Bassanite mineral
Bassanite is the grandfathered calcium sulfate hemihydrate mineral, Ca(SO4)·0.5H2O, distinct from gypsum, anhydrite, manufactured plaster specifications and mixed sulfate residues. Natural mineral identity is established separately from laboratory phase assignments. The evidence here concerns mixed precipitates obtained with extracted bacterial extracellular polymers or from saline bacterial cultures. It establishes neither an isolated bassanite product yield nor an industrial recovery process.
Microbial & Biochemical Mechanisms (2)
Mixed sulfate formation with extracted bacterial extracellular polymers
biomineralization
Microbial
Al Disi2023 detected bassanite together with anhydrite in processed precipitates from evaporating synthetic saline solutions containing extracted EPS from source-designated Virgibacillus DF112 or DF2141. The microbial flag denotes the bacterial origin of the extracted material; the evaporation assay did not require growing cultures. The proposed effects of EPS on calcium binding and local water activity were not directly established.
Experimental Context & Analytical Limits:
Sections 2.1–2.3 describe five-day cultures at 35 degrees C, followed by centrifugation, ethanol precipitation, dialysis and freeze drying of EPS. The main comparison used 50 mg dry EPS in 50 mL synthetic solution formulated to represent 3.16-times evaporated seawater, in open 100 mL bottles at 35 degrees C for 5–6 days, in triplicate. Controls omitted EPS or used EPS from two other source-designated Bacillus cultures. Recovered material was centrifuged, washed with distilled water and air-dried at 40 degrees C before analysis. Thus the final diffraction pattern is not an in-situ measurement of exactly when the phase formed. The comparator called Bacillus cereus has conflicting strain labels Z27 in section 2.1, S27 in Results/Table 1, and S7D1 in Figure 2; these are not silently equated or assigned a verified strain identifier. This is a laboratory preparation study.
Sections 2.1–2.3 describe five-day cultures at 35 degrees C, followed by centrifugation, ethanol precipitation, dialysis and freeze drying of EPS. The main comparison used 50 mg dry EPS in 50 mL synthetic solution formulated to represent 3.16-times evaporated seawater, in open 100 mL bottles at 35 degrees C for 5–6 days, in triplicate. Controls omitted EPS or used EPS from two other source-designated Bacillus cultures. Recovered material was centrifuged, washed with distilled water and air-dried at 40 degrees C before analysis. Thus the final diffraction pattern is not an in-situ measurement of exactly when the phase formed. The comparator called Bacillus cereus has conflicting strain labels Z27 in section 2.1, S27 in Results/Table 1, and S7D1 in Figure 2; these are not silently equated or assigned a verified strain identifier. This is a laboratory preparation study.
Curated Evidence Points:
Support
Source:
aldisi2023
Original Figure 2A and Table 1 identify a bassanite/anhydrite mixture for DF112 and DF2141 EPS. The no-EPS comparison is reported as gypsum; the other EPS comparisons retain mainly gypsum with minor bassanite. These are semiquantitative phase proportions in processed mixed solids, not isolated bassanite recovery percentages. Figure 1 EDS supplies elemental context and cannot alone distinguish sulfate hydrates.
Partial
Source:
aldisi2023
Figure 3 and page 4 show additional gypsum reflections after suspending 0.2 g of DF2141-derived mixed precipitate in 5 mL water for seven days at 30 degrees C. Remaining bassanite/anhydrite reflections preclude a complete-conversion claim. The comparison does not demonstrate that EPS was quantitatively removed from the original solids. Higher EPS-dose experiments also contain calcite; their different phase mixture is not a pure bassanite optimization. Neither a phase-specific mass balance nor measured local water activity is supplied, and strain-label/workup uncertainties remain.
Context_only
Source:
ima_2026_09
The Bassanite row establishes the mineral species and formula, not the purity of any experimental precipitate or criticality.
Context_only
Source:
allen1953
Pages 1266–1268 identify bassanite-bearing natural drill-core material separately from synthetic laboratory products. The reported mineral proportions are calculated using assumptions about gypsum and celestite impurities; they are not a modern directly measured phase-purity certification.
Context_only
Source:
handbook_bassanite
The identity entry distinguishes the hemihydrate formula and natural occurrence from synthetic crystallographic measurements. Neither this reference nor the mineral name establishes a microbial origin for natural bassanite.
Bassanite assignment in precipitates from nutrient-amended saline cultures
biomineralization
Microbial
Silva-Castro2015 assigned bassanite and gypsum to mixed precipitates collected from bacterial cultures on nutrient-amended desalination brine agar. This is a culture-associated end-product observation, not strain-resolved proof of direct bassanite nucleation or a quantitative calcium recovery process.
