, and put them in boxes. The boxes with the now-dry opal specimens were packed away and stored in the garage, where they remained for more than 27 years.

Figure 2. Left: The side of the specimen after cleaning and rubbing on a diamond wheel. Right: The nearly finished opal midway through the cleaning process. Photos by Ted Grussing.

Figure 3. The finished piece, dry and ready for display. Photo by Ted Grussing.
In July 2019, the author found the boxes containing these beautiful and long-forgotten opals. The results were astonishing. They had not fallen apart, and they looked more stable than they had when dried and put away. The cracks were still there, but the look was different. They looked like they could be worked—if not on the wheels, then with a flex shaft. The first opal that caught the author’s eye (again, see figure 1) was cleaned and worked (figure 2). The completed piece, shown in figure 3, is named “Bonnie Jean.” There are many more to finish, and they are dry and unlikely to craze or crack any further. Source: GIA @topic:12


Title: Large Oolitic Opal Block Abstract: Figure 1. This exceptionally large 1.43 kg block of opal, which measures 12.8 × 10.1 × 5.8 cm, is rare not only for its size but also its oolitic texture. Photo by C. D. Mengason/GIA, courtesy of Tibor Shelley/Opals by GMT.

              Longtime opal dealer Tibor Shelley (Opals by GMT in Adelaide, Australia) recently brought a large 1.43 kg block of opal (figure 1) to GIA’s Carlsbad laboratory for examination. Mr. Shelley said he purchased it from a miner at the Andamooka opal fields in Australia more than 40 years ago. Since then, it has remained in his private collection. The RI measured on the polished face of this sawn and partially polished block was 1.45, consistent with opal.

	Figure 2. Numerous brown spheres scattered throughout precious opal were seen in this very large block of oolitic opal from Andamooka, Australia. Photomicrograph by Nathan Renfro, courtesy of Tibor Shelley/Opals by GMT; field of view 17 mm.
Upon initial observation, the semi-translucent to opaque opal appeared similar to typical matrix-type opal from Andamooka that is routinely treated black. Microscopic examination, however, revealed an interesting and unique texture rarely seen in Andamooka opal. The stone was composed of numerous dark spherical inclusions, known as “ooids,” with precious opal filling in the pore spaces between the spheres (figure 2). This type of opal has been previously reported (see Summer 1982 Lab Notes, p. 104; Winter 1984 Lab Notes, p. 229; and Spring 1986 Lab Notes, p. 50), but this example is especially rare due to its large size. Although an example of treated black oolitic opal has also been previously reported (Spring 1983 Lab Notes, p. 46), microscopic examination revealed that the overall gray bodycolor of this extremely large opal was due to the high density of dark ooids scattered throughout the block. There were also some light brown patches that appeared to be a sandstone type of matrix, as well as numerous veins and pockets of precious opal that did not contain ooids.

This unusual piece of natural-color oolitic opal is the largest of its type that GIA has examined to date. Source: GIA @topic:12


Title: New Nigerian Source of Blue Sapphire Abstract: This parcel of 30 fine-quality rough blue sapphires is reportedly from the Mambilla area of Nigeria. They weigh between 1 and 5 ct each. Photo by Vincent Pardieu/GIA.

                      The recent arrival of high-quality blue sapphire from a new source  in Africa has caused considerable excitement in the Bangkok marketplace. These gems, reportedly from the Mambilla Plateau in Nigeria’s Taraba State, are available in large rough sizes, some as big as 100–300 ct. Like previously documented Nigerian material, these sapphires are mined from basalt-related secondary deposits. Yet the quality is significantly better than any seen to date from those sources. Initial indications suggest that this new deposit might provide a winning combination of size, high clarity, attractive color, and good crystal habit from a cutter’s perspective. Indeed, one especially fine stone is rumored to have sold for in excess of US$1 million.

As a preliminary study for a future field expedition to this location, researchers from GIA’s Thailand laboratory obtained a selection of 30 fine-quality rough sapphires from a trusted supplier in Bangkok. Representative samples were fabricated into precisely oriented wafers for the collection of high-quality optical data using FTIR and UV-Vis-NIR spectroscopy. Inclusions were identified using Raman spectroscopy, and trace-element chemical composition was analyzed using LA-ICP-MS.

A new report by the GIA laboratory in Bangkok, “Blue Sapphires from the Mambilla Plateau, Taraba State, Nigeria,” presents their initial findings. Although the inclusion suites, spectroscopic features, and LA-ICP-MS trace-element results appear similar to those of sapphires from other basalt-related deposits—including Cambodia, South Vietnam, and some Australian localities—the composition of minute “nano-inclusions” within some of the gems appears promising for origin determination purposes. Source: GIA @topic:3


Title: Phenakite with Tourmaline Inclusion Containing Spiral Growth Abstract: A phenakite specimen from Ambohimanambola, Madagascar, contained a tourmaline with a spiral growth feature and a colorless crystal. Photomicrograph by Kimberly Abruzzo; field of view 0.88 mm.

A helix stands in high relief against the orangy pink of a well-defined tourmaline crystal—impressive screw dislocation growth is one of the main identifying characteristics detailing the inner world of a phenakite specimen from Ambohimanambola, Madagascar (see above).
Previously in the collection of longtime California mineral collector Kay Robertson, the unique inclusions in this gem were discovered during digitization for the Los Angeles Museum of Natural History’s Gem and Mineral Lab. After spotting a series of parti-color tourmaline needles with vivid interference patterns under crossed polarizers, magnification was subsequently increased to investigate further. Soon it became clear that the needles scattered throughout the phenakite crystal exhibited strongly pleochroic colors as well as distinctive growth features.
In the absence of polarized light, the needles appeared in desaturated orange to red and green to blue hues. When magnification was increased once again, the eclectic world of this phenakite unveiled another surprise: The tourmaline inclusions were not alone. Alongside and extending from the base of the striated needles were colorless euhedral crystals exhibiting hexagonal form and inclusions of their own. One pair of primary inclusions, a needle anchored to another stubby crystal, were of particular interest. Raman spectroscopy confirmed the identity of the needle-like inclusions as tourmaline, though it was not possible to confirm the identity of the colorless crystal.
The pictured set of inclusions features an orangy pink tourmaline emerging from the body of a colorless crystal. The host specimen’s high clarity highlights the growth features both inside and on the surface of its inclusions, not only showing striations parallel to the c-axis typical of tourmaline, but also more unusual “spiral” or screw dislocation growth. The entwined pair are crossed in the background by two larger dark greenish blue tourmaline needles that provide a striking geometric backdrop. Dislocation spirals like those seen here are formed when planes of atoms within a gemstone’s crystal lattice are displaced during growth and rearrange themselves in a helical pattern corresponding to the direction of stress.
Perhaps best known for their intricate liddicoatite crystals, the Anjanabonoina pegmatites in Madagascar also produce a wide array of other gem minerals such as phenakite, beryl, spodumene, and danburite, among others. This particular stone presents an excellent example of the diverse mineralization that occurs at Anjanabonoina, showing off the habit, optical properties, and growth features of two important gem silicates from this gemologically important locality. Source: GIA @topic:12


