Goldmanite, a vanadium garnet from laguna, New Mexico

Abstract

Goldmanite, Ca;;(V,Fe,Alh Si,,012, is a new garnet that occurs as a constituent of a metamorphosed uranium-vanadium deposit in the Laguna uranium mining district, about 45 miles west of Albuquerque, New Mexico. The garnet is sparsely to abundantly disseminated in thin dark vanadium-rich layers in a small uranium-vanadium deposit in the Entrada Sandstone \,-ithin a few feet of the base of a thick diabase sill. Viewed in thin sec. tion, the garnet is seen to occur as minute anhedral grains and euhedral dodecahedral crystals that are embedded in vanadium clay and calcite. Goldmanite is free from impurities, dark green to brownish green, and weakly anisotropic; measured G= 3.74::1: .03, n = 1.821 :!: .001, and probable a= 12.011 A. The calculated density is 3.737. The three strongest x-ray powder pattern lines with indices and intensities are 2.688 A (420) (100),3.005 A (400) (65), and 1.607 A (642) (49).' Microchemical analysis showed: CaO 33.3, MnO 0.3, MgO 0.7, V,03 18.3, Fe203 5.4, Al,03 4.9, SiO, 36.6, sum 99.5 per cent, or: