MINERALOGY OF THE NIEDERSCHLEMA ALBERODA U Se POLYMETALLIC DEPOSIT, ERZGEBIRGE, GERMANY. V. WATKINSONITE, NEVSKITE, BOHDANOWICZITE AND OTHER BISMUTH MINERALS
Bibliographic record
Abstract
The uranium deposit at Niederschlema-Alberoda, Germany, contains a rich variety of Bi minerals deposited between the Permian and the Cretaceous; these have been studied for paragenetic relations, composition, and conditions of formation. Particular attention is given to the rare Bi selenides watkinsonite, nevskite, and cuproan bohdanowiczite. Whereas watkinsonite and nevskite only occur intergrown with clausthalite, bohdanowiczite is more widespread and also is associated with Cu selenides. Watkinsonite from this second confirmed locality worldwide has an average composition (Cu1.47Ag0.49){sum}1.96(Pb1.01Hg0.01 Fe0.01){sum}1.03Bi3.98(Se7.98S0.05){sum}8.03, ideally (Cu,Ag)2PbBi4Se8. These findings suggest that the empirical formula of watkinsonite originally proposed for the type specimen from the Otish Mountains uranium deposit in Quebec [Cu2+xPb1+xBi4–x(Se,S,Te)8, x {approx} 0.3] requires revision. The composition of nevskite is (Pb0.06Bi0.95){sum}1.01Se0.99, on average. Bohdanowiczite from the Cu-selenide assemblage shows extensive substitution of Cu+ for Ag+, expressed by the crystallochemical formula (Ag1.80–0.94Cu0.16–1.05Pb0.00–0.05){sum}1.98–2.07Bi{sum}1.97–2.03Se{sum}3.96–4.04. This observation seems to argue for the natural existence of Cu2Bi2Se4, the Se-dominant analogue of emplectite. The Bi selenides were deposited at temperatures of about 100°C, in the Jurassic. The lack of thermodynamic data for all the Bi selenides limits reliable inferences on the fugacities of selenium and sulfur that prevailed during their formation. Other Bi minerals from this locality comprise members of the bismuthinite–aikinite solid-solution series of Permian age and, more importantly, native Bi and Bi sulfides (matildite, bismuthinite, wittichinite), deposited in the Cretaceous.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.001 |
| Science and technology studies | 0.001 | 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) | 0.003 | 0.001 |
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".