Organisms living near to extreme environments of volcanic origin are chronically exposed to a large range of chemical stressors, being therefore potential sentinels of the effects derived from such exposure. Energy-dispersive X-ray microanalysis was used to determine the elemental composition of the enamel and dentin of the lower incisor of Mus musculus inhabiting a volcanic hydrothermal field in the Azores, Portugal. Fracture faces were also investigated by scanning electron microscopy (SEM). Concentrations of major elements such as Ca, P and Na were found to be significantly higher in mice from the volcanic site, and enamel showed to have a significant higher ratio of Ca/P when compared with dentin. Cl was found to be common in enamel, but in contrast dentin showed to have very low proportions, near the detection limit (0.01), of such element. In contrast, K was found to be higher in dentin, but in enamel proportions near the detection limit were found. These results are discussed in consideration to the environment in which specimens were caught.