Magnetometric studies of sulphide and sulphosalt minerals were carried out using electron paramagnetic resonance (EPR) and a superconducting quantum interference device (SQUID). These have proved to be powerful tools to investigate not only the valence states of transition elements (TE) cations but also the site symmetries and magnetic interactions between neighbouring atoms. While only few investigations are found in literature concerning sulphide minerals in recent years, advanced resonance techniques, such as electron spin echoes (ESE) and high-frequency EPR (HF2EPR), allow us to supplement and extend the information that can be obtained with standard techniques. Sphalerite derivative structures, such as stannite and tetrahedrite, were object of a systematic and advanced EPR and SQUID investigation. Synthetic analogues with simple chemical composition are here used as reference materials for the interpretation of the spectra refined by computer simulation. Spectroscopic investigations on these materials allow us to establish the different nature of “free” electrons delocalized with respect to the usual unpaired electrons of Cu(II), while preliminary studies on the ZnS-archetype, doped with TE, prove to be very useful in refining the site symmetries of cations in the structure.