Title: Unusual Glass-and-Quartz Triplet Imitation of Emerald Abstract: Figure 1. This 11.30 ct sample (18.9 × 14.0 × 8.8 mm) was found to be a triplet composed of colorless glass and quartz held together by green cement. Photo by Biqian Xing.
Recently, an 11.30 ct emerald-cut sample sold as an emerald (figure 1) was provided by an anonymous jewelry manufacturer, who suspected an imitation. It resembled a natural emerald with its vivid bluish green color, inclusion abundance, and a vitreous luster. However, examination identified it as a glass-and-quartz triplet, an occasionally convincing imitation of emerald.

Figure 2. Illuminated with diffused transmitted light with water immersion, the assembled nature of this 11.30 ct triplet was obvious in profile view (top image shows a slight downward view, and bottom image shows a slight upward view). The pavilion is nearly colorless (both top and bottom images) due to the refraction and scattering of the green cement by a large number of inclusions, while the crown is colorless and clean under a certain observation angle (bottom image). Photo by Biqian Xing.

Figure 3. Microscopic observation of the triplet revealed numerous cracks (A), fluid inclusions, and lace-like partially healed fissures (B) in the pavilion. C: The cement slice could be seen under reflected light (as shown by the arrow). D: A maze-like pattern in the cement slice. Photomicrographs by Biqian Xing; fields of view 2.51 mm (A), 10.37 mm (B), 2.71 mm (C), and 1.15 mm (D).
When examined via water immersion in a direction parallel to the girdle plane, one can observe that this triplet was made of two pieces of colorless material (crown and pavilion), with a green cement slice in between (figure 2). Using water for the immersion test to observe the internal characteristics did not corrode the sample and yielded better experimental results. No inclusions were observed in the crown. Microscopic examination revealed two-phase (liquid and gas) inclusions, cracks (figure 3A), and lace-like partially healed fissures in the pavilion (figure 3B). In the middle cement layer, no gas bubbles were observed along the separation plane in the assemblage, unlike doublets previously described (H.A. Hänni and U. Henn, “Modern doublets, manufactured in Germany and India,” Journal of Gemmology, Vol. 34, No. 6, 2015, pp. 479–482; Spring 2019 Lab Notes, p. 92). However, the very thin layer of solidified cement (approximately 10 μm thick; figure 3C) showed a maze-like pattern under the microscope (figure 3D).
This triplet had refractive indexes of 1.515 (crown) and 1.544–1.553 (pavilion) and a hydrostatic specific gravity of 2.59. Its fluorescence under long-wave UV radiation was green for the crown and blue-white for the pavilion (affected by the fluorescence of the cement) and inert for both the crown and pavilion under short-wave UV radiation. No obvious absorption was observed with a handheld portable spectroscope, and no reaction was observed with the Chelsea filter.

Figure 4. FTIR spectroscopy identified the crown of the triplet as glass (peaks at 1061, 968, 770, and 465 cm–1) and the pavilion as quartz (peaks at 1174, 1140, 1084, 800, 781, 693, 540, 488, and 454 cm–1). Spectra are stacked for clarity.
The EDXRF and FTIR results identified the crown as soda-lime-silica glass (69.97 wt.% SiO2, 15.25 wt.% Na2O, and 8.94 wt.% CaO) with characteristic peaks at 1061 (asymmetric vibration modes of the Si-O-Si network), 770 (symmetric vibration modes of the Si-O-Si network), 968 (stretching vibration of the Si-O non-bridging oxygen group), and 465 cm–1 (Si-O-Si and O-Si-O bending modes) (figure 4) (A. Agarwal and M. Tomozawa, “Determination of fictive temperature of soda-lime silicate glass,” Journal of the American Ceramic Society, Vol. 78, No. 3, 1995, pp. 827–829; S.I. Amma et al., “Specular reflectance (SR) and attenuated total reflectance (ATR) infrared (IR) spectroscopy of transparent flat glass surfaces: A case study for soda lime float glass,” Journal of Non-Crystalline Solids, Vol. 428, 2015, pp. 189–196). The pavilion was identified as quartz, with 99.54 wt.% SiO2 and characteristic FTIR peaks at 1174, 1140, 1084 (antisymmetric stretching vibrations of the SiO4 tetrahedron), 800 (SiO4 symmetric stretching), 781 (SiO4 symmetric stretching), 693 (Si-O-Si bending transition modes), 540, 488, and 454 cm–1 (figure 4) (A. Hahn et al., “Using Fourier transform infrared spectroscopy to determine mineral phases in sediments,” Sedimentary Geology, Vol. 375, 2018, pp. 27–35). Unfortunately, the green cement was too thin to analyze with a micro-infrared spectrometer or Raman spectrometer.
The triplet was a typical imitation of emerald but surprisingly convincing when viewed table-up with the unaided eye. With its extremely thin cement slice, maze-like pattern, and lack of bubbles, even a jewelry manufacturer might mistake it for emerald. This investigation reminds us that the examination of potentially composite stones cannot be ignored. Source: GIA @topic:3


Title: Zircon with Unusual Color-Change Behavior Abstract: Figure 1. The color of the 4.60 ct zircon is shown in standard cool fluorescent illumination (left) and in warm (2700 K) LED illumination (right). There was little difference in bodycolor when viewed under the two light sources. Photos by Robert Weldon.
The Carlsbad laboratory recently had the chance to examine a 4.60 ct cushion-cut zircon with truly unusual color behavior. Standard gemological testing confirmed that the stone’s properties were consistent with zircon: an over-the-limit RI, an SG of 4.72, weak yellow fluorescence in short-wave UV and no fluorescence in long-wave UV, and a typical uranium-related pattern in the spectroscope with a prominent sharp peak at 653 nm. The zircon’s color was green using a standard white light fluorescent illuminant with a color temperature of 5500 K (figure 1).

