Fogoite-(Y), Na<sub>3</sub>Ca<sub>2</sub>Y<sub>2</sub>Ti(Si<sub>2</sub>O<sub>7</sub>)<sub>2</sub>OF<sub>3</sub>, a Group I TS-block mineral from the Lagoa do Fogo, the Fogo volcano, São Miguel Island, the Azores: Description and crystal structure
Bibliographic record
Abstract
Abstract Fogoite-(Y), Na 3 Ca 2 Y 2 Ti(Si 2 O 7 ) 2 OF 3 , is a new mineral from the Lagoa do Fogo, São Miguel Island, the Azores. It occurs in cavities as highly elongated (on [001]) prisms, up to 2000 μm long and 50 μm× 50 μm in cross-section, associated with sanidine, astrophyllite, fluornatropyrochlore, ferrokentbrooksite, quartz and ferro-katophorite. Crystals are generally transparent and colourless, with vitreous lustre, occasionally creamy white. Fogoite-(Y) has a white streak, splintery fracture and very good {100} cleavage. Mohs hardness is ∼5. D calc. = 3.523 g/cm 3 . It is biaxial (+) with refractive indices (λ = 590 nm) α = 1.686(2), β = 1.690(2), γ = 1.702(5); 2V meas. = 57(1)° and 2V calc. = 60°. It is nonpleochroic. Fogoite-(Y) is triclinic, space group P 1, a = 9.575(6), b = 5.685(4), c = 7.279(5) Å, α = 89.985(6), β = 100.933(4), γ = 101.300(5)°, V = 381.2 (7) Å 3 . The six strongest reflections in the powder X-ray diffraction data [ d (Å), I, ( hkl )] are: 2.954, 100, (1̄1̄2, 3̄10); 3.069, 42, (300, 01̄2); 2.486, 24, (310, 21̄2); 3.960, 23, (1̄1̄1, 2̄10); 2.626, 21, (2̄20); 1.820, 20, (1̄04). Electron microprobe analysis gave the following empirical formula calculated on 18 (O + F) (Na 2.74 Mn 0.15 ) ∑2.89 Ca 2 [Y 1.21 (La 0.01 Ce 0.03 Nd 0.03 Sm 0.02 Gd 0.08 Dy 0.08 Er 0.05 Yb 0.04 Lu 0.01 ) ∑0.35 Mn 0.16 Zr 0.11 Na 0.09 Fe 0.07 2+ Ca 0.01 ] ∑2 (Ti 0.76 Nb 0.23 Ta 0.01 ) ∑1 (Si 4.03 O 14 )O 1.12 F 2.88 , Z = 1. The crystal structure was refined on a twinnedcrystal to R 1 = 2.81% on the basis of 2157 unique reflections ( F o > 4σ F o ) and is a framework of TS (Titanium Silicate) blocks, which consist of HOH sheets (H – heteropolyhedral, O – octahedral) parallel to (100). In the O sheet, the the [6] M O (1) site is occupied mainly by Ti, <M O (1)–ϕ> = 1.980 Å, and the [6] M O (2) and [6] M O (3) sites are occupied by Na and Na plus minor Mn, <M O (2)–ϕ>= 2.490 Å and <M O (3)–ϕ> = 2.378 Å. In the H sheet, the two [4] Si sites are occupied by Si, with <Si–O> = 1.623 Å; the [6] M H site is occupied by Y and rare-earth elements (Y > REE ), with minor Mn, Zr, Na, Fe 2+ and Ca, <M H –ϕ> = 2.271 Å and the [6] A P site is occupied by Ca, < A P –ϕ> = 2.416 Å. The M H and A P octahedra and Si 2 O 7 groups constitute the H sheet. The ideal compositions of the O and two H sheets are Na 3 Ti(OF)F 2 and Y 2 Ca 2 (Si 2 O 7 ) 2 apfu. Fogoite-(Y) is isostructural with götzenite and hainite. The mineral is named after the type locality, the Fogo volcano in the Azores.
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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 | 0.003 | 0.003 |
| Meta-epidemiology (narrow) | 0.005 | 0.003 |
| Meta-epidemiology (broad) | 0.005 | 0.003 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.006 | 0.006 |
| Scholarly communication | 0.005 | 0.003 |
| Open science | 0.006 | 0.004 |
| Research integrity | 0.003 | 0.005 |
| 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 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".