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Fe-Bearing olenite with tetrahedrally coordinated Al from an Abyssal pegmatite at Kutná Hora, Czech Republic: structure, crystal chemistry, optical and xanes spectra

Cempírek, Jan and Novák, Milan and Ertl, Andreas and Hughes, John M. and Rossman, George R. and Dyar, M. Darby (2006) Fe-Bearing olenite with tetrahedrally coordinated Al from an Abyssal pegmatite at Kutná Hora, Czech Republic: structure, crystal chemistry, optical and xanes spectra. Canadian Mineralogist, 44 (1). pp. 23-30. ISSN 0008-4476. https://resolver.caltech.edu/CaltechAUTHORS:20130501-093010498

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Abstract

The pale blue rim of olenite on a black crystal of olenite–schorl tourmaline from an abyssal pegmatite at the locality Kuklík, near Kutná Hora, Czech Republic, has been chemically and structurally characterized. The optimized formula, calculated using chemical and structural data, is ^X(Na_(0.54)Ca_(0.14)K_(0.01)□_(0.31)) ^Y(Al_(2.15)Fe^(2+)_(0.78)Mn^(2+)_(0.06)Ti^(4+)_(0.01)) ^Z(Al_(5.90)Mg_(0.10))^T(Si_(5.60)Al_(0.40))B_3 O_(27)^V[(OH)_(2.49)O_(0.51)]^W(O_(0.99)F_(0.01)), with ɑ 15.8838(3), c 7.1056(2) Å and R = 0.017. The relatively short <Y–O> bond-length, 1.992 Å, confirms the high content of Al at the Y site (~2.1 atoms per formula unit, apfu). It is similar to that of olenite from the type locality, though the olenite from Kuklík contains significant amounts of Fe at the Y site, and significant amounts of ^([4])Al (~0.4 apfu) instead of ^([4])B in the T site. This finding is supported by results of the structure determination, which show an enlarged <T–O> bond-length of ~1.626 Å. This sample of olenite shows that nonstoichiometric content of Si does not always imply ^([4])B in aluminous tourmaline. No H could be found at the O1 site by refinement, and the spherical distribution of electron density in the difference-Fourier map around the O1 site supports the conclusion that this site is only or mainly occupied by O and not by OH. On a bond-angle distortion (σ_(oct)^2 of the ZO_6 octahedron) – <Y–O> distance diagram, the olenite from Kuklík lies between compositions containing 3 (OH) at the V site, and natural buergerite, which contains 0.3 (OH) and 2.7 O at the V site (O3 site). The (OH) content with ~2.5 (OH) pfu, which was calculated for a charge-balanced formula, is in a good agreement with these findings and with the integrated intensity of the OH overtones in the 7000 cm^(−1) region (690 cm^(−2) per cm thickness), which is one of the lowest measured to date for tourmaline. The OH seems to be ordered strongly at the O3 site. The composition of this sample of olenite shows a trend toward the proposed olenite end-member formula, which contains only 1 OH group. The low content of F (0.01 apfu) is uncommon for natural Al-rich and Mg-poor tourmaline from granitic pegmatites. Synchrotron micro-XANES was used to detect the valence state of Fe in this crystal; it was found to have 93 ± 10% of the total Fe as Fe^(2+). Optical absorption spectra show that the blue color is derived primarily from a combination of ^([6])Fe^(2+), together with ^([6])Fe^(2+) interaction with a minor amount of ^([6])Fe^(3+).


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.2113/gscanmin.44.1.23DOIUNSPECIFIED
http://canmin.geoscienceworld.org/content/44/1/23.abstractPublisherUNSPECIFIED
ORCID:
AuthorORCID
Rossman, George R.0000-0002-4571-6884
Dyar, M. Darby0000-0003-4272-793X
Additional Information:© 2006 Mineralogical Association of Canada. Received January 9, 2004, revised manuscript accepted October 22, 2005. The authors thank Joel Grice, Franklin F. Foit and Robert F. Martin for constructive comments that significantly improved the manuscript. The authors also thank Petr Sulovský for the boron determination at the University of Hanover. We thank Jeremy S. Delaney for assistance with the micro-XANES measurements. This work was supported by research projects MK 9486201 to JC and MSM 21622412 to MN, and by NSF grants EAR–9627222, EAR–9804768, and EAR–0003201 to JMH, and grants EAR–0125767 and EAR–0337816 to GRR.
Funders:
Funding AgencyGrant Number
UNSPECIFIEDMK 9486201
UNSPECIFIEDMSM 21622412
NSFEAR-9627222
NSFEAR-9804768
NSFEAR-0003201
NSFEAR-0125767
NSFEAR-0337816
Subject Keywords:Fe-bearing olenite, chemical analyses, crystal structure, optical absorption spectra, Kuklík, Kutná Hora, Czech Republic.
Issue or Number:1
Record Number:CaltechAUTHORS:20130501-093010498
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130501-093010498
Official Citation: Jan Cempírek, Milan Novák, Andreas Ertl, John M. Hughes, George R. Rossman, and M. Darby Dyar Fe-BEARING OLENITE WITH TETRAHEDRALLY COORDINATED Al FROM AN ABYSSAL PEGMATITE AT KUTNÁ HORA, CZECH REPUBLIC: STRUCTURE, CRYSTAL CHEMISTRY, OPTICAL AND XANES SPECTRA
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38201
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:01 May 2013 17:23
Last Modified:09 Mar 2020 13:18

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