Metahewettite, Ca(V5+6O16)(H2O)3, from Hodzha-Rushnai-Mazar, southern Kirgizia: occurrence and crystal structure
Bibliographic record
Abstract
Metahewettite was encountered in hypergene crusts in Paleozoic carbon-silica schists included in the carbon mélange matrix at Hodzha-Rushnai-Mazar in southern Kirgizia.Schist outcrops are marked by multicolored yellow, orange, brown and green crusts of vanadates and sulfates of chalсoalumite group, volborthite, V-bearing phosphates, Cr-V-bearing members of alunite subgroup, members of the pascoite group and vanadium-bronze oxides, including metahewettite.Metahewettite is acicular with individual crystals up to 1 mm in length, and forms radial aggregates 2-3 mm in diameter, or flattened aggregates in narrow fissures.Crystals are dark-brown to reddish-brown with a golden sheen.The crystal structure of metahewettite, Ca(V 5+ 6 O 16 )(H 2 O) 3 , monoclinic, a = 12.208(5), b = 3.6011(15), c = 18.358(7)Å, β = 118.538(8)°,V = 709.0(8)Å 3 , Z = 2, A2/m, was refined to an R 1 index of 2.4 % based on 1047 unique observed (F o > 4σF) reflections.Electron-microprobe analysis (EDS) showed no detectable constituents apart from Ca and V, and the scattering from each site in the structure is conformable with the ideal composition Ca(V 6 O 16 )(H 2 O) 3 .There are three V sites in the structure with scattering in accord with their complete occupancy by V.The V(1) site is [5]-coordinated by O 2-anions with a distance of 1.823 Å and a [2 + 3] arrangement of vanadyl <1.67 Å> and equatorial (<1.925Å>) bonds.The V(2) and V(3) sites are coordinated by O 2-anions with distances of 1.934 and 1.916 Å and [2 + 2 + 2] and [1 + 4 + 1] arrangements of vanadyl <1.652 Å>, equatorial <1.906 Å> and trans <2.237 Å> bonds, respectively.The V(1) square pyramids share edges and vertices to form chains extending parallel to b with a repeat distance of 3.6 Å.The V(2) and V(3) octahedra share edges and vertices to form ribbons also extending parallel to b.The chains and ribbons link by sharing polyhedron corners to form sheets of V polyhedra parallel to (001).These sheets are linked by interlayer Ca that occupies two interstitial Ca sites, and by (H 2 O) groups.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.001 | 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".