Nikolaev Anatolij Germanovich

Nizamutdinov Nazym Minsafovich

Popov Mihail Petrovich

Kazan Federal University Digital Repository

 SPRING 2018 VOLUME LIV THE CUARTERLY JOURNAL OF THE GEMOLOGICAL INSTITUTE OF AMERICA                                             Characteristics of Natural-Color Green Diamonds Iridescence in “Rainbow” Hematite DNA Identification of Japanese P. Fucata Pearls Tucson Report 2018                      2018 GIA SYMPOSIUM New Challenges. Creating Opportunities. Harvard Business Track Authentic Leadership, Disruptive Innovation and Customer Centricity GIA Research Track Scientific Findings and Industry Analysis   GIA® is accepting abstract submissions for oral and poster presentations through June 1.   Join us October 7 – 9, 2018 in Carlsbad, California    Seats are Limited. Register Now. symposium.GIA.edu ©2018 GIA. GIA® are registered trademarks of Gemological Institute of America, Inc.   EDITORIAL 1 The Beauty of Natural Green Diamonds Duncan Pay FEATURE ARTICLES 2 Natural-Color Green Diamonds: A Beautiful Conundrum Christopher M. Breeding, Sally Eaton-Magaña, and James E. Shigley Spring 2018 VOLUME 54, No. 1    pg. 9   pg. 45           pg. 59             pg. 68           pg. 92 Characterizes diamonds with exceptionally rare natural green color, based on GIA’s exten- sive database of samples. 28 Iridescence in Metamorphic “Rainbow” Hematite Xiayang Lin, Peter J. Heaney, and Jeffrey E. Post Analyzes the substructures that cause the intense iridescence observed in “rainbow” hematite from Minas Gerais, Brazil. 40 DNA Techniques Applied to the Identification of Pinctada Fucata Pearls From Uwajima, Ehime Prefecture, Japan Kazuko Saruwatari, Michio Suzuki, Chunhui Zhou, Promlikit Kessrapong, and Nicholas Sturman Shows how genetic material extracted from small amounts of pearl powder can be a useful indicator of this akoya cultured pearl species.      REGULAR FEATURES 52 The Dr. Edward J. Gübelin Most Valuable Article Award 54 2018 Gems & Gemology Challenge 56 Lab Notes Fracture-filled diamond with “rainbow” flash effect • HPHT-processed diamond  fraudu- lently represented as untreated • Cat’s-eye demantoid and brown andradite with horsetail inclusions • Unusual orange pyrope-spessartine-grossular garnet • New plastic opal imita- tion from Kyocera • Natural blister pearl from pearlfish within Pinctada maxima shell • Five CVD synthetics over three carats • Fancy Deep brown-orange CVD synthetic 66 G&G Micro-World Beryl crystal in fluorite • Diamond with extraordinary etch channels • Omphacite and chromite “bimineralic” inclusion in diamond • Agate-like banding in opal • Dendritic inclu- sion in Cambodian sapphire • Green crystals in yellow sapphires • Celestial inclusion scene in sapphire • Pink tourmaline in spodumene host • Quarterly crystal: Cr-diopside in diamond 74 Gem News International Tucson 2018 • Gem-cutting family from Idar-Oberstein •  Updates  on  Namibian  and Russian demantoid, Brazilian and  Colombian  emerald  •  Liddicoatite  exhibit  •  Mexican and Australian opal outlook • Indonesian opal • Cultured pearl update • Secondary gem market • Oregon sunstone • Kenyan tsavorite mining  •  Arkansas  turquoise  •  Vibrant colors on display • Michael Dyber on carving • Rex Guo on recutting • Jewelry designs by Erica Courtney, Paula Crevoshay • Responsible practices • Supply chain transparency • Buccellati design award • Aquamarine from Pakistan • Phenakite from the Urals • Fresh- water pearls from Texas • Very small akoya • Irradiated, annealed blue type Ia diamond • Microscope upgrade kit • International Diamond School • Gem-A photography award 101 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SPRING 2018     Figure 44. Phenakite with beryl in mica (left) and yellow phenakite (right). Photos by Mikhail Popov; fields of view 5 cm.      ppmw, Rb 10–64 ppmw, and Cs 310–3220 ppmw. The amount of total alkali content including Li, Na, K, Rb, and Cs ranged from 1296 to 6033 ppmw. As alkali ions (mainly for Na) were associated with “type II” water molecules in structural channels (D.L. Wood and K. Nassau, “The char- acterization of beryl and emerald by visible and infrared absorption spectroscopy,” American Mineralogist, Vol. 53, No. 5, 1968, pp. 777–800), the relatively low Na content was in agreement with the low peak intensity of “type II” H2O revealed by Raman and IR spectroscopy. The low con- centration of alkali content and lack of “type II” water  in our aquamarine samples were similar to that in aquama- rine from Italy and Vietnam (R. Bocchio et al., “Aquama- rine from the Masino-Bregaglia Massif, Central Alps, Italy,” Fall 2009 G&G, pp. 204–207; L.T.