Pyrophanite from Chvaletice (Bohemia)

L. Žák
Department of mineralogy, geochemistry, and crystallography, Charles University, Prague, Czechoslovakia

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.

Mineralogical Magazine; September 1971 v. 38; no. 295; p. 312-316; DOI: 10.1180/minmag.1971.038.295.04
© 1971, The Mineralogical Society
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