The Chemistry and Crystal Structure of Potassic-Fluoro-Richterite from Rother Kopf, Eifel Volcanic Fields, Germany
Bibliographic record
Abstract
Abstract Potassic-fluoro-richterite, ideally AKB(CaNa)CMg5TSi8O22F2, from Rother Kopf, Eifel Volcanic Fields, Germany, is monoclinic, C2/m, a = 9.9615(6), b = 18.0526(9), c = 5.2846(4) Å, β = 104.484(7)°, V = 920.13 Å3, Z = 2. Chemical analysis by electron microprobe gave SiO2 54.01, Al2O3 0.21, TiO2 1.24, FeO 11.15, MnO 0.10, MgO 16.13, CaO 5.07, Na2O 5.55, K2O 2.99, F 4.50, O ≡ F −1.89, sum 99.06 wt.%. The formula unit, calculated on the basis of 24 (O + OH + F) with F = 2 apfu and and Fe3+ = 0.0 apfu (determined from the distance) is A(K0.56Na0.43)B(Na1.18Ca0.80Mn0.01Fe2+0.01)C(Mg3.53Fe2+1.37Mn2+0.01Ti0.11)T(Si7.93Al0.04Ti4+0.03)O22F2. The crystal structure was refined to an R1 index of 3.87% for 1014 reflections Fo > 4σF. A very unusual feature of this amphibole is that, unlike most amphiboles, the A-cations occupy the A(2/m) site within the A-cavity. Examination of the T(1)–O(7) and A(2/m)–O(7) distances in several hydroxy- and fluoro-amphiboles with TSi = 8 apfu shows that the H···O(7) bond in richterite and potassic-richterite is of negligible strength in A-site-vacant amphiboles in accord with the principal OH-stretching frequencies in these minerals.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".