Löllingite mineral
Löllingite, commonly written loellingite, is the orthorhombic iron arsenide mineral with ideal formula FeAs2. The September 2026 IMA list records it as grandfathered, with original-description year 1845. It is distinct from arsenopyrite, skutterudite, elemental arsenic and a mixed arsenic-bearing ore. Natural compositions need not be exact endmembers. The accepted microbial experiment concerns a quantified loellingite-arsenopyrite feed mixed with pyrite, not purified loellingite. Its flotation response does not establish dissolved-metal extraction, an isolated loellingite product or industrial deployment. No constituent-element criticality is inherited.
Microbial & Biochemical Mechanisms (1)
Culture- and supernatant-associated flotation of a loellingite-bearing mixture
separation
Microbial
Associated Organisms:
Leptospirillum ferrooxidans (NCBITaxon:180)
Almojadah and Harmer tested living Leptospirillum ferrooxidans DSM 2705 cultures and cell-filtered culture supernatants as modifiers of flotation in a pyrite-arsenopyrite-loellingite mixture. The source reports distinct loellingite phase-partitioning bars and generally depressed flotation of the arsenic-bearing phases under selected treatments. Outcomes depended on culture substrate, conditioning time and chemical collector. The supernatant remained microbial in origin but did not require living cells during flotation; its effects are not proof of a specific purified EPS component or a loellingite-specific metabolic pathway.
Experimental Context & Analytical Limits:
Sections 2.1-2.5 report a supplier-sourced Chinese arsenopyrite/loellingite material assigned by quantitative XRD to about 38.8% arsenopyrite and 60.6% loellingite, with less than 1% other impurities, alongside a Peruvian pyrite material reported as about 97.4% pyrite. The minerals were ground, wet-sized and stored under nitrogen at -80 degrees C. The culture was grown in modified HH medium at pH 1.8, 30 degrees C and 155 rpm, with soluble ferrous sulfate or adaptation to the pyrite or arsenopyrite/ loellingite material. Culture cycles were about 4, 28 and 70 days, respectively. Microflotation used 1 g of a 1:1 mixture of the pyrite and arsenopyrite/loellingite materials, conditioning for 6, 8 or 10 hours in a 100-mL flask at 30 degrees C and 155 rpm. The conditioning liquid volume is not specified. Living-culture arms used 1.5 x 10^7 cells/mL. The reported free-EPS supernatant was prepared from late-exponential mineral cultures by 5-micrometre filtration, centrifugation at 15000 rpm and 0.2-micrometre filtration; it was not purified or dose-standardized by measured EPS composition. Room-temperature flotation in a modified Hallimond tube lasted 5 minutes with 0.4 L/min air, with or without 10^-4 M potassium isopropyl xanthate (PIPX). Abiotic comparisons used HH medium at pH 1.8 or Milli-Q water adjusted to pH 9 without cells or supernatant. All flotation experiments were reported in triplicate with means and standard deviations. Floated and tailing fractions were examined by Rietveld quantitative XRD; full patterns, raw replicate data and an explicit recovery calculation are not supplied in the article.
Sections 2.1-2.5 report a supplier-sourced Chinese arsenopyrite/loellingite material assigned by quantitative XRD to about 38.8% arsenopyrite and 60.6% loellingite, with less than 1% other impurities, alongside a Peruvian pyrite material reported as about 97.4% pyrite. The minerals were ground, wet-sized and stored under nitrogen at -80 degrees C. The culture was grown in modified HH medium at pH 1.8, 30 degrees C and 155 rpm, with soluble ferrous sulfate or adaptation to the pyrite or arsenopyrite/ loellingite material. Culture cycles were about 4, 28 and 70 days, respectively. Microflotation used 1 g of a 1:1 mixture of the pyrite and arsenopyrite/loellingite materials, conditioning for 6, 8 or 10 hours in a 100-mL flask at 30 degrees C and 155 rpm. The conditioning liquid volume is not specified. Living-culture arms used 1.5 x 10^7 cells/mL. The reported free-EPS supernatant was prepared from late-exponential mineral cultures by 5-micrometre filtration, centrifugation at 15000 rpm and 0.2-micrometre filtration; it was not purified or dose-standardized by measured EPS composition. Room-temperature flotation in a modified Hallimond tube lasted 5 minutes with 0.4 L/min air, with or without 10^-4 M potassium isopropyl xanthate (PIPX). Abiotic comparisons used HH medium at pH 1.8 or Milli-Q water adjusted to pH 9 without cells or supernatant. All flotation experiments were reported in triplicate with means and standard deviations. Floated and tailing fractions were examined by Rietveld quantitative XRD; full patterns, raw replicate data and an explicit recovery calculation are not supplied in the article.
