We report the first use of a CuFeS2 froth flotation mineral concentrate (MC) as an energy storage material in a fixed bed flow cell (FBFC). The performance of a graphite felt (GF) MC negative electrode (GF–MC) was also compared to a synthetic CuFeS2 electrode in the same FBFC. The Fe(II)/Fe(III) redox reaction (in the presence of Cu(II)) on the GF positive electrode (GF–Fe/Cu) supported the charge/discharge process. The kinetic parameters calculated from individual cyclic voltammetry scans of negative and positive electrodes revealed that the electrochemical processes in the FBFC were quasi-reversible. In cell C–1 (GF–CuFeS2/GF–Fe/Cu), a continuous increase in specific capacity (∼9–48 mAh g−1) and energy (2–6.3 Wh kg−1) in 500 charge/discharge cycles was attributed to the capacitive behavior of the S2 2−/S2− species present on the CuFeS2. However, during 400 GCD cycles of C–2 (GF–MC/GF–Fe/Cu), a monotonic increase in the specific capacity (20–49 mAh g−1) and energy (3.5–8.5 Wh kg−1) was associated with an additional capacitive response from FeS2 in the MC. Advantageously, 10.3 and 12.7% Cu was also extracted from the C–1 and C–2 cells, respectively, which is unique to this system and provides a positive offset for the relatively low energy storage compared to existing battery systems. An observed improvement in the specific capacity during repetitive cycling was related to the presence of Cu and sulfide sulfur species on the CuFeS2 particles as revealed from the characterization of retrieved CuFeS2.