Bennesherite, Ba2Fe2+Si2O7: A new melilite group mineral from the Hatrurim Basin, Negev Desert, Israel

Arkadiusz Krzatała, Biljana Krüger, Irina Galuskina, Yevgeny Vapnik, Evgeny Galuskin

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The first barium member of the melilite group, bennesherite Ba2Fe2+Si2O7 [P4¯21m, Z = 2, a = 8.2334(14) Å, c = 5.2854(8) Å, V = 359.29(13) Å3], was discovered in thin veins of rankinite paralava within pyrometamorphic gehlenite hornfels at Gurim Anticline, Hatrurim Basin, Negev Desert, Israel. Bennesherite occurs in small intergranular spaces between large crystals of rankinite, gehlenite, and garnet together with other Ba-minerals such as fresnoite, walstromite, zadovite, gurimite, hexacelsian, and celsian. It forms transparent, light yellow to lemon-colored crystals with a white streak and a vitreous luster. They exhibit good cleavage on (001), a brittle tenacity, and a conchoidal fracture. The estimated Mohs hardness is 5. Bennesherite has a melilite-type structure with the layers composed of disilicate (Si2O7)6- groups and (Fe2+O4)6- tetrahedra, connected by large eightfold-coordinated Ba atoms. In some grains, epitaxial intergrowths of bennesherite and fresnoite are observed. The structure of the fresnoite, Ba2TiO(Si2O7) with a P4¯bm space group and unit-cell parameters a = 8.5262(5) Å, c = 5.2199(4) Å, is closely related to the structure of bennesherite. Among all the known minerals of the melilite group, bennesherite has a structure characterized by the lowest misfit degree between the tetrahedral (T1 and T2 sites) and polyhedral (X-site) layers, as it was shown in both natural and synthetic melilite-type phases.

Original languageEnglish
Pages (from-to)138-146
Number of pages9
JournalAmerican Mineralogist
Volume107
Issue number1
DOIs
StatePublished - 27 Jan 2022

Keywords

  • Bennesherite
  • Hatrurim
  • Israel
  • Raman
  • crystal structure
  • fresnoite
  • melilite group
  • new mineral
  • paralava

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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