Cámaraite, Ba<sub>3</sub>NaTi<sub>4</sub>(Fe<sup>2+</sup>,Mn)<sub>8</sub>(Si<sub>2</sub>O<sub>7</sub>)<sub>4</sub>O<sub>4</sub>(OH,F)<sub>7</sub>. II. The crystal structure and crystal chemistry of a new group-II Ti-disilicate mineral
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Bibliographic record
Abstract
Abstract Cámaraite — ideally Ba 3 NaTi 4 Fe 8 2+ (Si 2 O 7 ) 4 O 4 (OH) 4 F 3 — is triclinic, space group C , a = 10.6965(7) Å, b = 13.7861(9) Å, c = 21.478(2) Å, α = 99.345(1)°, β = 92.315(2)°, γ = 89.993(2)°, V = 3122.6(4) Å 3 , Z = 4, D calc. = 4.018 g cm –3 , from the Verkhnee Espe alkaline deposit, Akjailyautas Mountains, Kazakhstan, has been solved and refined to R 1 5.87% on the basis of 6682 unique reflections (F o >4σ F ). The crystal structure of cámaraite can be described as a combination of a TS block and an intermediate ( I ) block. The TS (titanium silicate) block consists of HOH sheets (H-heteropolyhedral, O-octahedral), and is characterized by a minimal cell based on translation vectors t 1 and t 2 , with t 1 ~5.5 and t 2 ~7 Å and t 1 ^ t 2 close to 90°. We describe the crystal structure of cámaraite using a double minimal cell, with 2 t 1 and 2 t 2 translations. In the O sheet, there are eight [6]-coordinated M O sites occupied mainly by Fe 2+ and Mn, with minor Fe 3+ , Mg, Zr, Ca and Zn with <M O –ϕ> = 2.185 Å. Eight M O sites give, ideally Fe 8 2+ p.f.u. In the H sheet, there are four [6]-coordinated M H sites occupied almost solely by Ti (Ti = 4 a.p.f.u.), with < M H –ϕ= = 1.963 Å, and eight [4]-coordinated Si sites occupied solely by Si, with <Si—0> = 1.621 Å. The topology of the TS block is as in Group II of the Ti-disilicates (Ti = 2 a.p.f.u. per minimal cell) in the structure hierarchy of Sokolova (2006). There are six peripheral ( P ) sites, four [8–12]-coordinated Ba-dominant A P sites, giving ideally 3 Ba p.f.u., and two [10]-coordinated Na-dominant B P sites, giving ideally 1 Na p.f.u. There are two I blocks: the I 1 block is a layer of Ba atoms (two A P sites); the I 2 block is a layer of Ba (two A P sites) and Na atoms (two B P sites). Along c , there are two types of linkage of TS blocks: (1) TS blocks link via A P cations which constitute the I 1 block, and (2) TS blocks link via common vertices of M H octahedra (as in astrophyllite-group minerals) and A P and B P cations which constitute the I 2 block. Cámaraite is the only mineral of Group II with two types of linkage of TS blocks and two types of I blocks in its structure. The relation of cámaraite to the Group-II minerals is discussed.
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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 | 0.004 | 0.003 |
| Meta-epidemiology (narrow) | 0.009 | 0.007 |
| Meta-epidemiology (broad) | 0.008 | 0.004 |
| Bibliometrics | 0.002 | 0.006 |
| Science and technology studies | 0.004 | 0.005 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.006 | 0.005 |
| Research integrity | 0.005 | 0.007 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it