A high content of fluorine was found in ornithogenic soils around penguin rookeries on King George Island. South Shetland Islands. Fluorine is inherent in 0.11% in krill (Euphausia superba). eaten by penguins. Fluorine content in penguins excreta increased approximately to 0.43%. and after decomposition and leaching to 1.03%. The concentration grew during mineralization of organic matter in guano (up to 2.2%). In a surface layer of guano fluorine occurred in apatite. A phosphatization was noted in a subsurface zone as the result of a reaction between guano leachates and weathered volcanic rocks. In the upper part of this zone near the large rookeries a fluorine occurred in minyulite (aluminium phosphate containing potassium and fluorine) and fluorine content here reached 3.5%. Sometimes fluorine was also bound with amorphous aluminium phosphate (up. to 2.0%). formed as a result of incongruently dissolving of minyulite in pure water.