Parasymplesite mineral
Parasymplesite is the monoclinic ferrous arsenate mineral Fe(II)3(AsO4)2·8H2O, a vivianite-group species dimorphous with symplesite. The September 2026 IMA list records grandfathered status G and historical year 1954, not a numbered approval proposal. It is distinct from ferric arsenate scorodite, phosphate vivianite, dissolved arsenic and the arsenate-bearing ferrihydrite precursor. The laboratory observation below assigns parasymplesite to mixed solids after bacterial reduction; it does not establish a pure natural-mineral product or an arsenic recovery yield. No constituent criticality designation is inherited.
Microbial & Biochemical Mechanisms (1)
Parasymplesite-assigned precipitation during arsenate-bearing ferrihydrite bioreduction
biomineralization
Microbial
Associated Organisms:
Citrobacter sp. (NCBITaxon:1896336)
Citrobacter sp. JH012-1, reported from a Shayang aquifer in Hubei, China, reduced iron in laboratory arsenate-loaded ferrihydrite incubations. Post-reaction powder diffraction assigned parasymplesite in the arsenate-bearing, no-added-calcium arm (As-Fh), consistent with secondary ferrous arsenate precipitation during bioreduction. The study compared unloaded ferrihydrite and calcium-preloaded arsenate-bearing ferrihydrite (As-Ca-Fh). It also measured aqueous arsenic release and reduction, so precipitation is not evidence that the treatment eliminated arsenic mobilization. The phase assignment, iron assays and microscopy belong to one experiment, not independent demonstrations of mineral-specific recovery.
Experimental Context & Analytical Limits:
Methods 2.1-2.4 describe washed cells in 200 mL anaerobic minimal salt medium in 250-mL bottles, nitrogen purging for over 30 min, 32 degrees C, 200 rpm and pH 7.5 buffered with 30 mM Bis-Tris. The medium contains 0.6 g/L glucose and 0.5 g/L yeast extract; KH2PO4 is printed as 0.027 mg/L. The inoculum is inconsistently described as 5% bacterial suspension and as 2 mL concentrated cells added to 200 mL medium; these descriptions are not reconciled. Precursors were prepared from 10 mM ferrihydrite and 2 mM arsenate at pH 7.5 for 96 h; the calcium arm first contacted 5 mM CaCl2 for 30 min. The bioreduction assay specifies a 3 mM precursor dosage. Experiments were in triplicate, with three parallel bottles sampled at each time point and their recovered mineral powders pooled for characterization after centrifugation and vacuum drying. Time courses extend to about 21 days, but the exact harvest time of the displayed post-reaction diffraction and microscopy specimens is not separately specified. Figures 5 and 7 include sterile solution-chemistry comparators; no matched sterile post-reaction diffraction trace is displayed to establish that microbial activity was necessary for this particular phase.
Methods 2.1-2.4 describe washed cells in 200 mL anaerobic minimal salt medium in 250-mL bottles, nitrogen purging for over 30 min, 32 degrees C, 200 rpm and pH 7.5 buffered with 30 mM Bis-Tris. The medium contains 0.6 g/L glucose and 0.5 g/L yeast extract; KH2PO4 is printed as 0.027 mg/L. The inoculum is inconsistently described as 5% bacterial suspension and as 2 mL concentrated cells added to 200 mL medium; these descriptions are not reconciled. Precursors were prepared from 10 mM ferrihydrite and 2 mM arsenate at pH 7.5 for 96 h; the calcium arm first contacted 5 mM CaCl2 for 30 min. The bioreduction assay specifies a 3 mM precursor dosage. Experiments were in triplicate, with three parallel bottles sampled at each time point and their recovered mineral powders pooled for characterization after centrifugation and vacuum drying. Time courses extend to about 21 days, but the exact harvest time of the displayed post-reaction diffraction and microscopy specimens is not separately specified. Figures 5 and 7 include sterile solution-chemistry comparators; no matched sterile post-reaction diffraction trace is displayed to establish that microbial activity was necessary for this particular phase.
