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Roscoelite mineral

Roscoelite is a vanadium-bearing mica mineral with the ideal formula KV3+2(Si3Al)O10(OH)2 in the September 2026 IMA list. The list records status A and the special-procedure entry 1998 s.p.; that entry is not an original discovery year or a conventional numbered approval. Blake's 1876 description concerns natural mica from Granite Creek, El Dorado County, California, and explicitly corrects his initial chromium identification to vanadium. The species is distinct from vanadium as an element, generic vanadium-bearing mica, and mixed shale or ore feeds. Ito's synthetic material was assigned to roscoelite by powder diffraction indexed as a 1M mica; its mixed-valence, nonideal bulk chemistry and microscopic oxide inclusions must not be replaced by the ideal all-V3+ formula. No criticality designation is inherited from vanadium, and neither the natural occurrence nor abiotic synthesis establishes microbial extraction or industrial recovery.

Microbial & Biochemical Mechanisms (1)

Abiotic hydrothermal formation of a roscoelite-assigned mica

other

Ito (1965) produced pale green micaceous material from chemically prepared potassium silicate and vanadium-aluminium silicate starting mixtures in sealed gold capsules. Table 3 assigns roscoelite by X-ray diffraction in seven runs between 300 and 600 degrees C, at the separately tabulated pressures and durations. For example, run 1 used 300 degrees C, 18,000 psi and 48 hours; its powder pattern in Table 6 was indexed assuming a 1M mica structure. These are laboratory synthesis observations, not measurements of extraction from ore or isolated vanadium recovery.

Experimental Context & Analytical Limits:
The general method used coprecipitated gels containing initially V4+, dried below 100 degrees C, in electrically sealed gold tubing 2-5 mm in diameter. No additional water was introduced because the starting materials retained water. The author states that precise atmospheric control was impossible and residual organic matter and ammonium chloride made the intended inert system weakly reducing. The remaining Table 3 runs are 400 degrees C/20,000 psi/25 hours, 450/36,000/48, 500/38,000/48, 500/33,000/48, 500/24,000/24 and 600/35,000/72. These are distinct conditions within one study, not independent replication. Detailed gel proportions, quantitative phase fractions and mass-balanced yields are not reported for these runs. Bulk wet chemistry used a different synthetic sample, run 4, so its valence measurements do not describe every run.
Curated Evidence Points:
Support Source: ito1965
Methods pages 300-301, Table 3 page 304 and Table 6 page 307 support formation of the diffraction-assigned mica under the individually reported synthetic conditions. Table 6 compares synthetic run 1 with published natural powder data; the comparison is identification evidence rather than a fresh experiment on natural ore.
Partial Source: ito1965
Pages 311-312 and Table 8 report wet-chemical V3+/V4+ estimates for synthetic run 4, with oxidation during chemical treatment requiring a correction step. Page 314 notes minute opaque vanadium-oxide spots at some flake fringes despite no other phase being detected by powder X-ray diffraction. Bulk valence is therefore not an unequivocal site-specific mica measurement, and no phase-purity percentage is assigned. The page 314 prose gives a broader 300-700 degrees C and 10,000-40,000 psi synthesis envelope than the seven Table 3 entries; that wider envelope is not treated as additional verified runs. Proposed oxygen-pressure control and natural paragenetic relations were not established by precise atmosphere measurements or reversible equilibrium experiments.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026. Roscoelite row, PDF page 187: KV3+2(Si3Al)O10(OH)2, A, 1998 s.p.; status and special-procedure definitions page 1.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. blake1876: Blake J (1876). On roscoelite, a vanadium mica. American Journal of Science s3-12(67):31-32. Original description: natural locality and morphology page 31; correction of chromium misidentification and incomplete acid extraction page 32.
    https://doi.org/10.2475/ajs.s3-12.67.31 (accessed 2026-10-15)
  3. ito1965: Ito J (1965). Synthesis of vanadium silicates: haradaite, goldmanite and roscoelite. Mineralogical Journal 4(4):299-316. Complete original: precursor and capsule methods pages 300-301; seven roscoelite runs in Table 3 page 304; powder data Table 6 page 307; optical observations Table 7 and Figure 4 pages 310-311; valence assay and composition Table 8 pages 311-312; conflicting synthesis envelope and oxide inclusions page 314.
    https://doi.org/10.2465/minerj1953.4.299 (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T17:15:17.968437Z codex (GPT-6; codex) CREATE Created a distinct roscoelite mineral record with original natural identity and qualified abiotic synthetic evidence, retaining mixed chemistry, microscopic inclusions, uncontrolled atmosphere and source condition discrepancies.

Record source: data/records/roscoelite.yaml