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Vanadium- and chromium-bearing andalusite: Occurrence and optical-absorption spectroscopy

Carlson, William D. and Rossman, George R. (1988) Vanadium- and chromium-bearing andalusite: Occurrence and optical-absorption spectroscopy. American Mineralogist, 73 (11-12). pp. 1366-1369. ISSN 0003-004X.

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A graphitic quartz-muscovite schist in the Llano uplift of central Texas bears euhedral porphyroblasts of andalusite with unusual yellow-to-colorless pleochroism. They contain, by weight, up to 0.81% V_2O_3 and 0.12% Cr_2O_3, but less than 0.07% Fe_2O_3, 0.22% TiO_2, and 0.004% Mn_2O_3. Optical absorption spectra in all principal vibration directions are dominated by an intense charge-transfer band in the ultraviolet, on which are superimposed broad absorption maxima at 420 and 565 nm (intense in ɑ but weaker in β and y), and broad maxima at 745 and 370 nm (without strong polarization dependence). The intensity of each of these absorption bands is quantitatively correlated with V + Cr content. Weak absorption is also observed in the y spectrum near 320 nm. Assignment of the bands at 320, 420, and 565 nm to V^(3+) and Cr^(3+) in the octahedral site gives good agreement with data from other vanadian minerals for the relation of the absorption peak position to the mean bond length for the sites. The absorption peak at 745 nm probably results from octahedral V^(4+), but the origin of the 370-nm band is uncertain. The distinctive pleochroism results from the strong polarization dependence of the 420-nm absorption band.

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Rossman, George R.0000-0002-4571-6884
Additional Information:© 1988 Mineralogical Society of America. Manuscript received March 14, 1988. Manuscript accepted August 1, 1988. Support for this work was provided by NSF grant EAR-8603755 to W.D.C. and by NSF grant EAR-8212540 to G.R.R. The Geology Foundation of the University of Texas at Austin also helped to defray the costs of publication. We thank Karen Carter, University of Texas at Austin, for providing some preliminary microprobe analyses. G. Waychunas and M. Hochella offered helpful reviews.
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University of Texas at Austin Geology FoundationUNSPECIFIED
Issue or Number:11-12
Record Number:CaltechAUTHORS:20130515-082554444
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Official Citation: William D. Carlson and George R. Rossman Vanadium- and chromium-bearing andalusite; occurrence and optical-absorption spectroscopy American Mineralogist, December 1988, v. 73, p. 1366-1369
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38513
Deposited By: Ruth Sustaita
Deposited On:15 May 2013 21:17
Last Modified:26 Nov 2019 11:15

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