Putnisite, SrCa<sub>4</sub>Cr<sub>8</sub><sup>3+</sup> (CO<sub>3</sub>)<sub>8</sub>SO<sub>4</sub>(OH)<sub>16</sub>·25H<sub>2</sub>O, a new mineral from Western Australia: description and crystal structure
Why this work is in the frame
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Bibliographic record
Abstract
Abstract Putnisite, SrCa 4 Cr 8 3+ (CO 7 ) 8 SO 4 (OH) 16 ·25H 2 O, is a new mineral from the Polar Bear peninsula, Southern Lake Cowan, Western Australia, Australia. The mineral forms isolated pseudocubic crystals up to 0.5 mm in size in a matrix composed of quartz and a near amorphous Cr silicate. Putnisite is translucent, with a pink streak and vitreous lustre. It is brittle and shows one excellent and two good cleavages parallel to {100}, {010} and {001}. The fracture is uneven and the Mohs hardness 1½−2. The measured density is 2.20(3) g/cm3 and the calculated density based on the empirical formula is 2.23 g/cm3. Optically, putnisite is biaxial negative, with α = 1.552(3), β = 1.583(3) and γ = 1.599(3) (measured in white light). The optical orientation is uncertain and pleochroism is distinct: X pale bluish grey, Y pale purple, Z pale purple. Putnisite is orthorhombic, space group Pnma , with a = 15.351(3), b = 20.421(4) Å, c = 18.270(4) Å, V = 5727(2) Å 3 (single-crystal data), and Z = 4. The strongest five lines in the X-ray powder diffraction pattern are [d(Å)( I )( hkl )]: 13.577 (100) (011), 7.659 (80) (200), 6.667 (43) (211), 5.084 (19) (222, 230), 3.689 (16) (411). Electron microprobe analysis (EMPA) gave (wt.%): Na 2 O 0.17, MgO 0.08, CaO 10.81, SrO 5.72, BaO 0.12, CuO 0.29, Cr 2 O 3 31.13, SO 3 3.95, SiO 2 0.08, Cl − 0.28, CO 2calc 17.94, H 2 O calc 30.30, O=Cl−0.06, total 100.81. The empirical formula, based on O + Cl = 69, is: Cr 8.02 3+ Ca 3.78 Sr 1.08 Na 0.11 Cu 0.07 2+ Mg 0.04 Ba 0.02 [(SO 4 ) 0.96 (SiO 4 ) 0.03 ] 0.99 (CO 3 ) 7.98 (OH) 16.19 C l0.15 ·24.84H 2 O. The crystal structure was determined from single-crystal X-ray diffraction data (Mo K α, CCD area detector and refined to R 1 = 5.84% for 3181 reflections with F 0 > 4σ F . Cr(OH) 4 O 2 octahedra link by edge-sharing to form an eight-membered ring. A 10-coordinated Sr 2+ cation lies at the centre of each ring. The rings are decorated by CO3 triangles, each of which links by corner-sharing to two Cr(OH) 4 O 2 octahedra. Rings are linked by Ca(H 2 O) 4 O 4 polyhedra to form a sheet parallel to (100). Adjacent sheets are joined along [100] by corner-sharing SO 4 tetrahedra. H 2 O molecules occupy channels that run along [100] and interstices between slabs. Moderate to weak hydrogen bonding provides additional linkage between slabs.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.006 | 0.006 |
| Meta-epidemiology (broad) | 0.006 | 0.002 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.003 | 0.003 |
| Scholarly communication | 0.005 | 0.004 |
| Open science | 0.004 | 0.003 |
| Research integrity | 0.004 | 0.005 |
| Insufficient payload (model declined to judge) | 0.001 | 0.002 |
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