A contribution to geochemical prospecting for fluorite

Abstract

With fluorine as indicator, eight different extraction methods were tested for their suitability in geochemical prospecting for fluorite in stream sediments. Since this material can be regarded as coarse-grained, clastic fragments derived from the bedrock - i.e. granites, gneisses, and fluorite veins as well - it was concluded that the fluorine content of the stream sediments comes mostly from fluorine-bearing bedrock minerals. Anomalous samples contain fluorine predominantly as fluorite from fluorspar mineralization. Five of the commonest fluorine-bearing minerals - fluorite, mica, apatite, amphibole and tourmaline - were treated with the different extractants and with various times of reaction and mineral grain size. Fluorine analysis was by ion-selective electrode. The ratio cx-F (fluorite) vs. cx-F (mica, apatite) was found to be a useful measure of the applicability of the respective method. In order to test this conclusion 41 stream sediment samples ( −177 microns ≜ −80 mesh ) from the area under investigation were treated with eight different extractants. The most suitable extraction solution - boric acid solution - was used for the reconnaissance stream sediment survey in an area of 400 km 2 in the southeastern part of the Black Forest (F.R. Germany).