Experimental Context & Analytical Limits:
Sections 2.1–2.5 describe six isolates, M1–M3 from Mediterranean seawater and S1–S3 from Ibiza desalination brine. The solid SM1–SM6 assays used real brine with the differing yeast extract, protease peptone and glucose recipes in Table 1, 18 g/L agar, initial pH 7.2, and medium autoclaving at 112 degrees C for 20 minutes. Aerobic cultures were incubated at 25 degrees C for 30 days. The authors state triplicate experiments repeated three times and both uninoculated and autoclaved-cell controls. Partial 16S matches range from 89 to 99 percent in Table 3; source species labels are therefore not treated as verified identities of every isolate, and no strain CURIE is assigned. The main paper refers mineralogical preparation to an earlier method that was not acquired; an unmeasured workup contribution to hydrate identity cannot be excluded.
Sections 2.1–2.5 describe six isolates, M1–M3 from Mediterranean seawater and S1–S3 from Ibiza desalination brine. The solid SM1–SM6 assays used real brine with the differing yeast extract, protease peptone and glucose recipes in Table 1, 18 g/L agar, initial pH 7.2, and medium autoclaving at 112 degrees C for 20 minutes. Aerobic cultures were incubated at 25 degrees C for 30 days. The authors state triplicate experiments repeated three times and both uninoculated and autoclaved-cell controls. Partial 16S matches range from 89 to 99 percent in Table 3; source species labels are therefore not treated as verified identities of every isolate, and no strain CURIE is assigned. The main paper refers mineralogical preparation to an earlier method that was not acquired; an unmeasured workup contribution to hydrate identity cannot be excluded.
Curated Evidence Points:
Partial
Source:
silvacastro2015
Original Figure 3 labels bassanite features in the solid-medium series, while Table 5 reports mixed-phase estimates by medium rather than separately resolved isolate/replicate outcomes. Its last two rows are both labelled SM5, so no corrected SM6 percentage is inferred. The text reports no precipitation in uninoculated controls, but equivalent phase-resolved control diffractograms are not provided in Figure 3. Figure 5 shows sulfate-bearing morphologies and elemental spectra without mineralized cells on the sulfate surfaces; carbonate-cell images are not evidence for a bassanite-specific nucleation mechanism. Liquid-culture carbonate results and calcium-depletion values are not assigned to this solid-medium sulfate experiment.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Definitions on PDF page 1 and Bassanite row on page 21; grandfathered species, Ca(SO4)·0.5H2O. The 1910 entry is a historical year, not an approval CURIE.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15) -
allen1953: Allen and Kramer (1953). Occurrence of bassanite in two desert basins in southeastern California. American Mineralogist 38:1266–1268. Complete three-page original; natural drill-core specimens, optical properties, chemical analysis and discussion of possible drilling artifacts.
https://msaweb.org/AmMin/AM38/AM38_1266.pdf (accessed 2026-10-15) -
handbook_bassanite: Handbook of Mineralogy. Bassanite. Complete one-page identity entry, copyright 2001–2005, including natural occurrence and synthetic diffraction.
https://www.handbookofmineralogy.org/pdfs/bassanite.pdf (accessed 2026-10-15) -
aldisi2023: Al Disi et al. (2023). Microbially influenced formation of anhydrite at low temperature. Science of the Total Environment 902:165820. Complete five-page original from the University of Basel repository; sections 2.1–2.3, Figures 1–3 and Table 1 include bassanite-containing mixed precipitates and a rehydration comparison.
https://doi.org/10.1016/j.scitotenv.2023.165820 (accessed 2026-10-15) -
silvacastro2015: Silva-Castro et al. (2015). Bioprecipitation of Calcium Carbonate Crystals by Bacteria Isolated from Saline Environments Grown in Culture Media Amended with Seawater and Real Brine. BioMed Research International 2015:816102. Complete PMC full text and original Figures 3 and 5; sections 2.1–2.5, Tables 1, 3 and 5, and Results describe sulfate phases as well as carbonate phases.
https://doi.org/10.1155/2015/816102 (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T13:59:12.901818+00:00 |
codex (GPT-6; codex) | CREATE | Created bassanite mineral identity with qualified extracted-bacterial-EPS and saline-culture mixed-phase observations; retained source contradictions and absence of isolated-product recovery evidence. |
2026-10-15T14:04:57.272496+00:00 |
Codex (GPT-6; codex) | EDIT | Corrected the Al Disi 2023 source description to five pages after independent review F1; scientific claims remain unchanged. |
Record source: data/records/bassanite.yaml