Khvorovite, Pb<sup>2+</sup><sub>4</sub>Ca<sub>2</sub>[Si<sub>8</sub>B<sub>2</sub>(SiB)O<sub>28</sub>]F, a new hyalotekite-group mineral from the Darai-Pioz alkaline massif, Tajikistan: Description and crystal structure
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Bibliographic record
Abstract
Abstract Khvorovite, ideally Pb 4 2+ Ca 2 [Si 8 B 2 (SiB)O 28 ]F, is a new borosilicate mineral of the hyalotekite group from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, Tajikistan. Khvorovite was found in a pectolite aggregate in silexites (quartz-rich rocks). The pectolite aggregate consists mainly of pectolite, quartz and fluorite, with minor aegirine, polylithionite, turkestanite and baratovite; accessory minerals are calcite, pyrochlore-group minerals, reedmergnerite, stillwellite-(Ce), pekovite, zeravshanite, senkevichite, sokolovaite, mendeleevite-(Ce), alamosite, orlovite, leucosphenite and several unknown Cs-silicates. Khvorovite occurs as irregular grains, rarely with square or rectangular sections up to 150 μm, and grain aggregates up to 0.5 mm. Khvorovite is colourless, rarely white, transparent with a white streak, has a vitreous lustre and does not fluoresce under ultraviolet light. Cleavage and parting were not observed. Mohs hardness is 5–5.5, and khvorovite is brittle with an uneven fracture. The measured and calculated densities are 3.96(2) and 3.968 g/cm 3 , respectively. Khvorovite is biaxial (+) with refractive indices (λ = 589 nm) α = 1.659(3), β calc. = 1.671(2), γ = 1.676(3); 2V meas. = 64(3)°, medium dispersion: r < v . Khvorovite is triclinic, space group I 1¯, a = 11.354(2), b = 10.960(2), c = 10.271(2) Å, α = 90.32(3), β = 90.00(3), γ = 90.00(3)°, V = 1278(1) Å3, Z = 2. The six strongest lines in the powder X-ray diffraction pattern [ d (Å), I, ( hkl )] are: 7.86, 100, (110); 7.65, 90, (101); 7.55, 90, (011); 3.81, 90, (202); 3.55, 90, (301); 2.934, 90, (312, 312). Chemical analysis by electron microprobe gave SiO 2 36.98, B 2 O 3 6.01, Y 2 O 3 0.26, PbO 40.08, BaO 6.18, SrO 0.43, CaO 6.77, K 2 O 1.72, Na 2 O 0.41, F 0.88, O=F –0.37, sum 99.35 wt.%. The empirical formula based on 29 (O+F) a.p.f.u. is (Pb 2.76 2+ Ba 0.62 K 0.56 Na 0.16 ) Σ4.10 (Ca 1.86 Sr 0.06 Y 0.04 Na 0.04 ) Σ2 [Si 8 B 2 (Si 1.46 B 0.65 ) Σ2.11 O 28 ](F 0.71 O 0.29 ), Z = 2 , and the simplified formula is (Pb 2+ , Ba, K) 4 Ca 2 [Si 8 B 2 (Si,B) 2 O 28 ]F. The crystal structure of khvorovite was refined to R 1 = 2.89% based on 3680 observed reflections collected on a four-circle diffractometer with Mo K α radiation. In the crystal structure of khvorovite, there are four [4]-coordinated Si sites occupied solely by Si with <Si–O>= 1.617 Å. The [4]-coordinated B site is occupied solely by B, with <B–O> = 1.478 Å. The [4]-coordinated T site is occupied by Si and B (Si 1.46 B 0.54 ), with <T–O> = 1.605 Å; it ideally gives (SiB) a.p.f.u. The Si, B and T tetrahedra form an interrupted framework of ideal composition [Si 8 B 2 (SiB)O 28 ] 11– . The interstitial cations are Pb 2+ , Ba and K (minor Na) [ A (11–22) sites] and Ca [ M site]. The two A sites are each split into two subsites ∼0.5 Å apart and occupied by Pb 2+ and Ba + K. The [8]-coordinated M site is occupied mainly by Ca, with minor Sr, Y and Na. Khvorovite is a Pb 2+ analogue of hyalotekite, (Ba,Pb 2+ ,K) 4 (Ca,Y) 2 [Si 8 (B,Be) 2 (Si,B) 2 O 28 ]F and a Pb 2+ -, Ca-analogue of kapitsaite-(Y), (Ba,K) 4 (Y,Ca) 2 [Si 8 B 2 (B,Si) 2 O 28 ]F. It is named after Pavel V. Khvorov (b. 1965), a Russian mineralogist, to honour his contribution to the study of the mineralogy of the Darai-Pioz massif.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.003 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it