The Laser Raman Identity of Gibbsite Pseudomorphous after Crocoite from Dundas, Tasmania

Gibbsite both invests and replaces crocoite in late supergene ores of the Dundas district, Tasmania. The laser Raman spectrum of the gibbsite shows strong, well-developed v-OH stretching bands at about 3370, 3440, 3525, 3620 cm-I, confirming its identity. Crocoite gives bands at 840 em-Iv!, 853 and 825 cm-l v3, 348 cm-l v 2, 400, 377, 358, 338 and 326 cm-l v 4, and at 179,135, and 118 em-I, corresponding to crystal field components ofPb-O vibrations and lattice modes. The chemistty of the late, mineralising fluids is unknown and the relative stabilities of crocoite and gibbsite can not be determined.