Ferrobobfergusonite, □Na2Fe2+5Fe3+Al(PO4)6, a new mineral of the bobfergusonite group from the Victory Mine, Custer County, South Dakota, USA
Bibliographic record
Abstract
ABSTRACT A new mineral species, ferrobobfergusonite, ideally □Na2Fe2+5Fe3+Al(PO4)6, has been found in the Victory Mine, Custer County, South Dakota, USA. It is massive and associated with ferrowyllieite, schorl, fillowite, arrojadite, quartz, and muscovite. Broken pieces of ferrobobfergusonite are blocky or tabular with single crystals up to 0.9 × 0.7 × 0.4 mm. No twinning or parting is observed macroscopically. The mineral is deep green-brown and transparent with a pale green-yellow streak and vitreous luster. It is brittle and has a Mohs hardness of ∼5, with perfect cleavage on {010}. The measured and calculated densities are 3.68(1) and 3.69 g/cm3, respectively. Optically, ferrobobfergusonite is biaxial (+), with α = 1.698 (2), β = 1.705 (2), γ = 1.727 (2) (white light), 2V (meas.) = 65(2)°, 2V (calc.) = 60°, with orientation of the optic axes α ∧ X = 16°, β = Y, with X = yellowish brown, Y = brown, and Z = deep brown. The dispersion is very strong with r > v. The calculated compatibility index based on the empirical formula is 0.017 (superior). An electron microprobe analysis yielded an empirical formula (based on 24 O apfu) of (Na1.72□1.28)Σ3.00(Fe2+3.50Mn0.89Mg0.44Ca0.13)Σ4.96(Fe3+0.77Al0.23)Σ1.00Al(PO4)6. Ferrobobfergusonite is isostructural with bobfergusonite, a member of the alluaudite supergroup. It is monoclinic, with space group P21/n and unit-cell parameters a = 12.7156(3), b = 12.3808(3), c = 10.9347(3) Å, β = 97.3320(10)°, and V = 1707.37(7) Å3. The crystal structure of ferrobobfergusonite contains six octahedral M (= Fe2+, Mg, Mn2+, Al, Fe3+) sites and five X (= Na, Mn2+, Ca) sites with coordination numbers between 6 and 8. The six MO6 octahedra share edges to form two types of kinked chains extending along [101], with one consisting of M1–M4–M5 linkages and the other of M2–M3–M6 linkages. These chains are joined by PO4 tetrahedra to form sheets parallel to (010), which are linked together through corner-sharing between PO4 tetrahedra and MO6 octahedra in the adjacent sheets, leaving open channels parallel to a, where the large X cations are situated. The M cations are strongly ordered over the six sites, with M1, M2, M3, and M4 being dominantly occupied by Fe2+, and M5 and M6 by Fe3+ and Al, respectively. Among the five X sites, the X1 site is filled with Mn2+ and Ca, whereas the X2–X5 sites are partially occupied by Na.
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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 | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".