A new anhydrous amphibole from the Eifel region, Germany: Description and crystal structure of obertiite, NaNa <sub>2</sub> (Mg <sub>3</sub> Fe <sup>3+</sup> Ti <sup>4+</sup> )Si <sub>8</sub> O <sub>22</sub> O <sub>2</sub>
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Bibliographic record
Abstract
Obertiite is a new amphibole species from Bellerberg, Laccher See district, Eifel, Germany. It occurs with tridymite, fluororichterite, hematite, rutile, aegirine-augite, kinoshitalite, and fluor-apatite in vugs in volcanic rocks, and crystallized from late-stage hydrothermal fluids associated with recent volcanism. Obertiite occurs as pale-pink elongated blades and divergent aggregates. It is brittle, H = 5, Dcalc = 3.16 g/cm3, has a colorless streak, vitreous luster, and does not fluoresce; it has perfect cleavage on {110} and conchoidal fracture. In plane-polarized light, obertiite is slightly pleochroic in shades of pink to red-orange; X ^ a = 2° (in β obtuse), Z = b, Y ^ c = 12° (in b obtuse) with absorption X ~ Y ~ Z. It is biaxial negative, α = 1.643(1), β =1.657(1), γ = 1.670(3), 2Vx = 81(1)°, no dispersion visible. Obertiite is monoclinic, space group C2/m, a = 9.776(2), b = 17.919(3), c = 5.292(1) Å, b = 104.05(2)°, V = 899.3(3) Å3, Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(I,hkl)]: 8.414(10,110), 2.705(7,331,151), 3.390(6,131), 4.467(5,040), 3.117(5,310), 2.531(5,202), 3.255(3,240), 2.577(3,061), 2.163(3,171,261), 4.013(2,111). Analysis by a combination of electron microprobe, SIMS, and crystal-structure refinement gives SiO2 54.53, Al2O3 0.15, TiO2 7.75, Fe2O3 2.61, Mn2O3 3.27, FeO 3.36, ZnO 0.08, MgO 14.13, Li2O 0.05, CaO 0.52, Na2O 9.51, K2O 0.98, F 0.55, H2O 0.20, O ≡ F -0.23, Ni, Cr, V, Cl not detected, sum 97.46 wt%. The formula unit, calculated on the basis of 24(O,OH,F) is (K0.18Na0.84)(Na1.86Ca0.08Fe2+0.06) (Mg3.09Zn0.01Li0.03Fe3+0.29Mn3+0.37Fe2+0.41Ti4+0.86Al0.03)Si8.00O22[(OH)0.20F0.26O1.54], and is close to the ideal endmember composition Na Na2 (Mg3Fe3+Ti4+) Si8 O22 O2.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.003 | 0.003 |
| Meta-epidemiology (broad) | 0.003 | 0.001 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.002 | 0.005 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it