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Rivadavite mineral

Rivadavite is the approved sodium-magnesium borate mineral Na6Mg[B6O7(OH)6]4·10H2O, IMA1966-010, in the September 2026 IMA-CNMNC list. Hurlbut and Aristarain's 1967 original study described natural nodular crystal aggregates embedded in borax at Tincalayu, Argentina, with wet chemistry, morphology and diffraction evidence. Its historical Na6MgB24O40·22H2O formula expresses the same total elemental inventory as the current formula, but does not resolve the modern OH/water partition. The authors distinguished measured density 1.905(2) g/cm3 from calculated density 1.910 g/cm3 and reported P21/m from diffraction, etching and negative pyroelectric tests. Their unexplained small extinction angle remained a qualification. The later 1973 atomic-structure note was verified at the publisher only as metadata; its full text was not acquired, so no atomic model or revised lattice parameters are adopted from it. This species is distinct from associated borax, kernite, elemental boron and the borates commodity; criticality, microbial activity and industrial recovery are not inferred.

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Identifiers & Classification

System Identifier Label
IMA IMA:1966-010 Rivadavite

Microbial & Biochemical Mechanisms (1)

Rivadavite other Laboratory thermal alteration of natur

Laboratory thermal alteration of natural rivadavite

other

The natural mineral became amorphous during laboratory heating and later formed a crystalline substance before fusion. Separate isothermal holds released different fractions of its water inventory. This demonstrates program-dependent thermal alteration, without establishing a chemically identified recovered boron product.

Experimental Context & Analytical Limits:
The 1967 study examined natural Tincalayu aggregates. Figure 5 specifies differential thermal analysis at 20 degrees C per minute, a Pt/Pt-13%Rh thermocouple, zero-degree reference junction and Al2O3 reference. Atmosphere, thermal sample mass and replicate count are not reported. Optical freedom from impurities was described for material used in chemical analysis; it is not a quantitative purity assay for every thermal aliquot. Separate holds at 110 degrees C for 24 hours and 300 degrees C for 30 minutes are distinct from the rapid DTA program and from Table 4's 95-degree, 24-hour H2O-minus determination. No microorganisms, processing pilot or isolated boron product were tested.
Curated Evidence Points:
Pages 333-334 and Figure 5 report major endotherms at 218, 632 and 797 degrees C and an exotherm at 672 degrees C. The first endotherm accompanied amorphization; continuous heating beyond the exotherm but below melting produced crystals described by optical properties and selected powder spacings. The final endotherm was attributed to fusion. The printed first temperature is 218 degrees C; an OCR rendering of 278 is not adopted.
The authors interpreted the first major endotherm as structural-water loss and the second as OH loss; a minor 97-degree feature may represent adsorbed water. These assignments were not established by evolved-gas analysis. Page 334 reports 45 percent of the water lost in 24 hours at 110 degrees C and 90 percent in 30 minutes at 300 degrees C. These percentages refer to water, not total mineral mass or extracted boron; weighing protocol and uncertainty are unspecified. The same page calls the latter loss nearly all the water. Product chemistry and recovery yield remain unresolved despite the supplied optical and diffraction observations.

Sources & References

  1. ima_2026_09: IMA-CNMNC, The New IMA List of Minerals, September 2026, PDF page 186, Rivadavite row: Na6Mg[B6O7(OH)6]4·10H2O, status A, approval 1966-010; page 1, field definitions. Current official landing page and dated PDF checked 16 October 2026. The row's second-reference volume 69 conflicts with the 1973 publisher metadata, which gives volume 60, page 350; this bibliographic discrepancy does not change the verified species approval number.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-16)
  2. hurlbut_aristarain1967: Hurlbut and Aristarain (1967), Rivadavite, Na6MgB24O40·22H2O, a new borate from Argentina, American Mineralogist 52, 326-335. Complete ten-page original inspected: occurrence pp. 326-328; diffraction and etching pp. 329-330; Tables 1-3 pp. 330-332; chemical analysis Table 4 and thermal Figure 5 p. 333; thermal results and comparison Figure 6 p. 334. Table 2 prints b=0.010 whereas the abstract gives 8.010 angstrom; no new cell model is derived from this mismatch.
    https://msaweb.org/AmMin/AM52/AM52_326.pdf (accessed 2026-10-16)
  3. dal_negro1973_metadata: Dal Negro, Ungaretti and Sabelli (1973), Crystal structure of rivadavite, Naturwissenschaften 60(7), 350, DOI 10.1007/BF00599902. Publisher landing metadata and Crossref verified. The PDF endpoint returned subscription preview HTML rather than a PDF; this source supplies bibliographic context only, not inspected atomic-model evidence.
    https://doi.org/10.1007/BF00599902 (accessed 2026-10-16)

Curation History

Timestamp Curator Action Summary
2026-10-16T09:20:43Z codex create Created a rivadavite species record from current IMA identity and the complete 1967 original, with bounded thermal observations and explicit later-structure access, bibliographic and water-loss limits.

Record source: data/records/rivadavite.yaml