Implications of the mineralogy and chemical composition of lead beads from Frobisher's assay site, Kodlunarn Island, Canada: prelude to Bre-X?
Bibliographic record
Abstract
Lead beads recovered from a 16th century archaeological site on Kodlunarn Island in Frobisher Bay are believed to be a by-product of assaying rocks mined from various locations by Martin Frobisher's expeditions in 15771578. The lead beads were melted in crucibles to separate gold from its rock matrix. Microprobe analyses of galena grains in the lead indicate that they contain up to 0.4 wt.% silver but no gold. The chemical composition of the lead beads was determined in situ by electron microprobe and in bulk by inductively coupled plasma mass spectrometry (ICP-MS) and pyrolysis assay. The lead beads form two chemical composition groups that were recovered from different sites: (Shop 1) Cu-poor, Bi-free, Sb-rich, with 3743 g/t Ag and no detectable gold; (Shop 2) Cu-rich, Bi-rich, Sb-poor, with 7896 g/t Ag and one sample that yielded 0.72 g/t Au. These two groups also have different lead isotope compositions: Shop 1 has low 206Pb/204Pb and 208Pb/204Pb compared with Shop 2. These compositions suggest that Shop 1 leads are derived from England, whereas Shop 2 has a composition typical of Cyprus ores and of some deposits in England. The composition of the lead beads indicates that the flux and collector used for the assays on Kodlunarn Island did not introduce a gold-rich contamination. Silver was likely added from the flux or collector used to assay the rocks, a contamination well-known to Renaissance assayers.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Science and technology studies | 0.004 | 0.002 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".