Lowering the symmetry of pyrite crystals

Anatoliy Pshenichkin, Andrey Kryazhov

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The pyrites belong to the cubic system (m3) with elements of 3L24L33PC symmetry. At the most deposits and ore occurrences, the crystals of pyrite usually are founded in simple forms such as Cube - {100}, pentagonal dodecahedron - {210}, octahedron - {111}, and the combination of them. However, quite often there are the crystals of pyrite in the rhombohedral form with blunt or sharp shape, such crystals are found in metamorphic shales, and near the deposits of metosomatic low-temperature ore. The formation of rhombohedral crystals of pyrites is explained by the degeneration of sixth or twelfth edges and the uneven development of the edges of pentagonal dodecahedron - {210} It can also bound with the position of the crystal relative to the direction of schistosity when rhombohedral of pyrites are oriented by third-order axis perpendicular to the schistosity level, and overgrowth of the crystal pyrite {210} by small plots of {100} edges, in the result that the surface of the edge is curved, and its angle decreases. The formation of the rhombohedral crystals may be explained with the elemental analysis the cell of pyrite. In our opinion, the symmetry has not cubic nature in the crystal but it is trigonal with a the single of third-order axis. Secondly, because of its cubic structure pyrite must be optically isotropic. However, current research suggests that the mineral is often anisotropic and had the double reflection. The anisotropy of pyrite some researchers connect with the influence of the internal strain due to an excess of As or Fe, or with Ni impurities, and with the replacement of the iron on sulfur. The phenomenon of anisotropy was studied in detail by Stanton. He statistically showed that double reflection at the pyrite appears in any plane other except {111} (This direction is the same as that dual sulfur atom in the center of the unit cell of pyrite, causing only the third-order axis if the pyrite has a trigonal symmetry). Usually, anisotropy of pyrite is associated with the vibrations of the Fe atoms in relation to the S atoms or because of low symmetry (class 23) of its crystals. The anisotropic structure of pyrite was researched by the method of powder and monocrystal filming. The diffraction patterns of the anisotropic pyrite showed that additional reflection, which is lowering the symmetry of the pyrite crystals with the spatial group from cubic to trigonal symmetry.

Original languageEnglish
Title of host publication16th International Multidisciplinary Scientific GeoConference, SGEM 2016
Subtitle of host publicationEcology, Economics, Education and Legislation - Conference Proceedings
PublisherInternational Multidisciplinary Scientific Geoconference
Number of pages8
ISBN (Electronic)9786197105551, 9786197105582, 9786197105612, 9786197105636, 9786197105650, 9786197105681
Publication statusPublished - 2016
Event16th International Multidisciplinary Scientific GeoConference: Science and Technologies in Geology, Exploration and Mining, SGEM 2016 - Albena, Bulgaria
Duration: 30 Jun 20166 Jul 2016


Conference16th International Multidisciplinary Scientific GeoConference: Science and Technologies in Geology, Exploration and Mining, SGEM 2016


  • Pyrites
  • Trigonal symmetry

ASJC Scopus subject areas

  • Geology
  • Geotechnical Engineering and Engineering Geology

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