Mn distribution in sphalerite: an EPR study

A study on Zn replacement in sphalerite by divalent Mn has been performed by using EPR spectroscopy. Twelve natural and synthetic samples with different Mn-contents were selected for the spectroscopic investigation. The EPR spectra vary from an hyperfine sextet to a single broad line according to their Mn-content. Three components, attributed to Mn(II) in different chemical coordination (namely isolated ions, interacting ions, clusters) have been determined by means of spectral simulation. The variations of the EPR signals among the different spectra are due only to the mixing of these components, without any variation of each spectral parameter. Differing distribution of Mn(II) was, therefore, observed at a local scale. Consequently, the specific interactions driving the coalescence of Mn(II) ions to form clusters may be responsible for the banded pattern in sphalerite crystals.