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Hydromagnesite mineral

Hydromagnesite is the hydrated magnesium carbonate mineral species Mg5(CO3)4(OH)2(H2O)4. The September 2026 IMA-CNMNC list gives grandfathered status and original-description year 1828, not an IMA approval number. It is distinct from dypingite, nesquehonite, elemental magnesium and the magnesite commodity. The culture evidence concerns a reported component of mixed carbonate products, not magnesium metal or a purified hydromagnesite commodity; constituent criticality is not inherited.

Microbial & Biochemical Mechanisms (1)

Hydromagnesite assigned in aerobic halophile culture precipitates

biomineralization Microbial

The study reports hydromagnesite among mixed mineral products from separate aerobic halophilic bacterial cultures on calcium- and magnesium-amended agar. Medium-dependent phase identification supports culture-associated formation, with source reporting and control limits retained.

Experimental Context & Analytical Limits:
Separate surface-inoculated cultures from a panel reported as 21 moderately halophilic bacterial strains, predominantly historical Halomonas labels plus Marinomonas, Marinobacter, Chromohalobacter and Salibacillus, were incubated aerobically at 30 degrees C for up to 30 days. These were separate strain cultures, not one mixed consortium. The agar medium contained 1% yeast extract, 0.5% proteose peptone, 0.1% glucose, 3.5% NaCl (all weight/volume), and 20 g/L Bacto-Agar, initially adjusted to pH 7.2 with 0.1 M KOH. Calcium and magnesium were supplied as acetate salts. End-point surface pH was measured with indicator paper. Uninoculated and dead-cell controls were described for all experiments. Solids were scraped, washed with distilled water and dried at 37 degrees C before XRD and SEM-EDX; unchanged morphology after washing does not establish unchanged phase hydration. Table 1 spans initial calcium 5.7-22 mM and magnesium 18.7-187 mM across C1-C12. Table 3 assigns hydromagnesite to C1-C6, C8, C9 and C12, but not C7, C10 or C11; the latter are reported as high-magnesium calcite only.
Curated Evidence Points:
Sections 2.3-2.4 and Table 3 report XRD-based hydromagnesite assignments in mixed products. Figure 1C depicts hydromagnesite associated with dolomite in C4; Figure 1F labels a hydromagnesite spherulite from C12 with an Mg-bearing EDX spectrum. The figure caption specifies 30-day incubation for analytical material. These are one study and related medium arms, not independent experimental replications.
Section 2.3 describes uninoculated and dead-cell controls; Section 4.1 explicitly reports no precipitation in those controls. However, Section 3 literally states that no precipitates occurred in any culture experiments, contradicting its surrounding positive results. The record retains this source inconsistency and uses the explicit control statement only as a reported result, not an independently tabulated control measurement. Replicate counts, strain-specific phase replicates and quantitative matched-control spectra are not supplied.
The mineral assemblages in Table 3 and Figure 1 are resolved by medium, not by an independently documented strain-to-phase matrix. Table 2 reports only struvite versus carbonate onset, not phase-specific onset times. Methods and Table 2 disagree on strain names/accessions, including H. pantelleriensis DSM 9661 versus DSM 3051 and the presence of H. halmophila versus H. meridiana; H. eurihalina and H. salina also share a printed ATCC 49509. These conflicts are not silently corrected. No exact taxon identifier or claim that every named strain individually forms the target phase is assigned.
Section 3 calls C5 high-magnesium-calcite-only, whereas Table 3 includes hydromagnesite and struvite in C5. Table 2 has struvite-onset entries even in C7/C10/C11, which Table 3 describes as high-magnesium-calcite-only. Table 5 omits hydromagnesite isotope values for C5 and C8 despite its Table 3 phase assignments; absence of an isotope value is not evidence of phase absence. Table 1 gives final pH 8.5 for several arms whereas prose summarizes a rise to 9. No universal phase yield or exact phase-onset timeline is inferred.
XRD phase assignments are reported in Table 3, supported by SEM-EDX morphology/composition, but the article does not display the underlying XRD patterns for this phase. Its mineral percentages are not treated as calibrated product purity or recovered-magnesium yield. Surface alkalinization and organic-matter degradation are compatible with the proposed mechanism, but microsite pH, individual metabolic pathways and a specific molecular nucleator were not directly demonstrated. PHREEQC saturation indices are modeled initial bulk conditions, not measured cell-surface conditions; the model input Na/Cl concentrations also differ from those calculated from the stated NaCl recipe. The experiment does not establish industrial deployment or net atmospheric carbon sequestration.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Pages 1-2 definitions and terms; hydromagnesite page 98, huntite page 97, nesquehonite page 154. Grandfathered description years are not approval identifiers.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14)
  2. sanchez_roman_2011: Sánchez-Román et al. (2011). Aerobic biomineralization of Mg-rich carbonates: Implications for natural environments. Chemical Geology 281:143-150. DOI 10.1016/j.chemgeo.2010.11.020. Sections 2.1-2.6, 3 and 4.1-4.2; Tables 1-6 and Figure 1. Complete original inspected from the University of Granada author-group copy.
    https://doi.org/10.1016/j.chemgeo.2010.11.020 (accessed 2026-10-14)

Curation History

Timestamp Curator Action Summary
2026-10-14T07:24:42.406309+00:00 codex (GPT-6; codex) CREATE Created mineral identity and bounded culture-associated phase evidence from inspected primary originals; retained source contradictions, control limits and distinct material scope.

Record source: data/records/hydromagnesite.yaml