GEORGEROBINSONITE, Pb4(CrO4)2(OH)2FCl, A NEW CHROMATE MINERAL FROM THE MAMMOTH - ST. ANTHONY MINE, TIGER, PINAL COUNTY, ARIZONA: DESCRIPTION AND CRYSTAL STRUCTURE
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Bibliographic record
Abstract
Georgerobinsonite, Pb 4 (CrO 4 ) 2 (OH) 2 FCl, is a new chromate mineral species from the Mammoth – St. Anthony mine, Tiger, Pinal County, Arizona. It occurs as minute intergrowths of thin tabular orange crystals less than 0.1 mm across with {001} dominant and minor {010} and {110}, associated with caledonite, a cerchiaraite-related mineral, cerussite, diaboleite, Cr-bearing leadhillite, matlockite, murdochite, pinalite, wulfenite and yedlinite, in vugs in a silicified matrix. Georgerobinsonite is orange-red, transparent and has a pale orange streak and an adamantine luster, and it does not fluoresce under ultraviolet light. No cleavage or parting was observed. The Mohs hardness is 2½–3; georgerobinsonite is brittle with an uneven fracture. The calculated density is 6.23 g/cm 3 . The indices of refraction are α ≈ 2.07, β > 2.11, γ > 2.11; 2 V (obs) = 84(2)°; it is strongly pleochroic, α orange, γ yellow; optical orientation: X = a , Y = c and Z = b , and the dispersion is strong with r > v . Georgerobinsonite is orthorhombic, space group Pmmn , a 7.613(2), b 11.574(3), c 6.883(2) A, V 606.5(3) A 3 , Z = 2, a:b:c = 0.6578:1:0.5947. The strongest six lines in the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 2.131(100)(232), 3.308(80)(012), 3.195(80)(211, 220), 6.371(60) (110), 3.357(60)(031, 201) and 3.143(60)(102). Chemical analysis with an electron microprobe gave CrO 3 14.79, PbO 77.99, SO 3 1.64, F 1.47, Cl 3.39, H 2 O (calc.) 1.52, sum 99.42 wt.%; the valence states of Pb, Cr and S, and the amount of H 2 O, were determined by crystal-structure analysis. The resulting empirical formula, on the basis of 12 (O, F, Cl, OH) anions, is Pb 4.09 (Cr 6+ 1.73 S 6+ 0.24 ) ∑1.97 O 8 (OH) 1.98 F 0.90 Cl 1.12 . The crystal structure of georgerobinsonite was solved by direct methods and refined to an R 1 index of 2.0% based on 574 observed reflections collected on a four-circle diffractometer with Mo K α X-radiation. There are two Pb 2+ cations coordinated by eight and nine anions, and both show prominent lone-pair stereoactive behavior. The Pb polyhedra share faces and edges to form layers parallel to {001} that are linked into a heteropolyhedral framework by (CrO 4 ) groups, with hydrogen bonding between OH and Cl anions. The mineral is named after Dr. George Willard Robinson (b. 1946), mineral curator, researcher, teacher and field collector.
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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 | 0.000 | 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) | 0.003 | 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 it