STEEDEITE, NaMn2[Si3BO9](OH)2: CHARACTERIZATION, CRYSTAL-STRUCTURE DETERMINATION, AND ORIGIN
Bibliographic record
Abstract
Steedeite, ideally NaMn 2 Si 3 BO 9 (OH) 2 , is a new mineral discovered in altered sodalite syenite at the Poudrette quarry, La Vallee-du-Richelieu, Monteregie (formerly Rouville County), Quebec, Canada. Crystals of steedeite are colorless to pale pink, and acicular with average dimensions of 0.006 × 0.011 × 0.51 mm. They occur as radiating to loose, randomly oriented groupings within vugs associated with aegirine, nepheline, sodalite, eudialyte-group minerals, analcime, natron, pyrrhotite, catapleiite, and two other unidentified minerals temporarily designated UK78 and UK80. Steedeite is transparent to translucent with a vitreous luster and has a weak pale green to pale yellow fluorescence under medium-wave radiation. No partings or cleavages were observed, although crystals exhibit an uneven fracture. The calculated density is 3.106 g/cm 3 . Steedeite is nonpleochroic, biaxial with n min = 1.636(2) and n max = 1.656(2) and a positive elongation. Chemical analyses (n = 14) from seven crystals gave an average (range, standard deviation) of: Na 2 O 7.51 (6.78–8.32, 0.44), CaO 0.17 (0.08–0.22, 0.03), MnO 31.02 (29.91–32.83, 0.93), FeO 0.86 (0.76–1.01, 0.07), SiO 2 46.34 (40.39–49.29, 2.56), S 0.39 (*b.d.– 2.36, 0.71) (*b.d. = below detection), B 2 O 3 (calc.) 8.73, and H 2 O (calc.) 4.52, total 99.53 wt.%. The empirical formula is: Na 0.97 (Mn 1.75 Fe 0.05 Ca 0.01 ) ∑1.83 (Si 3.07 S 0.02 ) ∑3.09 BO 9 (OH) 2 , or ideally NaMn 2 Si 3 BO 9 (OH) 2 . The presence of both B and OH in steedeite were inferred from the refinement of the crystal structure. The Raman spectrum for steedeite show bands at 3250–3500 cm –1 attributed to O–H stretching, strong sharp bands at 575–750 cm −1 and 825–1075 cm −1 attributed to Si–O bonds and possibly B–O bonding, as well as weak to strong bands at 50–500 cm −1 attributed to Na–O/Mn–O bonds. Steedeite crystallizes in space group P 1 ¯ (#2) with a 6.837(1), b 7.575(2), c 8.841(2) A, α 99.91(3), β 102.19, γ 102.78(3)°, V 424.81 A 3 , and Z = 2. The strongest six lines on the X-ray powder-diffraction pattern [ d in A (I) ( hkl )] are: 8.454 (100) (00 1 ¯ ), 7.234 (39) (00 1 ¯ ), 3.331 (83) (1 2 ¯ 1, 0 1 ¯ 2 ¯ , 20 1 ¯ , 1 1 ¯ 2), 3.081 (38) (0 2 ¯ 1 ¯ ), 2.859 (52) (0 1 ¯ 3), and 2.823 (80) (21 1 ¯ ). The crystal structure of steedeite was refined to R = 1.68% and wR 2 = 4.96% for 2409 reflections ( F o > 4σ F o ). It is based on silicate chains with a periodicity of three (i.e., dreier chain) consisting of four-membered borosilicate rings of composition [BSi 3 O 9 (OH) 2 ] 5− . The borosilicate chains are classed as single loop-branched dreier chains that are linked together through shared corners to bands of edge-sharing MnO 5 (OH) octahedra. Steedeite is a chain silicate mineral closely related to the serandite-pectolite series of the pyroxenoid group and is the first mineral found to contain single loop-branched dreier silicate chains.
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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 | 0.000 | 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) | 0.000 | 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".