Metavivianite mineral
Metavivianite is the approved mixed-valence iron phosphate mineral species Fe2+Fe3+2(PO4)2(OH)2(H2O)6, IMA 1973-049. It is distinct from vivianite, elemental iron or phosphorus, and an unidentified oxidized iron-phosphate mixture. Laboratory abiotic precipitation provides diffraction-supported formation in a mixed product. A separate bacterial enrichment study proposed a metavivianite-like intermediate without diffraction confirmation; that observation is retained as provisional and does not establish formation of the accepted mineral species. No constituent criticality designation or industrial recovery claim is inherited.
Microbial & Biochemical Mechanisms (2)
Abiotic precipitation of a metavivianite-bearing mixed product
other
Heating an aqueous ferrous sulfate and diammonium hydrogen phosphate reaction produced a precipitate assigned by powder X-ray diffraction to metavivianite together with vivianite and spheniscidite. This is direct chemical synthesis in reagent solution, not microbial precipitation or a pure isolated product.
Experimental Context & Analytical Limits:
Chiba2020 Experimental Procedure, printed pages 485-486, describes 0.60 g (NH4)2HPO4 in 18 mL distilled water and addition of 1.80 g FeSO4.7H2O while stirring at 300 rpm. In the direct hot-solution series, precipitates were filtered after 24 h stirring and dried at 24 degrees C; reaction temperatures are initially listed as 50, 60, 70 and 90 degrees C. The next sentence instead calls the second sample viv-S65, whereas Results, Figure 3 and Table 2 use viv-S60. The 50-60 degrees C assignment follows those results and the conclusion while retaining this unresolved methods-label conflict. The separate dry-heating and water-aging series are not the direct-synthesis arm. Reaction pH, gas atmosphere, direct-series drying duration and replicate count are not reported. No culture or biological reagent is used.
Chiba2020 Experimental Procedure, printed pages 485-486, describes 0.60 g (NH4)2HPO4 in 18 mL distilled water and addition of 1.80 g FeSO4.7H2O while stirring at 300 rpm. In the direct hot-solution series, precipitates were filtered after 24 h stirring and dried at 24 degrees C; reaction temperatures are initially listed as 50, 60, 70 and 90 degrees C. The next sentence instead calls the second sample viv-S65, whereas Results, Figure 3 and Table 2 use viv-S60. The 50-60 degrees C assignment follows those results and the conclusion while retaining this unresolved methods-label conflict. The separate dry-heating and water-aging series are not the direct-synthesis arm. Reaction pH, gas atmosphere, direct-series drying duration and replicate count are not reported. No culture or biological reagent is used.
Curated Evidence Points:
Support
Source:
chiba_2020
Figure 3 and Results on printed page 487 show direct-synthesis patterns compared with calculated vivianite and metavivianite patterns; marked reflections support metavivianite in viv-S50 and viv-S60. Unassigned additional reflections are attributed to co-precipitated spheniscidite. The authors describe a larger metavivianite/vivianite ratio at 60 degrees C but do not report a quantified phase fraction, isolated mass, purity or mineral-specific recovery yield. Figure 4 and Table 2 concern bulk Fe K-edge spectra of mixed samples, not an independent phase-yield assay.
Partial
Source:
chiba_2020
Figures 1-2 and Table 1 separate other outcomes from the direct-synthesis arm. The initially synthesized, partly oxidized vivianite lost crystalline order upon 24 h dry heating to 90 degrees C; the authors assigned an amorphous santabarbaraite-like end product. Water aging at 90 degrees C for 24 h instead produced patterns attributed to a beta-Fe2(PO4)O / Fe4(PO4)3(OH)3 solid solution. Neither sequence showed a metavivianite intermediate. These bounded laboratory comparisons refute an assumption that any vivianite oxidation or color change necessarily forms metavivianite; they do not prove that every possible transient phase was absent.
Bacterial Fe(II) oxidation with a provisional metavivianite-like assignment
redox transformation
Microbial
An unidentified nitrate-reducing, Fe(II)-oxidizing enrichment converted an initially abiotic vivianite-like precipitate through a green mixed-valence iron-phosphate intermediate. Erbs2004 proposed a metavivianite-like phase using spectroscopy, but did not obtain diffraction confirmation. The microbial flag describes the culture-associated oxidation experiment, not verified biological formation of crystalline metavivianite. Direct enzymatic oxidation of solid iron was not isolated from indirect chemical processes.
Experimental Context & Analytical Limits:
Erbs2004 Chapter 2 Sections 2.2.1-2.2.4 and Table 2.1 used a mixed enrichment from town ditches in Bremen, Germany, supplied by K. Straub; no species, accession or culture-collection identifier is given, so no taxon identifier is assigned. Anoxic bicarbonate-buffered mineral medium at pH 7.0 contained 30 mM bicarbonate, 4 mM total phosphate, 4 mM nitrate, trace elements and vitamins, with ammonium omitted. Addition of 10 mM Fe(II) as chloride or sulfate precipitated whitish material before inoculation. Experiments used 50-400 mL butyl-stoppered bottles with a 90% N2/10% CO2 headspace described as 10% of total volume. Less than 1% inoculum from old reddish cultures was added; incubation was in the dark at room temperature with gentle daily agitation. Uninoculated same-medium controls and nitrate-omission cultures were included. The individual iron salt, bottle size and replicate structure are not assigned to every displayed spectrum or time series.
