Strengite mineral
Strengite is the orthorhombic ferric phosphate dihydrate mineral Fe3+(PO4)(H2O)2, conventionally FePO4·2H2O. The September 2026 IMA-CNMNC list records grandfathered status G and original-description year 1877, which is not an approval identifier. It is distinct from its monoclinic dimorph phosphosiderite, ferrous phosphate vivianite, amorphous iron phosphate and iron metal. The curated mechanism is an abiotic foundation for phosphate-phase transformation; no microbial mechanism or constituent-derived criticality is assigned.
Microbial & Biochemical Mechanisms (1)
Abiotic crystallization of strengite in a mixed phosphate assemblage
other
An amorphous ferric-phosphate precursor produced a mixed strengite/phosphosiderite assemblage in the 100 degrees C experiment. XRD and microscopy characterize the nine-day solid. Internal disagreements about crystallization timing prevent assignment of a precise onset or completion time; no isolated pure-strengite recovery is established.
Experimental Context & Analytical Limits:
Abiotic batch experiments mixed 5 mL of 0.1 M Fe(NO3)3·9H2O solution with 5 mL of 0.1 M KH2PO4 plus 0.09 M KOH. For the 100 degrees C arm, solutions were preheated to 98 degrees C, mixed in preheated Teflon-lined reactors, sealed immediately and placed in the oven; reactors were shaken three times per day. The reported mixed-fluid pH of about 1.6 was measured at 25 degrees C, not in situ at 100 degrees C. Samples were quenched to 25 degrees C before analysis; solids were centrifuged, washed three times with Milli-Q water and dried at room temperature. There was no inoculated arm, microbial taxon or biological control. This was a laboratory precipitation experiment, not demonstrated industrial phosphorus recovery.
Abiotic batch experiments mixed 5 mL of 0.1 M Fe(NO3)3·9H2O solution with 5 mL of 0.1 M KH2PO4 plus 0.09 M KOH. For the 100 degrees C arm, solutions were preheated to 98 degrees C, mixed in preheated Teflon-lined reactors, sealed immediately and placed in the oven; reactors were shaken three times per day. The reported mixed-fluid pH of about 1.6 was measured at 25 degrees C, not in situ at 100 degrees C. Samples were quenched to 25 degrees C before analysis; solids were centrifuged, washed three times with Milli-Q water and dried at room temperature. There was no inoculated arm, microbial taxon or biological control. This was a laboratory precipitation experiment, not demonstrated industrial phosphorus recovery.
Curated Evidence Points:
Support
Source:
roncal2009
Methods p.5198; Table 1, Figure 2, Section 3.2 and Figures 7–10 support the iron series. Figure 7b XRD and Figure 8a SEM identify both strengite and phosphosiderite in the nine-day, 100 degrees C sample. The 12-hour solids at 50 or 100 degrees C were amorphous; higher-temperature 150/200 degrees C, 12-hour solids were ferric giniite rather than strengite.
Partial
Source:
roncal2009
Section 3 p.5199 says amorphous iron phosphate persisted for at least nine days, whereas Section 3.2 p.5200 says transformation occurred within five days. Table 1 and Figures 2, 7–8 and 10 document a nine-day mixed crystalline product. The record preserves that endpoint without silently choosing an exact crystallization time from the conflicting prose.
Partial
Source:
roncal2009
No refined strengite/phosphosiderite fractions, phase-specific product yield or replicate-based recovery uncertainty are given. Section 3 and Tables 2–3 use measured aqueous concentrations to calculate saturation indices, but the PHREEQC comparison lacked data for phosphosiderite and ferric giniite. Predicted strengite stability does not prove that it was the only or actual phase in every temperature arm. Solution depletion into amorphous precursor is not a strengite-specific recovery yield.
Context_only
Source:
roncal2009_author_copy
The full author-hosted original supplies the inspected graphics and methods. The same paper is reproduced in the thesis; neither reproduction nor the separate aluminum arm curated under variscite is an independent replication of strengite formation.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Definitions pages 1–2 and Strengite row PDF page 207: Fe3+(PO4)(H2O)2, G, 1877. Previously acquired official original re-inspected 14 October 2026.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
handbook_strengite: Handbook of Mineralogy, Strengite, version 1, 2001–2005. Formula, orthorhombic identity and dimorphism with phosphosiderite.
https://www.handbookofmineralogy.org/pdfs/strengite.pdf (accessed 2026-10-14) -
roncal2009: Roncal-Herrero, T.; Rodríguez-Blanco, J. D.; Benning, L. G.; Oelkers, E. H. (2009). Precipitation of Iron and Aluminum Phosphates Directly from Aqueous Solution as a Function of Temperature from 50 to 200 °C. Crystal Growth & Design 9(12):5197–5205. DOI 10.1021/cg900654m. Complete nine-page published original from the coauthor site; Figures 1–10 and Tables 1–5 inspected.
https://doi.org/10.1021/cg900654m (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T14:47:29.470484+00:00 |
codex (GPT-6; codex) | CREATE | Created strengite identity and a qualified abiotic mixed-phase precipitation mechanism from the complete 2009 original; preserved phase, timing, modeling and shared-experiment limitations. |
Record source: data/records/strengite.yaml