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Ulexite mineral

Ulexite is the NaCaB5O6(OH)6(H2O)5 mineral species in the September 2026 IMA-CNMNC list, with grandfathered status G and original-description year 1850 rather than a sequential approval identifier. It is distinct from elemental boron, the borates commodity, colemanite, borax and tincalconite. Ghose, Wan and Clark refined a natural Boron Mine, California, crystal in triclinic P-1, with isolated pentaborate groups and hydrogen-bonded sodium and calcium coordination polyhedra. The thermal products in the experiment below are explicitly identified phases or diffraction-amorphous material, not additional accepted mineral species. No commodity criticality, microbial activity or industrial recovery claim is inherited.

Microbial & Biochemical Mechanisms (1)

Humidity-driven rehydration of thermally altered natural ulexite

other

A natural ulexite specimen underwent heating-dependent phase changes, followed by partial or diffraction-complete return to ulexite during high-humidity exposure. The outcome depended on the preceding heat treatment; mixed products and an unreversed high-temperature product prevent describing all thermal alteration as reversible.

Experimental Context & Analytical Limits:
Yamaguchi et al. used natural Kramer, California, ulexite purchased from a mineral supplier, ground with acetone in an agate mortar. Approximately 50 mg portions in platinum crucibles were placed in an already heated furnace, held in air for 1 h, then cooled to 20 degrees C in a dry silica-gel desiccator. Treated material was subsequently held at 20 degrees C in a separate sealed desiccator at approximately 100% relative humidity, maintained by tissues wetted with pure water and monitored by a thermo-hygrometer. Synchrotron powder X-ray diffraction compared heat-treated and humidity-exposed material; micrographs provided complementary morphology. The reported 3- and 7-day exposures are discrete observations, not fitted rates or time-resolved completion times. This laboratory protocol contains no microorganisms.
Curated Evidence Points:
Methods p. 2 and Figure 1/p. 3 show that the product prepared at 120 degrees C for 1 h yielded an ulexite diffraction pattern after 3 days in high humidity, with no remaining dehydrated-ulexite reflections reported. This establishes the observed phase change within diffraction sensitivity, not a weighed 100% recovery yield or a shorter unobserved completion time. The separate Figure 2 optical example used 100 degrees C and 7 days and is not the Figure 1 diffraction protocol.
Figures 3-5/pp. 4-6 show that products made at 180, 220 and 500 degrees C were diffraction-amorphous before humidity exposure and developed ulexite plus borax reflections afterward. The 500-degree product had weaker recrystallized peaks; peak heights are not quantitative phase fractions. Figure 6/p. 7 retains both ulexite and the assigned anhydrous NaCaB5O9 phase after hydration of the 600-degree product. The p. 7 experiment reports no change in the CaB2O4 product made at 1000 degrees C after 7 days of high humidity. Probertite was not detected under these conditions.
The proposed dissolution-reprecipitation pathway for amorphous products and inheritance of borate structural units are interpretations, without an elemental mass balance or quantified water uptake in these humidity experiments. The fate of calcium accompanying borax formation remains unresolved; p. 5 discusses possible undetected calcium-rich material alongside a sodium-release statement, without a measured balanced reaction. The 600-degree, 1-h ex situ result is explicitly distinguished on p. 6 from a cited 647-degree thermal-analysis event at 10 degrees C/min. Neither is a universal transition threshold. No isolated boron product, recovery efficiency, controlled humidity series or industrial deployment is demonstrated. Replication and a matched, equal-duration low-humidity comparison are not reported.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026: PDF page 223, Ulexite row; pages 1-2, status and original-description definitions and terms.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. ghose1978: Ghose, Wan and Clark (1978), Ulexite, NaCaB5O6(OH)6·5H2O: structure refinement, polyanion configuration, hydrogen bonding, and fiber optics, American Mineralogist 63, 160-171: specimen and diffraction methods pp. 160-162, Table 1 and structural discussion.
    https://msaweb.org/AmMin/AM63/AM63_160.pdf (accessed 2026-10-15)
  3. yamaguchi2025: Yamaguchi, Okada, Hasegawa and Kyono (2025), Thermal decomposition and reversible transformation of ulexite NaCaB5O6(OH)6·5H2O, Journal of Mineralogical and Petrological Sciences 120:023, DOI 10.2465/jmps.250417. Final published ten-page article, Methods p. 2, Results pp. 3-7 and Figures 1-6; the advance pre-proof is the same study, not a replication.
    https://www.jstage.jst.go.jp/article/jmps/120/1/120_250417/_pdf (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T19:32:02.557646Z codex (GPT-6; codex) CREATE Created IMA-grounded ulexite species identity and bounded abiotic humidity-driven rehydration with mixed products, null results and mechanistic limits.

Record source: data/records/ulexite.yaml