TOURMALINE-BEARING QUARTZ VEINS IN THE BARABOO QUARTZITE, WISCONSIN: OCCURRENCE AND SIGNIFICANCE OF FOITITE AND "OXY-FOITITE"
Bibliographic record
Abstract
The alkali-deficient tourmaline, foitite [(Fe2+2Al)Al6Si6O18(BO3)3(OH)3(OH)], and associated hematite occur in quartz veins that cut the geon 17 Baraboo Quartzite in south-central Wisconsin. The bluish green prismatic crystals of tourmaline are chemically zoned from core to rim, with the cores being very aluminous, highly alkali-deficient and, in one sample, relatively magnesian. Electron-microprobe analyses demonstrate that the tourmaline has a prevailing alkali-deficiency in the X site, which ranges from 49 to 87%, with a mean of 73%, making this the most alkali-deficient tourmaline reported to date. In one sample, high contents of Al (up to 7.7 Al apfu) and high cation-charge excess demonstrate the likely existence of a dominant “oxy-foitite” component [(Fe2+Al2)Al6Si6O18(BO3)3(OH)3(O)], which is the first recognition of such in a natural occurrence. The wide range of chemical zoning in the tourmaline is most consistent with substitutions represented by the Al(NaR) –1, AlO[R(OH)]–1, FeAl –1 and MgFe–1 exchanges, where R symbolizes Fe + Mg. The alkali-deficient character of the Baraboo tourmaline largely reflects the alkali-depleted and chemically mature composition of the host Baraboo Quartzite, but core-to-rim compositional variation in the tourmaline records the evolving nature of the attendant hydrothermal fluid, from a Na-poor, relatively alkaline early stage to a more sodic, acidic later stage.
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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 | 0.001 |
| 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".