Fluorite mineral
Fluorite is the calcium fluoride mineral CaF2, listed with grandfathered status G in the IMA-CNMNC September 2026 mineral list. Its original-description year is unresolved in that list; no numbered approval accession is asserted. The Handbook of Mineralogy describes cubic fluorite and natural hydrothermal, sedimentary and igneous occurrences. This mineral owner is distinct from the traded fluorspar commodity and elemental fluorine. The experiments below use ground natural crystals reported as 99% CaF2 and concern bacterial-cell-associated flocculation and settling. They establish neither mineral dissolution nor production of a specified fluorspar grade. No criticality designation is inherited from the commodity or element, and no industrial deployment is claimed.
Microbial & Biochemical Mechanisms (1)
Bacterial-cell-associated flocculation and settling of fluorite particles
separation
Microbial
Associated Organisms:
Corynebacterium xerosis (NCBITaxon:1725)
Washed bacterial suspensions increased aggregation and settling of fine fluorite particles in laboratory jar tests. Optical microscopy and opposite surface-charge signs are consistent with cell adhesion and bridging, the authors' proposed explanation. The experiments do not isolate a molecular adhesin, extracellular polymer, enzyme or metabolic requirement. Cell viability was not established during flocculation, and microbial involvement here does not imply growth or dissolution of the mineral during the assay.
Experimental Context & Analytical Limits:
Haas et al. used natural crystals reported as 99% CaF2 from an unnamed mining company in Criciuma, Santa Catarina, Brazil. Laboratory grinding gave the Table 1 size distribution, with a reported median about 12.5 micrometres; no specimen accession, experimental XRD or detailed impurity assay is supplied. The source names Corynebacterium xerosis from Caroline Biological Supply Company, USA, without a strain number or sequence. Cells were cultivated for 72 h in nutrient broth in continuously shaken 300 mL flasks at 37 degrees C, centrifuged, washed twice in distilled water, suspended at 2 g/L and stored at 5 degrees C for use within 48 h. These cultivation conditions do not specify the physical jar-test temperature. Jar tests used 1000 mL suspensions at 10 g/L fluorite, 1 min stirring at 250 rpm, then 2 min at 50 rpm and gravity settling. Samples were withdrawn 10 cm below the water surface at specified settling times. The time and dosage series used pH 7.0 +/- 0.2; a separate series varied pH. No matched killed-cell, cell-free culture-supernatant or extracellular-polymer control is described. Jar-test replication and uncertainty are not specified in the 1999 paper; its 20-reading averages concern electrophoretic measurements, not 20 replicated settling tests.
Haas et al. used natural crystals reported as 99% CaF2 from an unnamed mining company in Criciuma, Santa Catarina, Brazil. Laboratory grinding gave the Table 1 size distribution, with a reported median about 12.5 micrometres; no specimen accession, experimental XRD or detailed impurity assay is supplied. The source names Corynebacterium xerosis from Caroline Biological Supply Company, USA, without a strain number or sequence. Cells were cultivated for 72 h in nutrient broth in continuously shaken 300 mL flasks at 37 degrees C, centrifuged, washed twice in distilled water, suspended at 2 g/L and stored at 5 degrees C for use within 48 h. These cultivation conditions do not specify the physical jar-test temperature. Jar tests used 1000 mL suspensions at 10 g/L fluorite, 1 min stirring at 250 rpm, then 2 min at 50 rpm and gravity settling. Samples were withdrawn 10 cm below the water surface at specified settling times. The time and dosage series used pH 7.0 +/- 0.2; a separate series varied pH. No matched killed-cell, cell-free culture-supernatant or extracellular-polymer control is described. Jar-test replication and uncertainty are not specified in the 1999 paper; its 20-reading averages concern electrophoretic measurements, not 20 replicated settling tests.
Curated Evidence Points:
Support
Source:
haas1999
Figures 1-3 show aggregated particles with cells, faster removal of suspended solids from the sampling level and lower residual turbidity than the no-flocculant comparison. Control particles also settle, increasingly with time. Solids were measured gravimetrically; page 226 defines efficiency as 100 times (initial minus final suspension solids concentration) divided by initial concentration. This sampling-level depletion is neither dissolved-fluoride removal nor an isolated mineral mass yield, impurity separation or product-grade measurement.
Partial
Source:
haas1999
Figures 4-5 support dosage and pH dependence, with high settling efficiency near neutral pH. The Results prose reports about 96% removal at 40 mg/L cells after 1 min and no improvement above that dosage, whereas Figure 4 visibly continues rising toward a plateau at higher plotted concentrations. An exact universal 40 mg/L optimum or 96% outcome is therefore not adopted. Figure 3's with-cell and no-cell traces also begin at different plotted turbidity levels; the prose's 130-to-20 NTU reduction is not treated as a shared measured baseline.
