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Pyrophanite from Chvaletice (Bohemia)

Published online by Cambridge University Press:  05 July 2018

L. Žák
L. Žák*
Affiliation:
Department of mineralogy, geochemistry, and crystallography, Charles University, Prague, Czechoslovakia
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Summary

Pyrophanite was found in quartz-rhodochrosite veins in hornstones of Algonkian pyritemanganese ores. Photometric reflectance falls from R0 24 and RE′ 19 at 405 mµ to R0 18 and RE′ 15% at 656 mµ (in air). Vickers microhardness (100 g load) demonstrates directional anisotropy, the average value is 611 kg/mm2. Besides the main constituents, subordinate to trace quantities of Mg, Si, Al, Ca, and Cu were recorded by a spectrographic analysis. Unit-cell dimensions are a = 5·131 and c = 14·27 Å. Electron-microprobe analysis gave MnO 43·3, FeO 3·8, MgO 0·05, TiO2 52·9, SiO2 0·1, total 100·15%. The origin of the Chvaletice pyrophanite was most probably connected with a hydrothermal metamorphism of an Alpine-paragenesis type. The source of elements was older sedimentary, basic volcanic, and metamorphic mineral assemblages.

Type
Research Article
Information
Mineralogical Magazine , Volume 38 , Issue 295 , September 1971 , pp. 312 - 316
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1971

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