We determined an isomorphic group of compounds with common formula K3Cu3(Fe3+, Al)O2(SO4)4 in products from fumarole activity of the Great Tolbatchik Fissure Eruption (GTFE, Kamchatka, 1975-1976). Within the isomorphic group, based on Fe and Al concentration we distinguished members on both sides of nominal 50 mol.% border. This fact along with variations in typical and diagnostically important physical characteristics of minerals was a factor for us to divide the group into two mineral species. Fe-members we called as "klyuchevskite", while Al-members were called as "alumoklyuchevskite". The latter is an aluminum analogue of klyuchevskite, compared to which Al is predominantly placed in Fe3+ positions.

The authors have studied the flat-topped Berg submarine-volcano. The volcano likely used to emerge above sea level in its past history, but suffered the top attrition subsequently. The edifice is composed as by dense rocks with prevailing andesibasalts and basalts, so by mouldy volcanic rock formations. The most magnetized lava flows effused near the top on the western slope after the volcano had sunk. These flows are possibly composed by basalts and are the youngest within the edifice.

The data on geology, petrography, mineralogy and petrochemistry for Kamen, Volcano in the central Kamchatka depression are presented. A study of the volcano's rocks and comparison with rocks of neighboring active volcanoes of the Klyuchevskoi group allow the establishment of some relationships. The rocks and minerals of Kamen, and Ploskie Sopki volcanoes show systematic differences in the chemistry of rocks and minerals such that they obviously could not be formed from the same primary melts. The rocks of dykes and Kamen' stratovolcano on one hand and the rocks of the Klyuchevskoi Volcano on the other hand form differently directed trends on petrochemical diagrams and differ in their compositions of rock-forming minerals, such they also could not originate from the same primary melts. The lavas of the monogenetic cones of Kamen' Volcano and moderately magnesian basalts of Klyuchevskoi Volcano are derivates of the same melts, i.e., the cones situated on the slopes of Kamen' are cones of Klyuchevskoi. The rocks of Kamen' and Bezymyannyi stratovolcanoes form a single narrow trend in all petrochemical diagrams in which the lavas of Bezymyannyi Volcano show a silica-rich branch, thus indicating a genetic relationship between these two volcanoes.