Figure 2. The color of the 4.60 ct zircon is shown in LED illumination with cool white light at 6500 K (left) and in warm white light at 2700 K (right). Photos by Robert Weldon.
The stone’s color was also checked using a standard incandescent illuminant, but there was no discernible difference from the cool fluorescent illuminant (table 1). However, the color of the zircon was markedly different using white light LEDs with variable color temperature from 2700 K (warm) to 6500 K (cool), where the color went from grayish purple in cool LED light to green in warm LED light (figure 2). Notably, the color observed in the cool LED light was quite similar to the color seen when the stone was taken outside and observed in diffused daylight.

Figure 3. The visible absorption spectrum of the color-change zircon (top) compared to the emission spectrum of a standard cool (6500 K) fluorescent illuminant showing the overlap of sharp emission bands from the fluorescent light and sharp absorption bands in the absorption spectrum (dashed line). Also shown is the emission spectrum of the cool (6500 K) LED used in the lab for color grading at GIA.
The discrepancy between the colors seen using the cool fluorescent illuminant (green) and either daylight or the cool LED illuminant (grayish purple) can be understood by studying the absorption spectrum of the zircon compared to the emission spectrum of the cool fluorescent bulb (figure 3). The perception of cool white light output from the fluorescent bulb is achieved with two relatively sharp emission bands at about 435 nm and 545 nm, which is in contrast to the much smoother broad-band emission pattern of true daylight. One of the sharp emission bands in the fluorescent illuminant overlaps significantly with sharp absorption bands in the zircon at 424 and 433 nm. The fact that a significant portion of the blue emission from the fluorescent bulb is selectively absorbed by the zircon skews its color away from the blue color that ought to be observed in true daylight. This blue can also be observed using cool LEDs, which tend to have smoother broad emission patterns more closely resembling black-body radiation patterns of true daylight and incandescent light. This unusual color-change behavior is only expected in gems with sharp absorption bands, likely related to either rare earth or actinide elements. Of particular note, these color-change zircons are occasionally recovered from the gem mining areas around Mogok, Myanmar. For these gems, LEDs should provide a more reliable color grading illumination environment than fluorescent light sources. Source: GIA @topic:3


Title: Lazurite in Spinel Abstract: This light gray spinel from Mogok, Myanmar, contains a vibrant blue inclusion of lazurite. Photomicrograph by Nathan Renfro; field of view 1.59 mm. Courtesy of Mark Smith, Thai Lanka Trading Ltd.

Spinel is often inclusion free but occasionally showcases unusual inclusions. This was the case with a 1.02 ct light gray Burmese spinel from Mogok, courtesy of Mark Smith (Thai Lanka Trading Ltd., Bangkok), that was recently examined by the authors. A striking vibrant blue inclusion reached the surface of the pavilion, making Raman analysis straightforward (see above). The identity of the blue inclusion was confirmed to be lazurite. The mineral has previously been found as an inclusion in Burmese ruby (Spring 2012 Lab Notes, pp. 51–52), but this is the first instance of a lazurite inclusion in spinel that we are aware of. Source: GIA @topic:2


Title: Letters: Trapiche Nomenclature Abstract: I wanted to offer hearty congratulations for the Fall 2015 issue. Robert Weldon’s cover is stunning, and the lead article on Colombian trapiche emeralds is a thought-provoking, important addition to crystallography and gemology.

I was interested in the authors’ trapiche nomenclature discussion in box A (p. 224). I understand the desire to distinguish sectoral zoning formed by inclusions or texture as “trapiche-like”; the trapiche pezzottaite reported in the Micro-World section of that same issue probably falls under that category (Skalwold and Koivula, 2015). I would argue that the cordierite-indialite intergrowths known as “cherry blossom stones,” described by the authors as “trapiche-like,” actually qualify as true trapiche growth on the basis that each sector is the result of individual crystal growth. These unique trapiches are the result of a very complex indialite-cordierite intergrowth phenomenon in which cordierite crystals grow epitaxially on the six prism faces of an indialite crystal. The latter’s remaining faces continue to grow and later alter to cordierite while grains of this intergrowth’s host accumulate along the sectors, forming the trapiche appearance. The indialite later alters to cordierite and eventually the entire intergrowth is replaced by muscovite, while retaining the outward appearance of the original mineral intergrowth (see Rakovan et al., 2006; Kitamura and Yamada, 1987).

Also, in Nassau and Jackson’s defense, I would add that later in 1970 they corrected the trapiche emerald locality information from their original American Mineralogist paper:
Based on information supplied by E.J. Tripp and L.H. Hernandez and E.J. Tripp (private communications) the actual origin of the trapiche emeralds previously attributed … to the Chivor mine is the Peña [sic] Blanca mine, near Muzo, Colombia. These have the clear center and are distinct from specimens from Muzo itself, which have a dark center. Most Peña Blanca trapiche emeralds were purchased and distributed by Mr. W.F. Bronkie, then manager of the Chivor mine, and were accordingly attributed to the Chivor locality (Nassau and Jackson, 1970). This erratum by the authors themselves is generally overlooked in articles that reference the original study.
Once again, congratulations on a superb paper, which is sure to be a classic reference across geological disciplines.

Elise A. Skalwold
Ithaca, New York
REPLY
We are glad you appreciated our work. Our judgment on “trapiche pezzottaite” can be based only on your account and not on a direct analysis of the sample. Looking at the accompanying figures, above all figure 7 on p. 327, we think that this pezzottaite sample can be classified as “trapiche-like” because the texture seems related to the zoning (probably sector zoning). There is another sample from Myanmar with similar features (http://www.mindat.org/photo-718381.html); thus, the zoning is likely due to the growth condition in this specific locality. Moreover, there are two other reasons to classify this sample as “trapiche-like”: The first is that the inclusions do not form sharp boundaries separating the equivalent sectors. The second is the absence of organic matter observed in all trapiche minerals.

