Monohydrocalcite mineral
Hydrated calcium carbonate mineral with ideal formula CaCO3·H2O, distinct from anhydrous calcite, vaterite and aragonite, magnesium carbonate minerals, calcium as an element and carbonate-bearing resources. The September 2026 IMA list gives grandfathered status and original-description year 1964, not a new-mineral approval accession. Laboratory phase-selective formation is curated without inheriting criticality from another material or asserting a critical-metal recovery application.
Microbial & Biochemical Mechanisms (1)
Monohydrocalcite in WMS2 calcium-magnesium mineralization cultures
biomineralization
Microbial
Associated Organisms:
Halomonas (NCBITaxon:2745)
The source-designated WMS2 culture, reported as Halomonas utahensis, produced monohydrocalcite in organic calcium-magnesium media, with phase composition dependent on Mg/Ca ratio and sampling time. Powder XRD and Rietveld fits assigned monohydrocalcite as the sole fitted crystalline phase at nominal Mg/Ca 7 after 27 days and Mg/Ca 9 after 14 and 27 days. Both ratios yielded monohydrocalcite/hydromagnesite mixtures at 140 days. These observations do not establish a pure product mass yield, a universally transient intermediate or direct conversion of individually tracked crystals into hydromagnesite. Growth-associated alkalinization, ammonia and carbonic-anhydrase assays support a proposed microbial contribution to carbonate formation, without isolating the causal necessity of each component.
Experimental Context & Analytical Limits:
WMS2 was screened from a saltern and identified by the authors using a 1477-bp 16S sequence and phylogeny. The cited ON000249.1 accession is currently annotated as uncultured Halomonas sp. clone WMS2, an environmental sample, rather than the stated cultured species. Halomonas is therefore used only as genus-level context; no species taxon or authenticated strain identifier is asserted. Section 5.3 specifies beef extract 5 g/L, tryptone 10 g/L, NaCl 30 g/L, KCl 2 g/L and nominal Ca2+ 0.01 M supplied by calcium chloride, with magnesium chloride supplying the Mg2+ series. For the accepted Mg/Ca 7 and 9 arms the stated Mg2+ values are 0.07 and 0.09 M. Into 150 mL of medium the recipe adds 3 mL 1 M Na2CO3 and 5 mL 1 M NaHCO3, then adjusts pH to 7.0 with NaOH/HCl. Experimental groups received 1% bacterial suspension, controls the same volume of sterile water, with three parallel samples per group. The inoculum percentage basis is not explicitly specified in Section 5.3. Growth and salinity assays used 37 degrees C and 120 rpm, but the mineralization subsection does not independently state its incubation temperature or agitation; these settings are not silently transferred. Solids were sampled at 14, 27 and 140 days for ex situ XRD, FTIR and microscopy. Mineral harvest washing/drying conditions are not detailed in Section 5.4. No matched-pH, killed-cell or isolated-enzyme phase-control series is reported. This is a laboratory salt-supplemented medium study, not industrial extraction or a metal-remediation trial.
WMS2 was screened from a saltern and identified by the authors using a 1477-bp 16S sequence and phylogeny. The cited ON000249.1 accession is currently annotated as uncultured Halomonas sp. clone WMS2, an environmental sample, rather than the stated cultured species. Halomonas is therefore used only as genus-level context; no species taxon or authenticated strain identifier is asserted. Section 5.3 specifies beef extract 5 g/L, tryptone 10 g/L, NaCl 30 g/L, KCl 2 g/L and nominal Ca2+ 0.01 M supplied by calcium chloride, with magnesium chloride supplying the Mg2+ series. For the accepted Mg/Ca 7 and 9 arms the stated Mg2+ values are 0.07 and 0.09 M. Into 150 mL of medium the recipe adds 3 mL 1 M Na2CO3 and 5 mL 1 M NaHCO3, then adjusts pH to 7.0 with NaOH/HCl. Experimental groups received 1% bacterial suspension, controls the same volume of sterile water, with three parallel samples per group. The inoculum percentage basis is not explicitly specified in Section 5.3. Growth and salinity assays used 37 degrees C and 120 rpm, but the mineralization subsection does not independently state its incubation temperature or agitation; these settings are not silently transferred. Solids were sampled at 14, 27 and 140 days for ex situ XRD, FTIR and microscopy. Mineral harvest washing/drying conditions are not detailed in Section 5.4. No matched-pH, killed-cell or isolated-enzyme phase-control series is reported. This is a laboratory salt-supplemented medium study, not industrial extraction or a metal-remediation trial.
