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Phosphate minerals hydroxylapatite, fluorapatite and crandallite were identified in nodules within phosphorites from Ervenik, Croatia. The minerals were identified using optical microscopy, XRD, SEM and EDS analyses. The presence of fungi was recognized only in association with phosphate-rich phases. Fungal activity resulted in the dissolution of apatite, producing hollow crystals, particularly in hydroxylapatite-enriched zones. A substantial number of hyphae were observed on the surface of phosphate minerals, in addition to saprophytic bacteria and bacterial spores. Induced activity of phosphate-accumulating bacteria in an aquatic environment caused dissolution of the phosphate minerals. The aqueous phase contained increased concentrations of several elements, including Ca, Sb, U, V and As. These elements are important constituents of minerals of the apatite group. As a consequence of the crystallization of apatite, the concentration of phosphate decreases with a corresponding increase in aluminium concentration, resulting in the prevalence of crandallite as the stable phase, forming the outer sector of the spherulites. [ABSTRACT FROM AUTHOR]