Arsenopyrite mineral
Arsenopyrite is the FeAsS mineral species listed in the September 2026 IMA-CNMNC master list. It is distinct from elemental arsenic, dissolved arsenic species, pyrite-arsenopyrite concentrates and refractory gold ores. The experiment below used a natural high-purity mineral specimen, not a measured gold-bearing ore. No criticality designation is inherited from arsenic or from an associated commodity.
Microbial & Biochemical Mechanisms (1)
Arsenic release and surface-film formation during inoculated bioleaching
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus ferrooxidans (NCBITaxon:920)
Laboratory cultures identified by the authors as Acidithiobacillus ferrooxidans accompanied arsenic mobilization from arsenopyrite and conversion of dissolved Fe(II) to Fe(III). The authors propose ferric attack on the mineral sustained by microbial iron oxidation, with an early compact arsenic/sulfur-rich surface film restricting subsequent dissolution. This is a culture-associated leaching observation and proposed passivation mechanism; a matched sterile comparison and a direct test separating cell contact from solution-mediated chemistry are not reported. The species identifier does not identify a strain.
Experimental Context & Analytical Limits:
Section 3.1 identifies natural high-purity arsenopyrite from Yaogangxian, Hunan, China, with XRF composition Fe1.00As0.99S0.97 and reported impurities Si 0.132%, Co 0.034% and Ni 0.062%. Wet-milled particles were over 90% below 74 micrometres; separate cut cubes were approximately 15 by 15 by 5 mm. Cultures were subcultured for three months with 10 g/L arsenopyrite. The stated cultivation setup was a 250 mL flask containing 100 mL 9K medium plus 15 mL inoculum, shaken at 160 rpm and 30 degrees C, with initial pH 1.8 adjusted using approximately 3 M sulfuric acid. Section 3.2 says bioleaching used the same conditions and 10 g/L FeAsS particles; the 100 mL medium and added inoculum should not be silently rewritten as a confirmed 100 mL final working volume. The 9K recipe contained 44.8 g/L FeSO4.7H2O, 3.0 g/L (NH4)2SO4, 0.50 g/L K2HPO4.3H2O, 0.1 g/L KCl, 0.5 g/L MgSO4.7H2O and 0.01 g/L Ca(NO3)2.4H2O. Particle observations extend to approximately day 23 in Figure 1a; cube morphology was examined at 36 h, 120 h and 8 days. The source does not identify the strain, initial inoculum cell density, explicit replicate number or definition of the plotted error bars. These are laboratory assays, without isolated arsenic product, measured gold recovery or industrial deployment.
Section 3.1 identifies natural high-purity arsenopyrite from Yaogangxian, Hunan, China, with XRF composition Fe1.00As0.99S0.97 and reported impurities Si 0.132%, Co 0.034% and Ni 0.062%. Wet-milled particles were over 90% below 74 micrometres; separate cut cubes were approximately 15 by 15 by 5 mm. Cultures were subcultured for three months with 10 g/L arsenopyrite. The stated cultivation setup was a 250 mL flask containing 100 mL 9K medium plus 15 mL inoculum, shaken at 160 rpm and 30 degrees C, with initial pH 1.8 adjusted using approximately 3 M sulfuric acid. Section 3.2 says bioleaching used the same conditions and 10 g/L FeAsS particles; the 100 mL medium and added inoculum should not be silently rewritten as a confirmed 100 mL final working volume. The 9K recipe contained 44.8 g/L FeSO4.7H2O, 3.0 g/L (NH4)2SO4, 0.50 g/L K2HPO4.3H2O, 0.1 g/L KCl, 0.5 g/L MgSO4.7H2O and 0.01 g/L Ca(NO3)2.4H2O. Particle observations extend to approximately day 23 in Figure 1a; cube morphology was examined at 36 h, 120 h and 8 days. The source does not identify the strain, initial inoculum cell density, explicit replicate number or definition of the plotted error bars. These are laboratory assays, without isolated arsenic product, measured gold recovery or industrial deployment.
