Cerchiaraite-(Fe) and cerchiaraite-(Al), two new barium cyclosilicate chlorides from Italy and California, USA
Bibliographic record
Abstract
Abstract The ideal formula for members of the cerchiaraite group is Ba 4 M 4 (Si 4 O 12 )O 2 (OH) 4 C l2 [Si 2 O 3 (OH) 4 ], where M represents Mn 3+ , Fe 3+ or Al in the octahedral site. A suffix-based naming scheme is used in which the original cerchiaraite is renamed cerchiaraite-(Mn) and two new minerals are named cerchiaraite-(Fe) and cerchiaraite-(Al). The type localities for cerchiaraite-(Fe) are the Cerchiara mine, Liguria, Italy and the Esquire No. 7 and No. 8 claims, Big Creek, Fresno County, California, USA. The type localities for cerchiaraite-(Al) are the Esquire No. 1 claim, Rush Creek, Fresno County, California, USA and the Esquire No. 7 and No. 8 claims noted above. At the Cerchiara mine, cerchiaraite-(Fe) occurs in small fractures and veinlets in a Jurassic ophiolitic sequence. It is of secondary hydrothermal origin and occurs as tan to brown thin prisms and matted fibres. Cerchiaraite(Fe) and cerchiaraite-(Al) from the Esquire No. 1, No. 7 and No. 8 claims occur in parallel-bedded quartz-sanbornite vein assemblages which formed as a result of fluid interaction along the margin of the vein. At the Esquire No. 1, No. 7 and No. 8 claims, both cerchiaraite-(Fe) and cerchiaraite-(Al) occur as subparallel aggregates of blue to bluish green irregular prisms. Both minerals are transparent with a vitreous lustre, Mohs hardness ~4½ , brittle tenacity, irregular fracture and no cleavage. The calculated density of cerchiaraite-(Fe) is 3.710 g cm -3 ; the measured density of cerchiaraite-(Al) is 3.69(3) g cm -3 and the calculated density is 3.643 g cm -3 . Cerchiaraite-(Fe) is uniaxial (+), with ω = 1.741(2) and ε = 1.768(2); it is weakly pleochroic and O is colourless and E is yellow. Cerchiaraite-(Al) is uniaxial (-), with ω = 1.695(2) and e = 1.677(2); it is strongly pleochroic and O is colourless and E is blue. Electron-microprobe analyses yielded empirical formulae ranging from (Ba 3.82 Na 0.02 Ca 0.04 ) Σ3.88 (Fe 3+ 3.42 Ti 4+ 0.27 Al 3+ 0.25 Mn 3+ 0.04 Mg 0.02 ) Σ4.00 Si 5.62 O 15.47 (OH) 9.31 Cl 2.22 (Cerchiara mine) to Ba 4.00 (Al 3+ 2.40 Fe 3+ 1.12 Mg 0.15 Fe 2+ 0.12 Mn 2+ 0.06 ) Σ3.85 Si 5.78 O 15.34 (OH) 8.75 Cl 2.91 (Esquire No. 1 claim). Cerchiaraite is tetragonal with Z = 2 and crystallizes in space group I 4/ mmm . The cell parameters for cerchiaraite-(Fe) are a = 14.3554(12), c = 6.0065(5) Å and V = 1237.80(5) Å 3 ; those for cerchiaraite(Al) are a = 14.317(4), c = 6.0037(18) Å and V = 1230.6(6) Å 3 . In the cerchiaraite-(Fe) structure, SiO 4 tetrahedra share corners forming a four-membered Si 4 O 12 ring. The ring is corner-linked to an edgesharing chain of Fe 3+ O 6 octahedra running parallel to c . A Cl site alternates along c with the Si 4 O 12 ring. A large channel in the framework contains Ba atoms around its periphery and statistically distributed Si 2 O 7 silicate dimers and Cl atoms. The strong blue pleochroic colour is attributed to Fe 2+ - Fe 3+ intervalence charge transfer along the octahedral chain.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".