Billwiseite, Ideally Sb3+5(Nb,Ta)3WO18, A New Oxide Mineral Species from the Stak Nala Pegmatite, Nanga Parbat - Haramosh Massif, Pakistan: Description and Crystal Structure
Bibliographic record
Abstract
Billwiseite, ideally Sb 3+ 5 (Nb,Ta) 3 WO 18 , is an oxide mineral from a granitic pegmatite on the eastern margin of the Nanga Parbat – Haramosh massif at Stak Nala, 70 km east of Gilgit, Pakistan. It is transparent, pale yellow (with a tinge of green), has a colorless to very pale-yellow streak, a vitreous luster, and is inert to ultraviolet radiation. Crystals are euhedral with a maximum size of ∽ 0.5 × 0.25 × 0.15 mm and show the following forms: {100} pinacoid ≈ {011} pinacoid ≈ {410} prism; contact twins on (100) are common. Cleavage is {100} indistinct, Mohs hardness is 5, and billwiseite is brittle with a hackly fracture. The calculated density is 6.330 g/cm 3 . The indices of refraction were not measured; the calculated index of refraction is 2.3, 2 V ( obs ) = 76(2)°. Billwiseite is colorless in transmitted light, non-pleochroic, and the optic orientation is as follows: X ‖ b , Y ^ c = 72.8° (in β acute). It occurs scattered across the surface of a large (∽5 × 2.5 × 1.3 cm) crystal of lepidolite from a miarolitic cavity. The most abundant minerals in the cavities at Stak Nala are albite, quartz, K-feldspar, tourmaline, muscovite or lepidolite, topaz and fluorite, and billwiseite can be partly mantled by B-rich muscovite. Billwiseite is monoclinic, space group C 2/ c , a 54.116(5), b 49143(5), c 5.5482(5) A, β 90.425(2)°, V 1475.5(2) A 3 , Z = 4, a:b:c = 11.012 : 1 : 1.131. The strongest seven lines in the X-ray powder-diffraction pattern [ d in A( I ) hkl ] are as follows: 3.147(100)(911, 911), 3.500(55) (511, 511), 1.662(53)(1422), 3.017(48)(1800), 1.906(47)(1820), 1.735(30)(113, 113), 1.762(25)(2711, 2711). Chemical analysis by electron microprobe gave Nb 2 O 5 12.03, Ta 2 O 5 19.31, Sb 2 O 3 48.34, TiO 2 0.99, WO 3 19.96, sum 100.63 wt.% where the valence state of Sb was determined by crystal-structure analysis. The resulting empirical formula on the basis of 18 O anions is Sb 3+ 4.87 (Nb 1.33 Ta 1.28 Ti 0.18 W 1.26 ) Σ4.05 O 18 . The crystal structure of billwiseite was solved by direct methods and refined to an R 1 index of 4.71% based on 2122 observed reflections collected on a three-circle diffractometer with Mo K α X-radiation. The structure consists of two distinct sheets of M (= Ta,Nb,W) octahedra and three distinct sheets of Sb 3+ polyhedra parallel to (100). These sheets alternate in the a direction to form a continuous structure.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".