-T. Huong et al., “Aquamarine from the Thuong Xuan District, Thanh Hoa Province, Vietnam,” Spring 2011 G&G, pp. 42–48). The chromophore Fe, responsible for blue color, was the richest among all transition elements between 1350 and 5080 ppmw; the samples showed the typical iron absorption at 375, 425, 620, and 820 nm in UV-Vis-NIR spectra. Transi- tion elements V and Mn were present at 1–33 ppmw and 17–56 ppmw, respectively, and the bluish white fluores- cence mentioned above may originate from Mn2+ or VO4 centers  (M.  Gaft  et  al.,  Modern  Luminescence Spec- troscopy of Minerals and Materials, 2005, Springer Berlin, pp. 97–99). Chemical and spectral characteristic suggested the Pakistani samples were low-alkali aquamarine colored by Fe ions rather than irradiation (i.e., Maxixe beryl). Yang Hu and Ren Lu Gemmological Institute China University of Geosciences, Wuhan Color origin of phenakites from the Ural emerald mines. Phenakite (Be2SiO4) was first discovered at Russia’s Ural emerald mines, and was chemically identified in 1833. The mineral is widely distributed in beryllium deposits, but crystals of gem quality or large size are rare. At the Ural mines, however, there are large transparent crystals that can be used in jewelry. Jewelry-grade phenakite is generally colorless or yellowish brown (figure 44; see M.P. Popov et al., “Features of phenakite mineralization from the Ural emerald mines,” Bulletin of the Ural Branch of the RMS, No. 13, 2016, pp. 105–111). The main mineral inclusions are chlorite, talc, phlogopite, actinolite, and ilmenite; fluid inclusions with a gas-liquid composition also occur. The color origin of phenakite using optical absorption spectroscopy has not been studied in detail. Many authors agree that the coloration is associated with electron-hole centers (see A.S. Marfunin, Spectroscopy, Luminescence and Radiation Centers in Minerals, 1975, Nedra, Moscow). This is indicated by the disappearance of color when phenakite is exposed to either ultraviolet radiation or high temperatures. According to one theory of absorption, this is related to the oxygen vacancies that have captured elec- trons (again, see Marfunin, 1975). Other researchers believe that the absorption features are associated with bridging electronic centers such as Al-O-Al, which are formed by isomorphous replacement of silicon by aluminum ions in the crystal lattice, in amounts up to 0.5% (see A.N. Platonov, Nature of Coloring of Minerals, 1976, Naukova Dumka, Kiev). To determine the color origin of yellow-brown phenakites, we obtained optical absorption spectra of col- orless and yellow-brown phenakite from the Mariinsky de- posit. These spectra were collected in the 185–700 nm wavelength range, at room temperature, on a specialized Shimadzu UV-3600 spectrophotometer. A broad absorption band was noted in the 225–325 nm range of the yellow- brown phenakite spectrum, with a maximum at 268 nm. Absorption in the ultraviolet range of the optical spectrum was not detected in transparent colorless phenakites (figure 45). To study electron-hole centers and to reveal color cen- ters in phenakite, crystals were examined using electron paramagnetic resonance (EPR). EPR is an informative method for studying dissymmetry of crystals, the role of the symmetry elements of the spatial group, and the dis- tribution of impurity ions and point defects in the bulk of the crystal. Dissymmetry of crystals, as a result of the un- even distribution of point defects in the process of crystal growth, is a widespread phenomenon (see G.R. Bulka et al., “Dissymmetrization of crystals: Theory and experiment,” Physics and Chemistry of Minerals, Vol. 6, 1980, pp. 283– 293; R.A. Khasanov et al., “Derivation of the conditions for equivalent positions in crystals: The dissymmetrization of barite by electron spin resonance,” Crystallography Re- ports, Vol. 57, No. 5, 2012, pp. 751–757; J.M. Hughes et al., SPRING 2018 102 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY              Figure 45. Absorption spectra of colorless phenakites (blue trace) and yellow-brown phenakites (black trace).   “Dissymmetrization in tourmaline: the atomic arrange- ment of sectorally zoned triclinic Ni-bearing dravite,” The Canadian Mineralogist, Vol. 49, 2011, pp. 29–40). We used an Adani CMS8400 spectrometer (frequency ν=9, 4 GHz) at room temperature to perform EPR on our samples. Dur- ing an experiment on the EPR spectra of the impurity rad- ical [PO4]4– phenakite of deposits in Volynskii (see A.I. Novozhilov et al., “Electron paramagnetic resonance in ir- radiated phenakite Be2SiO4,” Journal of Structural Chem- istry, Vol. 11, 1970, pp. 393–396), we found a difference in intensity of the lines of three magnetically nonequivalent centers for the impurity radical. The paramagnetic center [PO4]4– was only detected in the yellow-brown crystals (fig- ure 46), and active centers were absent in colorless speci- mens. From this we concluded that the origin of the yellow-brown color of phenakite is associated with a para- magnetic complex [PO4]4– that produces absorption bands   Figure 46. Phosphorus ions replace silicon ions in a tetrahedral structure to form a [PO4]4– complex in yel- low-brown phenakites. This complex is paramagnetic and gives several signals in the range of 320–340 mT. Splitting of the hyperfine structure of the signal oc- curs; lines 1, 2, and 3 appear and indicate the exis- tence of the [PO4]4– radical. When the crystal rotates along its c-axis, it changes the intensity of these lines. in the ultraviolet region, which in turn leads to the forma- tion of this color in the mineral. These results can be used in gemological identification of phenakites from the Ural emerald mines. This study was performed in the context of the Russian Government Program of Competitive Growth of Kazan Federal University, “Paleogeodynamics and evolution of structural-material complexes in the formation of the con- tinental-type crust ...,” theme no. 0393-2016-0019. Anatoliy G. Nikolaev and Nazym M. Nizamutdinov Kazan (Volga Region) Federal University Kazan, Russia Michael P. Popov Ural State Mining University Institute of Geology and Geochemistry Yekaterinburg,  Russia  Freshwater natural pearls from the Concho River, Texas. Throughout history, natural pearls have been found in many species of freshwater mollusk in North American lakes and rivers. They are most abundant within the Mis- sissippi River drainage basin, which provides the perfect habitat for these animals because of the large watershed areas with their underlying limestone substrata (J.L. Sweaney and J.R. Latendresse, “Freshwater pearls of North America,” Fall 1984 G&G, pp. 125–140). Lesser-known sources of natural freshwater pearls are the Colorado River and Brazos River and their tributaries in the state of Texas. However, the best samples are sometimes found in a species named Tampico Pearlymussel (Cyrtonaias tampi- coensis) that inhabits the Concho River in West Texas. The mollusk is distributed from northeastern Mexico into the Concho, Colorado, and Brazos Rivers of central Texas and has been collected by licensed harvesters. Mus- sel harvesting is restricted to hand collection only, and there is a legal minimum shell size requirement. In addi- tion, several areas in Texas have been designated mussel sanctuaries in order to provide protection and species con- servation (R.G. Howells, “The Tampico pearlymussel (Cyrtonaias tampicoensis), shades of the Old West,” http://www.conchologistsofamerica.org/articles/1996/the- tampico-pearlymussel.html). Pearlers find mussels by wad- ing into water that is three to four feet deep and feeling for the shells with their toes. Rattlesnakes on the banks and water moccasins and snapping turtles in the murky water (J. Morthland, “Irregular radiance: The rare beauty of Conch River pearls,” Texas Highways, April 2015) pose risks to these adventurers searching for gems. GIA’s New York laboratory recently received nine loose pearls from Stone Group Laboratories (Jefferson City, Mis- souri) for a joint study. The pearls ranged in size from 2.95 × 2.45 mm to 14.76 × 13.55 × 13.13 mm. Reportedly recov- ered from Tampico pearlymussel shells taken from the Concho River, they exhibited colors ranging from purplish pink to orangy pink. Some of the samples also possessed varying degrees of a brownish hue (figure 47). Most of tWAVELENGTH (nm) 700 600 500 400 300 200 268 UV-VIS ABSORPTION SPECTRA 255 275 295 315 335 355 375 395 MAGNETIC FIELD (mT) 0 [PO4]4– 2 3 1 [PO4]4– 2 1 3 EPR SPECTRA INTENSITY ABSORBANCE 101 GEM NEWS INTERNATIONAL GEMS & GEMOLOGY SPRING 2018    

Color origin of phenakites from the Ural emerald mines

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Color origin of phenakites from the Ural emerald mines

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