L. P. Vergasova, T. P. Kirsanova, T. M. Philosophova, I. A. Boikova

The paper describes finding of oxonium-alunite which appears to be a structural analogue to minerals of alunite group observed in products of fumarolic activity at Molodoy Sheveluch. Abundance of oxonium-alunite in new growth of fumaroles and altered rocks is supported by data acquired on the results of chemical, X-ray, petrographical, submicroscopic and microprobe analyses. Occurrence of alunite in the crater of Molodoy Sheveluch refers to volcanic type associated with its fumarolic and solfataric activity. The period of its long silence preceded a growth of cone in 1980- 1982 that shows direct link between alunitization and recent volcanic activity.