THE CRYSTAL STRUCTURE AND CRYSTAL CHEMISTRY OF MANITOBAITE, IDEALLY (Na16 )Mn2+ 25Al8(PO4)30, FROM CROSS LAKE, MANITOBA
Bibliographic record
Abstract
The crystal structures of green (brown) variants of manitobaite, ideally (Na 16 □)Mn 2+ 25 Al 8 (PO 4 ) 30 , monoclinic, Pc , Z = 2: green: a 13.4517(7), b 12.5266(7), c 26.6765(13) A, β 101.582(1)°, V 4403.6(7) A 3 , D calc. 3.642 g/cm 3 ; brown: 13.4499(6), b 12.5046(5), c 26.6148(11) A, β 101.221(1)°, V 4390.7(5)(3) A 3 , D calc. 3.621 g/cm 3 , from pegmatite #22 at Cross Lake, Manitoba, Canada, have been solved by direct methods and refined to R 1 = 5.0 (6.0)% for 22,580 (25,613) unique ( F o > 4σ F ) reflections collected on a Bruker single-crystal P 4 diffractometer equipped with a 4K CCD detector and Mo K α X-radiation. Chemical analysis by electron microprobe plus Fe 3+ determination by Mossbauer spectroscopy gave: green: P 2 O 5 44.19, Al 2 O 3 6.91, Fe 2 O 3 1.73, FeO 6.23, MnO 27.57, ZnO 0.54, MgO 0.73, CaO 1.71, Na 2 O 9.97, sum 99.58 wt%; brown: P 2 O 5 44.42, Al 2 O 3 6.96, Fe 2 O 3 3.54, FeO 4.66, MnO 27.86, ZnO 0.53, MgO 0.81, CaO 1.59, Na 2 O 8.94, sum 99.32 wt%. The resulting empirical formulae are as follows: green: Na 15.55 Ca 1.47 Mg 0.88 Fe 2+ 4.19 Mn 2+ 18.78 Zn 0.32 Al 6.54 Fe 3+ 1.05 P 30.08 O 120 ; brown: Na 13.90 Ca 1.37 Mg 0.97 Fe 2+ 3.12 Mn 2+ 18.92 Zn 0.31 Al 6.58 Fe 3+ 2.09 P 30.15 O 120 . The general formula of manitobaite is (Na 16 □)(Mn 2+ ,Fe 2+ ,Mg,Zn,Ca) 25 (Al,Fe 3+ ) 8 (PO 4 ) 30 , and the end-member formula is (Na 16 □)Mn 2+ 25 Al 8 (PO 4 ) 30 . There are 80 cation sites and 120 anion sites in the structure. There are 30 tetrahedrally coordinated sites occupied by P, 33 octahedrally coordinated sites occupied by Mn 2+ , Fe 2+ , Al, Fe 3+ plus minor Mg and Zn, and 17 sites occupied predominantly by Na with coordination numbers from [5] to [8]. Manitobaite is an ordered superstructure of the alluaudite structure. In particular, there are eight octahedrally coordinated sites occupied predominantly by Al, emphasizing the key role of Al in producing superstructures in these minerals.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.002 |
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".