Characterisation of conichalcite by SEM, FTIR, Raman and electronic reflectance spectroscopy

Abstract

The mineral conichalcite from Bagdad mine- West of, Bagdad, Eureka District, Yavapai Co., Arizona, USA has been characterised by electronic, Near-IR, Raman and infrared spectroscopy. SEM micrographs show the mineral consists of bundles of fibres. Calculations of the EDX analyses on the stoichiometric basis show the substitution of arsenate by 12 wt % of phosphate in the mineral. Raman and infrared bands are assigned in terms of the fundamental modes of AsO43- and PO43- molecules and are related to the mineral structure. Near-IR reflectance spectroscopy shows the presence of adsorbed water and hydroxyl units in the mineral. The Cu(II) coordination polyhedron in conichalcite can have at best pseudo-tetragonal geometry. The crystal field and tetragonal field parameters of Cu(II) complex were calculated and found to agree well with the values reported for known tetragonal distortion octahedral complexes.