Curated Evidence Points:
Support
Source:
almojadah2025
Sections 2.1 and 2.4-2.5, Table 1 and Figures 6-8 (pages 2-3 and 6-8) identify the mixed feed and show separate pyrite, arsenopyrite and loellingite flotation responses. Figure 8b shows strong pyrite flotation with low arsenic-phase flotation after pyrite-grown supernatant plus PIPX; section 3.3.3 reports 92.9% pyrite recovery at 10 hours. That number belongs to pyrite, not loellingite or arsenic extraction. The result supports selective partitioning in this laboratory mixture, not purity or yield of an isolated mineral or metal product.
Partial
Source:
almojadah2025
Figures 6-8 also retain weak or unfavorable arms: alkaline Milli-Q controls produced little flotation, and pyrite-grown living cultures depressed all three minerals. Arsenopyrite/loellingite-grown supernatant with PIPX did not reproduce the strong pyrite separation of pyrite-grown supernatant. The alkaline-water comparison changes both medium chemistry and pH. Filtered supernatants contain more than isolated EPS, and no composition-matched EPS-depleted control is reported. These comparisons do not establish universal biological improvement or identify a single causal biopolymer.
Partial
Source:
almojadah2025
Sections 2.3 and 3.2 and Figures 3-5 compare prepared SEM surfaces: cells/biofilm were more apparent on pyrite at early exposure times, while the arsenopyrite/loellingite material showed appreciable colonization at 72 hours. Individual imaged grains are not assigned independently to loellingite versus arsenopyrite. Fixation, washing, dehydration and coating precede imaging; morphology alone does not establish viability, an enzymatic attack or phase-specific dissolution. Proposed arsenic toxicity and indirect oxidation are interpretations, not isolated causal tests.
Partial
Source:
almojadah2025
Sections 3.4-4, Figures 9-11 and Tables 2-6 compare XPS of two flotation fractions with different culture products, collector addition and exposure times: arsenic-feed-grown culture at 8 hours versus pyrite-grown supernatant with PIPX at 10 hours. Surface composition is not a bulk dissolution measurement and cannot assign a molecular change uniquely to loellingite. Some prose trends also differ from the tables: Table 3's HO-C=O component decreases from 6.9 to 4.4%, and Table 6's elemental-sulfur component from 6.1 to 3.1%, despite statements grouping these components as increased. The component percentages have their own spectral denominators; they are not mineral recoveries. No precise molecular mechanism is accepted from those comparisons.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. PDF page 127, Löllingite row, and page 1 status and year definitions; FeAs2, G, 1845.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15) -
handbook_loellingite: Handbook of Mineralogy. Löllingite, complete one-page entry, version 1 (2001-2005). Orthorhombic identity, natural chemistry and safflorite-series context; the listed Pnnm cell and powder pattern are explicitly synthetic.
https://www.handbookofmineralogy.org/pdfs/lollingite.pdf (accessed 2026-10-15) -
almojadah2025: Almojadah SS and Harmer SL (2025). Separation of arsenopyrite/loellingite and pyrite through bio-flotation by selective attachment of Leptospirillum ferrooxidans. Minerals Engineering 230:109440. Complete 14-page original, sections 2-5, Figures 1-11 and Tables 1-6.
https://doi.org/10.1016/j.mineng.2025.109440 (accessed 2026-10-15) -
almojadah2025_fulltext: Flinders University repository copy of the complete Almojadah and Harmer (2025) publisher original; available online 20 May 2025, volume issue dated September 2025, one experiment lineage.
https://researchnow-admin.flinders.edu.au/ws/portalfiles/portal/159178863/Almojadah_Separation_P2025.pdf (accessed 2026-10-15) -
dsm2705: DSMZ catalogue, Leptospirillum ferrooxidans DSM 2705, type strain L15; aliases ATCC 29047 and VKM B-1339. Collection identity does not establish an independently sequenced culture in the flotation experiment.
https://www.dsmz.de/collection/catalogue/details/culture/DSM-2705 (accessed 2026-10-15) -
ncbi_180: NCBI Taxonomy 180, Leptospirillum ferrooxidans, species rank; DSM 2705 is listed among type-strain aliases. Species-level identifier only.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=180 (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T09:31:14.842906Z |
codex (GPT-6; codex) | CREATE | Added loellingite identity and qualified microbial-culture/supernatant flotation evidence for a characterized mixed feed, retaining null arms, phase-partitioning boundaries and source/protocol uncertainties. |
Record source: data/records/loellingite.yaml