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Borax mineral

Borax is the Na2B4O5(OH)4(H2O)8 mineral species in the September 2026 IMA-CNMNC list, with grandfathered status G. The list leaves its original description year and original locality unresolved; no sequential IMA approval identifier is assigned here. Its structural formula is equivalent in bulk composition to sodium tetraborate decahydrate, Na2B4O7·10H2O. This species is distinct from elemental boron, the borates commodity, manufactured products sold as borax, tincalconite, kernite and anhydrous sodium tetraborate phases. Nishiyasu and Kyono's thermal experiments characterized commercial reagent and recrystallized material, not a natural ore or an industrial recovery operation. Their borax single-crystal refinements were monoclinic C2/c. No commodity criticality or microbial activity is inherited.

Microbial & Biochemical Mechanisms (1)

Heating-associated transformation of reagent borax to tincalconite

other

In situ powder diffraction observed loss of borax reflections and appearance of tincalconite during heating. The measured temperature behavior depends on the preparation, containment and measurement protocol; it is not a universal natural transition threshold or an isolated boron recovery yield.

Experimental Context & Analytical Limits:
The starting material was guaranteed-reagent-grade sodium tetraborate decahydrate from Fujifilm Wako. Single crystals were recrystallized from saturated aqueous solution at 293 K. For the powder-XRD arm, material was loaded in a 0.7-mm Lindemann capillary with one end fully open, heated in ambient atmosphere from 303 to 473 K in 10-K steps, held 5 min at each temperature before a 3-min synchrotron exposure. A separate single crystal was protected with nitrocellulose adhesive in a capillary and measured from 113 to 323 K in 30-K steps using nitrogen-gas temperature control; its crystallinity was lost at 333 K. These are separate experimental arms, not a continuous single-crystal refinement through the powder phase transition. No organisms were used.
Curated Evidence Points:
Manuscript p. 12 and Figure 2 show borax reflections nearly unchanged through 353 K, weakening above 363 K and no longer observed at 403 K. Reflections assigned to tincalconite appeared above 353 K and persisted weakly to 473 K. The powder patterns establish a phase transformation within diffraction sensitivity; neither peak disappearance nor peak heights provide a weighed conversion fraction, reaction rate or element recovery yield.
Table 1, Figures 4-5 and Supplementary Tables S1-S2 show stronger thermal expansion along b and relatively small B-O bond changes over the separate 113-323 K single-crystal series. The manuscript reports no resolved loss of water/hydroxyl oxygen site occupancy at 323 K within its refinement uncertainty. Proposed persistence of borate structural units through transformation combines these refinements, comparison with earlier tincalconite structures and quantum-chemical calculations; it is not direct time-resolved tracking of individual units or a demonstrated palaeoenvironmental indicator.
The DSC arm used approximately 10 mg each of borax and an alpha-alumina reference, 10 K/min and argon at 50 mL/min. Its Methods p. 7 states a heating endpoint of 323 K, whereas Results p. 12 and Figure 1 report endothermic maxima at 349 and 408 K. This unresolved source inconsistency prevents asserting a fully reconciled DSC temperature program. The authors attribute DSC/XRD differences to open versus semi-open measurement systems. The separate loss of single-crystal diffraction at 333 K is not substituted for the powder transition. Repeated thermal cycles, a matched humidity-control series, quantified boron recovery and industrial deployment were not demonstrated by these experiments.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026: PDF page 28, Borax 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. nishiyasu2024: Nishiyasu and Kyono (2024), Thermal behavior of borax, Na2B4O5(OH)4·8H2O, American Mineralogist 109, 533-539, DOI 10.2138/am-2023-8970. Institutional Revision 1 manuscript: Methods pp. 7-11, Results pp. 12-18, Figures 1-6 pp. 32-37, Table 1 pp. 38-39; associated Supplementary Tables S1-S2 inspected.
    https://tsukuba.repo.nii.ac.jp/records/2010200 (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T20:23:57.642830Z codex (GPT-6; codex) CREATE Created an IMA-grounded borax mineral species record with bounded reagent thermal dehydration and retained DSC protocol inconsistency.

Record source: data/records/borax.yaml