THE CRYSTAL STRUCTURE OF BURGESSITE, Co2 (H2O)4 [AsO3(OH)]2 (H2O), AND ITS RELATION TO ERYTHRITE
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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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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 | 0.001 | 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) | 0.000 | 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 it