Petersite-(Ce), Cu<sup>2+</sup><sub>6</sub>Ce(PO<sub>4</sub>)<sub>3</sub>(OH)<sub>6</sub>·3H<sub>2</sub>O, A New Mixite Group Mineral From Yavapai County, Arizona, USA
Bibliographic record
Abstract
Abstract A new mineral, petersite-(Ce), ideally Cu 2+ 6 Ce(PO 4 ) 3 (OH) 6 ·3H 2 O (IMA2014-002), has been found in the Cherry Creek District of Yavapai County, Arizona, USA. It is a secondary alteration mineral associated with malachite, chlorite, a biotite phase, quartz, albite, orthoclase, hematite, chalcopyrite, and an uncharacterized hisingerite-like mineral. Petersite-(Ce) occurs as sprays of yellowish-green, acicular crystals approximately 20 × 20 × 50 μm in size. It has a white streak with vitreous luster. The mineral is brittle and has a Mohs hardness of ∼3.5; no cleavage or parting was observed. The calculated density is 3.424 g/cm 3 . An electron microprobe analysis resulted in an empirical chemical formula of Cu 6.05 (Ce 0.18 Y 0.16 La 0.12 Nd 0.09 Gd 0.03 Pr 0.02 Dy 0.01 Sm 0.01 Ca 0.42 ) Σ1.04 [(PO 4 ) 2.54 (SiO 4 ) 0.14 (PO 3 OH) 0.32 (OH) 6 ]·3.65H 2 O. Petersite-(Ce) is hexagonal, with space group P 6 3 / m and unit-cell parameters a 13.2197(18) A, c 5.8591(9) A, and V 886.8(4) A 3 , Z = 2. It is the Ce analogue of petersite-(Y) and exhibits the mixite structure type. The mixite group can be expressed by the general formula Cu 2+ 6 A ( T O 4 ) 3 (OH) 6 · 3H 2 O, where nine-coordinated A is a rare earth element, Al, Ca, Pb, or Bi, and T is P or As. The structure of petersite-(Ce) is characterized by chains of edge-sharing CuO 5 square-pyramids along c . These chains are connected in the a-b plane by edge-sharing CeO 9 polyhedra and corner-sharing PO 4 tetrahedra. Hydroxyl groups occupy each corner of the CuO 5 polyhedra not shared by a neighboring P or Ce atom. Each CeO 9 polyhedron is surrounded by three zeolitic channels. The walls of the channels, parallel to c , are six-membered, hexagonal rings composed of CuO 5 and PO 4 polyhedra in a ratio of 2:1, respectively, and contain H 2 O molecules. In our model of petersite-(Ce), we defined one distinct H 2 O site positioned to form a ring inside the channel, although there are many statistically possible locations.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 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 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".