THE CRYSTAL STRUCTURE OF BURGESSITE, Co2 (H2O)4 [AsO3(OH)]2 (H2O), AND ITS RELATION TO ERYTHRITE
Bibliographic record
Abstract
The crystal structure of burgessite, ideally Co 2 (H 2 O) 4 [AsO 3 (OH)] 2 (H 2 O), a newly recognized supergene mineral from the Keeley mine, South Lorrain Township, Timiskaming District, Ontario, Canada, has been solved by direct methods and refined to an R index of 4.3% based on 494 observed reflections collected on a four-circle diffractometer with Mo K α X-radiation. Burgessite is monoclinic, space group P 2 1 / n , a 4.7058(12), b 9.299(3), c 12.738(4) A, β 98.933(8)°, V 550.6(5) A 3 , Z = 2, D meas = 2.93 g/cm 3 . The structure consists of one unique As site that is [4]-coordinated by O atoms and occupied by As 5+ with a As –O> distance of 1.694 A. There is one Co site occupied by Co and [6]-coordinated, with a Co –O> distance of 2.096 A. Bond-valence analysis of the final structure indicates three O atoms (O 2− ), one (OH) group and three (H 2 O) groups in the asymmetric unit; note that the (OH) group is bonded to the As 5+ cation, forming an acid arsenate group: AsO 3 (OH). The resulting ideal formula is Co 2 (H 2 O) 4 [As 5+ O 3 (OH)] 2 (H 2 O), where the (H 2 O) groups before the arsenate group are bonded to Co, and the (H 2 O) group following the arsenate group is held in the structure solely by hydrogen bonds. A prominent motif in the burgessite structure is the [Co 2 (H 2 O) 4 [As 5+ O 3 (OH)] 2 ] chain, which extends in the [100] direction and occurs at the vertices of an orthorhombic net. These chains are linked into a three-dimensional structure by hydrogen bonds that involve (OH) bonded to As 5+ , (H 2 O) bonded to Co, and (H 2 O) held in the structure solely by hydrogen bonds. The crystal structure of erythrite is based on [Co 2 (H 2 O) 4 (As 5+ O 4 ) 2 ] chains of the same bond-topology as that found in burgessite.
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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 | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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 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".