Strontium Dependence of the Lattice Constants of Barites from the Kreševo Area in Central Bosnia (Bosnia and Herzegovina)

Abstract

The lattice constants of a synthetic BaS04 and fourteen naturalbarite samples from the Kreševo area (Central Bosnia) were determinedby X-ray powder diffraction. The natural samples containedfrom 0.3 - 7.6 mole % SrS04 and negligible concentrations of Ca andPb <0.03 and 0.02 wt. %, respectively), thus representing almostpure (Ba,Sr)S04 solid solutions.The diffraction lines of most natural samples were broadened inreflection to those of synthetic BaS04. This results from obvious compositional heterogeneity, e.g. the heterogeneous distribution of strontium, as is clearly observed from Sr variation patterns across a surface of the barite obtained by proton microprobe analysis. Nevertheless, the present values of unit-cell parameters are in agreement with those of synthetic (Ba,Sr)SO4 solidsolutions documented in the literature.It has been proven that the interplanar spacing d004 may be usedfor determination of thc Sr content of natural barites; the absoluteerror varies from ±O.3 mole % SrS04 (for homogeneous samples havingthe difrraction line 004 clearly resolved in spectral doublet components) up to ±O.5 mole % SrS04 (for the samples with compositionalheterogeneity having a broadened and relative poorly defined diffractionline 004).