Iron-rich reevesite from the Ni-Fe ores of Mt. Radočelo, Serbia, a possible new member of the hydrotalcite subgroup

Abstract

The Ni-Fe ores represent the reworked part of the Paleozoic weathering crust on ultramafics. Talcose serpentinite, with a small accumulation of Ni-talc, represents the lowermost part of the destroyed weathering crust. XRD and EPMA study of the ore revealed its complex composition: magnetite is most abundant, with cores of detrital chromite; Ni-chlorite is also abundant; talc, goethite, hematite, maghemite, magnesite and Fe-rich reevesite occur in variable amounts. XRD of the ore revealed weak reflections of reevesite, with the strongest at 7.60 A. Nine electron probe analyses of this mineral were performed. The richest in nickel gives the following recalculated formula: (Fe2+4.03 Ni1.97)6.00 (Fe3+11.96 Al0.03 Cr0.01)2.00 CO3 (OH)16 . 4H2O. According to this composition, the mineral is the Fe-analog of reevesite and a new member of the Hydrotalcite Group.