Low-temperature Ni-rich lollingite from Haje, Pribram, Czech Republic.: Rietveld crystal structure refinement

Ni-rich lollingite is described from silver mineralization of the complex uranium -polymetallic deposit of Haje ore nodal point, ii km SE of Pribram. A new paragenetic type - called thereafter "lollingite" - is described in the paper. Major minerals of this paragenesis are Ni-lollingite, roscoelite, calcite (of stage K5), pyr-rhotitc, galena, silver, and acanthite. Ni-lollingite forms radial spherulitic huddles of trillings composed of thin lenticular- or spindle-shaped crystals about 2 mm long and 100 mum thick. Trillings on (101) yield very nice well-developed stellate shapes specimens in cross-sections. The color is silver-metallic. The elongation of observed Ni-lollingite crystals is: along axis b. Recalculation of average of 8 chemical analyse on the basis of 3 atoms pfu gives the empirical formula (Fe0.61Ni0.36Co0.04)(Sigma = 1.01) (As1.94S0.01Sb0.03)(Sigma =1.98). Unit cell dimensions and densities from the Rietveld crystal structure refinement (assuming orthorhombic s.g. Pnnm and Z = 2) are a = 5.243(1), b = 5.978(1), c = 2.9783 (6) Angstrom, D-x = 7.371 (3)g/cm(3) for Ni-lollingite from Haje and a = 5.2684(2), b = 5.9631(3), c = 2.9007(1) Angstrom, D-x = 7.496(1) g/cm(3) for lollingite from DoIni Bory. Correlation between individual unit cell parameters and molar ratio R = Fe/(Fe +Ni) computed from data for members of FeAs2 - NiAs2 series gives regression equations: a [] = - 0.5319 . R-2 + 1.0795 . R + 4.7560, b [] = -0.1971 . R-2 + 0.3899 . R + 5.7937, c [Angstrom] = 0.5416 . R-2 - 1.2114 . R + 3.5476. The parameter R can be satisfactorily estimated from equation R = 1.01475 - root (9.9712 - 1.8800 . a). In the present work crystal structures of Ni-lollingite from Haje and lollingite from Dolni Bory are refined. Also, low-temperature conditions under which studied Ni-lollingite trillings formed and their morphology are discussed in detail.