Bridgesite-(Ce), a new rare earth element sulfate, with a unique crystal structure, from Tynebottom Mine, Cumbria, United Kingdom
Bibliographic record
Abstract
Abstract Bridgesite-(Ce), (IMA2019-034), was discovered at Tynebottom Mine, Cumbria, UK. It occurs as thin (1–2 μm) translucent blue crystals with a lath-like to acicular habit, aggregated into thin crusts and is associated mainly with brochantite, malachite, serpierite, devilline, gypsum, aragonite, jarosite, pyrite, lanthanite-(Ce) and undifferentiated iron oxyhydroxides, it is often intergrown with these other minerals. The lustre, hardness, cleavage and parting could not be determined, nor could density be measured due to crystal size. It has a pale blue streak and is brittle with a splintery fracture. Bridgesite-(Ce) is biaxial (–), shows no pleochroism and has refractive indices (white light): α = 1.526(2), β = 1.564(2), γ = 1.572(2) and 2V(calc) = 48.3°. The empirical formula calculated on the basis of 44 negative charges is Ca0.86REEΣ1.99Al0.07Cu5.95(SO4)3.99(SiO4)0.05(PO4)0.02(OH)11.52⋅8H2O. The idealised formula is CaCe2Cu6(SO4)4(OH)12⋅8H2O, requiring (wt.%): 3.91 CaO, 22.89 Ce2O3, 33.28 CuO, 22.33 SO3 and 17.59 H2O. Bridgesite-(Ce) is monoclinic, space group C2/m, a = 24.801(5), b = 6.3520(13), c = 11.245(2) Å, β = 114.51(3)°, V = 1611.9(6) Å and Z = 2. The five most intense X-ray diffraction peaks in the measured pattern are [d in Å (I, %) (hkl)]: 11.3 (100) (200), 6.391 (15) (201), 2.770 (8) (420), 3.194 (6) (402) and 4.858 (5) (310). The crystal structure was solved using single crystal data and refined to an R1 index of 5.86%. Bridgesite-(Ce) contains three distinct Cu sites containing Cu2+, two are coordinated octahedrally and one is square pyramidal. The octahedra form chains through edge sharing parallel to the b-axis which are linked by the square pyramid to form sheets oriented parallel to {100}. Sulfate tetrahedra decorate the sheets which are held together by interstitial REE3+, Ca2+ and hydrogen bonding. The structure is unique. Despite apparent similarity in chemical formula, bridgesite-(Ce) is not closely related to any other natural Cu-sulfate mineral. An FTIR absorption spectra is presented for reference purposes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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; a candidate call from one source (direct Gemma or distilled Codex), 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".