gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1976.040.313.05 A Note on Some Dalradian Stilpnomelanes and Their Oxidation Graham Colin M. 1 Department of Geology, University of California, Los Angeles, California 90024

Present address: Dept. of Geology, The University, Edinburgh EH9 3JW

 3 1976 40 313 467 472 20 11 1974 3 3 1975 Copyright © 1976, The Mineralogical Society 1976 Summary

The widespread ferristilpnomelane in Dalradian metabasites of the south-west Scottish Highlands has usually formed by secondary oxidation of primary ferrostilpnomelane, probably during weathering. Ferrostilpnomelane oxidizes readily in polished thin sections open to the atmosphere over a period of months, and microprobe examination of the resulting ferristilpnomelane suggests a change in the role of potassium in the structure during oxidation.