The crystal structure of pezzottaite and the crystal chemistry of the beryl–pezzottaite series
Bibliographic record
Abstract
Abstract Crystal structures along the join beryl–pezzottaite have been refined and their compositions determined by electron-microprobe analysis. All crystals show sharp uniform diffraction spots but are microscale mixtures of more than one structure. Three distinct phases were identified with different diffraction characteristics: (1) hexagonal ( P 6/ mcc ) Cs-rich beryl; (2) hexagonal–rhombohedral ( $R\overline 3 c$ ) twinned pezzottaite; (3) incommensurate phases with cell dimensions resembling those of beryl with a doubled c -dimension and l indices deviating from integer values by ±0.05–0.10. Beryl ( P 6/ mcc ) structures refined to R 1 indices from 2.36 to 2.91% and pezzottaite structures refined to R 1 indices from 3.31 to 5.83%. In pezzottaite, the Cs 1 and Cs 2 sites are each occupied by Cs + , Rb + and (H 2 O) with Cs + showing a preference for Cs 1; and the Na 1 and Na 2 sites are occupied by Na + and Ca 2+ . Na + bonds to one (H 2 O) group and (H 2 O) bonds to one Na + . The ordering of (Cs + + Rb + ) and (Na + + Ca 2+ ) in pezzottaite is driven by the incident bond-valence requirements of the anions coordinating the ( Li O 4 ) tetrahedron. The valence-sum rule is maintained through the (Cs + + Rb + ) + Li + → □ + Be 2+ variation in beryl by cooperative relaxation of bonds at the Si and Be tetrahedra, and in pezzottaite by cooperative relaxation of bonds at the Si, Al and Li tetrahedra. The valence-sum rule mandates that Na + must bond to one channel (type-II) (H 2 O) group which, when combined with the constraint of electroneutrality, requires that compositions along the beryl–pezzottaite join must lie below the line (Cs + + Rb + ) + 2(Na + + Ca 2+ ) = 1 – 2Ca 2+ apfu. The occurrence of an incommensurate phase at intermediate compositions is due to the interaction of the species in adjacent columns of the P 6/ mcc beryl structure.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.003 |
| 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 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".