Partial
Source:
haas1999
Figure 6 and the Methods show negative cell and positive fluorite zeta potentials near pH 7 in a separate 1 mmol/L NaNO3 measurement medium. These signs are compatible with electrostatic association but do not establish its exclusive causal role. The favorable pH interval is an empirical suspension result, not proof of selective separation of fluorite from gangue or a cell-specific chemical reaction.
Support
Source:
rigo2002
The later study compares cells with three commercial polymers and a no-flocculant control using 1000 mL, 10 g/L suspensions initially at pH 6.0 +/- 0.5, the same stated stirring sequence and sampling after 1 min of settling. Cells were prepared similarly, but the 2 g/L stock is explicitly on a dry basis and was used within 24 h. Table 1 reports three replicates as mean and standard deviation: 40 mg/L cells gave 97.3 +/- 0.2% solids removal, versus 12.2 +/- 2.1% without flocculant. Corresponding residual turbidities were 33 +/- 16.2 and 99 +/- 1.4 NTU; equilibrium pH values were 7.30 +/- 0.10 and 6.85 +/- 0.06. Thus the endpoints were not pH-matched, and the reported suspension-solids removal is not a dissolved metal extraction or purified fluorite yield.
Partial
Source:
rigo2002
Table 1 uses 2 mg/L for each polymer: anionic Nalco 9915 gave 99.2 +/- 0.7% solids removal and 31 +/- 1.7 NTU, cationic Nalco 8589 gave 96.6 +/- 1.6% and 43 +/- 12.4 NTU, and nonionic Nalco 4032 gave 50.3 +/- 3.8% and 88 +/- 1.6 NTU. Efficient settling therefore did not require bacterial cells. The authors describe larger bacterial flocs but more variable residual turbidity and unattached cells remaining in water; these observations do not establish microbial superiority. The cell dosage exceeds the polymer dosage, and the source explicitly calls for future large-scale production research. No industrial competitiveness, deployment or recovery rate is inferred from these bench comparisons.
Context_only
Source:
rigo2002
The later article cites the 1999 study and uses overlapping authorship, commercial culture provenance and source region. It is a separate stated comparison, not an independent-laboratory replication or proof of a newly sampled mineral lot. Its official HTML gives the grinding cutoff as 37 mm alongside 400# Tyler, an unresolved unit inconsistency; no corrected size distribution is reconstructed. Neither study measures mineral dissolution, fluoride speciation, cell viability during settling or the composition of an isolated product.
Context_only
Source:
ncbi_xerosis
Taxon 1725 identifies the currently named species. Neither paper provides an accession that links its experimental stock to the NCBI type strain or a genome, so species mapping does not authenticate the culture or establish strain-level causality.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Definitions on PDF page 1; Fluorite row on page 75: CaF2, G, original year shown as a question mark, country unknown. Fresh issuing-site original inspected.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-12) -
handbook_fluorite: Handbook of Mineralogy, Fluorite, CaF2. Complete one-page original, version 1, copyright 2001-2005. Natural occurrence and cubic identity; its reference powder pattern is explicitly synthetic.
https://handbookofmineralogy.org/pdfs/fluorite.pdf (accessed 2026-10-12) -
haas1999: Haas SR, Nascimento FR, Schneider IAH and Gaylarde C (1999). Flocculation of fine fluorite particles with Corynebacterium xerosis. Revista de Microbiologia 30(3), 225-230. DOI 10.1590/S0001-37141999000300007. Complete six-page original PDF, all six figures, Table 1 and efficiency equation inspected and cross-checked with official SciELO full text; no separate supplement identified in the inspected article and official inventory.
https://doi.org/10.1590/S0001-37141999000300007 (accessed 2026-10-12) -
rigo2002: Rigo LN, Pinto AM, Denardin ND and Schneider IAH (2002). Flocculation of fine fluorite particles with Corynebacterium xerosis and commercial long chain polymers. Brazilian Journal of Microbiology 33(4), 331-332. DOI 10.1590/S1517-83822002000400010. Complete official SciELO HTML and its original Table 1 graphic inspected; local PDF acquisition failed, so print-layout inspection is not claimed. No separate supplement identified in the official full-text inventory.
https://doi.org/10.1590/S1517-83822002000400010 (accessed 2026-10-12) -
ncbi_xerosis: NCBI Taxonomy, taxon 1725, Corynebacterium xerosis, species. The mapping does not authenticate the unnumbered commercial cultures used by Haas et al. or Rigo et al.; no type-strain ID is substituted.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=1725&mode=Info (accessed 2026-10-12)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-12T14:46:58.159293Z |
codex (GPT-6; codex) | create | Added the fluorite mineral owner and qualified cell-associated settling evidence from complete primary sources. Retained polymer and no-cell comparisons, denominator and source conflicts, taxon/phase/scale limits, and separation from the fluorspar commodity. |
Record source: data/records/fluorite.yaml