Iron K-Edge Xanes Study of Heated Green Beryl from Madagascar



Rough green beryls from Madagascar were studied for their gemological characteristics after heat treatment. The conversion of the iron oxidation state after heating was studied using the modern technique of X-ray absorption spectroscopy. The X-ray absorption near edge spectroscopy (XANES) results are in conclusively agreement with the traditional Ultraviolet-visible-near infrared (UV-Vis-NIR) technique, where Fe3+ in an octahedral site is changed into Fe2+ after heat treatment. The undesirable yellow tinge in the stone, therefore, is expelled and, thus, an attractive blue color is developed. The green beryls contained moderate amounts of chromophore iron (up to 1.08 wt.% FeO(total)), and relatively low amounts of Cs and Na. Fourier transform infrared (FTIR) spectroscopic features and chemical analyses are consistent with alkali-poor beryl. The gemological characterization of Malagasy green beryl is also presented in detail.


Beryl, heat treatment, UV-Vis-NIR, FTIR, XANES

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WL Bragg and J West. The structure of beryl, Be3Al2Si6O18. Proc. Roy. Soc. 1926; 111, 691-713.

C Aurisicchio, O Grubessi and P Zecchini. Infrared spectroscopy and crystal chemistry of the beryl group. Can. Miner. 1994; 32, 55-68.

DS Goldman, GR Rossman and KM Parkin. Channel constituents in beryl. Phys. Chem. Miner. 1978; 3, 225-35.

RR Viana, H Jordt-Evangelista, GM de Costa and WB Stern. Characterization of beryl (aquamarine variety) from pegmatites of Minas Gerais, Brazil. Phys. Chem. Miner. 2002; 29, 668-79.

DL Wood and K Nassau. The characterization of beryl and emerald by visible and infrared absorption spectroscopy. Am. Miner. 1968; 53, 777-800.

L Yan, D Jun, L Guowu and S Guanghai. Structure refinement of Cs-rich Na-Li beryl and analysis of its typomorphic characteristics of configurations. Acta Geol. Sinica 2007; 81, 61-7.

A Lacroix. Minéralogie de Madagascar, Tome II, Appliquée, Lithologie. Augustin Challamel, Paris, 1922.

F Pezzotta. Madagascar, A Mineral and Gemstone Paradise, ExtraLapis English 1. Lapis International LLC, East Hampton, CT USA, 2001.

AR Blak, S Isotani and S Watanabe. Optical absorption and electron spin resonance in blue and green natural beryl. Phys. Chem. Miner. 1982; 8, 161-6.

G Mathew, RV Karanth, TKG Rao and RS Deshpande. Colouration in natural beryls: A spectroscopy investigation. Curr. Sci. India 1997; 73, 1004-11.

CE McManus, NJ McMillan, RS Harmon, RC Whitmore, FC DeLucia and AW Miziolek. Use of laser induced breakdown spectroscopy in the determination of gem provenance: Beryls. Appl. Optics 2008; 47, 72-9.

DC Price, ER Vance, G Smith, A Edgar and BL Dickson. Mössbauer effect studies of beryl. J. Phys. 1976; 37, 811-7.

M Newville. IFEFFIT: Interactive XAFS analysis and FEFF fitting. Synchrotron Rad. 2001; 8, 322-4.

B Ravel and MJ Newville. ATHENA, ARTEMIS, HEPHAESTUS: Data analysis for X-ray absorption spectroscopy using IFEFFIT. Synchrotron Rad. 2005; 12, 537-41.

G Spinolo, I Fontana and A Galli. Optical absorption spectra of Fe2+ and Fe3+ in beryl crystals. Phys. Status Solidi B 2007; 244, 4360-8.

MN Taran and GR Rossman. Optical spectroscopy of tuhualite and a re-examination of the beryl, cordierite, and osumilite spectra. Am. Miner. 2001; 86, 973-80.

I Adamo, A Pavese, L Prosperi, V Diella, D Ajò, GD Gatta and CP Smith. Aquamarine, Maxixe-type beryl, and hydrothermal synthetic blue beryl: Analysis and identification. Gems Gemol. 2008; 44, 214-26.

LTT Huong, W Hofmeister, T Häger, NN Khoi, NT Nhung, W Atichat and V Pisuta-Arnond. Aquamairne from the Thuong Xuan district, Thanh Hoa province, Vietnam. Gems Gemol. 2011; 47, 42-8.

R Bocchio, I Adamo and F Caucia. Aquamarine from the Masino-Bregaglia Massif, Central Alps, Italy. Gems Gemol. 2009; 45, 204-7.

FC Howthorne and P Černý. The alkali-metal positions in Cs-Li beryl. Can. Miner. 1977; 15, 414-21.

JC Zwaan, DE Jacob, T Häger, MTOC Neto and J Kanis. Emeralds from the Fazenda Bonfim region, Rio Grande do Norte, Brazil. Gems Gemol. 2012; 48, 2-17.


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