Rundqvistite-(Ce), Na<sub>3</sub>(Sr<sub>3</sub>Ce)(Zn<sub>2</sub>Si<sub>8</sub>O<sub>24</sub>), a new mineral from the Darai-Pioz alkaline massif, Tien-Shan Mountains, Tajikistan: mineral description and crystal structure
Bibliographic record
Abstract
Abstract Rundqvistite-(Ce), ideally Na 3 (Sr 3 Ce)(Zn 2 Si 8 O 24 ), is a new mineral from the Darai-Pioz alkaline massif, Tien-Shan Mountains, Tajikistan. The mineral occurs as elongated grains up to 0.1 mm long and up to 0.03 mm thick embedded in quartz–pectolite aggregate in a silexite-like peralkaline pegmatite. Associated minerals are quartz, fluorite, pectolite, baratovite, aegirine, leucosphenite, neptunite, reedmergnerite, orlovite, sokolovaite, mendeleevite-(Ce), odigitriaite, pekovite, zeravshanite, kirchhoffite and garmite. The mineral is colourless with a vitreous lustre and a white streak, brittle, D meas. is 3.70(2) and D calc. is 3.709 g/cm 3 . Rundqvistite-(Ce) is monoclinic, space group P 2 1 / c , a = 5.1934(16), b = 7.8934(16), c = 26.011(5) Å, β = 90.02(3)° and V = 1066.3(4) Å 3 . The chemical composition of rundqvistite-(Ce) is SiO 2 40.17, La 2 O 3 2.64, Ce 2 O 3 7.55, Pr 2 O 3 0.80, Nd 2 O 3 2.43, Sm 2 O 3 0.33, Eu 2 O 3 0.09, Gd 2 O 3 0.24, Tb 2 O 3 0.18, Dy 2 O 3 0.21, PbO 1.03, SrO 19.83, FeO 0.37, ZnO 13.08, CaO 2.55, Na 2 O 8.04, total 99.54 wt.%. The empirical formula calculated on 24 O apfu (atoms per formula unit) is Na 3.10 Sr 2.29 Ca 0.54 Pb 0.06 (Ce 0.55 La 0.19 Nd 0.17 Pr 0.06 Sm 0.02 Gd 0.02 Eu 0.01 Tb 0.01 Dy 0.01 ) Σ1.04 Zn 1.92 Fe 0.06 Si 8.00 O 24 Z = 2. The structural formula based on refined site-occupancies is (Na 2.94 Sr 0.06 ) Σ3.00 [(Sr 2.23 Ca 0.54 Pb 0.06 Na 0.13 ) Σ2.96 Ln 3+ 1.04 ] Σ4.00 [(Zn 1.92 Fe 2+ 0.06 ) Σ1.98 Si 8 O 24 ], where Ln 3+ 1.04 = (Ce 0.55 La 0.19 Nd 0.17 Pr 0.06 Sm 0.02 Gd 0.02 Eu 0.01 Tb 0.01 Dy 0.01 ) Σ1.04 . The crystal structure of rundqvistite-(Ce) was refined to R 1 = 2.76% on the basis of 3184 unique reflections [ F > 4σ| F |]. In rundqvistite-(Ce), the main structural unit is a (Zn 2 Si 8 O 24 ) 12– sheet parallel to (100). In the sheet, the Si and Zn tetrahedra form four-, five- and eight-membered rings. The interstitial cations at the Na and M (1–3) sites sum to [Na 3 (Sr 3 Ce)] 12– apfu. The Na and M(1–3) polyhedra share common edges to form a layer. Rundqvistite-(Ce) is a structural analogue of vladykinite, ideally Na 3 Sr 4 (Fe 2+ Fe 3+ )Si 8 O 24 . Rundqvistite-(Ce) and vladykinite are related by the following substitution: [8] Ce 3+ + [4] (Zn 2+ ) 2 ↔ [8] Sr 2+ + [4] (Fe 2+ Fe 3+ ). The mineral is named after Dmitry Vasilievich Rundqvist (1930–2022), a prominent Russian geologist and an expert on the geology of ore deposits, metallogeny and mineralogy of Precambrian rocks.
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How this classification was reachedexpand
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 | 0.002 |
| Meta-epidemiology (broad) | 0.003 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.001 | 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; both teacher heads agree on what is shown here.
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".