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Dostęp zamkniętyBohseite, ideally Ca4Be4Si9O24(OH)4, from the Piława Górna quarry, the Góry Sowie Block, SW Poland
| dc.abstract.en | Bohseite is an orthorhombic calcium beryllium aluminosilicate with variable Al content and an end-member formula Ca4Be4Si9O24(OH)4, that was discovered in the Piława Górna quarry in the eastern part of the Góry Sowie Block, ∼50 km southwest of Wrocław, SW Poland. It occurs in a zoned anatectic pegmatite dyke in close association with microcline, Cs-rich beryl, phenakite, helvite, ‘lepidolite’, probably bertrandite and unidentified Be-containing mica as alteration products after a primary Be mineral, probably beryl. Bohseite forms fan-like or parallel aggregates (up to 0.7 cm) of white, platy crystals (up to 2 mm long) with characteristic striations. It is white with a white streak, is translucent and has a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is perfect on {001} and fair on {010}, and neither parting nor twinning was observed. Bohseite is brittle with a splintery fracture and Mohs hardness is 5–6. The calculated density is 2.719 g cm–3. The indices of refraction are α = 1.579, β = 1.580, γ = 1.597, all ±0.002; 2Vobs = 24(3)°, 2Vcalc = 27°; the optic orientation is as follows: X ^ a = 16.1°, Y ^ b = 16.1°, Z // c. Bohseite shows orthorhombic diffraction symmetry, space group Cmcm, a = 23.204(6), b = 4.9442(9), c = 19.418(6) Å, V = 2227.7(4) Å3, Z = 4. The crystal structure was refined to an R1 value of 2.17% based on single-crystal data, and the chemical composition was determined by electron-microprobe analysis. Bohseite is isostructural with bavenite. Bohseite was originally approved with an end-member composition of Ca4Be3AlSi9O25(OH)3, but subsequent discovery of compositions with Be > 3.0 apfu led to redefinition of its end-member composition, holotype sample and locality, as reported here. There is extensive solid solution in bavenite–bohseite according to the scheme O(2)OH– + T(4)Si4 + + T(3)Be2+ ↔ O(2)O2– +T(4)Al3+ + T(3)Si4+, and a general formula for the bavenite–bohseite minerals may be written as Ca4BexSi9Al4–xO28–x(OH)x, where x ranges from 2–4 apfu: Ca4Be2Si9Al2O26(OH)2 (bavenite) to Ca4Be4Si9O24(OH)4 (bohseite). |
| dc.affiliation | Uniwersytet Warszawski |
| dc.contributor.author | Szełęg, Eligiusz |
| dc.contributor.author | Zuzens, B. |
| dc.contributor.author | Hawthorne, F.C. |
| dc.contributor.author | PIECZKA, ADAM |
| dc.contributor.author | Szuszkiewicz, Adam |
| dc.contributor.author | Turniak, Krzysztof |
| dc.contributor.author | Nejbert, Krzysztof |
| dc.contributor.author | Ilnicki, Sławomir |
| dc.contributor.author | Friis, H. |
| dc.contributor.author | Makovicky, E. |
| dc.contributor.author | Weller, M.T. |
| dc.contributor.author | Lemée-Cailleau, M.-H. |
| dc.date.accessioned | 2024-01-24T18:40:31Z |
| dc.date.available | 2024-01-24T18:40:31Z |
| dc.date.issued | 2017 |
| dc.description.finance | Nie dotyczy |
| dc.description.number | 1 |
| dc.description.volume | 81 |
| dc.identifier.doi | 10.1180/MINMAG.2016.080.066 |
| dc.identifier.issn | 0026-461X |
| dc.identifier.uri | https://repozytorium.uw.edu.pl//handle/item/102418 |
| dc.language | eng |
| dc.pbn.affiliation | earth and related environmental sciences |
| dc.relation.ispartof | Mineralogical Magazine |
| dc.relation.pages | 35-46 |
| dc.rights | ClosedAccess |
| dc.sciencecloud | nosend |
| dc.subject.en | bohseite bavenite crystal-structure refinement infrared spectrum electron-microprobe analysis beryllium end-member solid-solution |
| dc.title | Bohseite, ideally Ca4Be4Si9O24(OH)4, from the Piława Górna quarry, the Góry Sowie Block, SW Poland |
| dc.type | JournalArticle |
| dspace.entity.type | Publication |