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Gemmological investigation of a synthetic blue beryl: a multi-methodological study

Published online by Cambridge University Press:  05 July 2018

I. Adamo ,
G. D. Gatta ,
N. Rotiroti ,
V. Diella  and
A. Pavese
I. Adamo
Affiliation:
Dipartimento di Scienze della Terra, Universita' degli Studi di Milano, Italy
G. D. Gatta*
Affiliation:
Dipartimento di Scienze della Terra, Universita' degli Studi di Milano, Italy CNR-Istituto per la Dinamica dei Processi Ambientali, Milano, Italy
N. Rotiroti
Affiliation:
Dipartimento di Scienze della Terra, Universita' degli Studi di Milano, Italy CNR-Istituto per la Dinamica dei Processi Ambientali, Milano, Italy
V. Diella
Affiliation:
CNR-Istituto per la Dinamica dei Processi Ambientali, Milano, Italy
A. Pavese
Affiliation:
Dipartimento di Scienze della Terra, Universita' degli Studi di Milano, Italy CNR-Istituto per la Dinamica dei Processi Ambientali, Milano, Italy
*
*E-mail: diego.gatta@unimi.it
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Abstract

A multi-methodological investigation of a synthetic Cu/Fe-bearing blue beryl [IV(Be2.86Cu0.14)∑=3.00VI(Al1.83Fe3+0.14Mn2+0.03Mg0.03)∑=2.03IV(Si5.97Al0.03∑=6.00O18.(Li0.12Na0.04.0.40H2O)] has been performed by means of gemmological standard testing, electron microprobe chemical analyses, laser ablation inductively coupled plasma mass spectroscopy, thermo-gravimetric analyses, infrared spectroscopy and single-crystal X-ray diffraction in order to determine the gemmological properties, crystal structure and crystal-chemistry of this material. The increasing production of marketable hydrothermal synthetic beryls with 'exotic' colours and the small number of studies on the accurate location of chromophores in the crystal structure inspired this multi-methodological investigation. The X-ray structural refinements confirm that the space group of the Cu/Fe-bearing blue beryl is P6/mcc, with unit-cell parameters: 9.2483 ≤ a ≤ 9.2502 Å and 9.2184 ≤ c ≤ 9.2211 Å. The analysis of the difference Fourier maps of the electron density suggests that Cu is located at the tetrahedral site (Wyckoff 6fposition) along with Be, whereas Fe shares the octahedral site with Al (4c position). No evidence of extra-framework Cu/Fe-sites (i.e. channel sites) has been found. The Li is probably located at the extra-framework 2b site. Infrared spectra show that the H2O molecules are present with two configurations: one with the H···H vector oriented ‖[0001] and the other with H···H vector oriented ⊥[0001].

Keywords

synthetic berylcrystal chemistryICP-MSIR spectroscopysingle-crystal XRDstructurally incorporated water
Type
Research Article
Information
Mineralogical Magazine , Volume 72 , Issue 3 , June 2008 , pp. 799 - 808
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2008

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