Cummingtonite-(<i>P</i>2<sub>1</sub>/<i>m</i>): Crystal-structure refinement, Mössbauer spectroscopy and infrared spectroscopy, and some aspects of classification of the magnesium-iron-manganese amphiboles
Bibliographic record
Abstract
Abstract The crystal structure of cummingtonite-( P 2 1 / m ) was characterised by single-crystal structure-refinement, infrared spectroscopy and 57 Fe Mössbauer spectroscopy. Previous cummingtonite-( P 2 1 / m ) specimens characterised have Mn 2+ as the dominant constituent at M (4) but this amphibole has Fe 2+ dominant at M (4). The formula of the amphibole was corrected for minor exsolved calcium-amphibole and is (Mg 5.66 Fe 2+ 1.28 Mn 0.06 ) Σ7.00 Si 8.00 O 22 (OH) 2 . The crystal structure ( a = 9.4885(19), b = 18.040(4), c = 5.2891(11) Å, β = 102.06(3)°, V = 885.4(3) Å 3 , space group P 2 1 / m and Z = 2), was refined to an R 1 -index of 3.34% for 2338 observed reflections. Site-occupancy refinement gave the following site-populations: M (1) = 1.972(8) Mg + 0.028 Fe 2+ , M (2) = 2.000 Mg, M (3) = 0.989(6) Mg + 0.011 Fe 2+ , M (4) = 0.815(8) Mg + 1.125 Fe 2+ + 0.060 Mn 2+ apfu. Infrared spectroscopy in the principal (OH)-stretching region shows two peaks, at 3367 and 3652 cm –1 , that were assigned to the local arrangements M (1) Mg M (1) Mg M (3) Mg–OH and M (1) Mg M (1) Fe 2+ M (3) Mg–OH (≈ M (1) Mg M (1) Mg M (3) Fe 2+ –OH) with relative intensities in accord with the refined site-populations. 57 Fe Mössbauer spectrum shows three quadrupole-split doublets with parameters indicative of octahedrally coordinated Fe 2+ at M (4) and M (1,2,3), and octahedrally coordinated Fe 3+ that occurs in exsolved calcium amphibole. All three techniques indicate a small amount of Fe 2+ at M (1,2,3) despite the fact that there is more than sufficient C Mg to completely fill the M (1,2,3) sites: 5.66 Mg pfu. Issues involving the current and possible future nomenclature and classification of the magnesium-iron-manganese amphiboles are discussed in detail.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| 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 teacher head, 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".