Andreas Kamradt, Juliane Schaefer
Black shale ore from Kupferschiefer-type deposits in Central Europe represents a world-class copper
resource and is mined and processed since more than 800 years. However, the extraction of copper
and by-products is accompanied by technical issues due to the high content of organic carbon and the
complexity of the ore. The ore mineralization is largely characterized by minute and finely disseminated
sulphide particles commonly marked by complex intergrowth textures.
In this study, flotation tests on black shale ore from the former Sangerhausen mining district in Central
Germany as well as from the Lubin-Sieroszowice mining district of southwest Poland were carried
out to examine differences in the flotability of black shale ores subjected to a pre-treatment with
ethanol in comparison to black shale feed untreated prior to the flotation. The composition of both
black shale ores, flotation products and tailings were analysed using a SEM-EDX-based automated
mineralogy tool by Bruker. The analyses revealed the distribution of sulphides and gangue minerals
and thus, indicated the efficiency of the recovery of sulphides. Generally, flotation test applied to
black shale ore pre-treated by ethanol show a higher copper recovery in the flotation products as
achieved by flotation of black shale ore not pre-treated. Most efficient was the flotation of black shale
ore from the Rudna Mine in Poland, which attained a doubled copper recovery in comparison to the
flotation of the not pre-treated ore. The increased extraction yield was achieved by a successful enrichment
of chalcocite and bornite. Similar, but to a lower extend, were copper-bearing sulphides
extracted from the pre-treated Sangerhausen black shale ore. The flotation of the ethanol pre-treated
Sangerhausen black shale resulted in a slightly better copper recovery, in particular improved by
increased recovery of chalcopyrite and chalcocite. Additionally, the relative enrichment of gangue at
least in the flotation tailings of the pre-treated Rudna black shale implies that the ethanol pre-treatment
can improve a successful depression of gangue-type minerals.
Compositional analysis of copper flotation concentrates extracted from different Kupferschiefer-type black shale-hosted ores