Fall 2000 Gems & Gemology - Gemfrance

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REFERENCES Arem J.E. (1987) Color Encyclopedia of Gemstones, 2nd ed. Van Nostrand Reinhold, New York, 248 pp. Bank H. (1977) Durchsichtiger, schleifwürdiger Hauyn aus der Eifel. Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 26, No. 4, p. 207. Bank H. (1978–1979) Gemological notes: Blue gem haüyne. Gems & Gemology, Vol. 16, No. 4, p. 123. Clark A.M. (1993) Hey’s Mineral Index, 3rd ed. Natural History Museum Publications, Chapman & Hall, London. Deer W.A., Howie R.A., Zussman J. (1963) Rock-Forming Minerals, Vol. 4: Framework Silicates. Longman, London, 435 pp. Deer W.A., Howie R.A., Zussman J. (1992) An Introduction to the Rock-Forming Minerals, 2nd ed. Longman Scientific & Technical, Essex, England, 696 pp. Fisher K., Bürger H. (1976) Hauyn. Lapis, Vol. 1, No. 2, pp. 30-32. Harms E., Schmincke H.-U. (2000) Volatile composition of the phonolitic Laacher See magma (12,900 yr BP): Implications for syn-eruptive degassing of S, F, Cl and H 2 O. Contributions to Mineralogy and Petrology, Vol. 138, pp. 84–98. Henn U., Bank H. (1990) Über die Farbe der Sodalith-Minerale: Sodalith, Lasurit (Lapis lazuli) und Hauyn. Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 39, No. 2/3, pp. 159–163. Johnson M.L., Elen S., Muhlmeister S. (1999) On the identification of various emerald filling substances. Gems & Gemology, Vol. 35, No. 2, pp. 82–107. Kiefert L., Hänni H.A., Chalain J.P., Weber W. (1999) Identification of filler substances in emeralds by infrared and Raman spectroscopy. Journal of Gemmology, Vol. 26, No. 8, pp. 501–520. Linde C. (1998) Hauyn-Kristalle von Teneriffa. Lapis, Vol. 23, No. 1, p. 22. (while supplies last) Maestrati R. (1989) Contribution à l’édification du catalogue Raman des gemmes. Unpublished diploma thesis, Diplôme d’Université de Gemmologie, Université de Nantes, France. Mandarino J.A. (1999) Fleischer’s Glossary of Mineral Species 1999. The Mineralogical Record Inc., Tucson, AZ. Marfunin A.S. (1979) Spectroscopy, Luminescence and Radiation Centers in Minerals. Springer-Verlag, Berlin, p. 282. Matthes S. (1983) Mineralogie. Eine Einführung in die spezielle Mineralogie, Petrologie und Lagerstättenkunde. Springer- Verlag, Berlin, p. 183. Mertens R. (1984) Hauyn, ein seltener Edelstein. Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 33, No. 1/2, pp. 65–67. Sapozhnikov A.N., Ivanov V.G., Piskunova L.F., Vasil’ev E.K. (1997) X-ray powder diffraction data of hauyne with incommensurate modulated structure from volcanic rocks of Laacher Lake, Germany. Powder Diffraction, Vol. 12, No. 1, pp. 3–6. Schmincke H.-U. (2000) Vulkanismus. Wissenschaftliche Buchgesellschaft, Darmstadt, Germany, 264 pp. Vassilikou-Dova A.B., Lehmann G. (1990) Paramagnetic defects in the mineral haüyne. Crystal Research and Technology, Vol. 25, No. 5, pp. 525–529. Webster R. (1994) Gems, Their Sources, Descriptions and Identification, 5th ed. Rev. by P. G. Read, Butterworth- Heinemann Ltd., Oxford, England, p. 342. Wörner G., Schmincke H.-U. (1984) Mineralogical and chemical zonation of the Laacher See tephra sequence (East Eifel, W. Germany). Journal of Petrology, Vol. 25, Part 4, pp. 805–835. Xu H., Veblen D.R. (1995) Transmission electron microscopy study of anisotropic and isotropic haüyne. American Mineralogist, Vol. 80, No. 1/2, pp. 87–93. Notes and New Techniques GEMS & GEMOLOGY Fall 2000 253
An Unusual CAT’S-EYE CHRYSOBERYL When the West Coast laboratory recently received a translucent gray chatoyant cabochon for identification from K & K International in Falls Church, Virginia (figure 1), the last thing we thought it could be was chrysoberyl, even though that was how it was represented by our client. Nothing about its appearance suggested chrysoberyl, not even the appearance of the inclusions. Gemological testing revealed a spot refractive index of 1.75, a specific gravity of 3.69 (measured hydrostatically), and no visible absorption spectrum or fluorescence. Although these properties could indicate chrysoberyl, they were Figure 1. Although chatoyancy is common in chrysoberyl, this 7.29 ct cabochon is the first gray cat’seye chrysoberyl seen in the laboratory. The color in this stone appears to be caused by dense concentrations of gray platelets, which are also the cause of the chatoyancy (inset, magnified 30×). also consistent with several other gems. Nevertheless, the spectrum obtained with the Raman microspectrometer was a perfect match to our reference for chrysoberyl. This is the first gray cat’s-eye chrysoberyl we have seen in the laboratory. Microscopic examination of the 7.29 ct stone indicated that the inclusions were the probable cause of the gray color; they looked gray in transmitted light, while the host material appeared near-colorless. Chrysoberyl is seldom colorless, especially in gem quality. Instead of the long, fine needles or “silk” that are normally present in cat’s-eye chrysoberyl, these gray inclusions formed a dense cloud of tiny, oriented reflective platelets. Light reflection from these platelets caused the chatoyancy. Even more