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Studies on manganese-bearing silicate minerals from metamorphosed manganese formations of india. II. Blanfordite, manganoan diopside, and brown manganiferous pyroxene

Published online by Cambridge University Press:  05 July 2018

Supriya Roy
Supriya Roy*
Affiliation:
Department of Geological Sciences, Jadavpur University, Calcutta 32, India
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Summary

Three members of the pyroxene group, blanfordite, manganoan diopside, and brown manganiferous pyroxene, form important constituents of the manganese silicate rocks (gondite) of the metamorphosed manganese formations of India. The chemical composition of blanfordite is variable within the diopside-acmite series, that of the manganoan diopside corresponds to the diopside end of this series, and the brown manganiferous pyroxenes are related to aegirine-augites. The majority of the blanfordites studied have a composition within the aegirine-augite field, so that compositionally most of the blanfordites and brown manganiferous pyroxenes are similar in spite of the difference in their pleochroic schemes; The chemical composition of blanfordite varies: in association with calc-magnesian metasediments it has a high percentage of diopside, whereas in gondites and pegmatites its composition approaches more towards the acmite end. The blanfordites are often associated with manganiferous amphiboles such as juddite (manganoan magnesioriebeckite) and winchite (richterite-tremolite with blue and pink pleochroism) but never with tirodite. The brown manganiferous pyroxenes, on the other hand, are associated intimately with tirodite (richterite-tremolite with pleochroism in shades of yellow) but never with winchite and juddite.

Type
Research Article
Information
Mineralogical Magazine , Volume 38 , Issue 293 , March 1971 , pp. 32 - 42
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1971

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