Metacinnabar mineral
Metacinnabar is the cubic mercury sulfide mineral beta-HgS, distinct from trigonal cinnabar, hypercinnabar, elemental mercury and unspecified Hg-S precipitates. The September 2026 IMA list gives grandfathered status and original-description year 1870, not a unique approval accession. The curated experiment concerns mercury mobilization and reduction from mineral feed, not microbial formation of this species or a purified recovery product. No mercury or selenium criticality designation is inherited.
Microbial & Biochemical Mechanisms (1)
Coupled chemical and bacterial mobilization and reduction of mineral-hosted mercury
redox transformation
Microbial
Associated Organisms:
Thiobacillus thioparus (NCBITaxon:931)
Axenic Thiobacillus thioparus ATCC 8158 incubations with source-assigned metacinnabar produced more volatile mercury than killed-cell or no-mineral controls. Sulfate production supports a contribution from microbial sulfur oxidation, while thiosulfate also promoted chemical dissolution. The results support coupled mobilization and Hg(II) reduction under these conditions, without establishing an exclusive molecular pathway or direct cellular attack on a pure mineral phase.
Experimental Context & Analytical Limits:
Laboratory aerobic, dark, unshaken incubations at room temperature in 100 mL serum vials used pH-7-buffered freshwater medium and 2 g/L ground natural museum metacinnabar, sieved below 250 micrometres and autoclaved under nitrogen. The natural specimen contains pyritic inclusions. Cells were pregrown for five days at 30 degrees C with 20 mM thiosulfate, concentrated and inoculated at 1:100; washed zero-added-thiosulfate assays also used 1:50. Residual elemental sulfur was carried with cells, and 40-100 micromolar thiosulfate arms used inoculum carryover rather than a separate addition. A 20 mM arm and a separate daily-spike comparison with commercial synthetic black HgS were also tested. Controls included no mineral, no cells and autoclave- or formaldehyde-killed cells; killed treatments are not chemically identical to living cells. Gold traps and cold-vapor fluorescence measured volatile Hg; cumulative emissions were interpolated from sampled rates. These laboratory transformations and separate field associations are not industrial deployment, detoxification proof or an isolated mercury recovery yield.
Laboratory aerobic, dark, unshaken incubations at room temperature in 100 mL serum vials used pH-7-buffered freshwater medium and 2 g/L ground natural museum metacinnabar, sieved below 250 micrometres and autoclaved under nitrogen. The natural specimen contains pyritic inclusions. Cells were pregrown for five days at 30 degrees C with 20 mM thiosulfate, concentrated and inoculated at 1:100; washed zero-added-thiosulfate assays also used 1:50. Residual elemental sulfur was carried with cells, and 40-100 micromolar thiosulfate arms used inoculum carryover rather than a separate addition. A 20 mM arm and a separate daily-spike comparison with commercial synthetic black HgS were also tested. Controls included no mineral, no cells and autoclave- or formaldehyde-killed cells; killed treatments are not chemically identical to living cells. Gold traps and cold-vapor fluorescence measured volatile Hg; cumulative emissions were interpolated from sampled rates. These laboratory transformations and separate field associations are not industrial deployment, detoxification proof or an isolated mercury recovery yield.
Curated Evidence Points:
Support
Source:
vazquez_rodriguez2015
Pure Culture Incubations and Figures 3-5 show relatively low aqueous Hg with viable cells but higher volatile Hg than killed-cell and no-HgS controls. Figure 5 reports two to four biological replicates, whereas Figures 3-4 use method-duplicate error bars. Aqueous Hg depletion alone therefore is not the evidence for dissolution. Gold-trap emissions, sulfate changes and the controls jointly support the narrower transformation claim.
Partial
Source:
vazquez_rodriguez2015
Table 1 calculates a microbial dissolution contribution from sulfate differences between live-plus-mineral, live-without-mineral and killed-plus-mineral arms after correcting sulfate carryover. Its reported 48-68 percent is a proxy-derived contribution to dissolution, not the fraction of total mineral or mercury recovered. Supplementary Figure S3 shows substantial sulfate production from inoculum sulfur without mineral. Thus sulfur carryover, pyritic inclusions and chemical dissolution limit mineral-specific mass attribution; no complete Hg mass balance or bulk phase-purity measurement is supplied.
Support
Source:
vazquez_rodriguez2015
Figure 4 retains substantial Hg release in killed incubations and the effect of thiosulfate; its panel B separately identifies an EDTA-containing series. Figures 6-7 compare natural and higher-surface-area synthetic material during daily thiosulfate additions and show variable volatile-Hg responses. Methods specify actual spikes of 125-132 micromolar despite the nominal 100 micromolar figure label. These comparisons do not isolate particle size or iron impurity as the cause and do not establish that biology is necessary for dissolution.
Partial
Source:
vazquez_rodriguez2015
Figures 1-2 and Supplementary Figures S1-S2 support the authors' beta-HgS assignment through mineral provenance and local sulfur XANES comparisons, with pyrite present; they are not quantitative whole-feed diffraction or proof of pure metacinnabar after sterilization. Six-week field sections developed sulfur oxidation products and Thiobacillus-rich classified reads. The sterile freshwater comparison in S1 lasted four weeks, and differs from field conditions, so this is an association rather than an isolated field causal test.
Partial
Source:
vazquez_rodriguez2015
The 285-base-pair merA fragment in Supplementary Data S1 establishes genetic potential, not expression, enzyme activity or necessity; no merA mutant or complementation experiment is reported. Main text and Table S3 express cell-normalized rates in attograms, whereas Figure S5 axis/caption says nanograms per cell per day; this unit conflict is left unresolved and no normalized rate is adopted. Table S3 also labels low-thiosulfate scenarios as 40 mM where S4-S5 and the main experiment use 40 micromolar. Its global extrapolation is not curated as an observed environmental flux.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Metacinnabar row, PDF page 141; page 1 defines grandfathered status and description years. Retained complete original rechecked.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
handbook_metacinnabar: Handbook of Mineralogy. Metacinnabar, version 1 (2001-2005), complete one-page entry: cubic HgS crystal data, synthetic powder pattern and distinction from cinnabar and hypercinnabar.
https://www.handbookofmineralogy.org/pdfs/metacinnabar.pdf (accessed 2026-10-14) -
vazquez_rodriguez2015: Vazquez-Rodriguez, Hansel, Zhang, Lamborg, Santelli, Webb and Brooks (2015). Microbial- and thiosulfate-mediated dissolution of mercury sulfide minerals and transformation to gaseous mercury. Frontiers in Microbiology 6:596. Complete 11-page original, Methods, Figures 1-7 and Table 1; official Supplementary Material, 11 PDF pages including cover, Figures S1-S5, Tables S1-S3 and Data S1.
https://doi.org/10.3389/fmicb.2015.00596 (accessed 2026-10-14) -
ncbi_thioparus: NCBI Taxonomy 931. Thiobacillus thioparus, species-rank entry; type material includes ATCC 8158 and DSM 505. Species mapping does not independently authenticate the experimental culture.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=931&mode=Info (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T21:50:30Z |
codex (GPT-6; codex) | CREATE | Created metacinnabar from complete primary and official supplementary evidence for coupled chemical dissolution and microbial mercury reduction, retaining mixed-feed identity, controls, proxy denominators and unresolved source-unit conflicts without recovery or criticality extrapolation. |
Record source: data/records/metacinnabar.yaml