Optical absorption and EPR study of Cu2+ ions in vesuvianite (“cyprine”) from Sauland, Telemark, Norway
Dyrek, Krystyna; Platonov, Alexej N.; Sojka, Zbigniew; Źabiński, Witold
European Journal of Mineralogy Volume 4 Number 6 (1992), p. 1285 - 1290
published: Dec 15, 1992
manuscript accepted: Feb 6, 1992
manuscript received: Sep 12, 1991
ArtNo. ESP147050406010, Price: 29.00 €
Abstract Optical and EPR spectroscopic investigations of Cu-bearing vesuvianite ("cyprine") were performed in order to obtain new evidence for the lattice position of Cu2+ ions in this mineral and to confirm the origin of its blue colouration. The optical absorption spectrum of "cyprine" can be best explained assuming that Cu ions occupy irregular B-site of local symmetry close to D4h, which is consistent with EPR data and previous XRD analysis. The blue colour of "cyprine" is determined by the absorption bands 15600 cm-1 in the σ-spectrum and 16700 cm-1 in the π-spectrum. The EPR spectrum composed of an asymmetric signal with g|| = 2.3404, g⟂ = 2.0625, A|| = 14,78 mT and A⟂ = 2.5 mT is characteristic of Cu2+ in square planar symmetry. The molecular bonding parameters calculated on the basis of both optical and EPR spectra indicate that there is an appreciable covalent contribution to the predominantly ionic Cu-0 bond.