We disagree with your assessment, because in cherry blossom stones the trapiche-like aspect is due to the first formation of indialite, a mineral with the same point group as beryl. As a result, they have the same growth sectors. But the formation mechanism of cherry blossom stones is completely different, and even more complex, than that of trapiche minerals. In fact, the formation of cherry blossom stones requires intergrowth, phase transition, and pseudotwinning. On the contrary, a trapiche is a single crystal where the growth sectors are separated by inclusions.

Thank you for the complementary information about trapiche emerald origin from Nassau and Jackson. We were not aware of their correction, which is never cited in the literature. At the October 2015 International Emerald Symposium in Bogotá, researchers consistently referred to Chivor trapiche emerald. We are pleased to see that our field investigations in the Chivor-Macanal-Gachala mining districts were in keeping with the correction, and that in fact trapiche emerald is only present in the western emerald zone. Your letter will help to definitively correct this error of location.

Isabella Pignatelli
University of California, Los Angeles

Gaston Giuliani
Institute of Research for Development, Toulouse, France
French National Center of Research, Vandœuvre Source: GIA @topic:3


Title: Ametrine Quality Factors Abstract: The best ametrines show distinct areas of orangy yellow and purple. These colors are featured in this graceful cut design. Photo by Lydia Dyer, © John Dyer & Co., gem courtesy John Dyer & Co.

                      When Bolivia’s ametrine mine reopened in the 1960s after being lost for centuries, the gem’s bicolor appearance became popular with dealers and gem designers. Its colors range from pale to intense amethyst and citrine shades.

	The rough output from the Anahi mine produces amethyst, citrine, and ametrine finished
	gems in a range of tone and color intensities. Photo © GIA and Tino Hammid.
Color
Fine ametrine shows medium dark to moderately strong orange, and vivid to strong purple or violetish purple. Larger gems, usually those over five carats, tend to show the most intensely saturated hues. Dealers look for an attractive half-and-half distribution of each color, with a sharp boundary between the two colors at the center of the fashioned gemstone.

	Rectangular cuts show off ametrine’s unique appearance. Photo by Robert Weldon/GIA, courtesy Cynthia Renee Co.
Cut
Connoisseurs prize imaginative designer cuts that display ametrine’s two colors in artfully blended or contrasting combinations.

	This 48.50-ct. ametrine, fashioned by gem designer Dalan Hargrave, dazzles the eye. Photo by Robert Weldon/GIA, courtesy Minerales y Metales del Oriente, Bolivia, SA.
Clarity
Much of the faceted ametrine in the market is eye-clean, meaning it lacks eye-visible inclusions.

	Like most faceted ametrine, this bicolor rectangular step cut has no eye-visible inclusions. Photo by Van Rossen, © ICA, courtesy Columbia Gem House.
Carat Weight
When it comes to highly prized ametrine, size matters. That’s because the best, most intense citrine and amethyst colors are found in larger sizes, usually over 5 carats.

	This 87.66-ct. ametrine displays the rich purple of amethyst along with the contrasting orangy yellow of citrine. Photo by Robert Weldon/GIA, courtesy Minerales y Metales del Oriente, Bolivia, SA. Source: GIA @topic:1


Title: Amethyst From Morocco:An Update Abstract: Figure 1. These Moroccan amethyst crystals, which weigh 2.87 and 6.24 grams, display an attractive purple zoning conforming to the rhombohedral faces. Photo by Nuttaphol Kitdee.

Most major sources of fine amethyst are located in Africa. Yet African amethysts on the market, especially Zambian material, tend to be dark and difficult to find in sizes larger than 10 ct. Since the late 1980s, there have been additional discoveries in Malawi, Tanzania, Namibia, Nigeria, and the Democratic Republic of Congo. The most recent African source is Morocco (see Spring 2009 GNI, pp. 62–63), which has produced gem-quality amethyst with an appealing purple color and sizes larger than 10 ct.

GIA’s Bangkok laboratory recently examined several parcels of gem-quality Moroccan amethyst (figure 1) received from Tom Banker, a colored stone dealer. Gemological properties obtained from the crystals and faceted stones were similar to those reported in the 2009 GNI entry.

Figure 2. A closer view of the amethyst shows alternating bands of darker and lighter purple color zoning. Photo by Charuwan Khowpong; magnified 10×.
Common characteristic internal features were intense color zoning conforming to the rhombohedral faces (figure 2), reddish brown needle-like hematite inclusions (figure 3, left), and fingerprints consisting of two- and three-phase inclusions (figure 3, center). Dolomite and anhydrite inclusions were also found (figure 3, right).

Figure 3. Microscopic examination of the Moroccan amethyst samples revealed reddish brown hematite (left), two-phase inclusions (center), and dolomite crystals (right). Photomicrographs by Charuwan Khowpong; magnified 50×, 5×, and 80×.
A thin wafer with a thickness of 1.28 mm was prepared for FTIR and UV-Vis-NIR spectroscopy. The wafer plane was oriented parallel to the c-axis. The FTIR spectra were recorded using a Thermo Nicolet 6700 spectrometer with a resolution of 4 cm–1 and 200 scans, while the UV-Vis spectra were collected using a Hitachi U-2910 spectrometer at 1.5 nm slit width and 100 nm/min scan speed, integrated with a polarizer accessory controlled by Thorlabs APT.

FTIR spectroscopy revealed typical features of amethyst. The absorption peaks at 3585 and 3613 cm–1 were related to vibrations caused by Al substitutions. The absorption shoulder at 3595 cm–1 is common in natural quartz and rarely seen in synthetic quartz. The cause of this feature remains unknown (S. Karampelas et al., “Infrared spectroscopy of natural vs. synthetic amethyst: An update,” Fall 2011 G&G, pp. 196–201). Areas of dark, medium, and light purple zoning had very similar FTIR patterns.

Amethyst owes its purple color to color centers associated with Fe2+ or Fe3+ impurities (A.J. Cohen, “New data on the cause of smoky and amethystine color in quartz,” The Mineralogical Record, Vol. 20, No. 5, 1989, pp. 365–367). The UV-Vis-NIR absorption spectra showed bands in the visible range at 545 nm caused by Fe4+ charge transfer (E.H.M. Nunes, “Spectroscopic study of natural quartz samples,” Radiation Physics and Chemistry, Vol. 90, 2013, pp. 79–86; E. Neumann, “Mechanism of thermal conversion of color and color centers by heat treatment of amethyst,” Neues Jahrbuch für Mineralogie, Monatshefte, 1984, No. 6, pp. 272–282). The complexity of absorption bands in the ultraviolet region is related to the presence of Fe3+ in more than one environment in the α-quartz structure (F. Hassan and A.J. Cohen, “Biaxial color centers in amethyst quartz,” American Mineralogist, Vol. 59, Nos. 7–8, 1974, pp. 709–718).

