Mineralogical and petrological properties of black shale occurring in the copper ore deposit of the Foresudetic Monocline have been described. Specific character of the shale layer and its behaviour in the ore processing technology was discussed. A concept of recovery of the black shale from flotation circuits of the Lubin Concentrator by separating a by-product (middlings), which represents the tailings of the first cleaning flotation was presented. It was found that the investigated by-product cannot be practically upgraded using standard xanthate flotation. This is due to a remarkable enrichment in the organic carbon, similarly to the content of carbon in petrographically “pure” black shales. After a comprehensive examination it was assumed that the Lubin middlings can be regarded as a shale concentrate ready for bio- and hydrometallurgical processing. The effect of non-oxidative leaching of middlings with sulphuric acid on further flotation was presented. It was shown that non- oxidative leaching is a selective process, in which calcium and magnesium carbonates decomposition leads to effective liberation of sulphide minerals finely disseminated in hydrophilic gangue. Partial carbonates removal (between 70 and 90% of the total carbonates content) from the middlings resulted in evident liberation of valuable minerals. Consequently, it resulted in an increase of both recovery and the content of metals in concentrates obtained by flotation of shale by-product after non-oxidative leaching.