Mineralogy of the fuchsites from Gattihosahalli, Chitradurga District

Abstract

The fuchsites described here occur in the lower portions of a precambrian quartzite bed, which typically encloses small bands and lenses of barytes. Of the two fuchsites studied, one occurs in the main relatively fine grained quartzite and the other forming one of the small schistose segregations in the quartzite. While the commonly measured axial angles average 34^o and 32^o, small angles of 14^o and 19^o, which are possibly related to the formation of the mineral under high pressure, have been recorded in both the fuchsites. There is a close similarity in x-ray powder pattern between the two fuchsite samples studied and between these and muscovite. This observation is in accordance with the interpretation that fuchsites exhibit the same two layered mica structure as muscovite 2M₁. Chemically the fuchsites of Gattihosahalli are closely similar to the one reported from Manitoba and the cell contents are comparable to di-octahedral micas of muscovite character with Cr substituting for octahedarl Al. It is inferred that the fuchsites of Gattihosahalli are of sedimentary origin and the constituents required for their formation were all present in the shaly component of the sandstone or were partly or completely supplied by volcanic exhalations.