unusual was the presence of a weak star oriented off-center toward one end of the stone (not completely visible in the photo). We have seen only a few star chrysoberyls in the lab. The last one we reported on was greenish brown and also had the star oriented off-center (Summer 1989 Lab Notes, p. 102). SFM DIAMOND Blue and Pink, HPHT Annealed As part of our ongoing research for means to identify HPHT-annealed diamonds, the East Coast laboratory recently analyzed 11 pink and four blue diamonds that had been subjected to this process (see, e.g., figure 2). These diamonds were submitted to the laboratory from Bellataire Diamonds, which is responsible for marketing GE POL diamonds in the United States. The diamonds weighed 0.75 to 14.93 ct. The pink diamonds showed a wide range of color saturation, from the equivalent of Faint to Fancy Deep; the blue diamonds ranged from the equivalent of Very Light to Fancy Intense. The clarity grades ranged from IF to VS 2 and from VVS 1 to VVS 2 for the pink and blue diamonds, respectively. The pink diamonds were type IIa, based on their mid-infrared spectra and their transparency to short-wave UV radiation. The blue diamonds were type IIb; that is, they showed both electrical semi-conductivity and characteristic boron features in the mid-infrared. According to Chuck Meyer, managing director of Bellataire Diamonds, the pink and blue diamonds represent a very small fraction of the overall GE POL production. Because of the rarity of the starting material that can generate these colors, he does not expect them to be readily available commercial items. Gemologically, these HPHTannealed diamonds show properties that are commonly observed in natural-color type IIa pink and type IIb blue diamonds, particularly the details of color zoning, and reactions to longwave and short-wave UV. We would expect the same types of alteration of inclusions to occur as were previously reported for HPHT-annealed Editor’s note: The initials at the end of each item identify the editor(s) or contributing editor(s) who provided that item. Gems & Gemology, Vol. 36, No. 3, pp. 254–259 ©2000 Gemological Institute of America 254 Lab Notes GEMS & GEMOLOGY Fall 2000
Page 2 and 3:
pg. 237 pg. 217 pg. 247 REGULAR FEA
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Pearl Nucleation Misquote? It is di
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Figure 1. These two illustrations s
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When a type IIa diamond is exposed
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GE5 GGL1 2.72 ct 0.61 ct Before Aft
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after processing revealed little ch
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Figure 7. These UV/Vis/NIR absorpti
Page 16 and 17: A couple of samples also revealed p
Page 18 and 19: Figure 10. Because of the greater s
Page 20 and 21: Figure 11. The CL color of the GE P
Page 22 and 23: ditions, as described by Fisher and
Page 24 and 25: al., 1999). As described above, mos
Page 26 and 27: BOX C: RUSSIAN HPHT-PROCESSED DIAMO
Page 28 and 29: Collins A.T., Kanda H., Kitawaki H.
Page 30 and 31: island, approximately 90 km northea
Page 32 and 33: Quaternary. The 35-km-wide stratovo
Page 34 and 35: BOX A: SAPPHIRE PRODUCTION FROM THE
Page 36 and 37: parent without causing them to beco
Page 38 and 39: Figure 13. When viewed perpendicula
Page 40 and 41: Figure 20. In a view almost paralle
Page 42 and 43: earing natural sapphires, there has
Page 44 and 45: As shown in the correlation diagram
Page 46 and 47: Guo J., Wang F., Yakoumelos G. (199
Page 48 and 49: (Nicholson, 1993). The sites are lo
Page 50 and 51: applicable to this report. These is
Page 52 and 53: TABLE 1. Saladoid gem and ornamenta
Page 54 and 55: Figure 11. Note that there are two
Page 56 and 57: Baik, 1983; Cody, 1990; Rodríguez,
Page 58 and 59: occur on Antigua. These were found
Page 60 and 61: pathoids; figure 2). It has been re
Page 62 and 63: Figure 4. The haüyne samples exami
Page 64 and 65: tures sometimes showed orange to pi
Page 68 and 69: Figure 2. The laboratory recently e
Page 70 and 71: Figure 5. These round brilliants (t
Page 72 and 73: Figure 9. This 2.34 ct heated rough
Page 74 and 75: De Beers’s newly stated direction
Page 76 and 77: Aquamarine from southeast India. Fi
Page 78 and 79: Figure 9. This 0.69 ct fresnoite wa
Page 80 and 81: Natural History, New York) and S. S
Page 82 and 83: & Gemology, pp. 78-89). The massive
Page 84 and 85: fluorescent light; for this sample,
Page 86 and 87: groups found in organic matter such
Page 88 and 89: {tÄÄxÇzx j|ÇÇxÜá 2000 This y
Page 90 and 91: particular carat weight would be fo
Page 92 and 93: Gemological ABSTRACTS EDITOR A. A.
Page 94 and 95: and high-wavenumber (~3800-2800 cm
Page 96 and 97: chain is found in the highly public
Page 98 and 99: Tertiary-age diamondiferous fluvial
Page 100 and 101: JEWELRY RETAILING Mistakes jewelers
Page 102: Irradiation at doses of 7.6-187 kGy
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Fall 2000 Gems & Gemology - Gemfrance

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