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To help meet emission standards, hydrogen sulfide (H2S) from geothermal production may be injected back into the subsurface, where basalt offers, in theory, the capacity to mineralize H2S into pyrite. Ensuring the viability of this pollution mitigation technology requires information on how much H2S is mineralized, at what rate and where. To date, monitoring efforts of field‐scale H2S reinjection have mostly occurred via mass balance calculations, typically capturing less than 5% of the injected fluid. While these studies, along with laboratory experiments and geochemical models, conclude effective H2S mineralization, their extrapolation to quantify mineralization and its persistence over time leads to considerable uncertainty. Here, a geophysical methodology, using time‐domain induced polarization (TDIP) logging in two of the injection wells (NN3 and NN4), is developed as a complementary tool to follow the fate of H2S re‐injected at Nesjavellir geothermal site (Iceland). Results show a strong chargeability increase at +40 days, interpreted as precipitation of up to 2 vol.% based on laboratory relationships. A uniform increase is observed along NN4, whereas it is localized below 450 m in NN3. Changes are more pronounced with larger electrode spacing, indicating that pyrite precipitation takes place away from the wells. Furthermore, a chargeability decrease is observed at later monitoring rounds in both wells, suggesting that pyrite is either passivated or re‐dissolved after precipitating. These results highlight that a sequence of overlapping reactive processes (pyrite precipitation, passivation, pore clogging and possibly pyrite re‐dissolution) results from H2S injection and that TDIP monitoring is sensitive to this sequence. High‐temperature geothermal production is responsible for air pollution due to hydrogen sulfide (H2S) present in the magmatic fluid. To help meet emission standards, H2S may be injected back into the subsurface, where basalt offers the capacity to transform H2S into pyrite. Transformation into an immobile mineral prevents further transport into the atmosphere, sea, surface streams, or lakes. However, ensuring the viability of this pollution mitigation technology requires information such as how much H2S is mineralized, at what rate and where, which are highly uncertain due to the heterogeneity and inaccessibility of subsurface processes. Here, a geophysical monitoring methodology is developed and tested during the re‐injection of H2S at Nesjavellir geothermal site in south‐west Iceland. According to laboratory studies, pyrite precipitation is expected to increase the electrical capacitance, “chargeability,” of the subsurface. Using the so‐called time‐domain induced‐polarization (TDIP) method embedded in a wireline logging tool, the chargeability of a 2 m‐wide cylinder around the injection wells is measured with high spatial‐resolution before and during H2S injection. A strong chargeability increase at +40 days indicates that up to 2% pyrite is formed. A subsequent decrease at later rounds raises questions on whether pyrite is re‐dissolved or passivated by other secondary minerals. H2S reinjection in basalt and mineralization into pyrite was monitored using TDIP logging in two of the injection wellsChargeability increases observed at +40 days (first monitoring round) correspond to 1%–2% pyrite precipitation with great spatial variabilitySubsequent monitoring rounds show a decrease in chargeability, suggesting that pyrite is either passivated or re‐dissolved H2S reinjection in basalt and mineralization into pyrite was monitored using TDIP logging in two of the injection wells Chargeability increases observed at +40 days (first monitoring round) correspond to 1%–2% pyrite precipitation with great spatial variability Subsequent monitoring rounds show a decrease in chargeability, suggesting that pyrite is either passivated or re‐dissolved