PYRACMONITE, (NH4)3Fe(SO4)3, A NEW AMMONIUM IRON SULFATE FROM LA FOSSA CRATER, VULCANO, AEOLIAN ISLANDS, ITALY
Bibliographic record
Abstract
The new mineral species pyracmonite , ideally (NH 4 ) 3 Fe(SO 4 ) 3 , was found in a medium-temperature (~250°C) active intracrater fumarole at La Fossa crater, Vulcano, Aeolian Islands, Sicily, Italy. It occurs on a pyroclastic breccia as colorless to white prismatic crystals up to 0.2 mm in length, in association with salammoniac and kremersite. The mineral is trigonal, space group R 3 c (no. 161) with a 15.2171(14), c 8.9323(8) A, V 1791.3(3) A 3 and Z = 6. The strongest six reflections in the X-ray powder-diffraction pattern [ d obs in A( I )( hkl )] are: 7.596(100)(110), 3.320(30)(122), 3.371(26)(131), 4.358(23)(121), 2.829(14) (312), and 2.863(8)(321). The empirical formula, based on 12 anions, is [(NH 4 ) 2.74 K 0.23 ] ∑2.97 (Fe 0.94 Al 0.04 ) ∑0.98 S 3.02 O 12 , and the simplified formula (NH 4 ,K) 3 (Fe,Al)(SO 4 ) 3 . The measured density is 2.22(1) g/cm 3 , and D calc is 2.228 g/cm 3 . The mineral is uniaxial, and the average index of refraction index is 1.562(3) (λ= 589 nm). Using single-crystal X-ray-diffraction data, the structure was refined to a final R ( F ) = 0.039 for 1010 independent observed reflections [ I > 2σ( I) ]. The mineral is identical to the synthetic compound (NH 4 ) 3 Fe(SO 4 ) 3 and is isostructural to the high-temperature phase of the synthetic compound (NH 4 ) 3 In(SO 4 ) 3 . Building blocks of the structure are (Fe,Al)O 6 octahedra and SO 4 tetrahedra, which are linked together to form infinite columns [(Fe,Al)(SO 4 ) 3 ] ∞ along [001]. The two independent (Fe,Al)–O distances are 1.959(1) and 1.998(1) A; in the sulfate anion, the S–O distances range from 1.415(2) to 1.485(1) A. The ammonium ions, only partly replaced by K + ions, interact with the oxygen atoms of the sulfate groups via hydrogen bonds.
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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 | 0.002 | 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) | 0.001 | 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".