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

Abstract

The first barium member of the melilite group, bennesherite Ba 2 Fe 2+ Si 2 O 7 (P 4 2 1 m, Z = 2, a = 8.2334(14) Å, c = 5.2854(8) Å, V = 359.29(13) Å 3 ), 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 This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

Natural cubic perovskite, Ca(Ti,Si,Cr)O3–δ, a versatile potential host for rock-forming and less-common elements up to Earth’s mantle pressure

“…However, there are significant departures from melilite stoichiometry (Ca ~2.3 apfu instead of 2, sum of other cations ~2.8 apfu instead of 3) and substantial enrichment in Fe as compared to surrounding gehlenite (Table 1), towards the compositions of Fe-rich members of melilite group (cf. Krzątała et al 2022). (calculated on the basis of Σ = 2 cations per ABO 3-δ formula unit).…”

Bianchiniite, Ba2(Ti4+V3+)(As2O5)2OF, a new diarsenite mineral from the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy

“…Bianchiniite has some resemblance with fresnoite (Masse et al, 1967;Moore and Louisnathan, 1969;Markgraf et al, 1985;Krzątala et al, 2021) and with melilite group minerals (Bindi et al, 2020). Fresnoite, ideally Ba 2 Ti(Si 2 O 7 )O, has unit-cell parameters a = 8.52, c = 5.21 Å, with space group P4bm.…”

“…As first noted by Moore and Louisnathan (1969), this mineral displays some structural features in common with melilite group phases. Among them, the recently described mineral bennesherite, Ba 2 Fe 2+ Si 2 O 7 , is the first Ba member of this group (Krzątala et al, 2021). Its unit-cell parameters are a = 8.23, c = 5.29 Å, space group P 4 2 1 m. In agreement with the general formula of melilite group minerals, X 2 T(1)[T(2) 2 O 7 ] (e.g., Bindi et al, 2020), the T(1) tetrahedron is occupied by Fe 2+ , whereas Si 4+ is hosted at T (2) (Fig.…”

“…The c unit-cell parameters of fresnoite and melilite group minerals are very similar, usually about 5 Å (see Table 1 in Krzątala et al, 2021); such a periodicity is related to the alternation, along c, of (Ti/Si) and [T(1)/T (2)] layers with intercalated Ba and X layers in fresnoite and melilite group minerals, respectively. In bianchiniite, the c parameter is tripled.…”

Crystal chemistry and Raman spectroscopy study of bennesherite, Ba2Fe2+Si2O7, and rare accessory Ba minerals from Caspar quarry, Bellerberg volcano, Germany

“…Bennesherite was recently found in the veins of coarse-grained rankinite paralava in pyrometamorphic rocks of the Hatrurim Complex (Gurim Anticline locality) (Krzątała et al, 2022). The authors performed a series of investigations, including chemical, structural and spectroscopic analyses of this new mineral, and compared the data with other members of the melilite group.…”