Alkali sulfates with aphthitalite-like structures from fumaroles of the Tolbachik volcano, Kamchatka, Russia. II. A new mineral, natroaphthitalite, and new data on belomarinaite
Bibliographic record
Abstract
ABSTRACT Natroaphthitalite K(Na,K)2Na(SO4)2, a new aphthitalite-group mineral, was found in exhalations of the active Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka Peninsula, Russia. The associated minerals are anhydrite, langbeinite, hematite, tenorite, sanidine, johillerite, tilasite, and belomarinaite. Natroaphthitalite occurs as translucent yellow to colorless roundish single-crystal individuals up to 1 cm in diameter, sometimes combined in crusts up to 2 cm across, and as aqua-transparent colorless tabular to lamellar hexagonal crystals up to 2 mm across, sometimes skeletal, typically combined in parallel intergrowths or brush-like aggregates. Dcalc is 2.664 g/cm3. Natroaphthitalite is optically uniaxial (+), ω = 1.488(2), ε = 1.490(2). The chemical composition (wt.%, electron microprobe) is: Na2O 22.54, K2O 26.39, SO3 51.78, total 100.71. The empirical formula calculated based on 8 O apfu is K1.735Na2.252S2.002O8 (average of 15 spot analyses). The crystal structures of natroaphthitalite and the associated aphthitalite-group mineral belomarinaite, ideally KNaSO4, from the Arsenatnaya fumarole were solved using single-crystal X-ray diffraction and refined to R1 = 0.0283 and 0.0261, respectively. The unit-cell parameters, Z, and space groups are a = 5.6014(3), c = 7.1507(5) Å, V = 194.30(2) Å3, Z = 1, and for natroaphthitalite and a = 5.6088(3), c = 7.1858(4) Å, V = 195.77(1) Å3, Z = 2, and P3m1 for belomarinaite. The crystal chemical formulae of natroaphthitalite and belomarinaite (Z = 1) are XK1.00Y(Na1.28K0.72)Σ2.00MNa1.00(TSO4)2 and XK1.00Y1(Na0.96K0.04)Σ1.00Y2(K0.94Na0.06)Σ1.00MNa1.00(TSO4)2, respectively. Natroaphthitalite is isostructural with aphthitalite K3Na(SO4)2 = XKYK2MNa(TSO4)2 (both have centrosymmetric structures) with prevailing Na over K at the Y site of the crystal structure. Belomarinaite XKY2KY1NaMNa(TSO4)2 is the fully cation-ordered species, with acentric structure, in the series of natural aphthitalite-like K-Na sulfates.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".