Crystal Chemistry of Birefringent Uvarovite Solid Solutions
Bibliographic record
Abstract
The crystal chemistry of five optically anisotropic uvarovite samples from different localities (California, Finland, Russia, and Switzerland) were studied with electron-probe microanalysis (EPMA) and the Rietveld method. Monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data were used, and Rietveld refinement was carried out with the cubic space group, I a 3 ¯ d . The general formula for garnet is [8]X3[6]Y2[4]Z3[4]O12. Uvarovite has the ideal formula, Ca3Cr2Si3O12, which may be written as Ca3{Cr,Al,Fe}Σ2[Si3O12] because of solid solutions. HRPXRD traces show multiple cubic garnet phases in each sample that has a heterogeneous chemical composition. The optical and back-scattered electron (BSE) images and elemental maps contain lamellar and concentric zoning as well as patchy intergrowths. With increasing a unit-cell parameter for uvarovite solid solutions, the Z–O distance remains constant, and the average distance increases slightly in response to the Cr3+ ⇔ Al3+ cation substitution in the Y site. The Y–O distance increases most because Cr3+ (radius = 0.615 Å) is larger than Al3+ (radius = 0.545 Å) cations. The Fe3+ (radius = 0.645 Å) cation is also involved in this substitution. Structural mismatch between the cubic garnet phases in the samples gives rise to strain-induced optical anisotropy.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".