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
Bibliographic record
Abstract
Abstract Khvorovite, ideally Pb42+Ca2[Si8B2(SiB)O28]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/cm3, respectively. Khvorovite is biaxial (+) with refractive indices (λ = 589 nm) α = 1.659(3), βcalc. = 1.671(2), γ = 1.676(3); 2Vmeas. = 64(3)°, medium dispersion: r < v. Khvorovite is triclinic, space group I1¯, 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 SiO2 36.98, B2O3 6.01, Y2O3 0.26, PbO 40.08, BaO 6.18, SrO 0.43, CaO 6.77, K2O 1.72, Na2O 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 (Pb2.762+Ba0.62K0.56Na0.16)Σ4.10(Ca1.86Sr0.06Y0.04Na0.04)Σ2[Si8B2(Si1.46B0.65)Σ2.11O28](F0.71O0.29), Z = 2 , and the simplified formula is (Pb2+, Ba, K)4Ca2[Si8B2(Si,B)2O28]F. The crystal structure of khvorovite was refined to R1 = 2.89% based on 3680 observed reflections collected on a four-circle diffractometer with MoKα radiation. In the crystal structure of khvorovite, there are four [4]-coordinated Si sites occupied solely by Si with = 1.617 Å. The [4]-coordinated B site is occupied solely by B, with = 1.478 Å. The [4]-coordinated T site is occupied by Si and B (Si1.46B0.54), with = 1.605 Å; it ideally gives (SiB) a.p.f.u. The Si, B and T tetrahedra form an interrupted framework of ideal composition [Si8B2(SiB)O28]11–. The interstitial cations are Pb2+, 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 Pb2+ and Ba + K. The [8]-coordinated M site is occupied mainly by Ca, with minor Sr, Y and Na. Khvorovite is a Pb2+ analogue of hyalotekite, (Ba,Pb2+,K)4(Ca,Y)2[Si8(B,Be)2(Si,B)2O28]F and a Pb2+-, Ca-analogue of kapitsaite-(Y), (Ba,K)4(Y,Ca)2[Si8B2(B,Si)2O28]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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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 | 0.001 | 0.001 |
| 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) | 0.002 | 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".