Erbs2004 Chapter 2 Sections 2.2.1-2.2.4 and Table 2.1 used a mixed enrichment from town ditches in Bremen, Germany, supplied by K. Straub; no species, accession or culture-collection identifier is given, so no taxon identifier is assigned. Anoxic bicarbonate-buffered mineral medium at pH 7.0 contained 30 mM bicarbonate, 4 mM total phosphate, 4 mM nitrate, trace elements and vitamins, with ammonium omitted. Addition of 10 mM Fe(II) as chloride or sulfate precipitated whitish material before inoculation. Experiments used 50-400 mL butyl-stoppered bottles with a 90% N2/10% CO2 headspace described as 10% of total volume. Less than 1% inoculum from old reddish cultures was added; incubation was in the dark at room temperature with gentle daily agitation. Uninoculated same-medium controls and nitrate-omission cultures were included. The individual iron salt, bottle size and replicate structure are not assigned to every displayed spectrum or time series.
Curated Evidence Points:
Partial
Source:
erbs_2004
Printed pages 26-34, Figures 2.2-2.8 and Table 2.2 support sequential chemical changes and the author's tentative phase interpretation. Green color appeared within 2-3 days; spectra of light and dark green samples gave Fe(III) relative spectral areas of 26% and 38%, assuming area is proportional to abundance. These are not mineral phase percentages or a measurement of the modern ideal species composition. The thesis explicitly states that poor crystallinity prevented XRD analysis. Color, morphology and iron oxidation alone therefore do not resolve metavivianite versus defective oxidized vivianite or another poorly ordered phosphate. The later reddish material was interpreted as poorly crystalline goethite plus siderite; that mixed endpoint is not a recovered metavivianite product.
Partial
Source:
erbs_2004
Printed pages 34-38 and Figures 2.9-2.10 report incomplete bulk Fe(II) oxidation and no detected oxidation in uninoculated controls or nitrate-omission cultures. Nitrate-omission results are described as data not shown, and assay detection limits and complete replication are not given. Bulk Fe(II) measurements combine solid and dissolved fractions and cannot quantify oxidation of a particular mineral or its recovery. The mixed culture prevented estimation of Fe-oxidizer growth. Proposed solid-state oxidation and explanations for incomplete reaction remain interpretations; no enzyme, nitrite perturbation or complete elemental mass balance establishes the exclusive causal pathway. No industrial deployment is demonstrated.
Context_only
Source:
miot_2009
A different experiment with source-defined strain BoFeN1 provides a counterexample to equating a green microbial iron-phosphate intermediate with metavivianite. Its Methods used 4.4 mM phosphate, 5 mM acetate, 10 mM nitrate and 10 mM added Fe(II), 25 mL cultures in 58 mL bottles, 80% N2/20% CO2, 10% inoculum and 30 degrees C in darkness. XRD Methods on page 375 and Figure 2 on page 377 compare the initial vivianite with predominantly amorphous four-day and one-year products; the four-day pattern does not establish metavivianite. This separate strain/medium study neither reproduces nor directly disproves the Erbs enrichment. The accepted comparison is confined to the main-paper diffraction evidence. Announced Figures S1-S2 and Data S1 were inaccessible in the inspected publisher routes; quantitative XAS fits and microscopic cell-versus-mineral oxidation ratios are not imported here.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. PDF page 143, Metavivianite row; pages 1-2 definitions and distribution terms.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15) -
handbook_metavivianite: Handbook of Mineralogy. Metavivianite, version 1, copyright 2001-2005. Triclinic mineral identity and historical variable formula, which predates the current IMA ideal formula.
https://www.handbookofmineralogy.org/pdfs/metavivianite.pdf (accessed 2026-10-14) -
chiba_2020: Chiba, Takahashi, Ohshima, Kawamata and Sugiyama (2020). The synthesis of metavivianite and the oxidation sequence of vivianite. Journal of Mineralogical and Petrological Sciences 115:485-489. DOI 10.2465/jmps.200417. Full five-page original, Figures 1-4 and Tables 1-2.
https://doi.org/10.2465/jmps.200417 (accessed 2026-10-14) -
erbs_2004: Erbs, Marianne (2004). Formation and redox reactions of green rusts under geochemical conditions found in natural soils and sediments. ETH Zurich dissertation 15492, DOI 10.3929/ethz-a-004796330. Chapter 2, printed pages 17-42 (PDF pages 36-61), especially Methods 22-25, Figures 2.1-2.10 and Tables 2.1-2.2. Full thesis acquired from the public ETH repository API.
https://doi.org/10.3929/ethz-a-004796330 (accessed 2026-10-15) -
miot_2009: Miot, Benzerara, Morin, Bernard, Beyssac, Larquet, Kappler and Guyot (2009). Transformation of vivianite by anaerobic nitrate-reducing iron-oxidizing bacteria. Geobiology 7:373-384. DOI 10.1111/j.1472-4669.2009.00203.x. Full twelve-page author-hosted original; XRD Methods and Figure 2 provide the selected counterexample. Announced supplementary PDF was not acquired.
https://doi.org/10.1111/j.1472-4669.2009.00203.x (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T00:08:32Z |
codex (GPT-6; codex) | CREATE | Created metavivianite mineral identity with mixed abiotic synthesis, provisional culture oxidation and independent diffraction counterexample. |
Record source: data/records/metavivianite.yaml