RARE SULFOSALTS FROM VULCANO, AEOLIAN ISLANDS, ITALY. V. SELENIAN HEYROVSKYITE
Bibliographic record
Abstract
Heyrovskyite, a rare Pb-Bi sulfosalt, was found around a fumarole of ca. 500 °C at the La Fossa crater, Vulcano Island, Italy. The mineral occurs in the thin sulfosalt-rich crust covering the brecciated altered rocks of fumaroles, mainly admixed with selenian varieties of lillianite and cannizzarite, with subordinate galenobismutite and galena. Heyrovskyite occurs as thin needle-like crystals up to 300 /um in length and less than 1 /um in width. No traces of a breakdown texture have been noticed in any of the crystals studied. Electron-microprobe analyses show that the heyrovskyite from Vulcano has a composition close to the ideal Pb-rich composition of synthetic Phase ii, Pb6Bi2S9, obtained by Salanci &Moh in 1969. Particularly interesting is the absence of Ag and Cu, which makes the heyrovskyite from Vulcano unique, with respect to cations; only a minor amount of a Cd impurity is present. Like in other sulfosalts from Vulcano, significant Se concentrations are invariably present /(0.95-2.5 wt. %). The compositional field of heyrovskyite from Vulcano, expressed in terms of the mol.% Bi2S3, ranges from 14.23% (the most Pb-rich composition) up to 15.24% (the most Bi-rich), averaging 14.73 mol.%. This very narrow compositional spread (1 mol. %) is in the range attributable to analytical error;the composition of heyrovskyite from Vulcano is thus quite constant in terms of Pb- for-Bi substitution. The calculated average composition corresponds to the empirical formula (Pb5.95Cd0.02)5.97 Bi2.06 (S8.53Se0.44)8.97, which is close to the ideal end-member, Pb6Bi2S9. The cell parameters, resulting from an X-ray powder-diffraction study, are a=13.734(7), b=31.28(3), c=4.135(3) A. The reflections having h+l=2n are indicative of space group Bbmm. The cell parameters of heyrovskyite from Vulcano have been compared with those in the literature for heyrovskyite from various deposits and with those of synthetic Phase II. There is not general agreement among the data reported by different authors. These data, together with the compositional differences, in terms of mol.% Bi2S3, among various natural and synthetic products, suggest that the range occupied by synthetic Phase II consists of many chemically and structurally very similar compounds. In particular, the Pb-rich part of the compositional field of the Phase II might be considered as the synthetic analogue of heyrovskyite from Vulcano.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".