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Role of natural radiation in tourmaline coloration

Reinitz, Ilene M. and Rossman, George R. (1988) Role of natural radiation in tourmaline coloration. American Mineralogist, 73 (7-8). pp. 822-825. ISSN 0003-004X. http://resolver.caltech.edu/CaltechAUTHORS:20130430-074853342

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Abstract

The optical spectra of elbaite tourmalines subjected to large, controlled doses of gamma radiation have been compared to those of natural specimens. Both naturally pink and laboratory-irradiated elbaites show the same spectroscopic features. Optical absorption features of Mn^(2+) in nearly colorless elbaites are lost during laboratory irradiation, indicating a Mn^(2+) → Mn^(3+) transformation during the radiation process. Measurements of the radiation levels in tourmaline pockets in southern California pegmatites have been used to compute the doses that natural samples should have experienced over geologic time. These doses generally correspond to the doses required to restore the color to elbaites that have been decolorized by laboratory heat treatment, indicating that color in naturally pink tourmaline is a product of natural radiation. This radiation could have been effective only after the pegmatite cooled below the decolorizing temperature of tourmaline, suggesting that most pink elbaites originally grew nearly colorless in the pegmatites and only later attained their pink color through oxidation of Mn via ionizing radiation.


Item Type:Article
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http://www.minsocam.org/msa/collectors_corner/amtoc/toc1988.htmPublisherUNSPECIFIED
Additional Information:© 1988 Mineralogical Society of America. Manuscript received November 6, 1987; Manuscript accepted March 15, 1988. Tourmaline samples for this study were provided by R. H. Currier (Arcadia, Cal.), E. E. Foord, (Denver, Col.), M. E. Gray (Culver City, Cal.), and W. F. Larson (Fallbrook, Cal.). S. M. Mattson provided tourmaline analyses in advance of publication and valuable suggestions resulting from her work on some of the same samples. The cooperation of W. F. Larson in allowing us to conduct radiation measurements in a rich gem-pocket while he was actually mining it is especially noteworthy and appreciated This research was supported in part by NSF grants EAR-8313098 and EAR-8212540. Caltech Division of Geological and Planetary Sciences Contribution 4377.
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Funding AgencyGrant Number
NSFEAR-8313098
NSFEAR-8212540
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Caltech Division of Geological and Planetary Sciences4377
Record Number:CaltechAUTHORS:20130430-074853342
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20130430-074853342
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38171
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:30 Apr 2013 18:38
Last Modified:30 Apr 2013 18:38

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