{"title":"马丹铅锌矿区(保加利亚罗多佩地块)的拟立方三角黄铁矿:形态和孪晶","authors":"Y. Moëlo","doi":"10.5194/ejm-35-333-2023","DOIUrl":null,"url":null,"abstract":"Abstract. A new occurrence of pyrite crystals with rhombohedral\nhabit, up to several centimeters in length, is described from the Madan Pb–Zn\nore field (Rhodope Massif, south Bulgaria), where it constitutes a late\npyrite generation. As observed in the past in other deposits, the ideal\nrhombohedron is derived from the pyritohedron by suppression of half of its\nfaces (six “polar faces”) around a ternary axis. In studied crystals,\ntogether with six main “equatorial faces”, additional minor faces\ncorrespond to cube faces as well as polar faces. Such a dissymmetry\nindicates that the crystallographic point group of these crystals is\n3‾, a subgroup of the eigensymmetry 3‾2/m of a rhombohedron\ntaken as geometric face form. Twinning by metric merohedry confirms such a\nsymmetry decrease and permits the definition of this type of pyrite as a dimorph of\ncubic pyrite, i.e., pseudo-cubic trigonal pyrite (pyrite-R). Twin operations\nbelong to the set of symmetry operations absent in point group 3‾\nrelative to pyrite symmetry m3‾: reflection about the {100} plane or two-fold rotation about the <100> direction. Four twin types have been distinguished (name,\nchromatic point group): three contact twins (reflection, m′; rotation, 2′;\ntrapezoidal, (m(2)m(2)2(2))(4)), as well as one penetration twin\n(crossed, 2′/m′). Composition planes always correspond to {100}, but there are two types of twin interfaces. More\ncomplex twinned samples may develop erratically during crystal growth. Other\ntwin variations as well as genetic aspects of such a type of pyrite are\ndiscussed.\n","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":" ","pages":""},"PeriodicalIF":1.8000,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Pseudo-cubic trigonal pyrite from the Madan Pb–Zn ore field (Rhodope Massif, Bulgaria): morphology and twinning\",\"authors\":\"Y. Moëlo\",\"doi\":\"10.5194/ejm-35-333-2023\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Abstract. A new occurrence of pyrite crystals with rhombohedral\\nhabit, up to several centimeters in length, is described from the Madan Pb–Zn\\nore field (Rhodope Massif, south Bulgaria), where it constitutes a late\\npyrite generation. As observed in the past in other deposits, the ideal\\nrhombohedron is derived from the pyritohedron by suppression of half of its\\nfaces (six “polar faces”) around a ternary axis. In studied crystals,\\ntogether with six main “equatorial faces”, additional minor faces\\ncorrespond to cube faces as well as polar faces. Such a dissymmetry\\nindicates that the crystallographic point group of these crystals is\\n3‾, a subgroup of the eigensymmetry 3‾2/m of a rhombohedron\\ntaken as geometric face form. Twinning by metric merohedry confirms such a\\nsymmetry decrease and permits the definition of this type of pyrite as a dimorph of\\ncubic pyrite, i.e., pseudo-cubic trigonal pyrite (pyrite-R). Twin operations\\nbelong to the set of symmetry operations absent in point group 3‾\\nrelative to pyrite symmetry m3‾: reflection about the {100} plane or two-fold rotation about the <100> direction. Four twin types have been distinguished (name,\\nchromatic point group): three contact twins (reflection, m′; rotation, 2′;\\ntrapezoidal, (m(2)m(2)2(2))(4)), as well as one penetration twin\\n(crossed, 2′/m′). Composition planes always correspond to {100}, but there are two types of twin interfaces. More\\ncomplex twinned samples may develop erratically during crystal growth. Other\\ntwin variations as well as genetic aspects of such a type of pyrite are\\ndiscussed.\\n\",\"PeriodicalId\":11971,\"journal\":{\"name\":\"European Journal of Mineralogy\",\"volume\":\" \",\"pages\":\"\"},\"PeriodicalIF\":1.8000,\"publicationDate\":\"2023-05-24\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"European Journal of Mineralogy\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.5194/ejm-35-333-2023\",\"RegionNum\":3,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MINERALOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"European Journal of Mineralogy","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.5194/ejm-35-333-2023","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MINERALOGY","Score":null,"Total":0}
Pseudo-cubic trigonal pyrite from the Madan Pb–Zn ore field (Rhodope Massif, Bulgaria): morphology and twinning
Abstract. A new occurrence of pyrite crystals with rhombohedral
habit, up to several centimeters in length, is described from the Madan Pb–Zn
ore field (Rhodope Massif, south Bulgaria), where it constitutes a late
pyrite generation. As observed in the past in other deposits, the ideal
rhombohedron is derived from the pyritohedron by suppression of half of its
faces (six “polar faces”) around a ternary axis. In studied crystals,
together with six main “equatorial faces”, additional minor faces
correspond to cube faces as well as polar faces. Such a dissymmetry
indicates that the crystallographic point group of these crystals is
3‾, a subgroup of the eigensymmetry 3‾2/m of a rhombohedron
taken as geometric face form. Twinning by metric merohedry confirms such a
symmetry decrease and permits the definition of this type of pyrite as a dimorph of
cubic pyrite, i.e., pseudo-cubic trigonal pyrite (pyrite-R). Twin operations
belong to the set of symmetry operations absent in point group 3‾
relative to pyrite symmetry m3‾: reflection about the {100} plane or two-fold rotation about the <100> direction. Four twin types have been distinguished (name,
chromatic point group): three contact twins (reflection, m′; rotation, 2′;
trapezoidal, (m(2)m(2)2(2))(4)), as well as one penetration twin
(crossed, 2′/m′). Composition planes always correspond to {100}, but there are two types of twin interfaces. More
complex twinned samples may develop erratically during crystal growth. Other
twin variations as well as genetic aspects of such a type of pyrite are
discussed.
期刊介绍:
EJM was founded to reach a large audience on an international scale and also for achieving closer cooperation of European countries in the publication of scientific results. The founding societies have set themselves the task of publishing a journal of the highest standard open to all scientists performing mineralogical research in the widest sense of the term, all over the world. Contributions will therefore be published primarily in English.
EJM publishes original papers, review articles and letters dealing with the mineralogical sciences s.l., primarily mineralogy, petrology, geochemistry, crystallography and ore deposits, but also biomineralogy, environmental, applied and technical mineralogy. Nevertheless, papers in any related field, including cultural heritage, will be considered.