Bibliographic record
Abstract
Mineral grains are not just chemical compounds; they possess microtexture. The properties of crystallographically near-perfect “gem-quality ” alkali feldspar crystals are contrasted here with those of ordinary, “garden-variety ” specimens, exemplifi ed by perthitic phenocrysts from the granite at Shap, northern England. These are representative of common alkali feldspars in the crust. Two well-studied gem-quality materials (Madagascar orthoclase and Eifel sanidine) vary at the source in microtextural and other properties. Some crystals of Eifel sanidine exhibit much more rapid Si–Al ordering than ordinary feldspars, probably because of the presence of a hydrogen species. The complex microtextures of two feldspars from pegmatites that have been used in studies of dissolution rate, Perth perthite and Keystone microcline, are described and compared with textures in the Shap feldspars. Microtextures, in particular misfi t dislocations on regular exsolution-lamellae of albite, are crucially important in chemical dissolution and mechanical degradation during natural weathering in acid peat soils at Shap. In contrast, during laboratory dissolution-rate experiments carried out far from equilibrium, natural defects are less important than edges and steps produced during the grinding of the samples. Diagenetic replacement-type reactions in an overlying conglomerate at Shap are also strongly sensitive to microtexture. In arkosic sandstones in the Jurassic Fulmar Formation of the central North Sea, the detrital alkali feldspar inventory has been subject to microtextural winnowing, with relatively defect-free varieties of alkali feldspar being relatively more abundant than would be expected from the distribution of rock types known in the North Sea catchment.
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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 | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.009 | 0.004 |
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".