Further chemical analysis using advanced techniques such as EDXRF and ICP-MS will be conducted to summarize the characteristic chemical profile of the Moroccan material. Source: GIA @topic:1


Title: Moonstone Description Abstract: The beautiful shimmer of light that's characteristic of moonstone is apparent even in its rough form. This special property is maximized by a quality cut. - David Humphrey

                      Moonstone’s delicate beauty and its long-established heritage make it perhaps the most familiar gem-quality member of the feldspar group.

Feldspars are the most widespread minerals in the earth’s crust, as well as some of the most diverse. You can pick up a rock anywhere in the world, and you’ll probably find that it contains a mineral or two from the feldspar group.

	Blue sheen against a colorless background is a prized moonstones combination. This
	suite of finely crafted moonstones is arranged for a designer ensemble.
	- Courtesy Temple Trading Company
Moonstone is a variety of the feldspar-group mineral orthoclase. It’s composed of two feldspar minerals, orthoclase and albite. At first, the two minerals are intermingled. Then, as the newly formed mineral cools, the intergrown orthoclase and albite separate into stacked, alternating layers.

When light falls between these thin, flat layers, it scatters in many directions, producing the phenomenon called adularescence. Adularescence is the light that appears to billow across a gemstone, giving its surface a glowing appearance.

Perhaps the most captivating aspect of adularescence is its appearance of motion. The misty light seems to roll across the gem’s surface as you change the viewing angle.

Other feldspar minerals can also show adularescence. One is a labradorite feldspar found mainly in Labrador, Canada. Another labradorite—found in Madagascar—has a multicolored adularescence over a light bodycolor. It’s known in the trade as rainbow moonstone, despite the fact that it’s actually a variety of labradorite rather than orthoclase.

	A variety of labradorite is sometimes called rainbow moonstone.
Sanidine is another feldspar mineral that can include adularescent gems called moonstones. To be called moonstone, a mineral’s actual identity is not as important as the beauty of its adularescence. Source: GIA @topic:1


Title: Beryl from Newfoundland, Canada Abstract: Figure 1. Emerald and beryl specimens from Newfoundland, Canada. The chip on the right has a distinct green rim in this position, on its lower right edge. Photo by Emily Lane; courtesy of Art Gardner and Terry Russell.

Figure 2. In situ emerald and beryl from Newfoundland. The primary crystal shows a lively green hue. The crystal on the lower right shows strong concentric zonation with a green rim and a white core. Photo by Emma Hutchinson Photography; courtesy of Art Gardner.
Prospectors Art Gardner and Terry Russell recently discovered concentrically zoned beryl [Be3Al2(Si6O18)] in central Newfoundland, Canada, along the Bay D’Espoir Highway, and sent preliminary findings to GIA’s Carlsbad laboratory. The green rims of these beryls were often sufficiently green to be considered emerald. The outer rims were bright green or pale green, and the cores were very pale green or white (figures 1 and 2). Most zones had low transparency. They formed hexagonal columns at the 1–3 cm scale, associated with mica-quartz-feldspar veins and minor tourmaline, calcite, biotite, fluorite, pyrite, and arsenopyrite. Some stones were suitable for polishing and setting in jewelry, especially as cabochons. An individual specimen may have zones that fit into the definitions of emerald and white beryl, with the brighter greens at the rims.
Canada is host to a number of gem minerals, including emerald from Yukon and the Northwest Territories (G. Giuliani et al., “Emerald deposits: A review and enhanced classification,” Minerals, Vol. 9, 2019). This beryl deposit on Newfoundland Island is within the Great Bend Complex of ophiolites. The mica-quartz-feldspar veins hosting the beryl are found within a host rock rich with scheelite [Ca(WO4)]. Other pegmatitic dikes are regularly found within the bedrock, and a ~450 km belt of beryl-bearing pegmatite dikes extends across the island from east to west. This discovery adds another locality to Canada’s gemological map.

Figure 3. UV-Vis-NIR absorption spectrum of the first crystal on the left in figure 1. Absorption bands are seen at 420, 615, and 835 nm, and a low but sharp peak at 956 nm.
The ultraviolet/visible/near-infrared (UV-Vis-NIR) absorption spectrum of the green zone in the leftmost crystal in figure 1 displayed absorption bands at 420 (Fe3+), 615 (V3+, Cr3+), and 835 nm (Fe2+) and a sharp but low absorption peak at 956 nm (H2O) (figure 3). These are due to the combined effects of vanadium and iron, with minor influence of chromium. These features are common in emerald.

Figure 4. Cesium vs. lithium for emerald from worldwide localities, demonstrating the unique chemistry of Newfoundland (NFL) emeralds. Worldwide emerald data from GIA laboratories.

The beryls’ chemistry, as determined by laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS), is unique from other worldwide deposits; both the white cores and green rims had elevated lithium and cesium (figure 4). The lithium and cesium values are within the range expected more of a beryl from a lithium-cesium rich pegmatite, such as many morganites or goshenites. The green coloration is primarily due to vanadium, with minor chromium, which are both chromophores of emerald (table 1). The magnesium is consistently higher than iron, as expected for emeralds (R.E. Henry et al., “Crystal-chemical observations and the relation between sodium and H2O in different beryl varieties,” Canadian Mineralogist, Vol. 60, 2022, pp. 625–675). The magnesium and transition metals are higher in the green rims than in the white cores, which have higher lithium. However, the cesium is higher in the green rims. This is likely due to the near-mutual exclusivity of beryllium site and aluminum site cation substitutions, preventing significant lithium substitutions when there is a high level of magnesium and transition metals (R.E. Henry et al., “Predicting the crystal structure of beryl from the chemical composition,” Canadian Journal of Mineralogy and Petrology, Vol. 61, No. 4, 2023, pp. 873–897). As magnesium and iron require charge balancing, sodium and cesium can serve this purpose; while cesium is associated with lithium in geologic environments, it does not have the same crystal-chemical constraints as lithium in beryl.
These beryls’ formation at the intersection of an ophiolite and a pegmatite is consistent with conditions required to create emerald as it brings together a source of vanadium or chromium with a source of beryllium. The goshenite cores are a feature that have been seen in emeralds from some other localities, including Russian emeralds.
Due to their uniquely high cesium and lithium, emerald zones of beryl from this locality are easy to differentiate. Should gem-quality specimens come to the market, a method is in place to confirm their origin as Newfoundland. Efforts are underway to continue exploration for additional gem material. Source: GIA @topic:3


