Oxy-schorl, Na(Fe2+2Al)Al6Si6O18(BO3)3(OH)3O, a new mineral from Zlata Idka, Slovak Republic and Pribyslavice, Czech Republic
Bibliographic record
Abstract
Oxy-schorl (IMA 2011-011), ideally Na(Fe 2 2+ Al)Al 6 Si 6 O 18 (BO 3 ) 3 (OH) 3 O, a new mineral species of the tourmaline supergroup, is described. In Zlatá Idka, Slovak Republic (type locality), fan-shaped aggregates of greenish black acicular crystals ranging up to 2 cm in size, forming aggregates up to 3.5 cm thick were found in extensively metasomatically altered metarhyolite pyroclastics with Qtz+Ab+Ms. In Přibyslavice, Czech Republic (co-type locality), abundant brownish black subhedral, columnar crystals of oxy-schorl, up to 1 cm in size, arranged in thin layers, or irregular clusters up to 5 cm in diameter, occur in a foliated muscovite-tourmaline orthogneiss associated with Kfs+Ab+Qtz+Ms+Bt+Grt. Oxy-schorl from both localities has a Mohs hardness of 7 with no observable cleavage and parting. The measured and calculated densities are 3.17(2) and 3.208 g/cm3 (Zlatá Idka) and 3.19(1) and 3.198 g/cm 3 (Přibyslavice), respectively. In plane-polarized light, oxy-schorl is pleochroic; O = green to bluish-green, E = pale yellowish to nearly colorless (Zlatá Idka) and O = dark grayish-green, E = pale brown (Přibyslavice), uniaxial negative, ω = 1.663(2), ε = 1.641(2) (Zlatá Idka) and ω = 1.662(2), ε = 1.637(2) (Přibyslavice). Oxy-schorl is trigonal, space group R3m, Z = 3, a = 15.916(3) Å, c = 7.107(1) Å, V = 1559.1(4) Å 3 (Zlatá Idka) and a = 15.985(1) Å, c = 7.154(1) Å, V = 1583.1(2) Å 3 (Přibyslavice). The composition (average of 5 electron microprobe analyses from Zlatá Idka and 5 from Přibyslavice) is (in wt%): SiO 2 33.85 (34.57), TiO 2 <0.05 (0.72), Al 2 O 3 39.08 (33.55), Fe 2 O 3 not determined (0.61), FeO 11.59 (13.07), MnO <0.06 (0.10), MgO 0.04 (0.74), CaO 0.30 (0.09), Na 2 O 1.67 (1.76), K 2 O <0.02 (0.03), F 0.26 (0.56), Cl 0.01 (<0.01), B 2 O 3 (calc.) 10.39 (10.11), H 2 O (from the crystal-structure refinement) 2.92 (2.72), sum 99.29 (98.41) for Zlatá Idka and Přibyslavice (in parentheses). A combination of EMPA, Mössbauer spectroscopy, and crystal-structure refinement yields empirical formulas (Na 0.591 Ca 0.103 □ 0.306 ) Σ1.000 (Al 1.885 Fe 2+ 1.108 Mn 0.005 Ti 0.002 ) Σ3.000 (Al 5.428 Mg 0.572 ) Σ6.000 (Si 5.506 Al 0.494 ) Σ6.000 O 18 (BO 3 ) 3 (OH) 3 (O 0.625 OH 0.236 F 0.136 Cl 0.003 ) Σ1.000 for Zlatá Idka, and (Na 0.586 Ca 0.017 K 0.006 □ 0.391 ) Σ1.000 (Fe 2+ 1.879 Mn 0.015 Al 1.013 Ti 0.093 ) Σ3.00 (Al 5.732 Mg 0.190 Fe 3+ 0.078 ) Σ6.000 (Si 5.944 Al 0.056 ) Σ6.000 O 18 (BO 3 ) 3 (OH) 3 (O 0.579 F 0.307 OH 0.115 ) Σ1000 for Přibyslavice. Oxy-schorl is derived from schorl end-member by the AlOFe -1 (OH) -1 substitution. The studied crystals of oxy-schorl represent two distinct ordering mechanisms: disorder of R 2+ and R 3+ cations in octahedral sites and all O ordered in the W site (Zlatá Idka), and R 2+ and R 3+ cations ordered in the Y and Z sites and O disordered in the V and W sites (Přibyslavice).
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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 | 0.003 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".