TY - JOUR
T1 - Bennesherite, Ba2Fe2+Si2O7
T2 - A new melilite group mineral from the Hatrurim Basin, Negev Desert, Israel
AU - Krzatała, Arkadiusz
AU - Krüger, Biljana
AU - Galuskina, Irina
AU - Vapnik, Yevgeny
AU - Galuskin, Evgeny
N1 - Publisher Copyright:
© 2022 Mineralogical Society of America.
PY - 2022/1/27
Y1 - 2022/1/27
N2 - 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.
AB - 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.
KW - Bennesherite
KW - Hatrurim
KW - Israel
KW - Raman
KW - crystal structure
KW - fresnoite
KW - melilite group
KW - new mineral
KW - paralava
UR - http://www.scopus.com/inward/record.url?scp=85109219453&partnerID=8YFLogxK
U2 - 10.2138/am-2021-7747
DO - 10.2138/am-2021-7747
M3 - Article
AN - SCOPUS:85109219453
SN - 0003-004X
VL - 107
SP - 138
EP - 146
JO - American Mineralogist
JF - American Mineralogist
IS - 1
ER -