Curated Evidence Points:
Support
Source:
liu2019
Sections 3.3 and 4.1.1 and Figure 1a report arsenic measured by ICP-AES and an As leaching ratio of 30.4%, corresponding to reported total dissolved As of 1.3 g/L after 19 days, followed by a plateau. This percentage is the authors' As leaching ratio, not a measured percentage of the whole mineral destroyed or a recovered-product yield. A calculation formula and sampling-volume correction are not given, so no independent mass-normalized yield is reconstructed. The plotted time course supports the plateau; its earlier rate is not treated as an exact constant even though the prose calls it nearly linear.
Partial
Source:
liu2019
Figures 1b-1d show an early increase in suspended cell count and Fe(III), depletion of Fe(II), an initial pH rise followed by decline, and changing solution potential reported versus SHE. The medium already supplied substantial iron, so dissolved iron cannot be assigned solely to the mineral. No uninoculated or matched-pH kinetic series is presented. These observations are compatible with the authors' ferric-regeneration model but do not quantify the microbial increment above abiotic dissolution or prove a particular enzymatic mineral-attack pathway.
Support
Source:
liu2019
Sections 3.2-3.3 and 4.1.2 and Figure 2 identify arsenopyrite and newly detected realgar, orpiment, elemental sulfur and jarosite in washed particle residues by XRD and Rietveld quantitative phase analysis. Figure 2b shows relative phase weight fractions in the recovered solids, not an absolute arsenic balance or dissolution percentage. The paper writes realgar as As2S2; that source notation does not supply a separate mineral identifier. Jarosite becomes prominent later, while early arsenic/sulfur phases decline in relative abundance. Secondary-solid formation prevents equating arsenic in solution with total oxidative destruction of FeAsS.
Partial
Source:
liu2019
Figures 4-5 and Table 1 distinguish a dense surface film on polished cubes at 36 and 120 h from loose, porous jarosite-like deposits at 8 days. EDS spots on the dense film were enriched in As and S relative to Fe compared with the underlying mineral. Together with the separate particle XRD results, the authors infer an early realgar/orpiment/sulfur-rich passivating film; EDS alone does not identify those molecular phases or establish each phase's causal contribution. The source attributes visible film cracks to drying. Cubes were polished, ultrasonically cleaned in alternating 5 M HCl, methanol and water baths, then fixed, rinsed and dehydrated after incubation. This preparation and the different particle/cube geometries limit direct quantitative transfer between assays.
Partial
Source:
liu2019
Section 4.2 argues that the later porous jarosite overlayer is unlikely to be the principal passivating film in this particular system. Section 4.1.1 first notes that the nearly linear As release lacks an obvious kinetic sign of passivation, then infers inhibition from its weak response to increasing cell numbers and ferric iron. The early-film interpretation is therefore retained as proposed, not proven by a selective removal experiment. Figure 3 and Table 2 are thermodynamic predictions and possible reactions, calculated at 25 degrees C and 1 atm rather than the 30-degree culture temperature. The authors explicitly note disagreement between equilibrium predictions and early residue phases. No universal passivating role of jarosite, sulfur or an arsenic phase is asserted.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. PDF page 15, Arsenopyrite row, FeAsS, status A and 1962 s.p.; page 1 column definitions. The special-procedure year is not a fabricated mineral accession.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-11) -
liu2019: Liu, Li, Zhang, Yang, Xu and Jiang (2019). Formation Process of the Passivating Products from Arsenopyrite Bioleaching by Acidithiobacillus ferrooxidans in 9K Culture Medium. Metals 9(12), 1320. Complete publisher PDF and XML; sections 2-4, Figures 1-6, Tables 1-2 and Appendix A.
https://doi.org/10.3390/met9121320 (accessed 2026-10-11) -
ncbi_ferrooxidans: NCBI Taxonomy 920, Acidithiobacillus ferrooxidans, species-level entry. The source does not supply an experimental strain accession.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=920&mode=info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T19:47:29+00:00 |
codex (GPT-6; codex) | CREATE | Created arsenopyrite mineral identity and laboratory arsenic-release evidence, retaining proposed passivation, absent matched abiotic control, medium iron, assay-geometry and relative-phase limitations. |
Record source: data/records/arsenopyrite.yaml