From Structure Topology to Chemical Composition. XXX. Refinement of the Crystal Structure and Chemical Formula of Shkatulkalite, Na2Nb2Na3Ti(Si2O7)2O2(FO)(H2O)4(H2O)3, a Lamprophyllite-Group (Seidozerite Supergroup) TS-Block Mineral from the Lovozero Massif, Kola Peninsula, Russia
Bibliographic record
Abstract
ABSTRACT Shkatulkalite, ideally Na5TiNb2(Si2O7)2O3F(H2O)7, is a lamprophyllite-group (seidozerite supergroup) TS-block mineral from the Lovozero massif, Kola Peninsula, Russia. The crystal structure of shkatulkalite was refined as triclinic, space group P, a 5.464(1), b 7.161(1), c 15.573(1) Å, α 90.00(3), β 95.75(3), γ 90.00(3)°, V 606.3(4) Å3, R1 = 7.26%. The previously given chemical analysis has been modified to better fit the crystal structure: Nb2O5 24.15, TiO2 11.35, SiO2 27.22, BaO 1.15, SrO 2.20, MnO 1.68, CaO 0.46, K2O 0.29, Na2O 14.78, H2O 15.27, F 1.61, O = F −0.68, sum 99.48 wt.%; H2O was determined from structure-refinement results. The empirical formula was calculated on 25.27 (O + F) apfu (in accord with the crystal structure): (Na1.40Sr0.19Ba0.07K0.05)Σ1.71(Na2.86Mn0.10Ca0.07)Σ3.03(Nb1.62Ti1.27Mn0.11)Σ3Si4.03O24.52H15.11F0.75, Z = 1. The ideal structural formula is as follows: Na2Nb2Na3Ti(Si2O7)2O2(FO)(H2O)4(H2O)3. The crystal structure of shkatulkalite [basic structure type B5(LG)] is a combination of a TS (titanium-silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). The TS block exhibits linkage and stereochemistry typical for the lamprophyllite group where Ti (+ Nb + Fe3+ + Mg) = 3 apfu. The O sheet is composed of Ti-dominant MO(1) and Na-dominant MO(2,3) octahedra. In the H sheet in shkatulkalite, Si2O7 groups link to Nb-dominant MH octahedra. The AP site occurs in the plane of the H sheet and splits into AP(1) and AP(2) sites, occupied by Na at 70% and Sr (less Ba and K) at 11%. The I block consists of H2O groups. The I block of shkatulkalite is topologically identical to those in the derivative structures of kazanskyite and nechelyustovite. The structure of the lamprophyllite-group mineral shkatulkalite has a counterpart structure in the murmanite group (Ti = 4 apfu): kolskyite, ideally Na2CaTi4(Si2O7)2O4(H2O)7 [basic structure type B7(MG)]: the two structures have TS blocks of different topology and similar I blocks, mainly occupied by H2O 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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.018 | 0.005 |
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".