In this study, Raman micro spectroscopy is applied to investigate two manganese oxides: lithiophorite [(Al,Li)Mn4+O2(OH)2] and asbolane [(Ni,Co)xMn4+(O,OH)4.nH2O], along with their intermediates (“Asbolane-Lithiophorite Intermediates”: ALI). These oxides typically incorporate variable concentrations of Co, Ni, Cu and Li. They represent a group of economically interesting phases that are difficult to identify and characterize with classical X-ray diffraction techniques. We show that Raman micro spectroscopy is useful to the investigation of those phases, but they require to be tested in very low laser power conditions to avoid sample degradation (e.g. 0.2mW 532nm). We propose reference Raman spectroscopic signatures for lithiophorite, asbolane and ALI phases. These spectra are mainly composed of two spectral domains, the first one is located between 370-630 cm-1 and the second one between 900-1300 cm-1. We then assess the impact of their highly variable chemistry on their Raman peak positions, intensities and FWHM using a semi-systematic curve-fitting method profiled for these phases.

Peer Review, Impact Factor

Spectrometry, mineralogy