Presently, thermal spring water, as a rich source of mineral colloids (MCs) and other elements, has been used for treating various diseases. However, its therapeutic effects on different types of cancer including breast cancer (BC) have not been reported so far. In this study, we analyzed the characterization of nanoparticles presented in MCs of thermal spring water in Rabor County, Kerman Province, Iran. We conducted the present study using X-ray fluorescence spectra, inductively coupled plasma mass spectrometry, X-ray powder diffraction, and transmission electron microscopy methods. We compared the oxidative evaluation of MCs with the control group using the 2,2-diphenyl-1-picrylhydrazyl test. Also, the anti-cancer influences of MCs against BC cell lines (MCF-7) were assessed and compared with the human fibroblast cells (hFCs) using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) test. Finally, we investigated the impact of MCs on the liver and kidney tissues of normal rats. Results of this study confirmed the presence of various oxides, including SiO2, Al2O3, and CaO, as well as elements, such as Sr, V, and Cr, in MCs. Moreover, our results showed that with an increase in the concentration of used MCs, the cell survival of cancer cell lines significantly decreased compared to hFCs. Also, no histologic change was observed in normal tissues exposed to MCs; however, MCs that existed in thermal spring water showed a considerable anti-cancer effect against BC cell lines.