Demagistrisite, the Missing Link in a Polysomatic Series from Lawsonite to Orientite
Bibliographic record
Abstract
Abstract Demagistrisite, ideally BaCa2Mn3+4(Si3O10)(Si2O7)(OH)4·3H2O, is a new mineral found at the Cerchiara mine (eastern Liguria, La Spezia province, Italy). The ore consists of rhythmic interlaying of braunite-bearing metasediments (5–15 cm thick) and hematite-rich cherts. Demagistrisite occurs in association with cerchiaraite-(Mn), namansilite, noelbensonite, orientite, richterite, ruizite, and saponite in matrix consisting of braunite, calcite, cryptomelane, orthoclase, and quartz. Demagistrisite crystals occur as tightly intergrown blades or as millimeter-sized prisms and needles with square cross-section, typically with irregular terminations, and rarely terminated by a low-angle pyramid. The mineral is orange brown to red brown, streak is beige, and luster is vitreous, translucent to transparent. Fracture is irregular. In thin section, it is orange brown. The mineral is optically biaxial (–) with α 1.805(5), β 1.825(5), γ 1.8305(5) (white light); 2Vmeas 58(5)°, 2Vcalc 54.7°; optical orientation X = c, Y = b, Z = a. Dispersion is very strong, r > v. Pleochroism is strong with X orange yellow, Y red brown, Z red brown; X << Z < Y. It is unreactive in concentrated HCl at room temperature. Thirteen chemical analyses by WDS-EMPA gave the following empirical formula (based on 24 O apfu): (Ba0.69Ca1.25Mn2+0.70Sr0.21Na0.12Mg0.02)Σ2.99(Mn3+3.97Al0.03)Σ4(Si3O10)(Si2O7)(OH)3.87·3.13H2O. The mineral is orthorhombic, space group Amm2, with unit-cell parameters a 16.312(8), b 6.176(4), c 9.075(6) Å, V 914.2(10) Å3, and Z = 2. The seven strongest X-ray powder diffraction lines are [d Å (I%; hkl)]: 16.21 (49; 100), 4.86 (44; 111), 4.34 (56; 102,211), 2.871 (54; 220), 2.731 (100; 511,013), 2.671 (74; 320,113,502), and 2.426 (51; 222,313,611). The crystal structure (R1 = 0.0572 for 1485 reflections with I > 2σI) is based on straight edge-sharing chains of Mn3+-centered octahedra extending along [010], which are bridged by disilicate (Si2O7) and trisilicate (Si3O10) groups, yielding a framework. Cavities within this framework contain two large cation sites. The structure of demagistrisite can be considered transitional between the structures of orientite and noelbensonite. Demagistrisite is named in honor of Leandro de Magistris (1906–1990).
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".