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Hureaulite mineral

Hureaulite is the manganese(II) hydrogen phosphate hydrate mineral with current IMA formula Mn2+5(PO3OH)2(PO4)2(H2O)4. The September 2026 list records renamed status, 2007 s.p.; this is not a new-species approval number. Natural material can contain iron and other substitutions. Garcia Guajardo et al. (2024) prepared a synthetic manganese phosphate assigned to monoclinic C2/c hureaulite by powder diffraction and vibrational spectroscopy, then tested composite electrodes made from that powder. The synthetic reagent-derived material is distinguished from mined natural hureaulite, from lithiophilite and from a merely hureaulite-like phase. Its laboratory charge-storage behavior is not microbial transformation, extraction of manganese from ore, recovery of an isolated metal product or industrial deployment. Charge-partition and proton-transfer explanations are model-based interpretations, and the exact redox reaction remains unresolved. No constituent-element criticality is inherited.

Microbial & Biochemical Mechanisms (2)

Abiotic preparation of a hureaulite-assigned manganese phosphate

other

A reagent solution containing manganese chloride, sodium dodecyl sulfate and potassium hydrogen phosphate produced a filtered, washed powder assigned to hureaulite. Diffraction and Raman/FTIR support the assignment, without a quantified phase-purity fraction or isolated-product yield.

Experimental Context & Analytical Limits:
Garcia2024 section 2.1, page 2: a 5 wt% sodium dodecyl sulfate solution received MnCl2·4H2O to a nominal SDS/Mn molar ratio of 1.8. It was held at 70 degrees C for one hour before dropwise K2HPO4 addition to a nominal Mn/K2HPO4 molar ratio of 1, followed by 24 hours at 70 degrees C. Solids were filtered, washed repeatedly with water and acetone and dried at room temperature. Absolute reagent amounts, solution volume, reaction pH, yield and independent batch replication are not reported. No matched preparation without surfactant is shown, so a causal morphology benefit of SDS is not independently established.
Curated Evidence Points:
Section 2.1 and Figures 1a and 2, pages 2 and 4-5, show the synthesis, reference-pattern comparison to JCPDS 01-076-0804 and vibrational spectra. Figure 2a shows interconnected plates; the reported approximately 40 nm thickness is a morphological estimate, not a whole-particle diameter or measured size distribution.
Figure S1, page 1, supports the reported low specific surface area context; the main text reports approximately 4 m2/g. The acquired supplement does not supply a quantitative phase refinement, elemental mass balance or a surfactant-free morphology control.

Laboratory charge storage in composite electrodes containing synthetic hureaulite

other

Composite electrodes exhibited electrolyte- and scan-rate-dependent charge storage. The authors interpret voltammogram deconvolution as electric double-layer, pseudocapacitive and diffusion-dependent contributions and propose proton transfer coupled to possible manganese redox. The measurements establish electrochemical response, not direct proof of ion occupancy, a specific oxidation-state pathway or unchanged post-cycling mineralogy.

Experimental Context & Analytical Limits:
Garcia2024 section 2.3, pages 2-3: active powder/carbon black/PTFE mass ratio 70:20:10, ethanol-assisted films approximately 100 micrometres thick pressed on a stainless-steel grid at 1 GPa, reported active-material loading 7 mg/cm2. Three-electrode measurements used a Pt counter electrode and Hg/HgO reference in alkaline electrolytes or Ag/AgCl in neutral electrolytes. A separate symmetric two-electrode Swagelok cell used a fiberglass separator wetted with 0.5 mL 5 M KOH. Active-material-normalized results exclude the mass of the binder, conductive additive and complete device. Electrode blank subtraction, independent replicate counts and uncertainty intervals are not established in the inspected report. The different electrolytes change several factors together and are not a matched pH-only causal test.
Curated Evidence Points:
Figure 3c and Results pages 6-8 report 184 F/g at 5 mV/s in 3 M KOH versus 16 and 15 F/g in 5 M LiNO3 and 1 M Na2SO4, respectively. In 3 M KOH the value declines to about 100 F/g at 100 mV/s. These are active-material-normalized three-electrode capacitances, not metal recovery yields or complete-device energy densities. Figure 8d and text page 15 show capacitance loss in both two- and three-electrode cells over 5000 cycles; no universal stability or industrial service-life claim is made.
Figures S2-S4 show rate-dependent voltammograms, and the methods on pages 3-4 explain the fitted charge partitions plotted in Figures S5-S12 and main Figures 4-7. These mathematical partitions and the one-electron assumption in the page-11 active-thickness calculation do not independently identify the diffusing ion or prove the proposed Grotthuss/Mn2+-Mn3+ reaction. No post-cycling phase analysis or dissolved-manganese balance is provided in the accepted main/SI.
Table 1, page 9, labels the K3PO4 comparison as 1 M, whereas methods and Figures 3 and 6 use 3 M. Equations 2-3, page 3, label energy in Wh/kg and time in seconds but do not display the required time-unit conversion; exact energy/power values and cross-material superiority are not adopted. The manuscript itself says a specific faradaic reaction is difficult to assign (pages 14-15).
Page 11 gives inconsistent specific-surface-area units between the active-thickness and areal-capacitance definitions. Figure S13 labels the horizontal axis versus Ag/AgCl while describing the two-electrode Swagelok device. These unresolved source labels preclude treating the modelled active depth or device reference potential as independently verified measurements.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Hureaulite row, PDF page 97, Mn2+5(PO3OH)2(PO4)2(H2O)4, Rn, 2007 s.p.; status definitions page 1.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. handbook_hureaulite: Handbook of Mineralogy. Hureaulite. Complete one-page entry; natural Fe-bearing chemistry and monoclinic identity, with C2/c cell data explicitly labelled synthetic.
    https://www.handbookofmineralogy.org/pdfs/hureaulite.pdf (accessed 2026-10-15)
  3. garcia2024: Garcia Guajardo CI, Zuniga Martinez JA, Berlanga Perez R, Lopez Pavon LA, Lucio Porto R (2024). Synthesis of Hureaulite Mn5(H2O)4(PO3OH)2(PO4)2 with an Open 3D Network Structure as Electrode Material for Electrochemical Capacitors. Processes 12:1622. Complete eighteen-page publisher original and JATS; methods sections 2.1-2.3 pages 2-3, Figures 1-8 and Table 1 inspected.
    https://doi.org/10.3390/pr12081622 (accessed 2026-10-15)
  4. garcia2024_si: Official supplementary ZIP containing processes-3073306-supplementary.pdf, eleven pages. All Figures S1-S13, Trasatti-Dunn method pages 3-4 and active-thickness/areal-capacitance equations page 11 inspected.
    https://mdpi-res.com/d_attachment/processes/processes-12-01622/article_deploy/processes-12-01622-s001.zip (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T13:56:06.161852Z codex (GPT-6; codex) CREATE Added a distinct mineral identity from primary evidence and authority checks, preserving natural versus synthetic material scope, source conflicts and limits; no microbial or inherited criticality claim.

Record source: data/records/hureaulite.yaml