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Inyoite mineral

Inyoite is the CaB3O3(OH)5(H2O)3·H2O species in the September 2026 IMA-CNMNC list, with grandfathered status G and original-description year 1914, not a sequential approval identifier. Schaller's 1916 original investigation distinguishes glassy inyoite cores from meyerhofferite alteration products in specimens from Mount Blanco near Death Valley, California. Its small 0.1037-g inyoite analysis did not directly determine boron. The modern pressure experiment below concerns a separate museum crystal, not those historical specimens. Inyoite is distinct from borax, tincalconite, kernite, ulexite, colemanite and the borates commodity. Inyoite-II is the authors' experimental high-pressure phase label, not a second asserted IMA-approved natural mineral. No commodity criticality or microbial activity is inherited.

Microbial & Biochemical Mechanisms (1)

Pressure-induced transition of a natural inyoite crystal

other

In-situ single-crystal diffraction detected an abrupt volume decrease and a changed diffraction pattern under increasing pressure, assigned to inyoite-II. The high-pressure atomic structure remained unresolved, and return to the starting crystalline phase was not demonstrated.

Experimental Context & Analytical Limits:
A specimen supplied by the University of Milan Museum of Mineralogy was first checked by single-crystal X-ray diffraction. Its collection locality and a new quantitative chemical analysis were not reported. One approximately 20 x 15 x 10 micrometre crystal was compressed in a membrane-driven diamond-anvil cell at ESRF ID15B, with helium as the pressure medium and ruby pressure calibration with stated uncertainty of 0.05 GPa. Deposited CIFs specify approximately 293 K. This is an abiotic laboratory diffraction experiment; it does not test ore processing, biological action, boron recovery or concrete performance.
Curated Evidence Points:
Methods pp. 3-4, Results pp. 4-6, Table 1 and Figures 2-3 bracket the transition between 8.25(5) and 8.86(5) GPa. Table 1 gives respective volumes 824.75(6) and 762(2) cubic angstroms, an approximately 7.6% decrease across these sampled pressures, not a directly measured equilibrium transition pressure. The authors describe the high-pressure phase as metrically monoclinic, with diffraction extinctions suggesting preservation of P21/n.
Pages 4-5 report too few sufficiently intense reflections to solve the high-pressure structure. Pages 7-9 infer low-pressure deformation from refined non-hydrogen positions and oxygen-oxygen distances; hydrogen sites were not located. Increasing boron coordination from three to four at the transition is an analogy-based hypothesis, not a solved inyoite-II structure. Page 7 reports that repeated attempts to collect diffraction at ambient pressure after decompression found no reflections. This does not establish a reversible cycle, a recovered crystalline product or its phase yield.
Supplementary Table S1 and the 12 CIFs cover only the starting polymorph from ambient pressure through 8.25(5) GPa; no inyoite-II structure is supplied. The manuscript abstract says the experiment reached 19.80(5) GPa, whereas Table 1 ends at 18.91(5) GPa and the body states 18.9 GPa. At 2.00(5) GPa, manuscript Table 1 prints 944.0(1) cubic angstroms, while the matching deposited CIF gives 923.96(11). These discrepancies are retained rather than silently repairing the source or treating all listed values as one reconciled pressure-volume dataset. Deposited model contents are not an independent chemical assay or replication.
Context_only Source: schaller1916
Pages 35-40 and Plates I-II infer natural alteration from glassy inyoite cores surrounded by fibrous or prismatic meyerhofferite. They do not constitute a controlled observation of the high-pressure transition or establish its natural occurrence. The Mount Blanco locality in this original source differs from the Kramer locality attributed to Schaller in the 2022 introduction; neither determines the unreported provenance of the 2022 experimental specimen.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026: PDF page 102, Inyoite row; pages 1-2, status and original-description definitions.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. schaller1916: Schaller (1916), Inyoite and meyerhofferite, two new calcium borates, U.S. Geological Survey Bulletin 610, pp. 35-55: original specimens, locality, chemical-analysis limitations and inferred alteration, pp. 35-40 and Plates I-II.
    https://pubs.usgs.gov/bul/0610/report.pdf (accessed 2026-10-15)
  3. comboni2022: Comboni et al. (2022), High-pressure behaviour and atomic-scale deformation mechanisms in inyoite, CaB3O3(OH)5·4H2O, Physics and Chemistry of Minerals 49, 4, DOI 10.1007/s00269-021-01173-3. Open institutional accepted manuscript labelled Revision_1, Methods and Results pp. 3-9, Figures 1-5 and Tables 1-5.
    https://air.unimi.it/bitstream/2434/898884/6/inyoite_15-12-2021_revision_1.pdf (accessed 2026-10-15)
  4. comboni2022_deposits: Comboni et al. (2022), official article and linked supplementary file 1 (Table S1 and strain information) and files 2-13 (12 CIFs). Publisher-linked supplements were acquired and inspected separately from the institutional manuscript; the version-of-record PDF was not acquired.
    https://doi.org/10.1007/s00269-021-01173-3 (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T21:20:37.453689Z codex (GPT-6; codex) CREATE Created a distinct inyoite species record with historical natural identity and an abiotic pressure transition, retaining unsolved structure, decompression and source-data limitations.

Record source: data/records/inyoite.yaml