gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1966.036.276.07 Heating Experiments on Gudmundite Horrell Clark A. Dept. of Geology, University College, London, W.C. 1 12 1966 36 276 1123 1125 6 6 1966 Copyright © 1966, The Mineralogical Society 1966 Summary

In the absence of published experimental data on phase equilibria in the ternary system Fe-Sb-S and on the stability relations of gudmundite (FeSbS) and berthierite (FeSb2S4) , some preliminary investigations on the upper stability limit of natural gudmundite are briefly described. On heating in vacuo, As-free gudmundite broke down between 269° and 288°C, an approximate upper stability limit of 280±10°C conforming to the stability relations of the associated phases.