This work is a mineralogical study of fluorite samples (colourless, yellow and purple) from the mining districts of Villabona-Arlós and Caravia-Berbes (Asturias, Spain). It integrates data from UV fluorescence microscopy, SEM-EDS, fs-LA-ICP-TOFMS and fluid inclusions. Different growth stages were identified, some with abundant fluid and solid inclusions, and, in yellow fluorites, yellow bands alternated with colourless bands. UV fluorescence microscopy revealed growth bands with emissions of varying intensity and colour. SEM-EDS identified growth bands with inclusions of barite and celestine crystals, rich in aqueous fluid inclusions containing the same trapped minerals. In one fluorite crystal, an innermost colourless zone contained primary H₂O–NaCl–CaCl₂ fluid inclusions with trapped barite/celestite. Surrounding this zone was a yellow band full of tiny barite/celestite inclusions and an external colourless band hosting H₂O–NaCl fluid inclusions and sulphides. This growth zoning supports a fluid‑mixing process previously proposed by other authors. Such mixing induced a local transition from oxidizing to reducing conditions, facilitating the shift from sulphate to sulphide precipitation. Trace and ultra-trace element analyses by fs-LA-ICP-TOFMS were performed in the fluorite growth bands. The designed analytical conditions (15 μm spot size, 3-3.5 J/cm² fluence, 5 s of background and 5 s measurement, Ca as internal standard, NIST610 and 612 as external standards) show the REE distribution at a single crystal level. The REE patterns have an enrichment in the MREE, a positive yttrium (Y) anomaly and a LREE impoverishment. Yellow growth bands have higher REE and yttrium concentrations compared to colourless bands and violet fluorites. The bands with higher UV fluorescence intensity are those with higher concentrations of REE and Y. The results confirm that fluorites from the Villabona-Arlós district contain more ΣREE than those from the Berbes District. These results are consistent with bulk-sample chemical analyses reported by other authors (Sanchez et al., 2010).