Minerals were analysed that had been found in penguin guano and in underlying silicate weathering crust phosphatized by guano leachates. Struvite and hydroxylapatite were found in guano, leucophosphite, minyulite, amorphous aluminum phosphate and taranakite in phosphatized layer, and in some distance from the zone of ornithogenic soils — vivianite. Minerals were identified by the X—ray analysis and results of this identification were confirmed by the microscope studies and the analysis of chemical composition. Results of the thermogravimetric analysis of the selected minerals occurring in monomineral agglomerations (struvite, minyulite, amorphous aluminum phosphate, taranakite) are also presented. Relation between distribution of those minerals in ornithogenic soils and changes in chemical composition of mineral-forming guano leachates during their infiltration through soil, were described.

Mineral composition of bedrock is the main factor determining salt mineralization in the weathering zone of Seymour (Marambio) Island (maritime — Antarctic continent climatic boundary). Supply of salts by sea water spray can accelerate weathering process, modify chemical formula of salt minerals and give ephemeral efflorescences of easy soluble chlorides and partially longer lasting gypsum on the surface. Microbiologically mediated oxidation of sulphides and followed acid sulphate drainage formed K and Na jarosite, basic amorphous aluminium sulphate, gypsum, aluminium bearing ferrihydrite and ankerite in weathering zone of Paleogene sediments. Intense alteration of well-lithified, calcareous sandstones of unit 1 of the López de Bertodano Formation (Cretaceous) on old erosion surface led localy to surface mineralization comparable with that found in Antarctic Continent. Stones laying on the soil surface are covered by thin red film of ferrihydrite above the soil level and by light green crust of aragonite coloured by glauconite pigment on the underground side. Most of the Cretaceous sediment does not contain sulphides nor alteration susceptible silicates thus ephemeral sea salts efflorescences observed on its surface are more prominent than in another places.