Curated Evidence Points:
Support
Source:
han2022
Section 2.2, Figure 2 and Table 1 support the specified Mg/Ca 7 and 9 time courses. Section 5.3 gives the mineralization recipe and triplicate sterile-water comparator. Figures 5 and 8 provide complementary morphology and thermal characterization; the selected phase claim is based on diffraction, not shape alone. Figure 1 records separate growth/pH/ammonium/enzyme measurements; their correlation does not prove a uniquely necessary molecular pathway in each mineralization flask.
Support
Source:
han2022_si
Figure S6 panels d2/e1/e2 fit 100% monohydrocalcite among the modeled crystalline phases, while d3/e3 include hydromagnesite. Figure S5 and Table S1 provide FTIR assignments. Figure S4 shows control flasks at 0, 1, 7 and 14 days; it does not supply a 140-day control image or quantitative detection limit. The main text reports no minerals in controls, a broader assertion than this illustrated time window. Fitted percentages are not recovered mineral yields or proof of absence of amorphous material.
Partial
Source:
han2022
Section 5.3 lists the lowest Mg2+ concentration as 0.01 M while Figure 2/Table 1 label the lowest Mg/Ca arm as 0 at Ca2+ 0.01 M; that inconsistency is not repaired by assuming a zero recipe. At Mg/Ca 5 and 140 days, Section 2.3 calls some morphologies MHC, whereas Table 1, Figure 2 and SI Figure S6c3 assign aragonite and hydromagnesite. This disputed arm is not used as proof of MHC persistence. The measured phase series alone cannot distinguish direct solid-state conversion from dissolution and new precipitation. Figure 9's selected ultrathin-section diffraction is interpreted by the authors as intracellular/cell-associated MHC, but does not independently authenticate WMS2 or establish a transport pathway.
Partial
Source:
genbank_wms2
The accession resolves and names WMS2, but its current uncultured-Halomonas clone/environmental-sample annotation does not verify the paper's H. utahensis species and cultured-strain assignment. The experimental phenotype remains explicitly attributed to the source-designated WMS2 material.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; definitions pp. 1-2 and Monohydrocalcite row p. 147, Ca(CO3)·H2O, G, 1964.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
handbook_monohydrocalcite: Handbook of Mineralogy, Monohydrocalcite, CaCO3·H2O; Mineral Data Publishing, version 1, 2001-2005. Mineral identity.
https://www.handbookofmineralogy.org/pdfs/monohydrocalcite.pdf (accessed 2026-10-14) -
han2022: Han et al. (2022). Mineralogy of Bioprecipitate Evolution over Induction Times Mediated by Halophilic Bacteria under Various Mg/Ca Molar Ratios. ACS Omega 7(34):29755-29772. Sections 2-5, Tables 1-2 and Figures 1-10; complete primary JATS text and original figure images in PMC9435042.
https://doi.org/10.1021/acsomega.2c02443 (accessed 2026-10-14) -
han2022_si: Han et al. (2022), supporting information to DOI 10.1021/acsomega.2c02443; 19-page ao2c02443_si_001.pdf, Tables S1-S5 and Figures S1-S12. Control photographs Figure S4 p. S11 and Rietveld fits Figure S6 p. S13.
https://doi.org/10.1021/acsomega.2c02443.s001 (accessed 2026-10-14) -
ncbi_halomonas: NCBI Taxonomy 2745, Halomonas, genus. Parent-rank context only for the source-designated WMS2 culture, not confirmation of its species or strain.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=2745&mode=Info (accessed 2026-10-14) -
genbank_wms2: GenBank ON000249.1, Uncultured Halomonas sp. clone WMS2 16S ribosomal RNA gene, partial sequence; environmental sample, taxon 173971. This current accession annotation differs from the paper's cultured Halomonas utahensis WMS2 assignment.
https://www.ncbi.nlm.nih.gov/nuccore/ON000249.1 (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T13:15:30Z |
codex (GPT-6; codex) | CREATE | Created mineral identity and WMS2 monohydrocalcite formation mechanism; retained genus-only grounding, accession conflict, source recipe and phase contradictions, control and incubation-method limits. |
Record source: data/records/monohydrocalcite.yaml