Curated Evidence Points:
Support
Source:
chen2022
Results 3.3 and Figure 5d, page 8, identify multiple reflections in the As-Fh post-reaction trace using the parasymplesite reference pattern PDF 35-0461. Figure 1a shows the initial precursors as poorly ordered two-line ferrihydrite. Figure 6a shows strip-like products in reacted As-Fh, whereas Figure 6b shows the calcium-bearing comparator without those conspicuous strips. This supports the authors' secondary-phase assignment in a bacterial incubation, without identifying every observed particle as parasymplesite.
Partial
Source:
chen2022
Results 3.3 acknowledges unidentified diffraction peaks. No refined phase fraction, pure-product isolation, crystal-specific ferrous arsenate composition or direct hydration determination is supplied. The elemental maps in Figure 6c-f belong to the As-Ca-Fh comparator, not an isolated parasymplesite crystal. Methods 2.6 describes both cobalt radiation and a copper target; the radiation setting is unresolved. Vacuum drying may affect hydrated solids, and the wet-culture hydration state was not measured. Sterile iron-release controls support a biological effect on reduction, but do not exclude abiotic precipitation from biologically generated Fe(II).
Partial
Source:
chen2022
The Abstract and Results 3.3 assign 29.35% solid-associated Fe(II) to As-Fh and 12.30% to As-Ca-Fh. Figure 5c instead places the higher endpoint on squares and the lower one on circles, while its caption assigns squares to As-Ca-Fh and circles to As-Fh. This unresolved arm-label contradiction prevents using those percentages as an independently resolved calcium effect. The percentages concern solid-associated Fe(II) relative to solid-phase total iron, not parasymplesite abundance, arsenic recovery or initial-feed conversion. Figure 5d's explicitly labelled diffraction traces provide the narrower phase evidence.
Partial
Source:
chen2022
Figure 7 records dissolved arsenic and increasing As(III), including arsenic release in sterile comparators; mineral formation therefore coexists with mobilization. The 5.0 and 8.8 mg/L values discussed for the two inoculated arsenic arms refer to early release, not terminal removal yields. XPS proportions in Figure 7c-d characterize sampled surfaces, not a bulk mineral mass balance. The proposed calcium competition for Fe(II) retention is a mechanistic interpretation, not a demonstrated exclusive pathway. The reported arrA/arsC presence lacks gene-accession, expression or knockout evidence in this paper; MZ227386.1 verifies only the reported partial 16S sequence. No isolated arsenic product, long-term retention, field remediation performance or industrial deployment is established.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Parasymplesite row, PDF page 166, and status definitions on pages 1-2. Retained original bytes inspected and official URL checked live.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
handbook_parasymplesite: Handbook of Mineralogy. Parasymplesite, version 1, 2001-2005. Complete one-page entry: ideal composition, monoclinic structure, vivianite-group placement and dimorphism with symplesite.
https://www.handbookofmineralogy.org/pdfs/parasymplesite.pdf (accessed 2026-10-14) -
chen2022: Chen, Xie, Yang, Gao and Wang (2022). Effects of Calcium on Arsenate Adsorption and Arsenate/Iron Bioreduction of Ferrihydrite in Stimulated Groundwater. International Journal of Environmental Research and Public Health 19(6), 3465. DOI 10.3390/ijerph19063465. Complete fourteen-page original and official full-text XML inspected; Methods 2.1-2.7, Figures 1-7, Tables 1-2 and Discussion 4.
https://doi.org/10.3390/ijerph19063465 (accessed 2026-10-14) -
genbank_jh012_1: GenBank MZ227386.1. Citrobacter sp. strain JH012-1 16S ribosomal RNA gene, partial sequence. Current XML explicitly records strain JH012-1 and taxon 1896336; this is not an arrA or arsC accession.
https://www.ncbi.nlm.nih.gov/nuccore/MZ227386.1 (accessed 2026-10-14) -
ncbi_citrobacter_sp: NCBI Taxonomy, taxon 1896336, Citrobacter sp., current database rank species under unclassified Citrobacter. This unresolved species-level label does not identify a named species or a strain-specific taxon.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=1896336 (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T22:54:55.896022+00:00 |
codex (GPT-6; codex) | CREATE | Added authority-grounded parasymplesite identity and qualified bacterial ferrihydrite-transformation phase assignment, preserving mixed products, conflicting source arm labels and methods, arsenic mobilization and unresolved phase-specific recovery. |
Record source: data/records/parasymplesite.yaml