Title: Diopside Needles as Inclusions in Demantoid Garnet from Russia: A Raman Microspectrometric Study Abstract: Straight, acicular, colorless solid inclusions in demantoid garnet from the Ural Mountains of Russia were investigated by laser Raman microspectrometry. These “needles,” which occur in association with “horsetail” inclusions (curved, fibrous chrysotile), were identified as diopside. This study also demonstrated that Raman analysis is a highly sensitive method for distinguishing even between isomorphous mineral inclusions in gems, that is, minerals with similar crystal structures but different chemical compositions Source: GIA @topic:2


Title: Interesting Red Tourmaline from Zambia Abstract: This note describes the study of five small, gem-quality crystals and crystal fragments of a brownish red to red tourmaline from a new locality near Chipata, Zambia. The mineralogical nature of these tourmalines is briefly discussed. X-ray diffraction indicates that these tourmalines belong to the schorl-dravite series. Refractive indices, birefringence, specific gravity, and other gemological properties are given, as well as comments on the inclusions. This material is very similar in appearance, gemological characteristics, and chemistry to the red tourmalines from Kenya. Source: GIA @topic:12


Title: Jason Dow, 2013 JCK Rising Star Abstract: View Gallery

Background

	Originally from Denver, Colorado, I had amazing teachers in high school who taught metalsmithing and jewelry classes. That’s really what got me started, but I didn’t really think about jewelry too much again until I needed to be passionate about a lifelong career.

	I graduated from the University of Hawaii in 1996 and attended the University of Colorado School of Dentistry from 1998-2001. Three years into the program I decided I wasn’t going to be happy as a dentist so I moved to San Diego and went to GIA in Carlsbad. I knew I wanted to design and work at the bench and earned my Graduate Jeweler diploma in December of 2002.

	I took full advantage of everything GIA had to offer. I spent every day either in class or in the library reading books and taking notes, watching videos, attending seminars and lectures, etc. I read and absorbed everything I could – a daunting task considering how large and extensive the library and resources are at the Carlsbad Campus. I probably only made quite a small dent.

	I worked at a few different local San Diego jewelry stores trying to get experience as a bench jeweler then landed a job back in Hawaii with Maui Divers Jewelry, a large retail chain complete with its own factory. In three years I worked my way up to senior designer goldsmith and learned a tremendous amount about designing for production. I also got to learn and practice more advanced techniques, including CAD/CAM.

	I launched my own design line in 2008 and began selling through local jewelry stores as Jason Dow, Inc.

The Design Process

	It doesn’t take me long to come up with a concept, but the details always slow me down. I’m a little bit meticulous about how I like things to look, so I’ll obsess about something for quite a while. I also love to shelve something I’m working on and come back to it later – I always seem to be inspired to make it better.

	My whole challenge in designing is really very simple. As a person of dual ancestry (half Chinese and half Irish/English) I have roots in two different worlds and cultures that can often clash. My goal is to create designs that integrate ancient Asian motifs with more modern and Western concepts, which are reflected in my collections.

Lotus Collection: For thousands of years the flower of the lotus plant has been known for its hypnotic, celestial beauty and unsurpassed as a floral religious icon. A symbol in many Eastern cultures, the lotus corresponds to purity of body, speech and mind, floating above the muddy waters of desire and attachment. Eight distinct petals possess great luck, and for me, the eight Hawaiian Islands.

Mandala Collection: The word “Mandala” is from the classic Indian language of Sanskrit. Loosely translated it means “circle”, but it represents far more than a simple shape. Long embraced by Eastern teachings, it is a symbol of wholeness and a model of the structure and balance of the universe. The Mandala Collection was inspired by the power of meditation and serves as reminder that the importance of life lies in the process of creation.

Tattoo Collection: Inspired by the Henna tattoos covering beautifully adorned Indian brides, the Tattoo collection both makes a statement and is extremely comfortable to wear. Like a second skin, the designs elegantly cover your fingers and wrists without hindering your active lifestyle.

Favorite Gemstones and Metals

	I love, love, love high-karat gold and moonstones. I’m also infatuated with diamonds, of course.  Really though, there are so many gemstones out there I haven’t had a chance to work with yet … I’m excited to try to eventually work with them all.

Motivation

	I love the challenge of design. I’ve never found anything more challenging and rewarding than this. I love being excited to go to work every day – as long as I get exercise in between – I rarely ever get tired of what I am doing. There are always new ideas to explore, so hopefully I’ll never ever suffer from boredom.

	Jason Dow. Photo provided by Jason Dow. Source: GIA @topic:6


Title: Aragonite Spheres in Ethiopian Opal Abstract: Figure 1. This Ethiopian opal contained an interesting inclusion scene consisting of a string of octahedral pyrite crystals and aragonite spheres. Photomicrograph by Charuwan Khowpong; field of view 1.40 mm.

Recently, the authors examined an 88.51 ct pear-shaped white precious opal that displayed typical digit patterns and hydrophane behavior (see Fall 2013 Lab Notes, pp. 175–176). These properties were consistent with opal from the Wollo mining area in Ethiopia (see B. Rondeau et al., “Play-of-color opal from Wegel Tena, Wollo Province, Ethiopia,” Summer 2010 G&G, pp. 90–105). The stone also showed weak whitish blue fluorescence in long-wave UV and was inert to short-wave UV. No phosphorescence was observed.

