Abstract

Permingeatite from a new occurrence, the Příbram uranium-base metal ore district (central Bohemia, Czech Republic), has been studied in detail. Its occurrence is similar to the type occurrence in Předbořice (Czech Republic). Based on electron microprobe analysis, the empirical formula of the studied permingeatite (mean of 10 point analyses, based on Sb + Cu + Fe + Se + S = 8 apfu) is Cu3.00(Sb0.99Fe0.04)∑1.03(Se3.74S0.23)∑3.97. The unit-cell parameters refined from powder X-ray diffraction data are a 5.6323(2) Å, c 11.2354(7) Å, with V 356.41(2) Å3 (for space group I4¯2m). The Se-S substitution is characteristic for the permingeatite from Příbram, in contrast to permingeatite from Předbořice, where the As-Sb substitution dominates. Regarding substitution trends, only two, Sb-As and S-Se, play a role in the luzonite group minerals. The only other element (as documented by the present study) which enters the structure of the luzonite-group minerals in considerable concentrations is Fe. Raman spectroscopy was used to characterize vibrational properties of the luzonite group of minerals. The dominant feature in the Raman spectra of the studied minerals is a suite of spectral bands that corresponds to the stretching and bending vibrations of tetrahedral XY4 (X = As/Sb; Y = S/Se) groups. Intrinsic shifts in observed energies for distinct studied minerals are connected with different elemental compositions of the tetrahedral groups. The reflectance data obtained from the studied permingeatite are close to the published data, but more significant differences were found, particularly in the areas of 420–500 nm and about 640 nm. The studied association was formed, based on the presence of umangite, at temperatures below 112 °C.

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