THE CRYSTAL STRUCTURE OF BAKHCHISARAITSEVITE, [Na2(H2O)2] , A NEW MINERAL SPECIES OF HYDROTHERMAL ORIGIN FROM THE KOVDOR PHOSCORITE-CARBONATITE COMPLEX, RUSSIA
Bibliographic record
Abstract
The crystal structure of a new mineral species, bakhchisaraitsevite [Na 2 (H 2 O) 2 ]{(Mg,Fe) 5 (H 2 O) 5 (PO 4 ) 4 }, a 8.3086(8), b 12.906(1), c 17.486(2) A, β 102.01(1)°, V 1834.0(1) A 3 , space group P 2 1 / c , Z = 4, ρ calc = 2.499 g/cm 3 , has been determined [automated single-crystal diffractometer, Mo K α, graphite monochromator, T = 193 K, 21597 reflections, R = 0.033 for 3527 unique reflections with I ≥ 2σ( I ), wR 2 = 0.072]. It can be described as an open framework of Mg(Fe) octahedra and PO 4 tetrahedra. Extremely contorted chains of edge-sharing Mg(Fe) octahedra form layers parallel to the ab plane. The unit cell of bakhchisaraitsevite contains two layers of this kind. In the c direction, these layers are also joined by dimers of Mg(Fe) octahedra having common edges. The PO 4 tetrahedra consolidate the structure, sharing the majority of vertices with octahedra. Na atoms and H 2 O molecules are distributed in the channels of an open framework. The main feature of the crystal structure, layers of octahedra parallel to the ab plane, explains the flattened habit and the perfect cleavage of the crystals. The crystal-chemical formula of the mineral, [Na 2 (H 2 O) 2 ]{(Mg 4.5 Fe 0.5 )(H 2 O) 5 (PO 4 ) 4 }, where curly brackets enclose the framework component and square brackets show the contents of the channels, reflects the different functions of the H 2 O molecules in the structure. Bakhchisaraitsevite as a possible biomineral can be expected to play a role in accumulating phosphorus in recent sulfidic sediments with the participation of bacteria. We describe the close structural relations between bakhchisaraitsevite and rimkorolgite.
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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 | 0.000 |
| 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".