NATURE OF HEAVY METALS IN HEMIMORPHITE: A CATION-EXCHANGE AND SINGLE-CRYSTAL EPR STUDY
Bibliographic record
Abstract
Hemimorphite, a zeolite-like mineral commonly present in supergene non-sulfide Zn deposits and Zn mine tailings, is known to contain elevated levels of As, Cd, Cu and Pb. Cation-exchange experiments of a natural hemimorphite (Mapimi, Durango, Mexico) with 0.1 M CaCl 2 solution at 110 oC show that As and Cu are retained, whereas Cd and Pb are readily exchanged. The retention of As is consistent with previous single-crystal electron paramagnetic resonance (EPR) results that showed its occurrence as the substitutional As 5+ ion at the Si site. Single-crystal EPR spectra of hemimorphite from the M’Fouati Pb-Zn mine (Reneville, Congo), measured at 120 K and 295 K, show a Cu 2+ center. The best-fit spin Hamiltonian parameters g , A ( 63 Cu), P ( 63 Cu) and A ( 1 H) of this center at 120 K demonstrate that Cu 2+ resides at the tetrahedral Zn site, not in the channels as suggested by a previous powder EPR study. Cadmium and Pb in hemimorphite are probably present in the channels; this would account for their contrasting behavior from As and Cu during the cation-exchange experiments. However, single-crystal EPR spectra of ten samples of hemimorphite from various Pb-Zn deposits, including those taken after gamma-ray irradiation for doses up to 55 kGy, did not detect any paramagnetic Cd or Pb centers.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".