Figure 2. A single pyrite crystal is seen among spheres and clusters of translucent aragonite inclusions, both of which were identified by Raman spectroscopy. Oblique fiber-optic illumination. Photomicrograph by Charuwan Khowpong; field of view 1.05 mm.
In addition to its attractive digit pattern with spectral play-of-color, this opal hosted a number of unusual inclusions: opaque black octahedrons and translucent spheres. When viewed with a fiber-optic light, the opaque black octahedrons appeared a dark brassy metallic yellow (figure 1). Raman analysis identified them as pyrite, which has been previously reported in Ethiopian opal (N. Renfro and S.F. McClure, “Dyed purple hydrophane opal,” Winter 2011 G&G, pp. 260–270). Of particular interest is that the translucent spherical inclusions (figure 2), which formed as isolated spheres and clusters, were identified by Raman analysis as aragonite. The presence of aragonite spheres in opal is quite uncommon and has not been previously reported in precious opal from Ethiopia. Source: GIA @topic:12


Title: Fluorophlogopite in Burmese Spinel Abstract: Figure 1. This crystal broke the surface of a dark red spinel believed to be from Mogok. It had a lower luster than the spinel, and undercutting indicated a lower hardness. Photomicrograph by Richard W. Hughes, diffuse overhead illumination; field of view 2.5 mm.

Lotus Gemology in Bangkok received a large parcel of dark red spinels for identification. Their colors, inclusion features, and trace element chemistry suggested that they originated from Myanmar’s Mogok Stone Tract.

Figure 2. In darkfield illumination, cleavage was visible inside the crystal. Micro-Raman analysis showed it to be fluorophlogopite. Photomicrograph by Richard W. Hughes, darkfield illumination; field of view 2.5 mm.
In one faceted specimen, a crystal was found breaking the surface (figure 1). The crystal’s surface luster suggested a refractive index below that of the host spinel, and undercutting suggested it was also significantly lower in hardness. The inclusion’s interior also displayed signs of cleavage (figure 2). Thinking it was possibly a carbonate, we proceeded to do micro-Raman analysis on the crystal. To our surprise, the result was fluorophlogopite.
Fluorophlogopite, KMg3(AlSi3O10)(F,OH)2, is a species in the mica group and a member of the trioctahedral mica subgroup. To the best of our knowledge, this is the first reported instance of this species in spinel. Nor are we aware of it having been found included in any gem mineral to date. Source: GIA @topic:2


Title: Rare “Star and Cross” Quartz from Brazil Abstract: Figure 1. Face-up view of two quartz cabochons from Brazil, weighing 116.95 ct (left) and 44.12 ct (right) with cross-like quartz inclusions. Photo by Jaroslav Hyršl.

	The author purchased two very unusual quartz samples (figure 1) in Brazil in 2015. Both were cut as cabochons with a slightly curved bottom; one weighed 116.95 ct (35.0 × 30.3 × 15.6 mm), while the other weighed 44.12 ct (28.3 × 22.3 × 10.0 mm). The larger cabochon was slightly milky, while the smaller one was almost clear. Both showed a strong six-rayed star when illuminated (figure 2). The stars were centered on the top of the cabochons, which indicates that both were cut perpendicular to the c-axis. The most unusual feature was a cross-like inclusion in both stones. It was white and coarse-grained, only slightly translucent. The longer part of both crosses measured about 4 mm wide. The shorter part had a thickness 1.5 to 2 mm and the angle of the intersection was about 85 degrees in both cabochons, which meant that the two specimens were probably cut from the same crystal. Refractive index results and Raman analysis showed the cross to be quartz, rather than a foreign mineral. The origin of the cross inclusions is uncertain, but they are strong evidence of nature’s ability to produce rarities.

Figure 2. The stars in the quartz samples, seen from the base, are eye-visible in sunlight. Photo by Jaroslav Hyršl. Source: GIA @topic:2


Title: Cobalt-Doped Composite Sapphires: A Blessing or a Curse? Abstract: Gem mining is expensive and it is economically important to be able to enhance stones of lower quality. Treatments allow increasing the supply of gemstones making them available at affordable prices. Treated gemstones have been flooding the markets. The potential damage is a loss of consumer confidence. Are cobalt-doped composite sapphires a blessing or a curse? Only time will tell.

		Treatments of corundum are meant to enhance transparency, color, and stability, or to create optical effects.  Treatment options include: fissure filling with oil, dying, heating, irradiation, surface diffusion, heating with borax, lattice diffusion of beryllium, lead glass fissure filling, and cobalt glass fissure filling.

		Glass infilling in blue sapphire was developed by Tanusorn Lethaisong in Chantaburi in 2007, and in May 2012, a “new” type of cobalt-colored sapphire became available in the Bangkok market. Christopher P. Smith, in his recent article (“Cobalt-Colored Composite Sapphires,”InColor, Spring 2013,No. 22, pp. 32−37), explains what the fuss was all about.

		He discovered the sapphires to be a composite of natural, low-grade corundum and a high-lead glass that induces blue coloration and enhances clarity. The result is a sapphire with a medium-saturated color.

		These stones are not a challenge for a trained gemologist to identify. Gemological properties include readily evident color concentrations in surface reaching fissures and cavities, innumerable spherical to flat contraction bubbles, a “flash effect,” naturally occurring crystals, and short, fine unaltered rutile needles. The intact rutile indicates that the treatment takes place at relatively low temperatures.

		Figure 1:  Spherical to flattened contraction bubbles, irregular black reflective particles, “flash effect,” and color concentrations are observed in these glass-filled sapphires. Photo courtesy of Christopher P. Smith, InColor.

		The refractive index of the lead glass is similar to that of the host corundum, but the glass has a lower hardness. As a result, the polished surfaces of the stones reveal a mosaic network of narrow to thick tracks of glass. The stones glow bright red with the Chelsea filter. Using a standard hand-held spectroscope, a series of three distinct absorption bands positioned at approximately 528, 588, and 635 nm readily identify cobalt to be the main coloring agent. Such cobalt-related absorption bands do not occur naturally in sapphire.

		Figure 2:  Broad absorption bands centered at approximately 528, 588 and 635 nm identified the coloring agent as cobalt. Photo courtesy of Christopher P. Smith, InColor.

		Infrared spectroscopy recorded absorption bands at approximately 2290, 2620 and 3490 cm-1. These bands are related to the glass component of the composite sapphires. These specimens require special care, as standard manufacturing and bench jeweler practices, as well as household products can readily cause damage by etching the glass. The product has been classified as “composite sapphire” by the AGL (American Gemological Laboratories).  An in-depth study by Leelawatanasuk et al. (“Cobalt-doped glass-filled sapphires; an update”, The Australian Gemmologist, ,Vol. 25, No. 1, 2013, pp. 14–20)  provided additional information on the properties of the cobalt-colored composite sapphires. The report noted slightly elevated specific gravity in some specimens and a lack of pleochroism.DiamondView images showed a chalky blue fluorescence caused by the glass-filled fissures, and filled fractures appeared white on X-ray images.

