OPTICAL-ABSORPTION AND EPR STUDIES ON VARISCITE

Variscite is an aluminium mineral. EPMA of the sample indicate that it contains Fe2O=0.11 and Cr2O3=0.21 wt%. EPR results provide that Fe(II I) and Cr(III) replaces Al(III) in the crystal. g values for Fe(III) L ies in between 4.635 and 3.762 and Cr(III) 1.994 and D is 780 G. The h igh field EPR spectrum indicates the presence of VO(II) and its g and A values are g(11)=1.949, g(1)=1.986 and A(11)=192 and A(1)=64 G. The optical spectrum is mainly due to Cr(III). It has given energies at 15 380, 16660, 18180, 21735, 28565 and 30295 cm(-1). The bands at 16660 a nd 21735 cm(-1) are assigned to spin allowed transitions. The band at 18180 cm(-1) is assigned to split component of T-4(2g)(F) level. Which indicate the site symmetry of Cr(III) is lowered from octahedral to C -4V or C-3V. The values of B and C are evalued as 475 and 2200 cm(-1).