Relevance. The need to clarify the role of the youngest hypogenic processes in the formation of the Mesozoic-Cenozoic megacomplex of the Polar Urals. Aim. To study the mineral composition of fluidolites as peculiar unconventional formations associated with the functioning of pressurized water and gas flows within the activated tectonic structures of the Baydaratsky block. Methodology and methods. Generalization, analysis and synthesis of materials from the long-term study of the geology and minerageny of the Polar Urals, including the implementation of GDP200/2 sheets R-40-XXXI, XXXII, Q-42-I, II, VII, VIII and the Priority 2030 Program. The study of the morphology, internal structure, and chemical composition of the fluidolite was carried out at the research laboratory center of the Ural State Mining University (Yekaterinburg). The morphological study was carried out using an optical microscope MBS 10 in reflected light and a scanning electron microscope VEGA LMS from TESCAN; the composition of minerals was determined using an energy dispersive prefix Xplore 30 Oxford Instruments, the program "Aztec" U=20 kV, I=3 hA. X-ray examinations were performed using a POWDIX 600 diffractometer. Results. Fluidolites as products of fluid-gas processes are confined to the feathering seams of the Sebeta-Huuta fault system. They have a complex polymineral composition, where, along with the predominant aqueous sulfates of iron and magnesium – magnesiocopiapite, epsomite with their dehydration products fibroferrite, there are rarer ones, such as slavikite and microcrystals of an accurately undiagnosed sulfate containing magnesium and iron. Along with the clastic silicate material, small kaolinite crystals were found among needle clusters of fibroferrite and areas of a "microcavernous" structure were found, where aluminosilicate fine-dispersed material is relatively evenly distributed among sulfates. Clusters of nanominerals containing potassium are sometimes found in the composition of the latter. Conclusions. New data have been obtained on the mineralogical composition of fluidolites, as products of hypogenic fluid-gas processes of the quarter, close to fumarolic phenomena within the Baidaratsky block of the Polar Urals.