		The value of a gemstone depends on its inherent beauty and rarity. The artificial modification of a gemstone greatly reduces the rarity and therefore lowers the value. Treatment of these “composite sapphires” requires special care to retain it, or else the benefit of the treatment will be lost over time. The Federal Trade Commission therefore requires proper disclosure to buyers. Source: GIA @topic:3


Title: Book Review: Dreher Carvings: Gemstone Animals from Idar-Oberstein Abstract: By Wilhelm Lindemann, Will Larson, and Ekkehard Schneider. Hardcover, 240 pp., illus., publ. by Arnoldsche Verlagsanstalt, Stuttgart, Germany, 2018, $85.00.

Dreher Carvings: Gemstone Animals from Idar-Oberstein begins with a history of the lapidary arts of this region of southwest Germany, which is also the timeline of the Dreher family gem-carving tradition. The various authors describe the driving forces behind the development of this world-renowned lapidary area, and the impetus for the Dreher’s unique style has followed a very similar path. What began as a subsistence-level job for many residents of Idar-Oberstein developed into an art form as tools evolved, skills improved, and a growing client base provided the financial cushion needed to pursue their vision.
This progression is described in the early portions of the book, and it is mentioned or alluded to by several of the authors in their narratives. Idar’s earliest gem cutters worked to survive. They used sandstone to render agates into functional, and eventually, decorative items. Stone cutting became the backbone of the area’s economy. Over time, harder and more accurate cutting wheels allowed for faster, higher quality production. Mechanical advances brought about the water wheels that powered this industry for centuries. The stonecutting work evolved into contract work for merchants supplying the jewelers and studios with finished gemstones, which led to an era of prosperity starting in the fifteenth century.
Idar’s stone carvers were traditionally considered craftsmen rather than artists because they were not creating original pieces. The work was regarded as rote and unimaginative, easily reproduced, but this simplicity was desirable to their buyers. Pieces were styled after templates and models supplied by clients, such as the House of Fabergé. The economic models came from merchants who saw value in repeatability, consistent design themes, and competition for the contracts, which could be filled by any qualified lapidary. This arrangement was also associated with the dissolution of the guild system, in which secret techniques and tools were known only to members. In the early nineteenth century, local mining resources were exhausted, and it was necessary start importing rough, mostly from Brazil. This new material added a dimension to the creativity of the carvers. Later in the 1800s, many Idar-Obersteiners joined apprenticeships and opened studios in Paris to practice their art and reach their audience. The German stonecutters were expelled from France during the Franco-Prussian War in 1870-71 and returned home to establish Idar-Oberstein as a world center for gemstone carving. Gem cutters started to be recognized in the mid-twentieth century as artists, as appreciation of stone carving as a classical fine art developed. This could be called the advent of gem carving’s creative movement, where the rough, the concept, the techniques, and the artist come together to create masterpieces. This is the situation that the most recent generations of Drehers (Gerd and Patrick Dreher) have enjoyed.
After returning from World War II, Paul Dreher, father of Gerd Dreher, began to carve his own designs in addition to the commissions that were his primary income. These personal pieces gave the House of Dreher a reputation as an artistic studio. In 1960, Gerd abandoned the “proto-industrial tradition” and the templates that controlled the design ethos in Idar and focused on creating his own designs. Up to that point, the Drehers had focused on the techniques and skills that made them a well-respected lapidary house, but one that was mostly known for actualizing the designs of others, usually from a template or model, but Gerd Dreher’s concept involved a subjective view of nature that is a confluence of the subject, the artist, and the material. Due to by the popularity of their carvings, the Drehers were freed from the economic restraints that are the primary consideration when carving gemstones. The use of signatures on their work, starting in 1975, has been the physical validation of cultural recognition of their work as art, not craft.
Gerd Dreher specialized in showcasing the natural beauty of the raw material, and his son Patrick has followed suit. Ironically, their subject matter often includes creatures not usually associated with beauty, such as warthogs, toads, mice, and hippos. But they are all so lifelike, imbued with personality. Every detail of their forms exemplifies beauty. The synergy of the raw material, its colors and conformation, and the structure of the subject matter, is what animates the Drehers’ work. The planning, design, layout, and all of the grinding and polishing steps, which take hundreds of hours, are embodied in these immortal creatures.
Robert Weldon’s outstanding photography gives another dimension to the carvings. Weldon somehow creates an image that speaks to the viewer. The artists create the pieces, and the photography makes the pieces’ personalities more accessible to the public. Weldon’s narrative is technically informative and insightful.
The chronological order of the photos is an excellent detail of the book. The progression of Gerd’s technique is visibly illustrated, and the reader can follow Patrick’s progress as well. as the Drehers become more successful, the rough material becomes more and more fabulous. Advances in technology are obvious as the detail work improves from piece to piece: the bumps get closer together, and the polish becomes more consistent and thorough. Each piece is more sophisticated than the last.
On some level, the guild mentality still exists. The technical details of their workshop are extremely vague, and the description of the tools used is outdated. The Drehers continue to closely guard all information about their polishing processes. This is often the case with modern lapidaries, where cutters fear competitors’ advantage. Although this book was created to showcase the art and prolific portfolio of the Drehers, there would be considerable interest in more of the technical details of their work.
The homages to the family are a very nice touch: the tribute from another gem artist, personal vignettes by important industry leaders, and tales of their meetings and contacts with the Drehers. These stories combine to detail the journey their carvings have taken to become some of the most important gemstone art of the modern era. The homages tell of the eventual acceptance of their art in worldwide venues of fine gemstones including other parts of Germany, Russia, and the United States. Other important writers include collectors of these pieces, who speak of the Drehers’ commitment to their work.
The variety of narratives in this volume gives the reader many perspectives into the Dreher story and their carvings. It is enlightening to read the history of the family and understand the genesis of their art. What is lacking is a consistent narration, a voice throughout to link all of the speakers. It is left to the reader to piece it all together. It is marvelous that this excellent book has been published, as it validates gemstone carving as a fine art. The production values are beyond reproach, and the color and quality of the images is outstanding. This historic volume will surely need a sequel in the coming years as Patrick Dreher continues to work. Source: GIA @topic:9