IS NEAR-ENDMEMBER BIREFRINGENT GROSSULAR NON-CUBIC? NEW EVIDENCE FROM SYNCHROTRON DIFFRACTION
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Bibliographic record
Abstract
The crystal structures of three birefringent (samples 1 and 2 from Quebec and sample 3 from Tanzania) and one isotropic grossular (sample 4 from Afghanistan) were refined with the Rietveld method, cubic space group Ia 3 d, and monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Electron microprobe (EMPA) results indicate that the garnets are homogeneous with compositions as follows: (1) {Ca2.92Mn2+0.05Fe2+0.01}∑2.98[Al1.91Fe3+0.09Ti4+0.02]∑2.02(Si2.96Al0.04) ∑3O12, Grs94Adr3; (2) {Ca2.99}[Al1.65Cr3+0.22Fe3+0.05Ti4+0.05Mn3+0.04]∑2.01(Si2.94Al0.06)∑3O12, Grs82Uv11; (3) {Ca2.95Mg0.04Mn2+0.01} ∑3[Al1.04Fe3+0.86Ti4+0.07Mn3+0.01Mg0.01]∑1.99(Si2.94Al0.06)∑3O12, Grs51Adr43; and (4) {Ca2.95Mn2+0.01Fe2+0.01Mg0.01} ∑2.98[Al1.85Fe3+0.16Ti4+0.01]∑2.02(Si2.97Al0.03)∑3O12, Grs91Adr6. Samples 1 and 4 are near-endmember grossular. Two different cubic phases occur in the three birefringent samples, and a single cubic phase occurs in the isotropic sample 4. Their crystal structures are modelled well, as indicated by their Rietveld refinement reduced χ2 and corresponding overall R ( F 2) values for the four samples as follows: (1) 1.078 and 0.0368; (2) 1.081 and 0.0434; (3) 1.902 and 0.0361; and (4) 1.235 and 0.0491. The dominant phase has the following unit-cell parameters (A) and weight fractions (%) for the four samples: (1) a = 11.85140(1), 83.0(2); (2) a = 11.87707(2), 71.3(1); (3) a = 11.94161(1), 91.95(2); and (4) a = 11.85584(1) A, 100%. Their bond distances and site occupancy factors ( sofs ) are as follows: (1) = 2.4017, Al–O = 1.9269(4), Si–O = 1.6506(4) A; Ca( sof ) = 0.964(1), Al( sof ) = 0.954(1), and Si( sof ) = 0.917(1); (2) = 2.4057, Al–O = 1.9371(7), Si–O = 1.6508(6) A; Ca( sof ) = 0.953(1), Al( sof ) = 1.046(2), and Si( sof ) = 0.916(1); (3) = 2.4174, Al–O = 1.9675(4), Si–O = 1.6444(4) A; Ca( sof ) = 0.946(1), Al( sof ) = 1.355(2), and Si( sof ) = 0.932(1); and (4) = 2.4060, Al–O = 1.9292(4), Si–O = 1.6473(4) A; Ca( sof ) = 0.964(1), Al( sof ) = 0.994(1), and Si( sof ) = 0.925(1). The sofs are similar to those obtained by EMPA. The two cubic phases intergrown in the three birefringent samples cause strain that arise from mismatch of unit-cell and bond distances and give rise to strain-induced birefringence. Sample 4 is an isotropic single-phase grossular.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.013 | 0.002 |
Machine scores (provisional)
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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 it