Gemological Abstracts
Bibliographic record
Abstract
A new model is proposed for the formation of opal showing play-of-color, as well as potch (common opal).According to this new model, the essential requirements for opal formation are: (1) artesian "mound" springs with alkaline, silica-rich waters; (2) a mechanism for changing the physicochemical features of this water so that suitable silica spheres are precipitated in linear chains; and (3) the occurrence of suitable voids lined with clay-which acts as a semipermeable membrane to concentrate and purify the silica solution by ultrafiltration and dialysis.Active and extinct artesian mound springs are found in general proximity to several sedimentary rock-hosted opal fields in New South Wales, South Australia, and Queensland.In the Great Artesian Basin, the natural springs lie on a NEtrending line over 300 km long, subparallel to the Lightning Ridge opal fields.The lepispheres in play-of-color opal are very uniform in size (apparently within 2-3% of the mean size), indicating a batch process rather than a continuous one.The mixing of the high-pH spring water with cool, slightly acidic groundwater that has low total dissolved salts would decrease the pH, lower the temperature, and lower the ionic strength of the spring water; all three processes facilitate the formation of silica spheres.Montmorillonite (clay) can act as a semipermeable membrane and assist in the pressurization of the fluids for ultrafiltration.
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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.153 | 0.031 |
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".