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Violet-colored diopside from southern Baffin island, Nunavut, Canada

Herd, Chistopher D. K. and Peterson, Ronald C. and Rossman, George R. (2000) Violet-colored diopside from southern Baffin island, Nunavut, Canada. Canadian Mineralogist, 38 (5). pp. 1193-1199. ISSN 0008-4476. doi:10.2113/gscanmin.38.5.1193.

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Diopside with an unusual violet color from southern Baffin Island, Nunavut, Arctic Canada, is found in calc-silicate lenses, associated with marialite, pargasite, phlogopite, calcite, apatite, titanite, talc, chlorite, plagioclase and quartz. It occurs as massive aggregates of roughly equant grains. Basal parting is evident, and pyroxene cleavage is subtle. Indices of refraction are n_α 1.670(1), n_β 1.675(1), and n_γ 1.695(1), and 2V_Z is equal to 57.6(5)° at 589 nm. Pleochroism is nonexistent. D_(calc) = 3.30 g/cm^3. Cell dimensions determined from powder X-ray diffraction are ɑ 9.730(4), b 8.873(3), c 5.275(2) Å, β 105.95(3)°. A single-crystal X-ray structural refinement was performed to determine bond lengths and angles. The empirical formula, based on results of electron-microprobe analyses and absorption spectroscopy indicating 0.30 wt.% H_2O in the structure, is (Ca_(0.96)Na_(0.04))(Mg_(0.86)Al_(0.06) Fe^(2+)_(0.05)Ti^(4+)_(0.02))(Si_(1.89)Al_(0.11))O_(5.93)OH_(0.07). The unusual color is due to intervalence charge-transfer between Fe^(2+) and Ti^(4+) at the M1 site, and is observed owing to the low overall concentration of Fe in the diopside. Cathodoluminescence indicates that Mn^(2+) is present in the M1 site. Absorption spectroscopy demonstrates that Mn^(3+) does not contribute to the violet color.

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Rossman, George R.0000-0002-4571-6884
Additional Information:© 2000 Mineralogical Association of Canada. Received July 24, 1998, revised manuscript accepted July 4, 2000. This study was originally undertaken by CDKH as a Bachelor of Science Honours project. Many thanks to the Department of Geological Sciences, Queen’s University. In particular, we gratefully acknowledge Dugald Carmichael for help in selecting the project and Roger Innes and Jersez Advent for thin sections and grain mounts. We also thank Tony Mariano for help with the cathodoluminescence analysis, Marc St-Onge and the Geological Survey of Canada for the opportunity to collect and study material from southern Baffin Island, and Richard Herd for contributing to description of the mineral assemblage and a critical review of the manuscript. Liz Miura (Caltech) is gratefully acknowledged for her assistance in obtaining the optical spectroscopic measurements. The study was partially funded by a grant from the Natural Sciences and Engineering and Research Council (Canada) to RCP. GRR acknowledges support from the White Rose Foundation. We thank two anonymous reviewers and the editor for their constructive remarks.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Natural Sciences and Engineering and Research Council (Canada)UNSPECIFIED
White Rose FoundationUNSPECIFIED
Subject Keywords:diopside, violet color, spectroscopy, intervalence charge-transfer, clinopyroxene, Baffin Island, Nunavut, Canada.
Issue or Number:5
Record Number:CaltechAUTHORS:20130502-100609773
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Official Citation: Christopher D.K. Herd, Ronald C. Peterson, and George R. Rossman VIOLET-COLORED DIOPSIDE FROM SOUTHERN BAFFIN ISLAND, NUNAVUT, CANADA Can Mineral, October 2000, v. 38, p. 1193-1199, doi:10.2113/gscanmin.38.5.1193
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38232
Deposited By: Ruth Sustaita
Deposited On:02 May 2013 17:28
Last Modified:09 Nov 2021 23:36

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