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Szomolnokite mineral

Szomolnokite is the monoclinic ferrous sulfate monohydrate mineral, Fe(II)(SO4)·H2O, distinct from tetrahydrate rozenite and heptahydrate melanterite. The September 2026 IMA list recognizes it as a grandfathered species. The accepted laboratory experiment follows diffraction-assigned szomolnokite as a transient product during heating of a natural melanterite-rich powder. The same experiment supports the separate rozenite record; these records do not constitute independent experimental replication. Phase fractions and thermal mass losses are not isolated mineral recovery yields, and no microbial transformation is established.

Microbial & Biochemical Mechanisms (1)

Szomolnokite intermediate during heating of melanterite-rich powder

other

In situ powder diffraction identified poorly crystalline szomolnokite during dehydration of the mixed melanterite-rozenite starting material, followed by declining szomolnokite and increasing basic ferric sulfate, FeOHSO4. The 100-degree-C pattern contained weak, broadened szomolnokite peaks; only FeOHSO4 was identified at 200 degrees C. The paper's descriptions of the onset and disappearance intervals differ and are retained as limitations rather than a unique stability threshold.

Experimental Context & Analytical Limits:
Lacalamita et al., Methods on PDF page 3: natural Fornovolasco mine material from Tuscany, Italy, was ground in an agate mortar and placed on a corundum holder. Air-XRPD covered 25-775 degrees C in 25-degree steps with 5 min equilibration. The stated scan range was 10-82 degrees 2theta, step 0.0263 degrees and counting time 257 s/step. The initial refinement was 78 wt% melanterite and 22 wt% rozenite. About 50% RH is mentioned for the initial room-temperature-to-50-degree transition; a complete controlled humidity history is not supplied. No pure szomolnokite starting feed, independent heating replicate count, inoculum, microbial control, isolated product mass or mineral recovery yield is reported.
Curated Evidence Points:
Section 3.2 on PDF pages 5-6, Figures 2-3 and Figure 7 on page 9 identify the phases and refined weight fractions. Discussion on pages 10-12 describes weak, broadened szomolnokite peaks at 100 degrees C and its replacement by FeOHSO4. Figure 7 retains nonzero szomolnokite between 100 and 200 degrees C; section 3.2 identifies only FeOHSO4 in the 200-degree pattern. These are diffraction-phase observations in a changing mixture, not a mass-balanced extraction or recovery experiment.
Section 3.2 on page 5 introduces szomolnokite and FeOHSO4 from 100 degrees C, whereas page 10 identifies a szomolnokite peak at 75 degrees C. The infrared discussion on page 12 associates szomolnokite disappearance with 100-150 degrees C, whereas Figure 7 and the reaction scheme extend its loss toward 200 degrees C. These differing descriptions are unresolved. The nitrogen TG/DTA run used about 13 mg and 10 degrees C/min; its approximately 260-degree event is not interchangeable with the air-XRPD 200-degree endpoint. Infrared pellet effects and detector saturation are described on pages 3 and 12.
Discussion on pages 11-12 proposes oxidation of FeSO4·H2O to FeOHSO4 using atmospheric oxygen. An additional melanterite sample heated to 300 degrees C in nitrogen yielded a mixture assigned to szomolnokite and FeOHSO4; this qualitative comparison does not isolate oxygen uptake or establish every reaction step. The alternative anhydrous-FeSO4 route reported in earlier work was not observed in this natural-sample experiment. No universal reaction pathway or microbial cause is inferred.

Sources & References

  1. ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026; Szomolnokite row on PDF page 210 and field definitions on pages 1-2. Fe(SO4)(H2O), status G, 1891; the historical year is not a new-mineral accession.
    https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-15)
  2. handbook: Handbook of Mineralogy. Szomolnokite, version 1 (2001-2005), complete one-page entry. Ferrous sulfate monohydrate, monoclinic kieserite-group mineral; synthetic diffraction measurements are distinguished from natural-specimen chemistry.
    https://handbookofmineralogy.org/pdfs/szomolnokite.pdf (accessed 2026-10-15)
  3. lacalamita2021: Lacalamita, M., Ventruti, G., Della Ventura, G., Radica, F., Mauro, D. and Schingaro, E. (2021). In Situ High-Temperature X-ray Powder Diffraction and Infrared Spectroscopic Study of Melanterite, FeSO4·7H2O. Minerals 11(4), 392. DOI 10.3390/min11040392. Complete 15-page original, Table 1 and Figures 1-9 inspected.
    https://doi.org/10.3390/min11040392 (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T16:16:29Z codex (GPT-6; codex) CREATE Created the ferrous-sulfate-monohydrate species record from dated authorities and the complete shared melanterite-heating study, retaining mixed starting phases, temperature-description conflicts and absence of microbial or recovery evidence.

Record source: data/records/szomolnokite.yaml