Variscite mineral
Variscite is the orthorhombic hydrated aluminum phosphate mineral Al(PO4)(H2O)2, conventionally AlPO4·2H2O. The September 2026 IMA-CNMNC list records approved status A and 1967 s.p., a special-procedure entry rather than a numbered new-mineral proposal. It is distinct from monoclinic metavariscite, anhydrous berlinite, aluminum metal and mixed phosphate resources. 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 variscite in a mixed phosphate assemblage
other
An amorphous aluminum-phosphate precursor crystallized into a mixed variscite/metavariscite assemblage during heating at 100 degrees C. The characterized 21-day solid contains both polymorphs; the study does not establish an isolated pure-variscite product or a variscite-specific phosphate-removal yield.
Experimental Context & Analytical Limits:
Abiotic batch experiments mixed 5 mL of 0.1 M Al(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 Al(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 1, Section 3.1 and Figures 3–6 identify the aluminum series. XRD Figure 3b and SEM Figure 4a support coexisting variscite and metavariscite after 21 days. The 12-hour solid at 50 or 100 degrees C remained amorphous, and Figure 5 shows an amorphous 100 degrees C specimen after 12 days; a phase was not identified solely from Al/P chemistry.
Partial
Source:
roncal2009
The 150 degrees C, 12-hour solid comprised berlinite and a hydrous aluminum phosphate; the 200 degrees C, 12-hour solid was reported as berlinite. These are different temperature arms, not proof of quantitative conversion of an isolated variscite feed. No refined variscite/metavariscite phase fractions, phase-specific mass balance or replicate-based recovery uncertainty are reported.
Partial
Source:
roncal2009
Tables 2–3 and Section 3.3 distinguish measured aqueous chemistry from PHREEQC saturation calculations. The thermodynamic calculation omitted metavariscite and phosphosiderite because data were unavailable. Near-variscite saturation therefore does not establish exclusive variscite precipitation, pure-phase equilibrium or field control of phosphate. Initial solution depletion into amorphous solids is not a crystalline-variscite yield.
Context_only
Source:
roncal2009_author_copy
Complete original graphics and methods are available in this author-hosted copy. The journal copy and thesis reproduction represent the same experiment, including the distinct iron-phosphate arm curated under strengite.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Definitions pages 1–2 and Variscite row PDF page 227: Al(PO4)(H2O)2, A, 1967 s.p.. 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_variscite: Handbook of Mineralogy, Variscite, version 1, 2001–2005. Formula, orthorhombic identity and dimorphism with metavariscite.
https://www.handbookofmineralogy.org/pdfs/variscite.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 variscite 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/variscite.yaml