Noonkanbahite, BaKNaTi<sub>2</sub>(Si<sub>4</sub>O<sub>12</sub>)O<sub>2</sub>, a new mineral species: description and crystal structure
Bibliographic record
Abstract
Abstract Noonkanbahite, ideally BaKNaTi2(Si4O12)O2, is described as a new mineral species. At Liley [Löhley], Eifel Mountains, Germany (the holotype locality), it occurs as sprays of prismatic crystals (up to 8 mm) or single prismatic crystals (up to 4 mm) on walls of cavities in alkaline igneous rocks. At Murun, Siberia, Russia, noonkanbahite forms coarse lamellar crystals up to 0.05 cm × 0.7 cm × 1.5 cm embedded in kalsilite syenite. Noonkanbahite is brittle, H = 6, Dobs. = 3.39(1), Dcalc. = 3.49 g/cm3, has a vitreous lustre and does not fluoresce in ultraviolet light. It has poor cleavage on {010} and {100} and weak parting on {011}. Noonkanbahite is biaxial positive with 2Vobs. = 75(2)°, 2Vcalc. = 72.7(9)°, α 1.730(5), β 1.740(5) and γ 1.765(5), dispersion is medium, r < v. In transmitted plane-polarized light, noonkanbahite is strongly pleochroic, with X colourless, Y yellowish, Z straw-yellow; X = a, Y = b, Z = c. Noonkanbahite is orthorhombic, space group Imma, a = 8.0884(4), b = 10.4970(5), c = 13.9372(6) Å, V = 1183.3(1) Å3, Z = 4. The strongest ten X-ray diffraction lines in the powder pattern [d in Å (I)(hkl)] are: 2.907(100)(222), 8.353(50)(001), 3.196(50)(220), 2.097(50)(242), 2.241(40)(215), 2.179(40)(035), 3.377(30)(031), 2.694(30)(015), 2.304(30)(233), and 1.564(30)(064). Electron microprobe analysis gives SiO2 37.82, TiO2 15.54, ZrO2 0.42, Nb2O5 3.18, Al2O3 0.17, Fe2O3 (recalculated from FeO) 5.63, MnO 0.32, MgO 0.53, BaO 20.60, CaO 1.36, K2O 5.32, Na2O 6.14, F 0.78, H2O 0.58, sum 98.39 wt.%, (H2O determined by SIMS). The formula unit, calculated on the basis of 14 anions (O+OH+F), is (Ba0.85K0.13)Σ0.98(K0.59Na0.26Ca0.15)Σ1.00Na(Ti1.23Fe0.453+Nb0.15Mg0.08Mn0.03Zr0.02Al0.01)Σ1.97 (Si3.99Al0.01O12)(O1.33OH0.41F0.26)Σ2.00, Z = 4. The crystal structure was refined to R1 = 2.8% for 970 unique (F0 > 4σF) reflections collected on a Bruker single-crystal P4 diffractometer with a CCD detector and MoKα X-radiation. The crystal structure of noonkanbahite is isostructural with that of batisite, ideally BaNa2Ti2(Si4O12)O2, and scherbakovite, ideally K2NaTi2(Si4O12)O(OH). There are two octahedrally coordinated sites, M(1) and M(2), occupied by (Ti1.23Fe0.453+Nb0.15Mg0.08Mn0.03Zr0.02Al0.01), ideally Ti2 a.p.f.u. There are three interstitial A sites, [9]A(1), [8]A(2) and [6]A(3), occupied by Ba, K and Na, respectively. Si tetrahedra and M octahedra form a framework with interstitial cages occupied by Ba, K and Na atoms at the A sites. Noonkanbahite, BaKNaTi2(Si4O12)O2, is a K analogue of batisite, BaNa2Ti2(Si4O12)O2, and a Ba analogue of shcherbakovite, K2NaTi2(Si4O12)O(OH).
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".