A 57Fe MOSSBAUER SPECTROSCOPIC STUDY OF SUGILITE, KNa2(Fe3+,Mn3+,Al)2Li3Si12O30
Bibliographic record
Abstract
Sugilite, ideally KNa(2)(Fe(3+),Mn(3+),Al)(2)Li(3)Si(12)O(30), from the Wessels mine, Kalahari, South Africa, was studied using (57)Fe Mossbauer spectroscopy. The spectra confirm published electron-microprobe data and X-ray single-crystal results, which indicate that Fe(3+) is ordered at the A octahedral site. The magnitude of the quadrupole splitting, DEQ for Fe(3+) at both 84 K and room temperature is 0.00 mm/s. This value is very low for a silicate; reported DEQ values for octahedrally coordinated Fe(3+) are generally greater than 0.20 mm/s. Octahedron distortion, calculated from published X-ray-diffraction data, gives an octahedron-angle variance of 7 and a mean elongation of the octahedron of 1.002. This indicates nearly regular octahedral geometry, and hence a symmetric electric-field gradient around Fe(3+). A crystal-chemical interpretation for the regular octahedral geometry and the resulting low DEQ value for Fe(3+) in the Mossbauer spectrum of sugilite is that structural strain is largely taken up by weak Li-O bonds. They permit highly distorted LiO(4) tetrahedra, whose variance in the O-Li-O angle, 502, and mean elongation of the tetrahedron, 1.148, are among the largest observed values for inorganic crystal structures. Weak Li-O bonds allow the edge-shared, more strongly bonded Fe(3+)O(6) octahedra to remain regular in geometry.
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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 | 0.001 | 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) | 0.001 | 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".